Android PreferenceActivity点击Header 处理过程
2014-11-19 08:19
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转载请注明出处：http://blog.csdn.net/droyon/article/details/18009373
本文讲述PreferenceActivity中单击事件的处理，重点记述mCurrentHeader以及设置源代码Settings中的mLastHeader、mCurrentHeader、mParentHeader的作用。主要以多屏幕为例。
在PreferenceActivity中，当我们点击Header时，其处理流程分为 单屏幕和双屏幕两套流程。
1、单屏幕（SinglePane）
1.1、点击每一项，执行如下代码.
[java] view
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public void onHeaderClick(Header header, int position) {
Log.d(LOG_TAG, "Settings onHeaderClick Header is:"+header.title+",position is:"+position+",mLastHeader is:"+mLastHeader);
boolean revert = false;
if (header.id == R.id.account_add) {
revert = true;
}
Log.d(LOG_TAG, "Settings onHeaderClick Header id is:"+header.id+", R.id.account_add is:"+R.id.account_add+",revert is:"+revert);
super.onHeaderClick(header, position);
if (revert && mLastHeader != null) {
highlightHeader((int) mLastHeader.id);
} else {
mLastHeader = header;
}
}
关于hightlightHeader下面有详细介绍，这里就不介绍了。
主要执行父类的onHeaderClick方法。
1.2、
[java] view
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public void onHeaderClick(Header header, int position) {
if (header.fragment != null) {
if (mSinglePane) {
int titleRes = header.breadCrumbTitleRes;
int shortTitleRes = header.breadCrumbShortTitleRes;
if (titleRes == 0) {
titleRes = header.titleRes;
shortTitleRes = 0;
&nb
24000
sp; }
startWithFragment(header.fragment, header.fragmentArguments, null, 0,
titleRes, shortTitleRes);
} else {
switchToHeader(header);
}
} else if (header.intent != null) {
startActivity(header.intent);
}
}
因为mSinglePane为true，故执行startWithFragment。
1.3、
[java] view
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Intent intent = onBuildStartFragmentIntent(fragmentName, args, titleRes, shortTitleRes);
if (resultTo == null) {
startActivity(intent);
} else {
resultTo.startActivityForResult(intent, resultRequestCode);
}
我们看到这里会执行onBuildStartFragmentIntent。
1.4、
[java] view
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public Intent onBuildStartFragmentIntent(String fragmentName, Bundle args,
int titleRes, int shortTitleRes) {
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.setClass(this, getClass());
intent.putExtra(EXTRA_SHOW_FRAGMENT, fragmentName);
intent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, args);
intent.putExtra(EXTRA_SHOW_FRAGMENT_TITLE, titleRes);
intent.putExtra(EXTRA_SHOW_FRAGMENT_SHORT_TITLE, shortTitleRes);
intent.putExtra(EXTRA_NO_HEADERS, true);
return intent;
}
这个方法在子类中有重写。
Settings.java
[java] view
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public Intent onBuildStartFragmentIntent(String fragmentName, Bundle args,
int titleRes, int shortTitleRes) {
Intent intent = super.onBuildStartFragmentIntent(fragmentName, args,
titleRes, shortTitleRes);
// some fragments want to avoid split actionbar
if (DataUsageSummary.class.getName().equals(fragmentName) ||
PowerUsageSummary.class.getName().equals(fragmentName) ||
AccountSyncSettings.class.getName().equals(fragmentName) ||
UserDictionarySettings.class.getName().equals(fragmentName)) {
intent.putExtra(EXTRA_CLEAR_UI_OPTIONS, true);
}
intent.setClass(this, SubSettings.class);
return intent;
}
这里主要是为intent增加了SubSettings.class，因为Header中的fragment，需要有个Activity依附。
ps：//******log信息
01-08 21:55:05.857: D/Hlwang_Settings(25569): Settings onBuildStartFragmentIntent fragmentName is:com.android.settings.wifi.WifiSettings
//*************************
1.5、由1.3可知，这个intent会被startActivity(intent)发送出去。
Intent会被SubSettings接收，由于SubSettings继承自Settigns.java，因此，这个Intent还会被Settings.java执行。
[java] view
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public class SubSettings extends Settings {
}
1.6、在Settings.java的onCreate中：
在onCreate中会执行getMeteData以及getIntent。这两个方法共同作用得到了mFragmentClass。然后执行super.onCreate
[java] view
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private void getMetaData() {
try {
ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
PackageManager.GET_META_DATA);
if (ai == null || ai.metaData == null) return;
mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);
mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
// Check if it has a parent specified and create a Header object
final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);
String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
if (parentFragmentClass != null) {
mParentHeader = new Header();
mParentHeader.fragment = parentFragmentClass;
if (parentHeaderTitleRes != 0) {
mParentHeader.title = getResources().getString(parentHeaderTitleRes);
}
}
} catch (NameNotFoundException nnfe) {
// No recovery
}
}
[java] view
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public Intent getIntent() {
Intent superIntent = super.getIntent();
String startingFragment = getStartingFragmentClass(superIntent);
// This is called from super.onCreate, isMultiPane() is not yet reliable
// Do not use onIsHidingHeaders either, which relies itself on this method
if (startingFragment != null && !onIsMultiPane()) {
Intent modIntent = new Intent(superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT, startingFragment);
Bundle args = superIntent.getExtras();
if (args != null) {
args = new Bundle(args);
} else {
args = new Bundle();
}
args.putParcelable("intent", superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, superIntent.getExtras());
return modIntent;
}
return superIntent;
}
ps：//****log信息
01-08 21:55:05.897: D/Hlwang_Settings(25569): Settings getStartingFragmentClass intentClass is:com.android.settings.SubSettingsgetClassName is:com.android.settings.SubSettings
//***********
PreferenceActivity.java
[java] view
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String initialFragment = getIntent().getStringExtra(EXTRA_SHOW_FRAGMENT);
Bundle initialArguments = getIntent().getBundleExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS);
int initialTitle = getIntent().getIntExtra(EXTRA_SHOW_FRAGMENT_TITLE, 0);
int initialShortTitle = getIntent().getIntExtra(EXTRA_SHOW_FRAGMENT_SHORT_TITLE, 0);
这样initialFragment得到了初始化，并且。
[java] view
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if (initialFragment != null && mSinglePane) {
// If we are just showing a fragment, we want to run in
// new fragment mode, but don't need to compute and show
// the headers.
