Android自定义View仿微信LetterView效果

废话不多说了，具体代码如下所示：

 public class letterview extends view {
  private string tag = letterview.class.getsimplename();
  //a,b,c....z,#
  public list<string> letters;
  private paint mpaint;
  private int selectposition = -1;
  private textview mletter;
  public void setmletter(textview mletter) {
    this.mletter = mletter;
  }
  public letterview(context context) {
    this(context,null);
  }
  public letterview(context context, attributeset attrs) {
    this(context, attrs,0);
  }
  public letterview(context context, attributeset attrs, int defstyleattr) {
    super(context, attrs, defstyleattr);
    //生产字母
    letters = new arraylist<>();
    for (int i = 65; i < 91; i++) {
      letters.add(string.format(locale.china,"%c",i));
      log.e(tag, "letterview: "+ string.format(locale.china,"%c",i));
    }
    letters.add("#");//追加一个#
    //初始化画笔
    mpaint = new paint();
    mpaint.setantialias(true);
    mpaint.setcolor(color.blue);
    mpaint.settextsize(30);
  }
  @override
  protected void ondraw(canvas canvas) {
    super.ondraw(canvas);
    /**
     * 获取view的宽度
     * 获取view的高度
     */
    int width = getmeasuredwidth();
    int height = getmeasuredheight();
    //测量字的宽度
    int size = letters.size();
    for (int i = 0; i < size; i++) {
      float textwidth = mpaint.measuretext(letters.get(i));
      int singleheight = height / size;
      if (selectposition == i){//被选中的
        mpaint.setcolor(color.red);
      }else{
        mpaint.setcolor(color.blue);
      }
      canvas.drawtext(letters.get(i),(width - textwidth)/2, singleheight * (i + 1),mpaint);
      /**
       * drawtext() x y \_ 为基准线
       */
    invalidate();
    }
  }
  /**
   * android将触摸事件封装,包装了动作,位置信息;onclick也是一种motionevent
   * onclick 事件 实际上是 ontouchevent事件
   * @param event
   * @return
   */
  @override
  public boolean ontouchevent(motionevent event) {
    //包装了动作,位置信息
//    event.gety();//相对于view本身的坐标值
//    event.getrawy();//返回的是相对于屏幕的坐标值
    float y = event.gety();
    log.e(tag, "ontouchevent: y:"+ y);
//    log.e(tag, "ontouchevent: rawy:"+event.getrawy() );
    int measuredheight = getmeasuredheight();
    int singleheight = measuredheight / letters.size();
    int position = (int) (y / singleheight);
    log.e(tag, "ontouchevent: " + position );
    switch (event.getaction()) {
      case motionevent.action_move:
        log.e(tag, "ontouchevent: action_move" );
      case motionevent.action_down:
        log.e(tag, "ontouchevent: action_down" );
        selectposition = position;
        if (mletter != null) {
          mletter.setvisibility(view.visible);
          //极限情况有可能下标越界,需要判断一下
          if (position < letters.size() && position >= 0){
            mletter.settext(letters.get(position));
          }
        }
        break;
      case motionevent.action_up:
        log.e(tag, "ontouchevent: action_up" );
        selectposition = -1;
        if (mletter != null) {
          mletter.setvisibility(view.gone);
        }
        break;
    }
    //返回true代表事件被处理了
    return true;
  }
}