Window机制

public void addView(View view, ViewGroup.LayoutParams params) {
    try {
        if (mGlobal == null)
            mGlobal = WindowManagerGlobal.getInstance();
        mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
    } catch (WindowManager.BadTokenException e) {
        throw new WindowManager.BadTokenException(
            "Unable to add window -- token null is not valid");
    }
}

public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
    if (mGlobal == null)
        mGlobal = WindowManagerGlobal.getInstance();
    mGlobal.updateViewLayout(view, params);
}

private void showCustomWindow() {
    View view = LayoutInflater.from(this).inflate(R.layout.custom_window, null);
    WindowManager.LayoutParams params = new WindowManager.LayoutParams(
        WindowManager.LayoutParams.WRAP_CONTENT,
        WindowManager.LayoutParams.WRAP_CONTENT,
        WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY,
        WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
        PixelFormat.TRANSLUCENT
    );
    WindowManager windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
    windowManager.addView(view, params);
}