switchToHeader(initialFragment, initialArguments);
if (initialTitle != 0) {
CharSequence initialTitleStr = getText(initialTitle);
CharSequence initialShortTitleStr = initialShortTitle != 0
? getText(initialShortTitle) : null;
showBreadCrumbs(initialTitleStr, initialShortTitleStr);
}
}
这里跳用switchToHeader将Fragment切换到右边窗体中。
[java] view
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if (initialFragment != null && mSinglePane) {
// Single pane, showing just a prefs fragment.
findViewById(com.android.internal.R.id.headers).setVisibility(View.GONE);
mPrefsContainer.setVisibility(View.VISIBLE);
if (initialTitle != 0) {
CharSequence initialTitleStr = getText(initialTitle);
CharSequence initialShortTitleStr = initialShortTitle != 0
? getText(initialShortTitle) : null;
showBreadCrumbs(initialTitleStr, initialShortTitleStr);
}
}
这里，将左边窗体的Header 列表隐藏。
2、双屏幕（平板）
2.1、首先执行单击事件
[java] view
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public void onHeaderClick(Header header, int position) {
if (header.fragment != null) {
if (mSinglePane) {
int titleRes = header.breadCrumbTitleRes;
int shortTitleRes = header.breadCrumbShortTitleRes;
if (titleRes == 0) {
titleRes = header.titleRes;
shortTitleRes = 0;
}
startWithFragment(header.fragment, header.fragmentArguments, null, 0,
titleRes, shortTitleRes);
} else {
switchToHeader(header);
}
} else if (header.intent != null) {
startActivity(header.intent);
}
}
我们在这个方法内看到，首先判断fragment以及intent，然后会根据mSinglePane来判断进入那个逻辑里。mSinglePane是单屏幕或者双屏幕，此处为false。
在双屏幕中，此处会执行switchToHeader（header）方法。
2.2、
[java] view
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if (mCurHeader == header) {
// This is the header we are currently displaying. Just make sure
// to pop the stack up to its root state.
getFragmentManager().popBackStack(BACK_STACK_PREFS,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
} else {
int direction = mHeaders.indexOf(header) - mHeaders.indexOf(mCurHeader);
switchToHeaderInner(header.fragment, header.fragmentArguments, direction);
setSelectedHeader(header);
}
这里首先会判断mCurrentHeader是否为要切换的header。如果mCurrentHeader == header，那么执行：
[java] view
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getFragmentManager().popBackStack(BACK_STACK_PREFS,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
否则：
[java] view
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int direction = mHeaders.indexOf(header) - mHeaders.indexOf(mCurHeader);
switchToHeaderInner(header.fragment, header.fragmentArguments, direction);
setSelectedHeader(header);
在这里，direction没有发挥作用。这里应该是判断ListView是向上滚动还是向下滚动。
我们看switchToHeaderInnr方法。
2.3、
[java] view
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getFragmentManager().popBackStack(BACK_STACK_PREFS,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
Fragment f = Fragment.instantiate(this, fragmentName, args);
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
transaction.replace(com.android.internal.R.id.prefs, f);
transaction.commitAllowingStateLoss();
这个方法处理fragment的切换。例如：我们在左边，点击了Bluetooth的设置项，那么其fragment会在右边显示。
2.4,最后执行setSelectedHeader方法。
[java] view
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void setSelectedHeader(Header header) {
mCurHeader = header;
int index = mHeaders.indexOf(header);
if (index >= 0) {
getListView().setItemChecked(index, true);
} else {
getListView().clearChoices();
}
showBreadCrumbs(header);
}
在这个方法中主要处理ListView的setItemChecked状态。如上图中蓝牙设置项的选中底色。并且设置Breadcrumb（标题）
2.5、
[java] view
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void showBreadCrumbs(Header header) {
if (header != null) {
CharSequence title = header.getBreadCrumbTitle(getResources());
if (title == null) title = header.getTitle(getResources());
if (title == null) title = getTitle();
showBreadCrumbs(title, header.getBreadCrumbShortTitle(getResources()));
} else {
showBreadCrumbs(getTitle(), null);
}
}
[java] view
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if (mFragmentBreadCrumbs == null) {
View crumbs = findViewById(android.R.id.title);
// For screens with a different kind of title, don't create breadcrumbs.
try {
mFragmentBreadCrumbs = (FragmentBreadCrumbs)crumbs;
} catch (ClassCastException e) {
return;
}
if (mFragmentBreadCrumbs == null) {
if (title != null) {
setTitle(title);
}
return;
}
mFragmentBreadCrumbs.setMaxVisible(2);
mFragmentBreadCrumbs.setActivity(this);
}
mFragmentBreadCrumbs.setTitle(title, shortTitle);
mFragmentBreadCrumbs.setParentTitle(null, null, null);
//*****************************************************************************************
2.6、在设置应用的源代码中，Settings.java类中。上述的处理存在如下差别。
Settings.java重新了switchHeader方法：
[java] view
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public void switchToHeader(Header header) {
if (!mInLocalHeaderSwitch) {
mCurrentHeader = null;
mParentHeader = null;
}
super.switchToHeader(header);
}
mInLocalHeaderSwitch在我们点击条目的时候为false，故，Settings.java中定义的mCurrentHeader以及mParentHeader会赋值null。然后执行super.switchToHeader（）。
二、外部通过Action进入设置应用的流程。（多屏幕的状态下）
[java] view
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Intent intent=new Intent();
// intent.setClassName(this, "c");
// intent.setAction("android.intent.action.PICK_ACTIVITY");
intent.setAction("android.settings.WIFI_IP_SETTINGS");
startActivity(intent);
通过上述代码，会进入如下界面。
启动这个界面会经历如下流程，
首先Settigns.java的onCreate方法。
1、
[java] view
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protected void onCreate(Bundle savedInstanceState) {
if (getIntent().getBooleanExtra(EXTRA_CLEAR_UI_OPTIONS, false)) {
getWindow().setUiOptions(0);
}
getMetaData();
mInLocalHeaderSwitch = true;
super.onCreate(savedInstanceState);
mInLocalHeaderSwitch = false;
if (!onIsHidingHeaders() && onIsMultiPane()) {
highlightHeader();
// Force the title so that it doesn't get overridden by a direct launch of
// a specific settings screen.
