Android AccessibilityService拦截事件及VR眼镜返回按键捕捉

最新推荐文章于 2023-01-08 13:19:26 发布

原创最新推荐文章于 2023-01-08 13:19:26 发布 · 5.1k 阅读

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#AccessibilityService #android #VR #BACK

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本文介绍了如何使用Android的AccessibilityService来拦截VR眼镜上的返回按键。通过代码示例展示了如何设置AccessibilityService以拦截按键事件，并讨论了在实际应用中遇到的问题：虽然能捕获常规按键，但无法捕获VR眼镜的返回键。作者计划在后续文章中通过源码分析解决这一问题。

公司项目有个需求，就是拦截VR眼镜上的返回按键，既然要拦截按键，私以为有以下两种方式：

1. AccessibilityService，Android辅助工具可以实现拦截按键、焦点变化、触摸时间、姿势等。

2. 使用adb shell命令，getevent方式分析获取到的按键的值。

第一种方法最简单，代码如下：

AccessibilityService.java

public class AccessBackKeyService extends AccessibilityService {

        private static final String TAG = "AccessBackKeyService";

        @Override
        protected boolean onKeyEvent(KeyEvent event) {
            Log.i(TAG, "onKeyEvent");

            if(event.getAction() == KeyEvent.ACTION_DOWN){
                return super.onKeyEvent(event);
            }
            Log.i(TAG, "onKeyEvent ACTION_DOWN");

            int key = event.getKeyCode();
            switch(key){
                case KeyEvent.KEYCODE_VOLUME_DOWN:
                    break;
                case KeyEvent.KEYCODE_VOLUME_UP:
                    break;
                case KeyEvent.KEYCODE_BACK:

                   Log.i(TAG, "KEYCODE_BACK");
                    break; 
                case KeyEvent.KEYCODE_ESCAPE: break; 
          } 
      return super.onKeyEvent(event); 
     } 
    @Override 
    public void onInterrupt() { } 
    @Override 
    public void onCreate() { 
       super.onCreate(); 
     } 
    @Override 
    public void onAccessibilityEvent(AccessibilityEvent event) {  
        int eventType = event.getEventType();  
        String eventTypeName = "";  
        switch (eventType) {  
        case AccessibilityEvent.TYPE_VIEW_CLICKED:  
            eventTypeName = "TYPE_VIEW_CLICKED";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_FOCUSED:  
            eventTypeName = "TYPE_VIEW_FOCUSED";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_LONG_CLICKED:  
            eventTypeName = "TYPE_VIEW_LONG_CLICKED";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_SELECTED:  
            eventTypeName = "TYPE_VIEW_SELECTED";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED:  
            eventTypeName = "TYPE_VIEW_TEXT_CHANGED";  
            break;  
        case AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED:  
            eventTypeName = "TYPE_WINDOW_STATE_CHANGED"; 
            break;  
        case AccessibilityEvent.TYPE_NOTIFICATION_STATE_CHANGED:  
            eventTypeName = "TYPE_NOTIFICATION_STATE_CHANGED";  
            break;  
        case AccessibilityEvent.TYPE_TOUCH_EXPLORATION_GESTURE_END:  
            eventTypeName = "TYPE_TOUCH_EXPLORATION_GESTURE_END";  
            break;  
        case AccessibilityEvent.TYPE_ANNOUNCEMENT:  
            eventTypeName = "TYPE_ANNOUNCEMENT";  
            break;  
        case AccessibilityEvent.TYPE_TOUCH_EXPLORATION_GESTURE_START:  
            eventTypeName = "TYPE_TOUCH_EXPLORATION_GESTURE_START";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_HOVER_ENTER:  
            eventTypeName = "TYPE_VIEW_HOVER_ENTER";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_HOVER_EXIT:  
            eventTypeName = "TYPE_VIEW_HOVER_EXIT";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_SCROLLED:  
            eventTypeName = "TYPE_VIEW_SCROLLED";  
            break;  
        case AccessibilityEvent.TYPE_VIEW_TEXT_SELECTION_CHANGED:  
            eventTypeName = "TYPE_VIEW_TEXT_SELECTION_CHANGED";  
            break;  
        case AccessibilityEvent.TYPE_WINDOW_CONTENT_CHANGED:  
            eventTypeName = "TYPE_WINDOW_CONTENT_CHANGED";  
            break;  
        }  
        Log.i(TAG, "eventType:" + eventType);  
        Log.i(TAG, "eventTypeName:" + eventTypeName);  
    }  
    @Override protected boolean onGesture(int gestureId) { return super.onGesture(gestureId); }
}

AndroidMenifest.xml

 <service
            android:name="com.test.accessbackkey.AccessBackKeyService"
            android:enabled="true"
            android:exported="true"
            android:label="@string/app_name"
            android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE" >
            <intent-filter>
                <action android:name="android.accessibilityservice.AccessibilityService" />
            </intent-filter>

            <meta-data
                android:name="android.accessibilityservice"
                android:resource="@xml/access_backkey_service" />
        </service>

access_backkey_service.xml

<?xml version="1.0" encoding="utf-8"?>
<accessibility-service xmlns:android="http://schemas.android.com/apk/res/android"
    android:accessibilityEventTypes="typeAllMask"
    android:accessibilityFeedbackType="feedbackGeneric"
    android:accessibilityFlags="flagRequestFilterKeyEvents"
    android:canRetrieveWindowContent="true"
    android:canRequestFilterKeyEvents="true"
    android:description="@string/access_description"
    android:notificationTimeout="100"/>

完成了以上的工作后，在MainActivity.java去启动辅助功能设置，手动打开开关之后就可以开始拦截按键了。

    private void startService() {

        Intent intent = new Intent();

        intent.setAction(Settings.ACTION_ACCESSIBILITY_SETTINGS);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

        startActivity(intent);


    }

http://blog.youkuaiyun.com/dd864140130/article/details/51794318 AccessibilityService其他的知识可以参考这篇文章。

经测试，虚拟按键BACK键、HOME键、最近任务键和音量键全部拦截到，然而我们另一项任务却没有完成，始终拦截不到VR眼镜的返回键，甚至keyEvent都没有，这是为什么呢？莫非它是一个MotionEvent，让我们来验证一下。在MainActivity.java中复写onKeyDown方法

 @Override
    public boolean onTouchEvent(MotionEvent event) {

        int action = event.getAction();


        Log.i("key", "event source:"+event.getSource());


        return super.onTouchEvent(event);
    }

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {

        if(keyCode == KeyEvent.KEYCODE_BACK){
            Log.i("key", " main KEYCODE_BACK source:"+event.getSource());
        }

        return super.onKeyDown(keyCode, event);
    }
}

我们按下VR眼镜的BACK键之后onTouchEvent并没有反应，反倒是onKeyDown收到了，证明了VR眼镜的BACK键是Key事件，而不是MotionEvent。

为什么AccessibilityService的onKeyEvent没有收到BACK键，而这里却收到了呢？下一篇我们将从源码进行分析。