实现Material Design风格的点击水波荡漾效果

自Material Design的设计理念推出以来，整个安卓的UI跟UE界几乎发生了翻天覆地的变化，由此推出的设计理念也在一步一步的被引入到开发者的具体项目中，良心来说Google提出的这个设计理念跟相关的支持包确实也给开发者带来极大的便利，但是不足的是，向下兼容做的不是太好，好多效果使用起来一般都会要求API的版本在至少21以上，所以有些效果想要引入到项目中还是需要开发者做一些定制的，今天我来跟大家分享下MD风格中的点击水波荡漾的效果实现。

对自定义View比较熟的开发者肯定不陌生，定制一个View的时候，肯定会先定制一些相关的属性，一般会在attrs.xml文件中通过declare-styleable来自定义相关属性跟name

<?xml version="1.0" encoding="utf-8"?><resources>    <!--****************引入MD风格的点击水波荡漾效果***************-->    <declare-styleable name="MaterialLayout">        <attr name="alpha" format="integer" />        <attr name="alpha_step" format="integer" />        <attr name="framerate" format="integer" />        <attr name="duration" format="integer" />        <attr name="mycolor" format="color" />        <attr name="scale" format="float" />    </declare-styleable></resources>
然后自定义MaterialLayout文件继承自RelativeLayout
/** * 引入Material Design风格的点击水波荡漾效果布局 *         2017年2月6日10:30:19 */public class MaterialLayout extends RelativeLayout {    PRivate static final int DEFAULT_RADIUS = 10;    private static final int DEFAULT_FRAME_RATE = 10;    private static final int DEFAULT_DURATION = 200;    private static final int DEFAULT_ALPHA = 255;    private static final float DEFAULT_SCALE = 0.8f;    private static final int DEFAULT_ALPHA_STEP = 5;    /**     * 动画帧率     */    private int mFrameRate = DEFAULT_FRAME_RATE;    /**     * 渐变动画持续时间     */    private int mDuration = DEFAULT_DURATION;    /**     *     */    private Paint mPaint = new Paint();    /**     * 被点击的视图的中心点     */    private Point mCenterPoint = null;    /**     * 视图的Rect     */    private RectF mTargetRectf;    /**     * 起始的圆形背景半径     */    private int mRadius = DEFAULT_RADIUS;    /**     * 最大的半径     */    private int mMaxRadius = DEFAULT_RADIUS;    /**     * 渐变的背景色     */    private int mCirclelColor = Color.LTGRAY;    /**     * 每次重绘时半径的增幅     */    private int mRadiusStep = 1;    /**     * 保存用户设置的alpha值     */    private int mBackupAlpha;    /**     * 圆形半径针对于被点击视图的缩放比例,默认为0.8     */    private float mCircleScale = DEFAULT_SCALE;    /**     * 颜色的alpha值, (0, 255)     */    private int mColorAlpha = DEFAULT_ALPHA;    /**     * 每次动画Alpha的渐变递减值     */    private int mAlphaStep = DEFAULT_ALPHA_STEP;    private View mTargetView;    /**     * @param context     */    public MaterialLayout(Context context) {        this(context, null);    }    public MaterialLayout(Context context, AttributeSet attrs) {        super(context, attrs);        init(context, attrs);    }    public MaterialLayout(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        init(context, attrs);    }    private void init(Context context, AttributeSet attrs) {        if (isInEditMode()) {            return;        }        if (attrs != null) {            initTypedArray(context, attrs);        }        initPaint();        this.setWillNotDraw(false);        this.setDrawingCacheEnabled(true);    }    private void initTypedArray(Context context, AttributeSet attrs) {        final TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.MaterialLayout);        mCirclelColor = typedArray.getColor(R.styleable.MaterialLayout_mycolor, Color.LTGRAY);        mDuration = typedArray.getInteger(R.styleable.MaterialLayout_duration, DEFAULT_DURATION);        mFrameRate = typedArray.getInteger(R.styleable.MaterialLayout_framerate, DEFAULT_FRAME_RATE);        mColorAlpha = typedArray.getInteger(R.styleable.MaterialLayout_alpha, DEFAULT_ALPHA);        mCircleScale = typedArray.getFloat(R.styleable.MaterialLayout_scale, DEFAULT_SCALE);        typedArray.recycle();    }    private void initPaint() {        mPaint.setAntiAlias(true);        mPaint.setStyle(Paint.Style.FILL);        mPaint.setColor(mCirclelColor);        mPaint.setAlpha(mColorAlpha);        // 备份alpha属性用于动画完成时重置        mBackupAlpha = mColorAlpha;    }    /**     * 点击的某个坐标点是否在View的内部     *     * @param touchView     * @param x         被点击的x坐标     * @param y         被点击的y坐标     * @return 如果点击的坐标在该view内则返回true, 否则返回false     */    private boolean isInFrame(View touchView, float x, float y) {        initViewRect(touchView);        return mTargetRectf.contains(x, y);    }    /**     * 获取点中的区域,屏幕绝对坐标值,这个高度值也包含了状态栏和标题栏高度     *     * @param touchView     */    private void initViewRect(View touchView) {        int[] location = new int[2];        touchView.getLocationOnScreen(location);        // 视图的区域        mTargetRectf = new RectF(location[0], location[1], location[0] + touchView.getWidth(),                location[1] + touchView.getHeight());    }    /**     * 减去状态栏和标题栏的高度     */    private void removeExtraHeight() {        int[] location = new int[2];        this.getLocationOnScreen(location);        // 减去两个该布局的top,这个top值就是状态栏的高度        mTargetRectf.top -= location[1];        mTargetRectf.bottom -= location[1];        // 计算中心点坐标        int centerHorizontal = (int) (mTargetRectf.left + mTargetRectf.right) / 