setTitle(R.string.settings_label);
}
// Retrieve any saved state
if (savedInstanceState != null) {
mCurrentHeader = savedInstanceState.getParcelable(SAVE_KEY_CURRENT_HEADER);
mParentHeader = savedInstanceState.getParcelable(SAVE_KEY_PARENT_HEADER);
}
// If the current header was saved, switch to it
if (savedInstanceState != null && mCurrentHeader != null) {
//switchToHeaderLocal(mCurrentHeader);
showBreadCrumbs(mCurrentHeader.title, null);
}
if (mParentHeader != null) {
setParentTitle(mParentHeader.title, null, new OnClickListener() {
public void onClick(View v) {
switchToParent(mParentHeader.fragment);
}
});
}
// TODO Add support for android.R.id.home in all Setting's onOptionsItemSelected
// getActionBar().setDisplayOptions(ActionBar.DISPLAY_HOME_AS_UP,
// ActionBar.DISPLAY_HOME_AS_UP);
}
在这个方法内，首先执行getIntent方法，Settings重新了这个方法。
2、
[java] view
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public Intent getIntent() {
Intent superIntent = super.getIntent();
String startingFragment = getStartingFragmentClass(superIntent);
// This is called from super.onCreate, isMultiPane() is not yet reliable
// Do not use onIsHidingHeaders either, which relies itself on this method
if (startingFragment != null && !onIsMultiPane()) {
Intent modIntent = new Intent(superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT, startingFragment);
Bundle args = superIntent.getExtras();
if (args != null) {
args = new Bundle(args);
} else {
args = new Bundle();
}
args.putParcelable("intent", superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, superIntent.getExtras());
return modIntent;
}
return superIntent;
}
在这个方法内，会调用getStartingFragmentClass方法。
[java] view
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protected String getStartingFragmentClass(Intent intent) {
if (mFragmentClass != null) return mFragmentClass;
String intentClass = intent.getComponent().getClassName();
if (intentClass.equals(getClass().getName())) return null;
if ("com.android.settings.ManageApplications".equals(intentClass)
|| "com.android.settings.RunningServices".equals(intentClass)
|| "com.android.settings.applications.StorageUse".equals(intentClass)) {
// Old names of manage apps.
intentClass = com.android.settings.applications.ManageApplications.class.getName();
}
return intentClass;
}
这个方法中，intentClass为：com.android.settings.Settings$AdvancedWifiSettingsActivity
ps：//****************************************************************log信息
01-08 21:10:06.737: D/Hlwang_Settings(15602): Settings getStartingFragmentClass mFragmentClass is:null
01-08 21:10:06.737: D/Hlwang_Settings(15602): Settings getStartingFragmentClass intentClass is:com.android.settings.Settings$AdvancedWifiSettingsActivity
//************************************************
3、我们继续看onCreate方法。在往下会执行getMeteData方法。
[java] view
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private void getMetaData() {
try {
ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
PackageManager.GET_META_DATA);
if (ai == null || ai.metaData == null) return;
mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);
mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
// Check if it has a parent specified and create a Header object
final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);
String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
if (parentFragmentClass != null) {
mParentHeader = new Header();
mParentHeader.fragment = parentFragmentClass;
if (parentHeaderTitleRes != 0) {
mParentHeader.title = getResources().getString(parentHeaderTitleRes);
}
}
} catch (NameNotFoundException nnfe) {
// No recovery
}
}
这里，AdvancedWifiSettingsActivity在AndroidManifest.xml中的配置：
[html] view
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<activity android:name="Settings$AdvancedWifiSettingsActivity"
android:label="@string/wifi_advanced_settings_label"
android:configChanges="orientation|keyboardHidden|screenSize"
android:clearTaskOnLaunch="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<action android:name="android.settings.WIFI_IP_SETTINGS" />
<category android:name="android.intent.category.VOICE_LAUNCH" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
<meta-data android:name="com.android.settings.FRAGMENT_CLASS"
android:value="com.android.settings.wifi.AdvancedWifiSettings" />
<meta-data android:name="com.android.settings.TOP_LEVEL_HEADER_ID"
android:resource="@id/wifi_settings" />
<meta-data android:name="com.android.settings.PARENT_FRAGMENT_TITLE"
android:resource="@string/wifi_settings" />
<meta-data android:name="com.android.settings.PARENT_FRAGMENT_CLASS"
android:value="com.android.settings.Settings$WifiSettingsActivity" />
</activity>
故而：mTopLevelId = @+id/wifi_settigns，mFragmentClass为：com.android.settings.wifi.AdvancedWifiSettings，mParentClass为：com.android.settings.Settings$WifiSettingsActivity
ps：//************************log信息
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData mFragmentClass is:com.android.settings.wifi.AdvancedWifiSettings
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData parentFragmentClass is:com.android.settings.Settings$WifiSettingsActivity
//******************************
4、继续onCreate执行，接下来会执行：
[java] view
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mInLocalHeaderSwitch = true;
super.onCreate(savedInstanceState);
mInLocalHeaderSwitch = false;
这里会执行super.onCreate方法。之所以用mInLocalHeaderSwitch包裹，主要是因为super.onCreate方法，会执行到PreferenceActitivity.java中的 ：
[java] view
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if (!mSinglePane) {
if (initialFragment == null) {
Header h = onGetInitialHeader();
switchToHeader(h);
} else {
switchToHeader(initialFragment, initialArguments);
}
}
Settings.java重写了switchToHeader方法。
[java] view
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public void switchToHeader(Header header) {
if (!mInLocalHeaderSwitch) {
mCurrentHeader = null;
mParentHeader = null;
}
super.switchToHeader(header);
}
这样mInLocalHeaderSwitch为true，不会清楚mCurrentHeader以及mParentHeader。
最后会执行super.switchToHeader方法，这个方法的执行，会将AdvancedWifiSettings加载到如上图所示的右边的区域内。
Settings.java还重新了onGetInitialHeader方法，这个方法为Header赋了正确的值。
[java] view
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public Header onGetInitialHeader() {
String fragmentClass = getStartingFragmentClass(super.getIntent());
if (fragmentClass != null) {
Header header = new Header();
header.fragment = fragmentClass;
header.title = getTitle();
header.fragmentArguments = getIntent().getExtras();
mCurrentHeader = header;
return header;
}
return mFirstHeader;
}
5、最后一步，给上图左边的部分加上setItemChecked效果。也即是上图中的选中状态底纹。
[java] view
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if (!onIsHidingHeaders() && onIsMultiPane()) {
highlightHeader();
// Force the title so that it doesn't get overridden by a direct launch of
// a specific settings screen.
