PopUpWindow 位置分析

本段代碼實際是計算popupWindow相對母視窗內的位移值，即p.x,p.y的最終值  private boolean findDropDownPosition(View anchor, WindowManager.LayoutParams p,            int xoff, int yoff) {        //狀態列或titile欄的高度        final int anchorHeight = anchor.getHeight();        //狀態列或titile欄在視窗中的位置        anchor.getLocationInWindow(mDrawingLocation); p.x = mDrawingLocation[0] + xoff; p.y = mDrawingLocation[1] + anchorHeight + yoff; boolean onTop = false; p.gravity = Gravity.START | Gravity.TOP;        //狀態列或titile欄在螢幕中的位置                anchor.getLocationOnScreen(mScreenLocation);        //displayFrame最終視窗的可見大小，對service端的window而言，但在qmw中卻是實際的子視窗大小        final Rect displayFrame = new Rect();        anchor.getWindowVisibleDisplayFrame(displayFrame);        //screenY是計算相對螢幕，popUpWindow的y位置        int screenY = mScreenLocation[1] + anchorHeight + yoff;                //root指decore View，displayFrame.getWidth 和root.getWidth()基本一致        final View root = anchor.getRootView();        if (screenY + mPopupHeight > displayFrame.bottom ||                p.x + mPopupWidth - root.getWidth() > 0) {            // if the drop down disappears at the bottom of the screen. we try to            // scroll a parent scrollview or move the drop down back up on top of            // the edit box    //超過視窗高度了，使能scroolview            if (mAllowScrollingAnchorParent) {                int scrollX = anchor.getScrollX();                int scrollY = anchor.getScrollY();                Rect r = new Rect(scrollX, scrollY,  scrollX + mPopupWidth + xoff,                        scrollY + mPopupHeight + anchor.getHeight() + yoff);                anchor.requestRectangleOnScreen(r, true);            }            // now we re-evaluate the space available, and decide from that            // whether the pop-up will go above or below the anchor.            //重新計算            anchor.getLocationInWindow(mDrawingLocation);            p.x = mDrawingLocation[0] + xoff;            p.y = mDrawingLocation[1] + anchor.getHeight() + yoff;                        // determine whether there is more space above or below the anchor            anchor.getLocationOnScreen(mScreenLocation);            //判斷popupwindow是否上下顛倒？            onTop = (displayFrame.bottom - mScreenLocation[1] - anchor.getHeight() - yoff) <                    (mScreenLocation[1] - yoff - displayFrame.top);            if (onTop) {                p.gravity = Gravity.START | Gravity.BOTTOM;                p.y = root.getHeight() - mDrawingLocation[1] + yoff;            } else {                p.y = mDrawingLocation[1] + anchor.getHeight() + yoff;            }        }        //mClipToScreen使視窗是clip到screen上而非母視窗(container)        if (mClipToScreen) {            final int displayFrameWidth = displayFrame.right - displayFrame.left;            int right = p.x + p.width;            if (right > displayFrameWidth) {                p.x -= right - displayFrameWidth;            }           //qmw should change here           if (p.x < displayFrame.left) {                p.x = displayFrame.left;                p.width = Math.min(p.width, displayFrameWidth);            }            if (onTop) {                int popupTop = mScreenLocation[1] + yoff - mPopupHeight;                if (popupTop < 0) {                    p.y += popupTop;                }            } else {             //qmw should change here              p.y = Math.max(p.y, displayFrame.top); } } p.gravity |= Gravity.DISPLAY_CLIP_VERTICAL; return onTop; }