话不多说，我们先来看看效果：
Hi前辈搜索预览
这一张是《Hi前辈》的搜索预览图，你可以在这里下载这个APP查看更多效果：
http://www.wandoujia.com/apps/com.superlity.hiqianbei
LSearchView
这是一个MD风格的搜索框，集成了ripple动画以及search时的loading，使用很简单，如果你也需要这样的搜索控件不妨来试试：https://github.com/onlynight/LSearchView
RippleEverywhere
女友的照片：
女友的照片：
这是一个水波纹动画支持库，由于使用暂时只支持Android4.0以上版本。https://github.com/onlynight/RippleEverywhere
实现原理
使用属性动画完成该动画的实现，由于android2.3以下已经不是主流机型，故只兼容4.0以上系统。
关于属性动画，如果还有童鞋不了解可以去看看hongyang大神的这篇文章：
http://www.jb51.net/article/82668.htm
在我看来属性动画实际上就类似于定时器，所谓定时器就是独立在主线程之外的另外一个用于计时的线程，每当到达你设定时间的时候这个线程就会通知你；属性动画也不光是另外一个线程，他能够操作主线程UI元素属性就说明了它内部已经做了线程同步。
基本原理
我们先来看下关键代码：
@Override protected void onDraw(Canvas canvas) { if (running) { // get canvas current state final int state = canvas.save(); // add circle to path to crate ripple animation // attention: you must reset the path first, // otherwise the animation will run wrong way. ripplePath.reset(); ripplePath.addCircle(centerX, centerY, radius, Path.Direction.CW); canvas.clipPath(ripplePath); // the {@link View#onDraw} method must be called before // {@link Canvas#restoreToCount}, or the change will not appear. super.onDraw(canvas); canvas.restoreToCount(state); return; } // in a normal condition, you should call the // super.onDraw the draw the normal situation. super.onDraw(canvas); } Canvas#save()和Canvas#restoreToCount()
这个两个方法用于绘制状态的保存与恢复。绘制之前先保存上一次的状态；绘制完成后恢复前一次的状态；以此类推直到running成为false，中间的这个过程就是动画的过程。
Path#addCircle()和Canvas#clipPath()
addCircle用于在path上绘制一个圈；clipPath绘制剪切后的path（只绘制path内的区域，其他区域不绘制）。
radiusAnimator = ObjectAnimator.ofFloat(this, "animValue", 0, 1); /** * This method will be called by {@link this#radiusAnimator} * reflection calls. * * @param value animation current value */ public void setAnimValue(float value) { this.radius = value * maxRadius; System.out.println("radius = " + this.radius); invalidate(); }
这一段是动画的动效关键，首先要有一个随着时间推移而变化的值，当每次这个值变化的时候我们需要跟新界面让view重新绘制调用onDraw方法，我们不能手动调用onDraw方法，系统给我们提供的invalidate会强制view重绘进而调用onDraw方法。
以上就是这个动画的全部关键原理了，下面我们来一份完整的源码：
import android.animation.Animator; import android.animation.ObjectAnimator; import android.annotation.TargetApi; import android.content.Context; import android.graphics.Canvas; import android.graphics.Path; import android.util.AttributeSet; import android.view.View; import android.view.animation.AccelerateDecelerateInterpolator; import android.widget.ImageView; /** * Created by lion on 2016/11/11. * <p> * RippleImageView use the {@link Path#addCircle} function * to draw the view when {@link RippleImageView#onDraw} called. * <p> * When you call {@link View#invalidate()} function,then the * {@link View#onDraw(Canvas)} will be called. In that way you * can use {@link Path#addCircle} to draw every frame, you will * see the ripple animation. */ public class RippleImageView extends ImageView { // view center x private int centerX = 0; // view center y private int centerY = 0; // ripple animation current radius private float radius = 0; // the max radius that ripple animation need private float maxRadius = 0; // record the ripple animation is running private boolean running = false; private ObjectAnimator radiusAnimator; private Path ripplePath; public RippleImageView(Context context) { super(context); init(); } public RippleImageView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public RippleImageView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(); } @TargetApi(21) public RippleImageView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); init(); } private void init() { ripplePath = new Path(); // initial the animator, when animValue change, // radiusAnimator will call {@link this#setAnimValue} method. radiusAnimator = ObjectAnimator.ofFloat(this, "animValue", 0, 1); radiusAnimator.setDuration(1000); radiusAnimator.setInterpolator(new AccelerateDecelerateInterpolator()); radiusAnimator.addListener(new Animator.AnimatorListener() { @Override public void onAnimationStart(Animator animator) { running = true; } @Override public void onAnimationEnd(Animator animator) { running = false; } @Override public void onAnimationCancel(Animator animator) { } @Override public void onAnimationRepeat(Animator animator) { } }); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); centerX = (right - left) / 2; centerY = (bottom - top) / 2; maxRadius = maxRadius(left, top, right, bottom); } /** * Calculate the max ripple animation radius. * * @param left view left * @param top view top * @param right view right * @param bottom view bottom * @return */ private float maxRadius(int left, int top, int right, int bottom) { return (float) Math.sqrt(Math.pow(right - left, 2) + Math.pow(bottom - top, 2) / 2); } /** * This method will be called by {@link this#radiusAnimator} * reflection calls. * * @param value animation current value */ public void setAnimValue(float value) { this.radius = value * maxRadius; System.out.println("radius = " + this.radius); invalidate(); } @Override protected void onDraw(Canvas canvas) { if (running) { // get canvas current state final int state = canvas.save(); // add circle to path to crate ripple animation // attention: you must reset the path first, // otherwise the animation will run wrong way. ripplePath.reset(); ripplePath.addCircle(centerX, centerY, radius, Path.Direction.CW); canvas.clipPath(ripplePath); // the {@link View#onDraw} method must be called before // {@link Canvas#restoreToCount}, or the change will not appear. super.onDraw(canvas); canvas.restoreToCount(state); return; } // in a normal condition, you should call the // super.onDraw the draw the normal situation. super.onDraw(canvas); } /** * call the {@link Animator#start()} function to start the animation. */ public void startAnimation() { if (radiusAnimator.isRunning()) { radiusAnimator.cancel(); } radiusAnimator.start(); } }
以上所述是小编给大家介绍的Android自定义水波纹动画Layout实例代码，希望对大家有所帮助，如果大家有任何疑问请给我们留言，小编会及时回复大家的。在此也非常感谢大家对查字典教程网的支持！
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