setTitle(R.string.settings_label);
}
[java] view
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private void highlightHeader() {
if (mTopLevelHeaderId != 0) {
Integer index = mHeaderIndexMap.get(mTopLevelHeaderId);
if (index != null) {
getListView().setItemChecked(index, true);
getListView().smoothScrollToPosition(index);
}
}
}
mTopLevelHeaderId，我们在getMeteData方法中得到。
一、在多屏幕中，mFirstHeader的作用主要是为了正确的切换第一个Header。
mFirstHeader的初始化
[java] view
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if (mFirstHeader == null &&
HeaderAdapter.getHeaderType(header) != HeaderAdapter.HEADER_TYPE_CATEGORY) {
mFirstHeader = header;
}
如果为空，那么mFirstHeader为最靠前的第一个category。
mFirstHeader的使用：
[java] view
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public Header onGetInitialHeader() {
String fragmentClass = getStartingFragmentClass(super.getIntent());
if (fragmentClass != null) {
Header header = new Header();
header.fragment = fragmentClass;
header.title = getTitle();
header.fragmentArguments = getIntent().getExtras();
mCurrentHeader = header;
return header;
}
return mFirstHeader;
}
如果getStarttingFragmentClass为null，那么返回mFirstHeader。
[java] view
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public void onNewIntent(Intent intent) {
super.onNewIntent(intent);
// If it is not launched from history, then reset to top-level
if ((intent.getFlags() & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY) == 0
&& mFirstHeader != null && !onIsHidingHeaders() && onIsMultiPane()) {
switchToHeaderLocal(mFirstHeader);
}
}
二、mCurrentHeader的作用，显示当前Header的title。
初始化：
[java] view
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public Header onGetInitialHeader() {
String fragmentClass = getStartingFragmentClass(super.getIntent());
if (fragmentClass != null) {
Header header = new Header();
header.fragment = fragmentClass;
header.title = getTitle();
header.fragmentArguments = getIntent().getExtras();
mCurrentHeader = header;
return header;
}
return mFirstHeader;
}
外部跳转得到了fragmentClass，那么会初始化mCurrentHeader。
另外的一处初始化：
[java] view
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private void switchToParent(String className) {
final ComponentName cn = new ComponentName(this, className);
try {
final PackageManager pm = getPackageManager();
final ActivityInfo parentInfo = pm.getActivityInfo(cn, PackageManager.GET_META_DATA);
if (parentInfo != null && parentInfo.metaData != null) {
String fragmentClass = parentInfo.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
CharSequence fragmentTitle = parentInfo.loadLabel(pm);
Header parentHeader = new Header();
parentHeader.fragment = fragmentClass;
parentHeader.title = fragmentTitle;
mCurrentHeader = parentHeader;
switchToHeaderLocal(parentHeader);
highlightHeader();
mParentHeader = new Header();
mParentHeader.fragment
= parentInfo.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
mParentHeader.title = parentInfo.metaData.getString(META_DATA_KEY_PARENT_TITLE);
}
} catch (NameNotFoundException nnfe) {
Log.w(LOG_TAG, "Could not find parent activity : " + className);
}
}
使用：
在onCreate中。
[java] view
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if (savedInstanceState != null) {
mCurrentHeader = savedInstanceState.getParcelable(SAVE_KEY_CURRENT_HEADER);
mParentHeader = savedInstanceState.getParcelable(SAVE_KEY_PARENT_HEADER);
}
// If the current header was saved, switch to it
if (savedInstanceState != null && mCurrentHeader != null) {
//switchToHeaderLocal(mCurrentHeader);
showBreadCrumbs(mCurrentHeader.title, null);
}
三、mParentHeader，
初始化：
[java] view
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private void getMetaData() {
try {
ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
PackageManager.GET_META_DATA);
if (ai == null || ai.metaData == null) return;
mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);
mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
// Check if it has a parent specified and create a Header object
final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);
String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
if (parentFragmentClass != null) {
mParentHeader = new Header();
mParentHeader.fragment = parentFragmentClass;
if (parentHeaderTitleRes != 0) {
mParentHeader.title = getResources().getString(parentHeaderTitleRes);
}
}
} catch (NameNotFoundException nnfe) {
// No recovery
}
}
使用如上面的mCurrentHeader。
本文讲述PreferenceActivity中单击事件的处理，重点记述mCurrentHeader以及设置源代码Settings中的mLastHeader、mCurrentHeader、mParentHeader的作用。主要以多屏幕为例。
在PreferenceActivity中，当我们点击Header时，其处理流程分为 单屏幕和双屏幕两套流程。
1、单屏幕（SinglePane）
1.1、点击每一项，执行如下代码.
