使用WindowManager窗口管理员，把View显示在屏幕中间

        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);