Window和WindowManager

Window和WindowManager
Window表示一个窗口，可以实现在桌面上显示悬浮窗，Window是一个抽象类，具体实现是PhoneWindow。通过WindowManager创建Window，WindowManager是外界访问Window的入口，Window的具体实现位于WindowManagerService，WindowManager和WindowManagerService交互是一个IPC过程，Window实际是View的直接管理者

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
 
val btn = Button(baseContext)
        btn.text = "button"
        btn.setOnClickListener { toast("Window Demo") }
        val layoutParams = LayoutParams(LayoutParams.WRAP_CONTENT,
                LayoutParams.WRAP_CONTENT, 0, 0, PixelFormat.TRANSLUCENT)
        layoutParams.type = LayoutParams.TYPE_SYSTEM_OVERLAY/TYPE_SYSTEM_ERROR/TYPE_SYSTEM_OVERLAY/TYPE_APPLICATION_PANEL
        //不需要获取焦点，不需要接收各种输入事件
        layoutParams.flags = LayoutParams.FLAG_NOT_FOCUSABLE
                //window 区域以为的单击事件传递给底层window，当前window区域以内的自己处理，否则其他window无法收到单击事件
                .or(LayoutParams.FLAG_NOT_TOUCH_MODAL)
                //window 显示在锁屏上
                .or(LayoutParams.FLAG_SHOW_WHEN_LOCKED)
        layoutParams.gravity = Gravity.LEFT.or(Gravity.TOP)
        layoutParams.x = 100
        layoutParams.y = 300
        windowManager.addView(btn, layoutParams)

public interface WindowManager extends ViewManager

public interface ViewManager
{
    /**
     * Assign the passed LayoutParams to the passed View and add the view to the window.
     * <p>Throws {@link android.view.WindowManager.BadTokenException} for certain programming
     * errors, such as adding a second view to a window without removing the first view.
     * <p>Throws {@link android.view.WindowManager.InvalidDisplayException} if the window is on a
     * secondary {@link Display} and the specified display can't be found
     * (see {@link android.app.Presentation}).
     * @param view The view to be added to this window.
     * @param params The LayoutParams to assign to view.
     */
    public void addView(View view, ViewGroup.LayoutParams params);
    public void updateViewLayout(View view, ViewGroup.LayoutParams params);
    public void removeView(View view);
}

添加触摸事件

val btn = Button(baseContext)
        btn.isClickable = true
        btn.text = "button"

//        btn.setOnClickListener { toast("Window Demo") }
        val layoutParams = LayoutParams(LayoutParams.WRAP_CONTENT,
                LayoutParams.WRAP_CONTENT, 0, 0, PixelFormat.TRANSLUCENT)
//        layoutParams.type = LayoutParams.TYPE_SYSTEM_OVERLAY
        layoutParams.type =LayoutParams.TYPE_APPLICATION_PANEL
        layoutParams.flags =
                //不需要获取焦点，不需要接收各种输入事件
                LayoutParams.FLAG_NOT_FOCUSABLE
                        //window 区域以为的单击事件传递给底层window，当前window区域以内的自己处理，否则其他window无法收到单击事件
                        .or(LayoutParams.FLAG_NOT_TOUCH_MODAL)
                        //window 显示在锁屏上
                        .or(LayoutParams.FLAG_SHOW_WHEN_LOCKED)
        layoutParams.gravity = Gravity.LEFT.or(Gravity.TOP)
        layoutParams.x = 100
        layoutParams.y = 300
        btn.setOnTouchListener { v, event ->
            when (event.action) {
                MotionEvent.ACTION_MOVE -> {
                    layoutParams.x = event.rawX.toInt()
                    layoutParams.y = event.rawY.toInt()
                    windowManager.updateViewLayout(btn, layoutParams)
                }
                else -> {
                    Log.i("touch", "else")
                }
            }
            return@setOnTouchListener false
        }
        windowManager.addView(btn, layoutParams)

Window内部机制

Window是抽象概念，每一个Window对应一个View和ViewRootImpl，以View的形式存在

接口WindowManager实现类WindowManagerImpl

@Override
public void addView(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
       applyDefaultToken(params);
       mGlobal.addView(view, params, mContext.getDisplay(), mParentWindow);
}

@Override
public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
       applyDefaultToken(params);
       mGlobal.updateViewLayout(view, params);
}
   
@Override
public void removeView(View view) {
       mGlobal.removeView(view, false);
}