Android实现水波纹外扩效果

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。

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" ><ImageViewandroid:id="@+id/wave1"android:layout_width="150dp"android:layout_height="150dp"android:layout_centerInParent="true"android:background="@drawable/wave"/><ImageViewandroid:id="@+id/wave2"android:layout_width="150dp"android:layout_height="150dp"android:layout_centerInParent="true"android:background="@drawable/wave"/><ImageViewandroid:id="@+id/wave3"android:layout_width="150dp"android:layout_height="150dp"android:layout_centerInParent="true"android:background="@drawable/wave" /><ImageViewandroid: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() {@Overridepublic void handleMessage(Message msg) {switch (msg.what) {case MSG_WAVE2_ANIMATION:mWave2.startAnimation(mAnimationSet2);break;case MSG_WAVE3_ANIMATION:mWave3.startAnimation(mAnimationSet3);break;}}};@Overrideprotected 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();mNormal.setOnTouchListener(new View.OnTouchListener() {@Overridepublic 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() {AnimationSet as = new AnimationSet(true);ScaleAnimation sa = new ScaleAnimation(1f, 2.3f, 1f, 2.3f,ScaleAnimation.RELATIVE_TO_SELF, 0.5f,ScaleAnimation.RELATIVE_TO_SELF, 0.5f);sa.setDuration(OFFSET * 3);sa.setRepeatCount(Animation.INFINITE);// 设置循环AlphaAnimation aa = new AlphaAnimation(1, 0.1f);aa.setDuration(OFFSET * 3);aa.setRepeatCount(Animation.INFINITE);//设置循环as.addAnimation(sa);as.addAnimation(aa);return as;}private void showWaveAnimation() {mWave1.startAnimation(mAnimationSet1);mHandler.sendEmptyMessageDelayed(MSG_WAVE2_ANIMATION, OFFSET);mHandler.sendEmptyMessageDelayed(MSG_WAVE3_ANIMATION, OFFSET * 2);}private void clearWaveAnimation() {mWave1.clearAnimation();mWave2.clearAnimation();mWave3.clearAnimation();}
}

效果如下：