android仿微信联系人索引列表功能

public class SlideBar extends Button{  public interface OnTouchAssortListener{  public void onTouchAssortListener(String s);  }  // 分类  private static final String[] ASSORT_TEXT = {"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 Paint mPaint = new Paint();  private int mSelectIndex = -1;  private OnTouchAssortListener mListener = null; private Activity mAttachActivity; PopupWindow mPopupWindow = null; View layoutView; TextView text; public SlideBar(Context context){  this(context,null);  }  public SlideBar(Context context, AttributeSet attrs) {  this(context, attrs,0);  }  public SlideBar(Context context, AttributeSet attrs, int defStyle){  super(context, attrs, defStyle); mAttachActivity = (Activity)context; init(context); }  private void init(Context context) { layoutView = LayoutInflater.from(context).inflate(R.layout.alert_dialog_menu_layout, null); text = (TextView) layoutView.findViewById(R.id.content); } public void setOnTouchAssortListener(OnTouchAssortListener listener) { this.mListener = listener; } @Override  protected void onDraw(Canvas canvas){  super.onDraw(canvas); int nHeight = getHeight();  int hWidth = getWidth();  int nAssortCount = ASSORT_TEXT.length; int nInterval = nHeight / nAssortCount; for (int i = 0; i < nAssortCount; i++){   mPaint.setAntiAlias(true); // 抗锯齿   mPaint.setTypeface(Typeface.DEFAULT_BOLD); // 默认粗体   mPaint.setColor(Color.parseColor("#5f5f5f")); // 白色   if (i == mSelectIndex){   // 被选择的字母改变颜色和粗体   mPaint.setColor(Color.parseColor("#3399ff"));   mPaint.setFakeBoldText(true);   mPaint.setTextSize(30);   }   float xPos = hWidth / 2 - mPaint.measureText(ASSORT_TEXT[i]) / 2; // 计算字母的X坐标   float yPos = nInterval * i + nInterval; // 计算字母的Y坐标   canvas.drawText(ASSORT_TEXT[i], xPos, yPos, mPaint);   mPaint.reset();  }  }  @Override public boolean dispatchTouchEvent(MotionEvent event) { //判断是哪一个字母被点击了 int nIndex = (int) (event.getY() / getHeight() * ASSORT_TEXT.length); if (nIndex >= 0 && nIndex < ASSORT_TEXT.length){  switch (event.getAction()){   case MotionEvent.ACTION_MOVE:   // 如果滑动改变   if (mSelectIndex != nIndex){    mSelectIndex = nIndex;   showCharacter(ASSORT_TEXT[mSelectIndex]);   if (mListener != null){   mListener.onTouchAssortListener(ASSORT_TEXT[mSelectIndex]);   }  }   break;   case MotionEvent.ACTION_DOWN:   mSelectIndex = nIndex;   showCharacter(ASSORT_TEXT[mSelectIndex]);  if (mListener != null){    mListener.onTouchAssortListener(ASSORT_TEXT[mSelectIndex]);   }   break;   case MotionEvent.ACTION_UP:   disShowCharacter();  mSelectIndex = -1;   break;   }  } else {   mSelectIndex = -1;   disShowCharacter(); }  invalidate(); return true; } private void disShowCharacter() { if (mPopupWindow != null) {  mPopupWindow.dismiss();  mPopupWindow=null; } }  private void showCharacter(String string){ if (mPopupWindow != null){  text.setText(string); } else{   mPopupWindow = new PopupWindow(layoutView, 100, 100, false);  mPopupWindow.showAtLocation(mAttachActivity.getWindow().getDecorView(), Gravity.CENTER, 0, 0); } text.setText(string); }}