该效果是通过自定义界面来实现的
1、首先自定义属性，attrs.xml代码如下：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="RippleView">
<attr name="rippleColor" format="color" />
<attr name="rippleAlpha" format="float" />
<attr name="maskAlpha" format="float" />
<attr name="rippleTime" format="integer" />
</declare-styleable>
</resources>
其中属性rippleColor为水波动画的颜色，rippleAlpha为其透明度，rippleTime为动画持续时间，maskAlpha为触摸遮掩层的透明度。
2、自定义RippleView类继承RelativeLayout布局，也可以由需求所定继承于其它类，实现水波扩散效果主要的有两点：水波扩散的绘制和动画
1)水波的绘制其实就是绘制一个圆形
canvas.drawCircle(mDownX, mDownY, mRadius, mRipplePaint);
2)动画效果就是该圆形的绘制从小到大的过程，而该圆形到最大时的半径长度就是当前所在布局的对角线长度：
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// 获取最大半径
mMaxRadius = (float) Math.sqrt(w * w + h * h);
}
动画效果用属性动画ObjectAnimator来实现（ObjectAnimator是android3.0后出现的）如下
mRippleAnim = ObjectAnimator.ofFloat(this, "radius", 0, mMaxRadius); mRippleAnim.setInterpolator(new AccelerateDecelerateInterpolator()); mRippleAnim.setDuration(mRippleTime);
其中的radius为自定义的属性，在动画执行时会回调对应的方法，只需要在该方法中更新圆形的半径就行了
public void setRadius(final float radius) {
mRadius = radius;
invalidate();
}
RippleView完整代码如下：
public class RippleView extends RelativeLayout {
private int mRippleColor;// 水波颜色
private float mMaskAlpha;// 遮掩透明度
private float mRippleAlpha;// 水波透明度
private int mRippleTime;// 水波动画时间
private ObjectAnimator mRippleAnim;// 显示水波动画
private float mRadius;// 当前的半径
private float mMaxRadius;// 水波最大半径
private float mDownX; // 记录手指按下的位置
private float mDownY;
private boolean mIsMask;
private boolean mIsAnimating;// 是否正在播放动画
private RectF mRect;
private Path mPath;
private Paint mMaskPaint;
private Paint mRipplePaint;
public RippleView(Context context) {
this(context, null);
}
public RippleView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public RippleView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
// 获取自定义属性
TypedArray ta = context.obtainStyledAttributes(attrs,
R.styleable.RippleView);
mRippleColor = ta.getColor(R.styleable.RippleView_rippleColor,
mRippleColor);
mMaskAlpha = ta.getFloat(R.styleable.RippleView_maskAlpha, mMaskAlpha);
mRippleAlpha = ta.getFloat(R.styleable.RippleView_rippleAlpha,
mRippleAlpha);
mRippleTime = ta.getInt(R.styleable.RippleView_rippleTime, mRippleTime);
ta.recycle();
initLast();
}
// 初始化方法
private void init() {
mRippleColor = Color.BLACK;
mMaskAlpha = 0.4f;
mRippleAlpha = 0.8f;
mRippleTime = 800;
mPath = new Path();
mMaskPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mRipplePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
}
// 初始化
private void initLast() {
mMaskPaint.setColor(mRippleColor);
mRipplePaint.setColor(mRippleColor);
mMaskPaint.setAlpha((int) (mMaskAlpha * 255));
mRipplePaint.setAlpha((int) (mRippleAlpha * 255));
}
// 初始化动画
private void initAnim() {
mRippleAnim = ObjectAnimator.ofFloat(this, "radius", 0, mMaxRadius);
mRippleAnim.setInterpolator(new AccelerateDecelerateInterpolator());
mRippleAnim.setDuration(mRippleTime);
mRippleAnim.addListener(new Animator.AnimatorListener() {
@Override
public void onAnimationStart(Animator animator) {
mIsAnimating = true;
}
@Override
public void onAnimationEnd(Animator animator) {
setRadius(0);
mIsMask = false;
mIsAnimating = false;
}
@Override
public void onAnimationCancel(Animator animator) {
}
@Override
public void onAnimationRepeat(Animator animator) {
}
});
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
// 获取最大半径
mMaxRadius = (float) Math.sqrt(w * w + h * h);
// 获取该类布局范围
mRect = new RectF(0f, 0f, getMeasuredWidth() * 1.0f,
getMeasuredHeight() * 1.0f);
// 初始化动画
initAnim();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// 按下事件
if (event.getAction() == MotionEvent.ACTION_DOWN) {
mIsMask = true;
invalidate();
} else if (event.getAction() == MotionEvent.ACTION_MOVE) {
invalidate();
}
// 抬起事件
else if (event.getAction() == MotionEvent.ACTION_UP) {
mDownX = event.getX();
mDownY = event.getY();
if (mIsAnimating) {
mRippleAnim.cancel();
}
boolean isInView = mRect.contains(mDownX, mDownY);
if (isInView) {
mRippleAnim.start();
} else {
mIsMask = false;
invalidate();
}
}
return true;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// 绘制遮掩
if (mIsMask) {
canvas.save(Canvas.CLIP_SAVE_FLAG);
mPath.reset();
mPath.addRect(mRect, Path.Direction.CW);
canvas.clipPath(mPath);
canvas.drawRect(mRect, mMaskPaint);
canvas.restore();
}
// 绘制水波
canvas.save(Canvas.CLIP_SAVE_FLAG);
mPath.reset();
mPath.addCircle(mDownX, mDownY, mRadius, Path.Direction.CW);
canvas.clipPath(mPath);
canvas.drawCircle(mDownX, mDownY, mRadius, mRipplePaint);
canvas.restore();
}
// 属性动画回调的方法
public void setRadius(final float radius) {
mRadius = radius;
invalidate();
}
}
界面布局代码
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:ripple="http://schemas.android.com/apk/res/com.example.rippleview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000000" >
<com.example.rippleview.RippleView
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_centerInParent="true"
android:background="#ffffff"
android:clickable="true"
ripple:rippleColor="#ababab" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="click me"
android:textSize="18sp" />
</com.example.rippleview.RippleView>
</RelativeLayout>
