Android实现自定义华丽的水波纹效果

public class WaterWaveView2 extends View {

  //存放圆环的集合
  private ArrayList<Wave> mList;

  //界面刷新
  private Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      invalidate();//刷新界面,会执行onDraw方法
    }
  };

  public WaterWaveView2(Context context) {
    this(context, null);
  }

  public WaterWaveView2(Context context, AttributeSet attrs) {
    super(context, attrs);
    mList = new ArrayList<Wave>();
  }

/**
* Created by HongJay on 2016/8/30.
* 把wave的数据封装成一个对象
*/
public class Wave {
  public float x;//圆心x坐标
  public float y;//圆心y坐标
  public Paint paint; //画圆的画笔
  public float width; //线条宽度
  public int radius; //圆的半径
  public int ranNum;//随机数
  public int[] randomColor={Color.BLUE,Color.CYAN,
      Color.GREEN,Color.MAGENTA,Color.RED,Color.YELLOW};

  public Wave(float x, float y) {
    this.x = x;
    this.y = y;
    initData();
  }
  /**
   * 初始化数据,每次点击一次都要初始化一次
   */
  private void initData() {
    paint=new Paint();//因为点击一次需要画出不同的圆环
    paint.setAntiAlias(true);//打开抗锯齿
    ranNum=(int) (Math.random()*6);//[0,5]的随机数
    paint.setColor(randomColor[ranNum]);//设置画笔的颜色
    paint.setStyle(Paint.Style.STROKE);//描边
    paint.setStrokeWidth(width);//设置描边宽度
    paint.setAlpha(255);//透明度的设置(0-255),0为完全透明
    radius=0;//初始化
    width=0;
  }
}

public boolean onTouchEvent(MotionEvent event) {
    super.onTouchEvent(event);
    switch (event.getAction()) {
      case MotionEvent.ACTION_DOWN:

        float x = event.getX();
        float y = event.getY();
        deleteItem();
        Wave wave = new Wave(x, y);
        mList.add(wave);

        //刷新界面
        invalidate();
        break;

      case MotionEvent.ACTION_MOVE:
        float x1 = event.getX();
        float y1 = event.getY();
        deleteItem();
        Wave wave1 = new Wave(x1, y1);
        mList.add(wave1);

        invalidate();
        break;
    }
    //处理事件
    return true;
  }
  //删除透明度已经为0的圆环
  private void deleteItem(){
    for (int i = 0; i <mList.size() ; i++) {
      if(mList.get(i).paint.getAlpha()==0){
        mList.remove(i);
      }
    }
  }
}

protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    //避免程序一运行就进行绘制
    if (mList.size() > 0) {

      //对集合中的圆环对象循环绘制
      for (Wave wave : mList) {
        canvas.drawCircle(wave.x, wave.y, wave.radius, wave.paint);
        wave.radius += 3;
        //对画笔透明度进行操作
        int alpha = wave.paint.getAlpha();
        if (alpha < 80) {
          alpha = 0;
        } else {
          alpha -= 3;
        }

        //设置画笔宽度和透明度
        wave.paint.setStrokeWidth(wave.radius / 8);
        wave.paint.setAlpha(alpha);

        //延迟刷新界面
        mHandler.sendEmptyMessageDelayed(1, 100);
      }
    }
  }