水波纹

import java.util.ArrayList;


import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.os.Handler;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;


/**
 * 水波纹效果
 * @author leo
 *
 */
public class MyRingWave extends View{


/**
* 二个相临波浪中心点的最小距离
*/
private static final int DIS_SOLP = 13;


protected boolean isRunning = false;


private ArrayList<Wave> wList;


public MyRingWave(Context context, AttributeSet attrs) {
super(context, attrs);
wList = new ArrayList<MyRingWave.Wave>();
}

private Handler handler = new Handler(){
public void handleMessage(android.os.Message msg) {


//刷新数据
flushData();
//刷新页面
invalidate();
//循环动画
if (isRunning) {
handler.sendEmptyMessageDelayed(0, 50);
}


};
};

@Override
protected void onDraw(Canvas canvas) {
for (int i = 0; i < wList.size(); i++) {
Wave wave = wList.get(i);
canvas.drawCircle(wave.cx, wave.cy, wave.r, wave.p);
}
}

@Override
public boolean onTouchEvent(MotionEvent event) {
super.onTouchEvent(event);

switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:

int x = (int) event.getX();
int y = (int) event.getY();

addPoint(x,y);

break;


default:
break;
}

return true; 

}

/**
* 添加新的波浪中心点
* @param x
* @param y
*/
private void addPoint(int x, int y) {
if(wList.size() == 0){
addPoint2List(x,y);
/*
* 第一次启动动画
*/
isRunning = true;
handler.sendEmptyMessage(0);
}else{
Wave w = wList.get(wList.size()-1);

if(Math.abs(w.cx - x)>DIS_SOLP || Math.abs(w.cy-y)>DIS_SOLP){
addPoint2List(x,y);
}

};

}


/**
* 添加新的波浪
* @param x
* @param y
*/
private void addPoint2List(int x, int y) {
Wave w = new Wave();
w.cx = x;
w.cy=y;
Paint pa=new Paint();
pa.setColor(colors[(int)(Math.random()*4)]);
pa.setAntiAlias(true);
pa.setStyle(Style.STROKE);


w.p = pa;

wList.add(w);
}


private int [] colors = new int[]{Color.BLUE,Color.RED,Color.YELLOW,Color.GREEN};
/**
* 刷新数据
*/
private void flushData() {

for (int i = 0; i < wList.size(); i++) {

Wave w = wList.get(i);

//如果透明度为 0 从集合中删除
int alpha = w.p.getAlpha();
if(alpha == 0){
wList.remove(i);//删除i 以后，i的值应该再减1 否则会漏掉一个对象，不过，在此处影响不大，效果上看不出来。
continue;
}

alpha-=5;
if(alpha<5){
alpha =0;
}
//降低透明度
w.p.setAlpha(alpha);

//扩大半径
w.r = w.r+3;
//设置半径厚度
w.p.setStrokeWidth(w.r/3);
}

/*
* 如果集合被清空，就停止刷新动画
*/
if(wList.size() == 0){
isRunning = false;
}
}


/**
* 定义一个波浪
* @author leo
*/
private class Wave {
//圆心
int cx;
int cy;

//画笔
Paint p;
//半径
int r;
}
}