2;        int centerVertical = (int) ((mTargetRectf.top + mTargetRectf.bottom) / 2);        // 获取中心点        mCenterPoint = new Point(centerHorizontal, centerVertical);    }    private View findTargetView(ViewGroup viewGroup, float x, float y) {        int childCount = viewGroup.getChildCount();        // 迭代查找被点击的目标视图        for (int i = 0; i < childCount; i++) {            View childView = viewGroup.getChildAt(i);            if (childView instanceof ViewGroup) {                return findTargetView((ViewGroup) childView, x, y);            } else if (isInFrame(childView, x, y)) { // 否则判断该点是否在该View的frame内                return childView;            }        }        return null;    }    private boolean isAnimEnd() {        return mRadius >= mMaxRadius;    }    private void calculateMaxRadius(View view) {        // 取视图的最长边        int maxLength = Math.max(view.getWidth(), view.getHeight());        // 计算Ripple圆形的半径        mMaxRadius = (int) ((maxLength / 2) * mCircleScale);        int redrawCount = mDuration / mFrameRate;        // 计算每次动画半径的增值        mRadiusStep = (mMaxRadius - DEFAULT_RADIUS) / redrawCount;        // 计算每次alpha递减的值        mAlphaStep = (mColorAlpha - 100) / redrawCount;    }    /**     * 处理ACTION_DOWN触摸事件, 注意这里获取的是Raw x, y,     * 即屏幕的绝对坐标,但是这个当屏幕中有状态栏和标题栏时就需要去掉这些高度,因此得到mTargetRectf后其高度需要减去该布局的top起点     * ，也就是标题栏和状态栏的总高度.     *     * @param event     */    private void deliveryTouchDownEvent(MotionEvent event) {        if (event.getAction() == MotionEvent.ACTION_DOWN) {            mTargetView = findTargetView(this, event.getRawX(), event.getRawY());            if (mTargetView != null) {                removeExtraHeight();                // 计算相关数据                calculateMaxRadius(mTargetView);                // 重绘视图                invalidate();            }        }    }    @Override    public boolean onInterceptTouchEvent(MotionEvent event) {        deliveryTouchDownEvent(event);        return super.onInterceptTouchEvent(event);    }    @Override    protected void dispatchDraw(Canvas canvas) {        super.dispatchDraw(canvas);        // 绘制Circle        drawRippleIfNecessary(canvas);    }    private void drawRippleIfNecessary(Canvas canvas) {        if (isFoundTouchedSubView()) {            // 计算新的半径和alpha值            mRadius += mRadiusStep;            mColorAlpha -= mAlphaStep;            // 裁剪一块区域,这块区域就是被点击的View的区域.通过clipRect来获取这块区域,使得绘制操作只能在这个区域范围内的进行,            // 即使绘制的内容大于这块区域,那么大于这块区域的绘制内容将不可见. 这样保证了背景层只能绘制在被点击的视图的区域            canvas.clipRect(mTargetRectf);            mPaint.setAlpha(mColorAlpha);            // 绘制背景圆形,也就是            canvas.drawCircle(mCenterPoint.x, mCenterPoint.y, mRadius, mPaint);        }        if (isAnimEnd()) {            reset();        } else {            invalidateDelayed();        }    }    /**     * 发送重绘消息     */    private void invalidateDelayed() {        this.postDelayed(new Runnable() {            @Override            public void run() {                invalidate();            }        }, mFrameRate);    }    /**     * 判断是否找到被点击的子视图     *     * @return     */    private boolean isFoundTouchedSubView() {        return mCenterPoint != null && mTargetView != null;    }    private void reset() {        mCenterPoint = null;        mTargetRectf = null;        mRadius = DEFAULT_RADIUS;        mColorAlpha = mBackupAlpha;        mTargetView = null;        invalidate();    }}在布局中使用此效果的时候只需要把要实现该效果的View包裹在MaterialLayout节点下即可
<?xml version="1.0" encoding="utf-8"?><FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:app="http://schemas.android.com/apk/res-auto"    xmlns:tools="http://schemas.android.com/tools"    android:id="@+id/container"    android:layout_width="match_parent"    android:layout_height="match_parent">    <!--***********Material Design风格的点击水波荡漾效果****-->    <com.zhuandian.qxe.utils.MyView.MaterialLayout        android:layout_width="match_parent"        android:layout_height="match_parent">        <android.support.v4.widget.SwipeRefreshLayout            android:id="@+id/swipe_refresh"            android:layout_width="match_parent"            android:layout_height="match_parent">            <ListView                android:id="@+id/listView"                android:layout_width="match_parent"                android:layout_height="match_parent"                android:padding="2dp"></ListView>        </android.support.v4.widget.SwipeRefreshLayout>    </com.zhuandian.qxe.utils.MyView.MaterialLayout>    <android.support.design.widget.FloatingActionButton        android:id="@+id/search"        android:layout_width="60dp"        android:layout_height="60dp"        android:layout_gravity="bottom|right"        android:layout_margin="10dp"        android:src="@drawable/qy_taobao"        app:backgroundTint="#631263"        />    <include layout="@layout/load_animation" /></FrameLayout>当然你也可以根据attrs.xml文件中自定义的属性值在MaterialLayout节点下通过引入属性来调节此效果的具体细节包括颜色，透明度的渐变效果等