假设给Contact的List加一个用字母排序的导航

<?

xml version="1.0" encoding="utf-8"?

>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:rcm="http://schemas.android.com/apk/res/com.ringcentral.android"
android:id="@+id/contact_list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/bgColorMain"
android:orientation="vertical" >

<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent" >

<ListView
android:id="@android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:cacheColorHint="@android:color/transparent"
android:divider="@null"
android:listSelector="@drawable/bg_list_item_selector" />

<com.example.view.<strong>SectionIndexerView   //这个是右边的导航</strong>
android:id="@+id/section_indexer_view"
android:layout_width="70dip"
android:layout_height="fill_parent"
android:layout_gravity="right"
android:layout_marginBottom="4dip"
android:layout_marginRight="6dip"
android:layout_marginTop="4dip"
android:textSize="12.0sp" />

<<strong>TextView   //这个是中间的字母提示</strong>
android:id="@+id/section_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:background="@drawable/section_text_bg"
android:gravity="center"
android:textColor="#FFFFFF"
android:textSize="40sp"
android:visibility="gone" />
</FrameLayout>

<RelativeLayout
android:id="@+id/no_contact_indication"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<TextView
android:id="@+id/emptyListText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:singleLine="true"
android:text="No Contacts"
android:textColor="@color/text_no_items"
android:textSize="20sp" />

<ProgressBar
android:id="@+id/loading"
style="@style/RCMProgressBar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:visibility="gone" />
</RelativeLayout>

</LinearLayout>

public class SectionIndexerView extends View{

public static final String TAG = SectionIndexerView.class.getSimpleName();
private static final boolean DEBUG = true;
/** 写文字的画笔 */
private Paint mTextPaint;
/** 指定view的宽度 */
private int mViewWidth = 0;
/** 指定view的高度 */
private int mViewHeight = 0;
/** 每一个文字的高度 */
private float mPerTextHeight;
/** 是否是按下状态 */
private boolean mIsPressed = false;
/** 关联的listview */
private ListView mListview = null;
/** 关联的indexer */
private SectionIndexer mIndexer;
/** 关联的textview */
private TextView mView = null;
/** 依照A-Z排序的section */
private String[] mSectionIndexerText = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J",
"K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z","#" };
private static final float TEXTSIZE_RATIO = 0.84f;
/** 默认的字体大小常量 */
private static final int CHAR_WIDTH = 12;
/** 背景的透明度 */
private static final int BG_ALPHA = 153;
/** 背景的圆角弧度 */
private static final float BG_RADIAN = 20f;
/** 默认的字体大小 */
private int mCharwidth = CHAR_WIDTH;
/** Context */
private Context mContext = null;

/**
* 构造函数
*
* @param context
*            Context
*/
public SectionIndexerView(Context context) {
super(context);
init(context);
}

/**
* 构造函数
*
* @param context
*            Context
* @param attributeSet
*            AttributeSet
*/
public SectionIndexerView(Context context, AttributeSet attributeSet) {
super(context, attributeSet);
init(context);
}

/**
* 初始化基本信息
*
* @param context
*            Context
*/
private void init(Context context) {
mContext = context;
mCharwidth = (int) (mCharwidth * mContext.getResources().getDisplayMetrics().density);
this.mTextPaint = new Paint();
this.mTextPaint.setAntiAlias(true);
this.mTextPaint.setColor(-1);
}

/**
* 初始化SectionIndexer,指定listview,indexer及显示section的textview
*
* @param listview
*            关联的listview
* @param indexer
*            关联的SectionIndexer
* @param view
*            关联的TextView
*/
public void init(ListView listview, SectionIndexer indexer, TextView view) {
this.mListview = listview;
this.mIndexer = indexer;
this.mView = view;
}

@Override
protected void onDraw(Canvas paramCanvas) {
Paint localPaint = new Paint();
localPaint.setAntiAlias(true);
this.mTextPaint.setColor(Color.parseColor("#75797d"));
if (this.mIsPressed) {
localPaint.setColor(Color.parseColor("#838a98"));
localPaint.setAlpha(BG_ALPHA);
} else {
localPaint.setAlpha(0);
}

this.mTextPaint.setTextSize(this.mViewHeight * TEXTSIZE_RATIO / mSectionIndexerText.length);
System.out.println("==textSize="+(this.mViewHeight * TEXTSIZE_RATIO / mSectionIndexerText.length));
System.out.println("====mViewWidth="+mViewWidth+"mCharWidth="+mCharwidth);
//paramCanvas.drawRoundRect是画背景,BG_RADIAN为弯曲的弧度
paramCanvas.drawRoundRect(new RectF(50, 0.0F, this.mViewWidth,
this.mViewHeight), BG_RADIAN, BG_RADIAN,
localPaint);

