android 水波纹

public class MyWaveView extends View{

private ArrayList<Wave> list;
private int[] colors = {Color.RED,Color.BLUE,
Color.DKGRAY,Color.GREEN,Color.YELLOW};
public boolean isRunning = false;

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

public MyWaveView(Context context, AttributeSet attrs) {
this(context, attrs,0);
}

public MyWaveView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);

list = new ArrayList<MyWaveView.Wave>();

}

//用户用手触摸时触发
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
int x = (int) event.getX();
int y = (int) event.getY();

//创建水波纹，并放到集合中；
addWave(x, y);
break;
default:
break;
}
return true;
}

public void addWave(int x,int y ){
Wave wave = new Wave();
//确定圆心
wave.rX = x;
wave.rY = y;
//确定半径 radius: 0--->

Paint paint = new Paint();
paint.setColor(colors[(int)(Math.random()*5)]);
paint.setAntiAlias(true);
paint.setStyle(Paint.Style.STROKE);
wave.paint = paint;
addWaveToList(wave,x,y);
}

private void addWaveToList(Wave wave,int x,int y) {
if(list.size() == 0){
list.add(wave);
isRunning = true;
handler.sendEmptyMessage(0);
}else{
if(Math.abs(x - (list.get(list.size() -1)).rX) > 50
|| Math.abs(y - (list.get(list.size() -1)).rY) > 50){
list.add(wave);
}
}

}

Handler handler = new Handler(){
public void handleMessage(android.os.Message msg) {
refreshPaint();
invalidate();

if(isRunning){
handler.sendEmptyMessageDelayed(0, 18);
}
};
};

private void refreshPaint(){
for(int i = 0;i< list.size();i++){
Wave wave = list.get(i);
wave.radius += 4;

int alpha = wave.paint.getAlpha();

alpha -= 5;
if(alpha < 5 ){
alpha = 0;
}
wave.paint.setAlpha(alpha);
if(alpha == 0){
list.remove(i);

}
wave.radius = wave.radius + 3;
wave.paint.setStrokeWidth(wave.radius/3);

if(list.size() == 0){
isRunning = false;
}
}
}

//水波纹对象
public class Wave{
public int radius;
public int rX;
public int rY;
public Paint paint;

}

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

for(int i = 0; i < list.size();i++ ){
Wave wave = list.get(i);
canvas.drawCircle(wave.rX, wave.rY, wave.radius, wave.paint);
}
}
}