[java] view
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public void onHeaderClick(Header header, int position) {
Log.d(LOG_TAG, "Settings onHeaderClick Header is:"+header.title+",position is:"+position+",mLastHeader is:"+mLastHeader);
boolean revert = false;
if (header.id == R.id.account_add) {
revert = true;
}
Log.d(LOG_TAG, "Settings onHeaderClick Header id is:"+header.id+", R.id.account_add is:"+R.id.account_add+",revert is:"+revert);
super.onHeaderClick(header, position);
if (revert && mLastHeader != null) {
highlightHeader((int) mLastHeader.id);
} else {
mLastHeader = header;
}
}
关于hightlightHeader下面有详细介绍，这里就不介绍了。
主要执行父类的onHeaderClick方法。
1.2、
[java] view
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public void onHeaderClick(Header header, int position) {
if (header.fragment != null) {
if (mSinglePane) {
int titleRes = header.breadCrumbTitleRes;
int shortTitleRes = header.breadCrumbShortTitleRes;
if (titleRes == 0) {
titleRes = header.titleRes;
shortTitleRes = 0;
&nb
24000
sp; }
startWithFragment(header.fragment, header.fragmentArguments, null, 0,
titleRes, shortTitleRes);
} else {
switchToHeader(header);
}
} else if (header.intent != null) {
startActivity(header.intent);
}
}
因为mSinglePane为true，故执行startWithFragment。
1.3、
[java] view
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Intent intent = onBuildStartFragmentIntent(fragmentName, args, titleRes, shortTitleRes);
if (resultTo == null) {
startActivity(intent);
} else {
resultTo.startActivityForResult(intent, resultRequestCode);
}
我们看到这里会执行onBuildStartFragmentIntent。
1.4、
[java] view
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public Intent onBuildStartFragmentIntent(String fragmentName, Bundle args,
int titleRes, int shortTitleRes) {
Intent intent = new Intent(Intent.ACTION_MAIN);
intent.setClass(this, getClass());
intent.putExtra(EXTRA_SHOW_FRAGMENT, fragmentName);
intent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, args);
intent.putExtra(EXTRA_SHOW_FRAGMENT_TITLE, titleRes);
intent.putExtra(EXTRA_SHOW_FRAGMENT_SHORT_TITLE, shortTitleRes);
intent.putExtra(EXTRA_NO_HEADERS, true);
return intent;
}
这个方法在子类中有重写。
Settings.java
[java] view
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public Intent onBuildStartFragmentIntent(String fragmentName, Bundle args,
int titleRes, int shortTitleRes) {
Intent intent = super.onBuildStartFragmentIntent(fragmentName, args,
titleRes, shortTitleRes);
// some fragments want to avoid split actionbar
if (DataUsageSummary.class.getName().equals(fragmentName) ||
PowerUsageSummary.class.getName().equals(fragmentName) ||
AccountSyncSettings.class.getName().equals(fragmentName) ||
UserDictionarySettings.class.getName().equals(fragmentName)) {
intent.putExtra(EXTRA_CLEAR_UI_OPTIONS, true);
}
intent.setClass(this, SubSettings.class);
return intent;
}
这里主要是为intent增加了SubSettings.class，因为Header中的fragment，需要有个Activity依附。
ps：//******log信息
01-08 21:55:05.857: D/Hlwang_Settings(25569): Settings onBuildStartFragmentIntent fragmentName is:com.android.settings.wifi.WifiSettings
//*************************
1.5、由1.3可知，这个intent会被startActivity(intent)发送出去。
Intent会被SubSettings接收，由于SubSettings继承自Settigns.java，因此，这个Intent还会被Settings.java执行。
[java] view
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public class SubSettings extends Settings {
}
1.6、在Settings.java的onCreate中：
在onCreate中会执行getMeteData以及getIntent。这两个方法共同作用得到了mFragmentClass。然后执行super.onCreate
[java] view
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private void getMetaData() {
try {
ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
PackageManager.GET_META_DATA);
if (ai == null || ai.metaData == null) return;
mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);
mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
// Check if it has a parent specified and create a Header object
final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);
String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
if (parentFragmentClass != null) {
mParentHeader = new Header();
mParentHeader.fragment = parentFragmentClass;
if (parentHeaderTitleRes != 0) {
mParentHeader.title = getResources().getString(parentHeaderTitleRes);
}
}
} catch (NameNotFoundException nnfe) {
// No recovery
}
}
[java] view
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public Intent getIntent() {
Intent superIntent = super.getIntent();
String startingFragment = getStartingFragmentClass(superIntent);
// This is called from super.onCreate, isMultiPane() is not yet reliable
// Do not use onIsHidingHeaders either, which relies itself on this method
if (startingFragment != null && !onIsMultiPane()) {
Intent modIntent = new Intent(superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT, startingFragment);
Bundle args = superIntent.getExtras();
if (args != null) {
args = new Bundle(args);
} else {
args = new Bundle();
}
args.putParcelable("intent", superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, superIntent.getExtras());
return modIntent;
}
return superIntent;
}
ps：//****log信息
01-08 21:55:05.897: D/Hlwang_Settings(25569): Settings getStartingFragmentClass intentClass is:com.android.settings.SubSettingsgetClassName is:com.android.settings.SubSettings
//***********
PreferenceActivity.java
[java] view
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String initialFragment = getIntent().getStringExtra(EXTRA_SHOW_FRAGMENT);
Bundle initialArguments = getIntent().getBundleExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS);
int initialTitle = getIntent().getIntExtra(EXTRA_SHOW_FRAGMENT_TITLE, 0);
int initialShortTitle = getIntent().getIntExtra(EXTRA_SHOW_FRAGMENT_SHORT_TITLE, 0);
这样initialFragment得到了初始化，并且。
[java] view
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if (initialFragment != null && mSinglePane) {
// If we are just showing a fragment, we want to run in
// new fragment mode, but don't need to compute and show
// the headers.
