实现Material Design水波效果的Button

如果你的Android手机是5.0以上的系统，相信对下面这种按钮点击效果并不会陌生：

实现效果图：

快的那个是按下后的效果，慢的是长按后的效果！

实现逻辑：

1.我们继承ImageButton，当然你可以换成Button或者View,这里笔者想把龟放到中间才继承ImageButton

2.首先，创建两个Paint(画笔)对象，一个绘制底部背景颜色，一个绘制波纹扩散的

3.接着计算最大半径，开始半径每隔一段时间递增一次，直到等于最大半径，然后重置状态！

PS:大概的核心，刚学可能对自定义View感到陌生，没事，这里了解下即可，以后我们会讲，当然你可以自己扣扣，注释还是蛮详细的~

实现代码：

自定义ImageButton：MyButton.java

package demo.com.jay.buttondemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.ViewConfiguration;
import android.widget.ImageButton;

/**
 * Created by coder-pig on 2015/7/16 0016.
 */
public class MyButton extends ImageButton {


    private static final int INVALIDATE_DURATION = 15;     //每次刷新的时间间隔
    private static int DIFFUSE_GAP = 10;                  //扩散半径增量
    private static int TAP_TIMEOUT;                         //判断点击和长按的时间

    private int viewWidth, viewHeight;                   //控件宽高
    private int pointX, pointY;                          //控件原点坐标（左上角）
    private int maxRadio;                             //扩散的最大半径
    private int shaderRadio;                        //扩散的半径

    private Paint bottomPaint, colorPaint;          //画笔:背景和水波纹
    private boolean isPushButton;                 //记录是否按钮被按下

    private int eventX, eventY;                  //触摸位置的X,Y坐标
    private long downTime = 0;                 //按下的时间


    public MyButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        initPaint();
        TAP_TIMEOUT = ViewConfiguration.getLongPressTimeout();
    }


    /*
    * 初始化画笔
    * */
    private void initPaint() {
        colorPaint = new Paint();
        bottomPaint = new Paint();
        colorPaint.setColor(getResources().getColor(R.color.reveal_color));
        bottomPaint.setColor(getResources().getColor(R.color.bottom_color));
    }


    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                if (downTime == 0) downTime = SystemClock.elapsedRealtime();
                eventX = (int) event.getX();
                eventY = (int) event.getY();
                //计算最大半径：
                countMaxRadio();
                isPushButton = true;
                postInvalidateDelayed(INVALIDATE_DURATION);
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL:
                if(SystemClock.elapsedRealtime() - downTime < TAP_TIMEOUT){
                    DIFFUSE_GAP = 30;
                    postInvalidate();
                }else{
                    clearData();
                }
                break;
        }
        return super.onTouchEvent(event);
    }


    @Override
    protected void dispatchDraw(Canvas canvas) {
        super.dispatchDraw(canvas);
        if(!isPushButton) return; //如果按钮没有被按下则返回
        //绘制按下后的整个背景
        canvas.drawRect(pointX, pointY, pointX + viewWidth, pointY + viewHeight, bottomPaint);
        canvas.save();
        //绘制扩散圆形背景
        canvas.clipRect(pointX, pointY, pointX + viewWidth, pointY + viewHeight);
        canvas.drawCircle(eventX, eventY, shaderRadio, colorPaint);
        canvas.restore();
        //直到半径等于最大半径
        if(shaderRadio < maxRadio){
            postInvalidateDelayed(INVALIDATE_DURATION,
                    pointX, pointY, pointX + viewWidth, pointY + viewHeight);
            shaderRadio += DIFFUSE_GAP;
        }else{
            clearData();
        }
    }

    /*
        * 计算最大半径的方法
        * */
    private void countMaxRadio() {
        if (viewWidth > viewHeight) {
            if (eventX < viewWidth / 2) {
                maxRadio = viewWidth - eventX;
            } else {
                maxRadio = viewWidth / 2 + eventX;
            }
        } else {
            if (eventY < viewHeight / 2) {
                maxRadio = viewHeight - eventY;
            } else {
                maxRadio = viewHeight / 2 + eventY;
            }
        }
    }


    /*
    * 重置数据的方法
    * */
    private void clearData(){
        downTime = 0;
        DIFFUSE_GAP = 10;
        isPushButton = false;
        shaderRadio = 0;
        postInvalidate();
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        this.viewWidth = w;
        this.viewHeight = h;
    }
}

color.xml：

xml version="1.0" encoding="utf-8"?>

     name="reveal_color">#FFFFFF
     name="bottom_color">#3086E4
     name="bottom_bg">#40BAF8
 
  
activity_main.xml：
 
  
 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=".MainActivity">

    
        android:id="@+id/myBtn"
        android:layout_width="match_parent"
        android:layout_height="64dp"
        android:src="@mipmap/ic_tur_icon"
        android:background="@color/bottom_bg"
        android:scaleType="center"/>