微信曾经推出了一个查找附近好友的功能，大致功能是这样的：屏幕上有一个按钮，长按按钮的时候，会有一圈圈水波纹的动画向外扩散，松手后，动画结束。

现在简单来实现这样的一个动画功能：

思路: 主要用到了下面的蓝色的图片，定义三个ImageView，background都设置为蓝色的图片，然后定义一个包括缩放和透明度变化的动画集，然后每隔一段时间，让3个ImageView依次启动这个动画集，看起来就像蓝色的圆圈像水波纹向外扩散一样。


Android实现水波纹外扩效果_微信

    

Android实现水波纹外扩效果_ide_02

相关实现逻辑如下：

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
android:layout_width="match_parent"  
android:layout_height="match_parent" >  
  
<ImageView  
android:id="@+id/wave1"  
android:layout_width="150dp"  
android:layout_height="150dp"  
android:layout_centerInParent="true"  
android:background="@drawable/wave"  
/>  
  
<ImageView  
android:id="@+id/wave2"  
android:layout_width="150dp"  
android:layout_height="150dp"  
android:layout_centerInParent="true"  
android:background="@drawable/wave"/>  
  
<ImageView  
android:id="@+id/wave3"  
android:layout_width="150dp"  
android:layout_height="150dp"  
android:layout_centerInParent="true"  
android:background="@drawable/wave" />  
  
<ImageView  
android:id="@+id/normal"  
android:layout_width="166dp"  
android:layout_height="166dp"  
android:layout_centerInParent="true"  
android:background="@drawable/normal" />  
  
</RelativeLayout>

MainActivity.java 



package com.jackie.waveanimation;  
  
import android.app.Activity;  
import android.os.Bundle;  
import android.os.Handler;  
import android.os.Message;  
import android.view.MotionEvent;  
import android.view.View;  
import android.view.animation.AlphaAnimation;  
import android.view.animation.AnimationSet;  
import android.view.animation.ScaleAnimation;  
import android.widget.ImageView;  
  
public class MainActivity extends Activity {  
private ImageView mNormal, mWave1, mWave2, mWave3;  
  
private AnimationSet mAnimationSet1, mAnimationSet2, mAnimationSet3;  
  
private static final int OFFSET = 600;  //每个动画的播放时间间隔  
private static final int MSG_WAVE2_ANIMATION = 2;  
private static final int MSG_WAVE3_ANIMATION = 3;  
  
private Handler mHandler = new Handler() {  
@Override  
public void handleMessage(Message msg) {  
switch (msg.what) {  
case MSG_WAVE2_ANIMATION:  
                    mWave2.startAnimation(mAnimationSet2);  
break;  
case MSG_WAVE3_ANIMATION:  
                    mWave3.startAnimation(mAnimationSet3);  
break;  
            }  
        }  
    };  
  
@Override  
protected void onCreate(Bundle savedInstanceState) {  
super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
  
        mNormal = (ImageView) findViewById(R.id.normal);  
        mWave1 = (ImageView) findViewById(R.id.wave1);  
        mWave2 = (ImageView) findViewById(R.id.wave2);  
        mWave3 = (ImageView) findViewById(R.id.wave3);  
  
        mAnimationSet1 = initAnimationSet();  
        mAnimationSet2 = initAnimationSet();  
        mAnimationSet3 = initAnimationSet();  
  
new View.OnTouchListener() {  
@Override  
public boolean onTouch(View v, MotionEvent event) {  
switch (event.getAction()) {  
case MotionEvent.ACTION_DOWN:  
                        showWaveAnimation();  
break;  
case MotionEvent.ACTION_UP:  
                        clearWaveAnimation();  
break;  
case MotionEvent.ACTION_CANCEL:  
                        clearWaveAnimation();  
                }  
return true;  
            }  
        });  
    }  
  
private AnimationSet initAnimationSet() {  
new AnimationSet(true);  
new ScaleAnimation(1f, 2.3f, 1f, 2.3f,  
0.5f,  
0.5f);  
3);  
// 设置循环  
new AlphaAnimation(1, 0.1f);  
3);  
//设置循环  
        as.addAnimation(sa);  
        as.addAnimation(aa);  
return as;  
    }  
  
private void showWaveAnimation() {  
        mWave1.startAnimation(mAnimationSet1);  
        mHandler.sendEmptyMessageDelayed(MSG_WAVE2_ANIMATION, OFFSET);  
2);  
    }  
  
private void clearWaveAnimation() {  
        mWave1.clearAnimation();  
        mWave2.clearAnimation();  
        mWave3.clearAnimation();  
    }  
}

效果如下：



Android实现水波纹外扩效果_imageview_03

Android实现水波纹外扩效果_ide_04