switchToHeader(initialFragment, initialArguments);
if (initialTitle != 0) {
CharSequence initialTitleStr = getText(initialTitle);
CharSequence initialShortTitleStr = initialShortTitle != 0
? getText(initialShortTitle) : null;
showBreadCrumbs(initialTitleStr, initialShortTitleStr);
}
}
这里跳用switchToHeader将Fragment切换到右边窗体中。
[java] view
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if (initialFragment != null && mSinglePane) {
// Single pane, showing just a prefs fragment.
findViewById(com.android.internal.R.id.headers).setVisibility(View.GONE);
mPrefsContainer.setVisibility(View.VISIBLE);
if (initialTitle != 0) {
CharSequence initialTitleStr = getText(initialTitle);
CharSequence initialShortTitleStr = initialShortTitle != 0
? getText(initialShortTitle) : null;
showBreadCrumbs(initialTitleStr, initialShortTitleStr);
}
}
这里，将左边窗体的Header 列表隐藏。
2、双屏幕（平板）
2.1、首先执行单击事件
[java] view
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public void onHeaderClick(Header header, int position) {
if (header.fragment != null) {
if (mSinglePane) {
int titleRes = header.breadCrumbTitleRes;
int shortTitleRes = header.breadCrumbShortTitleRes;
if (titleRes == 0) {
titleRes = header.titleRes;
shortTitleRes = 0;
}
startWithFragment(header.fragment, header.fragmentArguments, null, 0,
titleRes, shortTitleRes);
} else {
switchToHeader(header);
}
} else if (header.intent != null) {
startActivity(header.intent);
}
}
我们在这个方法内看到，首先判断fragment以及intent，然后会根据mSinglePane来判断进入那个逻辑里。mSinglePane是单屏幕或者双屏幕，此处为false。
在双屏幕中，此处会执行switchToHeader（header）方法。
2.2、
[java] view
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if (mCurHeader == header) {
// This is the header we are currently displaying. Just make sure
// to pop the stack up to its root state.
getFragmentManager().popBackStack(BACK_STACK_PREFS,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
} else {
int direction = mHeaders.indexOf(header) - mHeaders.indexOf(mCurHeader);
switchToHeaderInner(header.fragment, header.fragmentArguments, direction);
setSelectedHeader(header);
}
这里首先会判断mCurrentHeader是否为要切换的header。如果mCurrentHeader == header，那么执行：
[java] view
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getFragmentManager().popBackStack(BACK_STACK_PREFS,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
否则：
[java] view
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int direction = mHeaders.indexOf(header) - mHeaders.indexOf(mCurHeader);
switchToHeaderInner(header.fragment, header.fragmentArguments, direction);
setSelectedHeader(header);
在这里，direction没有发挥作用。这里应该是判断ListView是向上滚动还是向下滚动。
我们看switchToHeaderInnr方法。
2.3、
[java] view
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getFragmentManager().popBackStack(BACK_STACK_PREFS,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
Fragment f = Fragment.instantiate(this, fragmentName, args);
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
transaction.replace(com.android.internal.R.id.prefs, f);
transaction.commitAllowingStateLoss();
这个方法处理fragment的切换。例如：我们在左边，点击了Bluetooth的设置项，那么其fragment会在右边显示。
2.4,最后执行setSelectedHeader方法。
[java] view
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void setSelectedHeader(Header header) {
mCurHeader = header;
int index = mHeaders.indexOf(header);
if (index >= 0) {
getListView().setItemChecked(index, true);
} else {
getListView().clearChoices();
}
showBreadCrumbs(header);
}
在这个方法中主要处理ListView的setItemChecked状态。如上图中蓝牙设置项的选中底色。并且设置Breadcrumb（标题）
2.5、
[java] view
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void showBreadCrumbs(Header header) {
if (header != null) {
CharSequence title = header.getBreadCrumbTitle(getResources());
if (title == null) title = header.getTitle(getResources());
if (title == null) title = getTitle();
showBreadCrumbs(title, header.getBreadCrumbShortTitle(getResources()));
} else {
showBreadCrumbs(getTitle(), null);
}
}
[java] view
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if (mFragmentBreadCrumbs == null) {
View crumbs = findViewById(android.R.id.title);
// For screens with a different kind of title, don't create breadcrumbs.
try {
mFragmentBreadCrumbs = (FragmentBreadCrumbs)crumbs;
} catch (ClassCastException e) {
return;
}
if (mFragmentBreadCrumbs == null) {
if (title != null) {
setTitle(title);
}
return;
}
mFragmentBreadCrumbs.setMaxVisible(2);
mFragmentBreadCrumbs.setActivity(this);
}
mFragmentBreadCrumbs.setTitle(title, shortTitle);
mFragmentBreadCrumbs.setParentTitle(null, null, null);
//*****************************************************************************************
2.6、在设置应用的源代码中，Settings.java类中。上述的处理存在如下差别。
Settings.java重新了switchHeader方法：
[java] view
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public void switchToHeader(Header header) {
if (!mInLocalHeaderSwitch) {
mCurrentHeader = null;
mParentHeader = null;
}
super.switchToHeader(header);
}
mInLocalHeaderSwitch在我们点击条目的时候为false，故，Settings.java中定义的mCurrentHeader以及mParentHeader会赋值null。然后执行super.switchToHeader（）。
二、外部通过Action进入设置应用的流程。（多屏幕的状态下）
[java] view
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Intent intent=new Intent();
// intent.setClassName(this, "c");
// intent.setAction("android.intent.action.PICK_ACTIVITY");
intent.setAction("android.settings.WIFI_IP_SETTINGS");
startActivity(intent);
通过上述代码，会进入如下界面。
启动这个界面会经历如下流程，
首先Settigns.java的onCreate方法。
1、
[java] view
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protected void onCreate(Bundle savedInstanceState) {
if (getIntent().getBooleanExtra(EXTRA_CLEAR_UI_OPTIONS, false)) {
getWindow().setUiOptions(0);
}
getMetaData();
mInLocalHeaderSwitch = true;
super.onCreate(savedInstanceState);
mInLocalHeaderSwitch = false;
if (!onIsHidingHeaders() && onIsMultiPane()) {
highlightHeader();
// Force the title so that it doesn't get overridden by a direct launch of
// a specific settings screen.
