使用WindowManager窗口管理员，把View显示在屏幕中间

太简单了，直接看代码。

        WindowManager mWindowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
        TextView mTrackingText = new TextView(this);
        mTrackingText.setTextColor(Color.WHITE);
        mTrackingText.setText("00:00");
        mTrackingText.setTextSize(30);
        WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
                LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.TYPE_APPLICATION,
                WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                        | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                PixelFormat.TRANSLUCENT);
        mWindowManager.addView(mTrackingText, lp);