Android自定义控件实现水波纹效果

package com.example.mhy.shuibowen;
 
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
 
public class MainActivity extends AppCompatActivity {
 
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
 
  tools:context="com.example.mhy.shuibowen.MainActivity">
 
  <com.example.mhy.shuibowen.MyRingWave
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    />
</RelativeLayout>

package com.example.mhy.shuibowen;
 
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
 
import java.util.ArrayList;
 
/**
 * 水波纹效果
 * Created by mhy on 2016/6/16.
 */
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>();
  }
 
  @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;
  }
 
  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);
      }
 
    }
  };
 
  /**
   * 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;
    }
  }
 
  /**
   * 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);
      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(Paint.Style.STROKE);
 
    w.p = pa;
 
    wList.add(w);
  }
 
  private int [] colors = new int[]{Color.BLUE,Color.RED,Color.YELLOW,Color.GREEN};
  private class Wave {
    //圆心
    int cx;
    int cy;
 
    //画笔
    Paint p;
    //半径
    int r;
  }
}

package com.example.mhy.shuibowen;
 
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
 
/**
 * Created by mhy on 2016/6/16.
 */
public class MyRing extends View {
 
  /**
   * 圆心的X坐标
   */
  private float cx;
 
  /**
   * 圆心的Y坐标
   */
  private float cy;
  /**
   * 圆环半径
   */
  private float radius = 0;
  /**
   * 默认画笔
   */
  private Paint paint;
  private boolean isRuning = false;
 
  public MyRing(Context context, AttributeSet attrs) {
    super(context, attrs);
    initView();
  }
 
  private void initView() {
    radius = 0;
    paint = new Paint();
    paint.setAntiAlias(true);
    paint.setStyle(Paint.Style.STROKE); // 空心圆
    paint.setStrokeWidth(radius / 4); // 画笔宽度 半径4分之一
    paint.setColor(Color.GREEN); // 画笔颜色
    paint.setAlpha(255); //不透明
  }
 
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  }
 
  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    if(changed) {
      cx = getWidth() / 2;
      cy = getHeight() / 2;
    }
  }
 
  @Override
  protected void onDraw(Canvas canvas) {
    canvas.drawCircle(cx, cy, radius, paint);
  }
 
  @Override
  protected void onAttachedToWindow() {
    super.onAttachedToWindow();
  }
 
  @Override
  protected void onDetachedFromWindow() {
    super.onDetachedFromWindow();
    isRuning = false;
  }
 
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    super.onTouchEvent(event);
 
    if(event.getAction() == MotionEvent.ACTION_DOWN) {
      cx = event.getX();
      cy = event.getY();
      initView();
      startAnim();
    }
    return true;
  }
 
  private Handler handler = new Handler(){
    @Override
    public void handleMessage(Message msg) {
 
      // 设置透明度
      int alpha = paint.getAlpha();
      if(alpha == 0) {
        isRuning = false;
      }
 
      // 透明度 慢慢变透明
      alpha = Math.max(0, alpha-10);
 
      paint.setAlpha(alpha);
 
      System.out.println(alpha);
 
      // 设置半径
      radius += 5;
      paint.setStrokeWidth(radius / 3);
      invalidate();
 
      if(isRuning) {
        handler.sendEmptyMessageDelayed(0, 50);
      }
    }
  };
  private void startAnim() {
    isRuning = true;
    handler.sendEmptyMessageDelayed(0, 50);
  }
 
}