Android开发学习之WindowManager实现弹窗

我们知道PopupWindow可以实现弹窗，但是如果要实现系统弹窗(即悬浮在所有view、dialog之上)，需要调用通过反射PopupWindow类的私有方法setWindowLayoutType()。但如果某个手机厂商的修改了framework层，这种反射调用就失败了，因此如果要实现系统弹窗，需要另辟蹊径。

解决方法就是使用WindowManager，及用来设置参数的WindowManager.LayoutParams

	WindowManager mWindowManager = getWindowManager();
	WindowManager.LayoutParams mWindowLayoutParams = new WindowManager.LayoutParams();

		mWindowView = (LinearLayout) LayoutInflater.from(this).inflate(R.layout.window_layout, null);

	mWindowLayoutParams.gravity = Gravity.START;
	mWindowLayoutParams.x = 0;
	mWindowLayoutParams.y = 0;

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            mWindowLayoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            mWindowLayoutParams.type = WindowManager.LayoutParams.TYPE_PHONE;
        }

        mWindowLayoutParams.flags |=  WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL;
        mWindowLayoutParams.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        mWindowView.setOnTouchListener(new View.OnTouchListener() { // 事件坐标转换
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                int[] popupLocation = new int[2];
                mWindowView.getLocationOnScreen(popupLocation);

                event.offsetLocation(popupLocation[0], popupLocation[1]);
                MainActivity.this.dispatchTouchEvent(event);
                return false;
            }
        });

WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL表示允许该弹窗外面的触摸事件发送到其下面的窗口，否则所有触摸事件都会发送到当前的弹窗窗口；
WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE表示弹窗不获取焦点，因此该弹窗不会接收任何按钮或按键事件，对应的事件会传到其下面的窗口。
mWindowView是弹窗的根布局，当触摸事件从弹窗传到下面的activity时，需要进行坐标转换。

		mWindowLayoutParams.format = PixelFormat.TRANSLUCENT;

		mWindowLayoutParams.height = 1800; // 单位是像素
        mWindowLayoutParams.width = WindowManager.LayoutParams.WRAP_CONTENT;

		mWindowLayoutParams.softInputMode = WindowManager.LayoutParams.SOFT_INPUT_ADJUST_RESIZE;

    @Override
    protected void onStop() {
        super.onStop();
        mWindowManager.removeView(mWindowView); // 移除view
    }

    @Override
    protected void onResume() {
        super.onResume();
        mWindowManager.addView(mWindowView, mWindowLayoutParams); // 添加view
    }

参见gitlab仓库