setTitle(R.string.settings_label);
}
// Retrieve any saved state
if (savedInstanceState != null) {
mCurrentHeader = savedInstanceState.getParcelable(SAVE_KEY_CURRENT_HEADER);
mParentHeader = savedInstanceState.getParcelable(SAVE_KEY_PARENT_HEADER);
}
// If the current header was saved, switch to it
if (savedInstanceState != null && mCurrentHeader != null) {
//switchToHeaderLocal(mCurrentHeader);
showBreadCrumbs(mCurrentHeader.title, null);
}
if (mParentHeader != null) {
setParentTitle(mParentHeader.title, null, new OnClickListener() {
public void onClick(View v) {
switchToParent(mParentHeader.fragment);
}
});
}
// TODO Add support for android.R.id.home in all Setting's onOptionsItemSelected
// getActionBar().setDisplayOptions(ActionBar.DISPLAY_HOME_AS_UP,
// ActionBar.DISPLAY_HOME_AS_UP);
}
在这个方法内，首先执行getIntent方法，Settings重新了这个方法。
2、
[java] view
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public Intent getIntent() {
Intent superIntent = super.getIntent();
String startingFragment = getStartingFragmentClass(superIntent);
// This is called from super.onCreate, isMultiPane() is not yet reliable
// Do not use onIsHidingHeaders either, which relies itself on this method
if (startingFragment != null && !onIsMultiPane()) {
Intent modIntent = new Intent(superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT, startingFragment);
Bundle args = superIntent.getExtras();
if (args != null) {
args = new Bundle(args);
} else {
args = new Bundle();
}
args.putParcelable("intent", superIntent);
modIntent.putExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS, superIntent.getExtras());
return modIntent;
}
return superIntent;
}
在这个方法内，会调用getStartingFragmentClass方法。
[java] view
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protected String getStartingFragmentClass(Intent intent) {
if (mFragmentClass != null) return mFragmentClass;
String intentClass = intent.getComponent().getClassName();
if (intentClass.equals(getClass().getName())) return null;
if ("com.android.settings.ManageApplications".equals(intentClass)
|| "com.android.settings.RunningServices".equals(intentClass)
|| "com.android.settings.applications.StorageUse".equals(intentClass)) {
// Old names of manage apps.
intentClass = com.android.settings.applications.ManageApplications.class.getName();
}
return intentClass;
}
这个方法中，intentClass为：com.android.settings.Settings$AdvancedWifiSettingsActivity
ps：//****************************************************************log信息
01-08 21:10:06.737: D/Hlwang_Settings(15602): Settings getStartingFragmentClass mFragmentClass is:null
01-08 21:10:06.737: D/Hlwang_Settings(15602): Settings getStartingFragmentClass intentClass is:com.android.settings.Settings$AdvancedWifiSettingsActivity
//************************************************
3、我们继续看onCreate方法。在往下会执行getMeteData方法。
[java] view
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private void getMetaData() {
try {
ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
PackageManager.GET_META_DATA);
if (ai == null || ai.metaData == null) return;
mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);
mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
// Check if it has a parent specified and create a Header object
final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);
String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
if (parentFragmentClass != null) {
mParentHeader = new Header();
mParentHeader.fragment = parentFragmentClass;
if (parentHeaderTitleRes != 0) {
mParentHeader.title = getResources().getString(parentHeaderTitleRes);
}
}
} catch (NameNotFoundException nnfe) {
// No recovery
}
}
这里，AdvancedWifiSettingsActivity在AndroidManifest.xml中的配置：
[html] view
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<activity android:name="Settings$AdvancedWifiSettingsActivity"
android:label="@string/wifi_advanced_settings_label"
android:configChanges="orientation|keyboardHidden|screenSize"
android:clearTaskOnLaunch="true">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<action android:name="android.settings.WIFI_IP_SETTINGS" />
<category android:name="android.intent.category.VOICE_LAUNCH" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
<meta-data android:name="com.android.settings.FRAGMENT_CLASS"
android:value="com.android.settings.wifi.AdvancedWifiSettings" />
<meta-data android:name="com.android.settings.TOP_LEVEL_HEADER_ID"
android:resource="@id/wifi_settings" />
<meta-data android:name="com.android.settings.PARENT_FRAGMENT_TITLE"
android:resource="@string/wifi_settings" />
<meta-data android:name="com.android.settings.PARENT_FRAGMENT_CLASS"
android:value="com.android.settings.Settings$WifiSettingsActivity" />
</activity>
故而：mTopLevelId = @+id/wifi_settigns，mFragmentClass为：com.android.settings.wifi.AdvancedWifiSettings，mParentClass为：com.android.settings.Settings$WifiSettingsActivity
ps：//************************log信息
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData mFragmentClass is:com.android.settings.wifi.AdvancedWifiSettings
01-08 21:10:06.747: D/Hlwang_Settings(15602): Settings getMetaData parentFragmentClass is:com.android.settings.Settings$WifiSettingsActivity
//******************************
4、继续onCreate执行，接下来会执行：
[java] view
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mInLocalHeaderSwitch = true;
super.onCreate(savedInstanceState);
mInLocalHeaderSwitch = false;
这里会执行super.onCreate方法。之所以用mInLocalHeaderSwitch包裹，主要是因为super.onCreate方法，会执行到PreferenceActitivity.java中的 ：
[java] view
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if (!mSinglePane) {
if (initialFragment == null) {
Header h = onGetInitialHeader();
switchToHeader(h);
} else {
switchToHeader(initialFragment, initialArguments);
}
}
Settings.java重写了switchToHeader方法。
[java] view
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public void switchToHeader(Header header) {
if (!mInLocalHeaderSwitch) {
mCurrentHeader = null;
mParentHeader = null;
}
super.switchToHeader(header);
}
这样mInLocalHeaderSwitch为true，不会清楚mCurrentHeader以及mParentHeader。
最后会执行super.switchToHeader方法，这个方法的执行，会将AdvancedWifiSettings加载到如上图所示的右边的区域内。
Settings.java还重新了onGetInitialHeader方法，这个方法为Header赋了正确的值。
[java] view
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public Header onGetInitialHeader() {
String fragmentClass = getStartingFragmentClass(super.getIntent());
if (fragmentClass != null) {
Header header = new Header();
header.fragment = fragmentClass;
header.title = getTitle();
header.fragmentArguments = getIntent().getExtras();
mCurrentHeader = header;
return header;
}
return mFirstHeader;
}
5、最后一步，给上图左边的部分加上setItemChecked效果。也即是上图中的选中状态底纹。
[java] view
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if (!onIsHidingHeaders() && onIsMultiPane()) {
highlightHeader();
// Force the title so that it doesn't get overridden by a direct launch of
// a specific settings screen.
