Android上下文菜单和上下文操作

定义上下文菜单资源

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >
<item android:id="@+id/menu_item_delete_crime"
android:icon="@android:drawable/ic_menu_delete"
android:title="@string/delete_crime"/>

</menu>

实例化上下文菜单

@Override
public void onCreateContextMenu(ContextMenu menu, View v,
ContextMenuInfo menuInfo) {
getActivity().getMenuInflater().inflate(R.menu.crime_list_item_context, menu);
}

默认情况下，长按视图不会触发上下文菜单的创建。需要调用下面的函数使能上下文菜单功能：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView");
getActivity().setTitle(R.string.crime_title);
View v = super.onCreateView(inflater, container, savedInstanceState);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
if (mSubtitleVisible) {
getActivity().getActionBar().setSubtitle(R.string.subtitle);
}
}
// 为上下文菜单登记视图
ListView listView = (ListView) v.findViewById(android.R.id.list);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
// 低版本使用浮动操作
registerForContextMenu(listView);
} else {
// 高版本使用操作栏模式，并开启多选
listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);
listView.setMultiChoiceModeListener(new MultiChoiceModeListener() {

@Override
public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
return false;
}

@Override
public void onDestroyActionMode(ActionMode mode) {
}

@Override
public boolean onCreateActionMode(ActionMode mode, Menu menu) {
MenuInflater inflater = mode.getMenuInflater();
inflater.inflate(R.menu.crime_list_item_context, menu);
return true;
}

@Override
public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
switch (item.getItemId()) {
case R.id.menu_item_delete_crime:
CrimeAdapter adapter = (CrimeAdapter) getListAdapter();
CrimeLab crimeLab = CrimeLab.get(getActivity());
for (int i = adapter.getCount() - 1; i >= 0; i--) {
if (getListView().isItemChecked(i)) {
crimeLab.deleteCrime(adapter.getItem(i));
}
}
mode.finish();
adapter.notifyDataSetChanged();
return true;
default:
return false;
}
}

@Override
public void onItemCheckedStateChanged(ActionMode mode, int position,
long id, boolean checked) {
}
});
}
return v;
}

改变背景

不向其它drawable资源,state list drawable资源通常和屏幕显示像素密度无关，因而只存放在不带修饰符的drawable目录中。

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

<item android:drawable="@android:color/darker_gray" android:state_activated="true"></item>

</selector>

以上XML告诉我们：当引用该drawable资源的视图处于激活状态时，则使用android:drawable属性指定的资源；反之，则不采取任何操作。

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