Window与WindowManager

Window

• Window表示窗口，比如可以实现桌面或者锁屏上的类似悬浮窗的效果，Android中所有的视图都是通过Window来呈现的，不管是Activity、Dialog还是Toast，实际上他们都是附加在Window上的，WindowManager提供了对这些Window的统一管理功能

Window与WindowManager的联系

• 为了分析Window的工作机制，需要先了解如何使用WindowManager来添加一个Window

WindowManager manager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(width, height, type, flags, format);
manager.addView(btn, layoutParams);

• WindowManager.LayoutParams的属性中type和flags参数比较重要

• flags的常用选项：

flag选项	意义
FLAG_NOT_FOCUSABLE = 0x00000008	表示此Window不需要获取焦点，不接受各种输入事件，此标记会同时启用FLAG_NOT_TOUCH_MODAL，最终事件会直接传递给下层具有焦点的Window
FLAG_NOT_TOUCH_MODAL = 0x00000020	自己Window区域内的事件自己处理；自己Window区域外的事件传递给底层Window处理，一般这个选项会默认开启，否则其他Window无法接受事件
FLAG_SHOW_WHEN_LOCKED	让Window无法收到事件

• Type参数是int类型的，表示Window的类型，Window有三种类型：应用Window、子Window和系统Window

• 应用Window对应着一个Activity，子Window不能独立存在（要依附在特定的父Window中），系统Window需要权限才能进行创建（Toast和系统状态栏）

Window层级：

• 应用Window的层级范围：1~99
• 子Window的层级范围：1000~1999
• 系统Window的层级范围：2000~2999
• 注意：

• 层级大的Window会覆盖在层级小的Window上
• 使用系统级Window，需要在AndroidMenifest.xml中配置

WindowManager的功能：

• 常用功能（定义在ViewManager中）：

public interface WindowManager ectends ViewManager
public interface ViewMananger{
    //添加View
    public void addView(View view, ViewGroup.LayoutParams params);
    //更新View
    public void updateViewLayout(View view, ViewGroup.LayoutParams params);
    //删除View
    public void remoteView(View view);
}

eg：桌面悬浮窗：

public class WindowDemoActivity extends AppCompatActivity implements View.OnTouchListener {


    private Button add_btn;
    private Button rem_btn;
    private CircleImageView imageView;
    private WindowManager.LayoutParams layoutParams;
    private WindowManager windowManager;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_window_demo);


        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.M){
            Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION);
            startActivityForResult(intent, 100);
        }
        add_btn = (Button)findViewById(R.id.add_btn);
        rem_btn = (Button)findViewById(R.id.rem_btn);
        windowManager = (WindowManager)getApplicationContext().getSystemService(Context.WINDOW_SERVICE);
        add_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                imageView = new CircleImageView(getApplicationContext());
                imageView.setImageResource(R.drawable.androidfirst);
                layoutParams = new WindowManager.LayoutParams(
                        WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.WRAP_CONTENT, 2099, WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
                        | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                        | WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED, PixelFormat.TRANSPARENT
                );
                layoutParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ERROR;
                layoutParams.gravity = Gravity.TOP | Gravity.LEFT;
                layoutParams.x = 0;
                layoutParams.y = 300;
                imageView.setOnTouchListener(WindowDemoActivity.this);
                windowManager.addView(imageView, layoutParams);
            }
        });
        rem_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(imageView != null) {
                    windowManager.removeView(imageView);
                }
            }
        });
    }




    @Override
    public boolean onTouch(View v, MotionEvent event) {


        int rawX = (int) event.getRawX();
        int rawY = (int) event.getRawY();
        switch (event.getAction()){
            case MotionEvent.ACTION_MOVE:{
                layoutParams.x = rawX;
                layoutParams.y = rawY;
                windowManager.updateViewLayout(imageView, layoutParams);
                break;
            }
            default:
                break;
        }
        return false;
    }
}