setTitle(R.string.settings_label);
}
[java] view
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private void highlightHeader() {
if (mTopLevelHeaderId != 0) {
Integer index = mHeaderIndexMap.get(mTopLevelHeaderId);
if (index != null) {
getListView().setItemChecked(index, true);
getListView().smoothScrollToPosition(index);
}
}
}
mTopLevelHeaderId，我们在getMeteData方法中得到。
一、在多屏幕中，mFirstHeader的作用主要是为了正确的切换第一个Header。
mFirstHeader的初始化
[java] view
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if (mFirstHeader == null &&
HeaderAdapter.getHeaderType(header) != HeaderAdapter.HEADER_TYPE_CATEGORY) {
mFirstHeader = header;
}
如果为空，那么mFirstHeader为最靠前的第一个category。
mFirstHeader的使用：
[java] view
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public Header onGetInitialHeader() {
String fragmentClass = getStartingFragmentClass(super.getIntent());
if (fragmentClass != null) {
Header header = new Header();
header.fragment = fragmentClass;
header.title = getTitle();
header.fragmentArguments = getIntent().getExtras();
mCurrentHeader = header;
return header;
}
return mFirstHeader;
}
如果getStarttingFragmentClass为null，那么返回mFirstHeader。
[java] view
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public void onNewIntent(Intent intent) {
super.onNewIntent(intent);
// If it is not launched from history, then reset to top-level
if ((intent.getFlags() & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY) == 0
&& mFirstHeader != null && !onIsHidingHeaders() && onIsMultiPane()) {
switchToHeaderLocal(mFirstHeader);
}
}
二、mCurrentHeader的作用，显示当前Header的title。
初始化：
[java] view
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public Header onGetInitialHeader() {
String fragmentClass = getStartingFragmentClass(super.getIntent());
if (fragmentClass != null) {
Header header = new Header();
header.fragment = fragmentClass;
header.title = getTitle();
header.fragmentArguments = getIntent().getExtras();
mCurrentHeader = header;
return header;
}
return mFirstHeader;
}
外部跳转得到了fragmentClass，那么会初始化mCurrentHeader。
另外的一处初始化：
[java] view
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private void switchToParent(String className) {
final ComponentName cn = new ComponentName(this, className);
try {
final PackageManager pm = getPackageManager();
final ActivityInfo parentInfo = pm.getActivityInfo(cn, PackageManager.GET_META_DATA);
if (parentInfo != null && parentInfo.metaData != null) {
String fragmentClass = parentInfo.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
CharSequence fragmentTitle = parentInfo.loadLabel(pm);
Header parentHeader = new Header();
parentHeader.fragment = fragmentClass;
parentHeader.title = fragmentTitle;
mCurrentHeader = parentHeader;
switchToHeaderLocal(parentHeader);
highlightHeader();
mParentHeader = new Header();
mParentHeader.fragment
= parentInfo.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
mParentHeader.title = parentInfo.metaData.getString(META_DATA_KEY_PARENT_TITLE);
}
} catch (NameNotFoundException nnfe) {
Log.w(LOG_TAG, "Could not find parent activity : " + className);
}
}
使用：
在onCreate中。
[java] view
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if (savedInstanceState != null) {
mCurrentHeader = savedInstanceState.getParcelable(SAVE_KEY_CURRENT_HEADER);
mParentHeader = savedInstanceState.getParcelable(SAVE_KEY_PARENT_HEADER);
}
// If the current header was saved, switch to it
if (savedInstanceState != null && mCurrentHeader != null) {
//switchToHeaderLocal(mCurrentHeader);
showBreadCrumbs(mCurrentHeader.title, null);
}
三、mParentHeader，
初始化：
[java] view
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private void getMetaData() {
try {
ActivityInfo ai = getPackageManager().getActivityInfo(getComponentName(),
PackageManager.GET_META_DATA);
if (ai == null || ai.metaData == null) return;
mTopLevelHeaderId = ai.metaData.getInt(META_DATA_KEY_HEADER_ID);
mFragmentClass = ai.metaData.getString(META_DATA_KEY_FRAGMENT_CLASS);
// Check if it has a parent specified and create a Header object
final int parentHeaderTitleRes = ai.metaData.getInt(META_DATA_KEY_PARENT_TITLE);
String parentFragmentClass = ai.metaData.getString(META_DATA_KEY_PARENT_FRAGMENT_CLASS);
if (parentFragmentClass != null) {
mParentHeader = new Header();
mParentHeader.fragment = parentFragmentClass;
if (parentHeaderTitleRes != 0) {
mParentHeader.title = getResources().getString(parentHeaderTitleRes);
}
}
} catch (NameNotFoundException nnfe) {
// No recovery
}
}
使用如上面的mCurrentHeader。
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