自定义控件之水波纹的实现

示例代码：

MainActivity.java

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);
    }
}

activity_main.xml

<?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>

MyRingWave.java

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;
    }
}

MyRing.java

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);
    }

}