//这个textPointX为
int textPointX = 140;

//textPointY为写text的Y的位置
float textPointY = (this.mPerTextHeight - this.mTextPaint.ascent()) / 2.0F;

int sectionslength = this.mSectionIndexerText.length;
int currentSection = 0;
int currentHeight = 0;
while (true) {
if (currentSection >= sectionslength) {
break;
}

//(mCharwidth - (int) this.mTextPaint.measureText(this.mSectionIndexerText[currentSection])) / 2
//这样写的原因是使每一个字母居中对齐
paramCanvas.drawText(
this.mSectionIndexerText[currentSection],
textPointX
+ (mCharwidth - (int) this.mTextPaint
.measureText(this.mSectionIndexerText[currentSection])) / 2,
textPointY + (3.0F + currentHeight * this.mPerTextHeight), this.mTextPaint);// SUPPRESS CHECKSTYLE : magic number
++currentHeight;
++currentSection;
}

}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = View.MeasureSpec.getSize(widthMeasureSpec);
this.mViewWidth = width;

int height = View.MeasureSpec.getSize(heightMeasureSpec);
this.mViewHeight = height;
setMeasuredDimension(this.mViewWidth, this.mViewHeight);
this.mPerTextHeight = (this.mViewHeight / this.mSectionIndexerText.length);
}

@Override
public boolean onTouchEvent(MotionEvent motionEvent) {
boolean returnvalue = false;
switch (motionEvent.getAction()) {
case MotionEvent.ACTION_DOWN:
if (DEBUG) {
Log.d(TAG, "action down!");
}
mListview.dispatchTouchEvent(MotionEvent.obtain(SystemClock.uptimeMillis(),
SystemClock.uptimeMillis(), MotionEvent.ACTION_CANCEL, 0, 0, 0));
returnvalue = processTouchEvent(motionEvent);
break;
case MotionEvent.ACTION_MOVE:
if (DEBUG) {
Log.d(TAG, "action move!");
}
returnvalue = processTouchEvent(motionEvent);
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
if (DEBUG) {
Log.d(TAG, "action up!");
}
setPressed(false);
mView.setText("");
mView.setVisibility(View.GONE);
returnvalue = true;

break;
default:
break;
}
invalidate();
return returnvalue;
}

/**
* 处理onTouch事件
*
* @param motionEvent
*            MotionEvent
* @return true 处理了触摸事件。false没有处理
*/
private boolean processTouchEvent(MotionEvent motionEvent) {
String selcected = "";

int backgroundPointX = this.mViewWidth - getPaddingRight() - mCharwidth * 3// SUPPRESS CHECKSTYLE
- getPaddingLeft();
if (motionEvent.getX() < backgroundPointX) {
mView.setVisibility(View.GONE);
setPressed(false);
return false;
}
setPressed(true);
int curruntSection = (int) (motionEvent.getY() / this.mPerTextHeight);

if (curruntSection >= 0 && curruntSection <= mSectionIndexerText.length - 1) {
selcected = mSectionIndexerText[curruntSection];
mView.setVisibility(View.VISIBLE);
} else {
if (curruntSection < 0) {
selcected = mSectionIndexerText[0];
} else if (curruntSection > mSectionIndexerText.length) {
selcected = mSectionIndexerText[mSectionIndexerText.length - 1];
}
mView.setVisibility(View.GONE);
}
boolean foundedPosition = false;
for (int i = 0; i < mIndexer.getSections().length; i++) {
SectionTitle title = (SectionTitle)mIndexer.getSections()[i];
if (selcected.equals(title.title)) {
mListview.setSelection(mIndexer.getPositionForSection(i));
foundedPosition = true;
break;
}
}

if (foundedPosition) {
mView.setBackgroundResource(R.drawable.section_text_bg);
mView.setText(selcected);
} else {
mView.setBackgroundResource(R.drawable.section_text_gray_bg);
mView.setText(selcected);
}
return true;
}
@Override
public void setPressed(boolean pressed) {
this.mIsPressed = pressed;
}

}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.contacts_list_content);
mEmtytext = (TextView) findViewById(R.id.emptyListText);
mLoadingBar = (ProgressBar) findViewById(R.id.loading);

mQueryHandler = new MyHandler(this);
mAdapter = new ContactsAdapter(this);

mSectionIndexer = (SectionIndexerView)findViewById(R.id.section_indexer_view);
TextView textView = (TextView)findViewById(R.id.section_text);

getListView().setOnScrollListener(mAdapter);
setListAdapter(mAdapter);
<strong>mSectionIndexer.init(getListView(), mAdapter, textView);</strong>
startQuery();
}