先上效果图：

Video_20190327_111654_826.gif

封面类CoverView：

public class CoverView extends View {
    private final static String TAG = "CoverView";
    private static final int DEFAULT_DERATION = 600;

    private Bitmap mBitmap,mContentBgBitmap;
    private Matrix mMatrix,mContentBgMatrix;
    private int mLeft,mTop,mRight,mBottom;
    private int mParentWidth,mParentHeight,mPivotx,mPivoty;
    private ActionCallBack mActionCallBack;
    private int mDuration = DEFAULT_DERATION;
    private ValueAnimator mValueAnimator;

    public CoverView(Context context) {
        this(context,null);
    }

    public CoverView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CoverView(Context context, @Nullable AttributeSet attrs,
                     int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initData();
    }

    public void setCol(int left,int top,int right,int bottom){
        mLeft = left;
        mTop = top;
        mRight = right;
        mBottom = bottom;
        invalidate();
    }

    private void initData() {
        mMatrix = new Matrix();
        mMatrix.reset();
        mContentBgMatrix = new Matrix();
        mContentBgMatrix.reset();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if(mBitmap != null && mContentBgBitmap != null) {
            canvas.drawBitmap(mContentBgBitmap, mContentBgMatrix, null);
            canvas.drawBitmap(mBitmap, mMatrix, null);
        }
    }

    @Override
    public void layout(int l, int t, int r, int b) {
        super.layout(mLeft,mTop,mRight,mBottom);
    }

    public void openOrClose(final boolean isOpen){
        final int width = mRight - mLeft;
        final int height = mBottom - mTop;
        final float[] src = {0,0,
                width,0,
                width, height,
                0, height};
        Log.d(TAG, "open: " + mParentWidth + "-" + width);
        if(mParentWidth == width || mParentHeight == height){
            return;
        }
        mPivotx = mLeft*width / (mParentWidth - width);
        mPivoty = mTop*height / (mParentHeight - height);
        final float scale = Math.max((float) mParentWidth/width,(float) mParentHeight/height);
        mValueAnimator = ValueAnimator.ofInt(100);
        mValueAnimator.setDuration(mDuration);
        mValueAnimator.setInterpolator(new LinearInterpolator());
        mValueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                int animatedValue = isOpen ? (int)animation.getAnimatedValue() : 100-(int)animation.getAnimatedValue();
                float j = (scale-1)/100 * animatedValue;

                mMatrix.reset();
                int polyX = (int) (width * (1 - animatedValue/50f));
                polyX = polyX == 0 ? 1 : polyX;
                Log.d(TAG, "onAnimationUpdate: "+polyX);
                float[] dst = {0,0,
                        polyX,-5*animatedValue,
                        polyX,height + 5*animatedValue,
                        0, height};
                mMatrix.setPolyToPoly(src,0,dst,0,src.length >> 1);
                mMatrix.postScale(1+j,1+j,mPivotx,mPivoty);

                mContentBgMatrix.reset();
                mContentBgMatrix.postScale(1+j,1+j,mPivotx,mPivoty);
                invalidate();

                if((int)animation.getAnimatedValue() == 100 && mActionCallBack != null){
                    if (isOpen) {
                        mActionCallBack.onOpened();
                    }else{
                        mActionCallBack.onClosed();
                    }
                }
            }
        });
        mValueAnimator.start();
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        if(mActionCallBack != null){
            mActionCallBack = null;
        }
        if(mValueAnimator != null){
            mValueAnimator.removeAllUpdateListeners();
        }
    }

    public void setActionCallBack(ActionCallBack mActionCallBack) {
        this.mActionCallBack = mActionCallBack;
    }

    public void setBitmap(Bitmap mBitmap) {
        this.mBitmap = mBitmap;
    }

    public void setContentBgBitmap(Bitmap mBitmap) {
        this.mContentBgBitmap = mBitmap;
    }

    public void setParentSize(int width, int height) {
        this.mParentWidth = width;
        this.mParentHeight = height;
    }

    public void setDuration(int mDuration) {
        this.mDuration = mDuration;
    }

    public interface ActionCallBack{
        void onOpened();
        void onClosed();
    }
}

打开或关闭书本方法

private void openBook(ImageView v, Bitmap bitmap) {
    final WindowManager wm = ((WindowManager) getSystemService(WINDOW_SERVICE));
    if(Build.VERSION.SDK_INT >= 26) {
        wm.addView(mRootView,
                new WindowManager.LayoutParams(WindowManager.LayoutParams.MATCH_PARENT,
                        WindowManager.LayoutParams.MATCH_PARENT,
                        WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY,
                        WindowManager.LayoutParams.FLAG_FULLSCREEN |
                                WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN,
                        PixelFormat.TRANSPARENT));
    }else{
        wm.addView(mRootView,
                new WindowManager.LayoutParams(WindowManager.LayoutParams.MATCH_PARENT,
                        WindowManager.LayoutParams.MATCH_PARENT,
                        WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
                        WindowManager.LayoutParams.FLAG_FULLSCREEN |
                                WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN,
                        PixelFormat.TRANSPARENT));
    }
    final CoverView coverView = new CoverView(ThemeActivity.this);
    int[] location = new int[2];
    v.getLocationInWindow(location);
    coverView.setCol(location[0], location[1], (location[0]+v.getWidth()),
            (location[1]+v.getHeight()));
    Point screenPoint = new Point();
    getWindowManager().getDefaultDisplay().getRealSize(screenPoint);
    coverView.setParentSize(screenPoint.x,screenPoint.y);
//        DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
//        coverView.setParentSize(displayMetrics.widthPixels,displayMetrics.heightPixels);
    coverView.setDuration(600);
    mRootView.removeAllViews();
    mRootView.addView(coverView);
    coverView.setActionCallBack(new CoverView.ActionCallBack() {
        @Override
        public void onOpened() {
            coverView.openOrClose(false);
        }

        @Override
        public void onClosed() {
            wm.removeView(mRootView);
            mIsClickable = true;
        }
    });
    coverView.setBitmap(getBitmap(v.getDrawable()));
    coverView.setContentBgBitmap(bitmap);
    coverView.openOrClose(true);
}

原理：
使用Matrix对bitmap进行放大和自定义变换实现

需要注意的是8.0之后悬浮窗type要写TYPE_APPLICATION_OVERLAY

todo:

• 现在只是放大到窗口大小，不能自定义放大后的区域位置
• 可以不依靠window实现

写于2019-3-27