自定義Toast懸浮停靠問題

0x00

模擬手機位置的桌面懸浮清理內存的效果

0x01

mParams = new WindowManager.LayoutParams();
            mParams.height = WindowManager.LayoutParams.WRAP_CONTENT;
            mParams.width = WindowManager.LayoutParams.WRAP_CONTENT;
            mParams.gravity = Gravity.LEFT | Gravity.TOP;
            mParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                    | WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON;
            mParams.format = PixelFormat.TRANSLUCENT;
            mParams.type = WindowManager.LayoutParams.TYPE_PRIORITY_PHONE;

其中的 mParams.gravity = Gravity.LEFT | Gravity.TOP; 會改變顯示位置的座標系（姑且理解爲改變）

如果不設置Gravity.TOP，打印出來的mParams.y在屏幕的y軸方向的中間處爲0，導致總達不到想要的效果

0x02

查詢源碼：
gravity屬性：

/**
         * Placement of window within the screen as per {@link Gravity}.  Both
         * {@link Gravity#apply(int, int, int, android.graphics.Rect, int, int,
         * android.graphics.Rect) Gravity.apply} and
         * {@link Gravity#applyDisplay(int, android.graphics.Rect, android.graphics.Rect)
         * Gravity.applyDisplay} are used during window layout, with this value
         * given as the desired gravity.  For example you can specify
         * {@link Gravity#DISPLAY_CLIP_HORIZONTAL Gravity.DISPLAY_CLIP_HORIZONTAL} and
         * {@link Gravity#DISPLAY_CLIP_VERTICAL Gravity.DISPLAY_CLIP_VERTICAL} here
         * to control the behavior of
         * {@link Gravity#applyDisplay(int, android.graphics.Rect, android.graphics.Rect)
         * Gravity.applyDisplay}.
         *
         * @see Gravity
         */
        public int gravity;

android.view.WindowManager.LayoutParams中的x，y屬性：

/**
         * X position for this window.  With the default gravity it is ignored.
         * When using {@link Gravity#LEFT} or {@link Gravity#START} or {@link Gravity#RIGHT} or
         * {@link Gravity#END} it provides an offset from the given edge.
         */
        @ViewDebug.ExportedProperty
        public int x;

        /**
         * Y position for this window.  With the default gravity it is ignored.
         * When using {@link Gravity#TOP} or {@link Gravity#BOTTOM} it provides
         * an offset from the given edge.
         */
        @ViewDebug.ExportedProperty
        public int y;

0xff

想要做左上角爲座標原點，最好設置：mParams.gravity = Gravity.LEFT | Gravity.TOP;

另可參考：
http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2012/1105/509.html