Android，如何清除大多数手机中可以从主页按钮获得的最近任务列表？反射(reflection)是一种可能的方式吗？

Question

我正在写一个启动器，它需要从系统中清除最近的应用程序/任务列表，而不是“没有在最近的任务列表中显示我的应用程序”，但我现在对此一无所知。我在 stackoverflow 中搜索过，只有 this issue匹配但答案没有任何帮助。其他人也问过同样的问题，他提到了来自 Android 4.0 的 RemoveTask。是的，我已经检查了Android 2.3.7和Android 4.0的源代码，在一个回合估计，如果我能删除ActivityMangerService.Java中定义的mRecentTasks列表，我想我几乎可以到达终点:

final ArrayList<TaskRecord> mRecentTasks = new ArrayList<TaskRecord>();

另一个可能有用的定义:

static ActivityManagerService mSelf;
public static ActivityManagerService self() {
    return mSelf;
}

因为我不熟悉Java&refelction，我需要帮助清除这个列表的方式，下面是我的代码:

    public static <T> void clearRecentTaskList(Launcher launcher){
    ActivityManager am = (ActivityManager) launcher.getSystemService(Context.ACTIVITY_SERVICE);
    Object systemRecentTask = new ArrayList<T>();

    Object receiver = null;
    Field recentTaskList = null;
    Class<?> service = null;
    Field self = null;        


    try {
        service = Class.forName("com.android.server.am.ActivityManagerService");
        Log.d(LOG_TAG, "clearRecentTaskList, service gotton"+service.getName());
    } catch (ClassNotFoundException e2) {
        Log.d(LOG_TAG, "clearRecentTaskList, class service not found");
    }

    try {
        self = service.getDeclaredField("mSelf");
    } catch (SecurityException e2) {
        Log.d(LOG_TAG, "clearRecentTaskList, SecurityException during get mSelf");

    } catch (NoSuchFieldException e2) {
        Log.d(LOG_TAG, "clearRecentTaskList, NoSuchFieldException during get mSelf");
    }
    Log.d(LOG_TAG, "clearRecentTaskList, self  gotton " + self.toGenericString());

    try {
        self.setAccessible(true);
        receiver = self.get(null);
    } catch (IllegalArgumentException e2) {
        Log.d(LOG_TAG, "clearRecentTaskList, IllegalArgumentException during use self to get the receiver");
    } catch (IllegalAccessException e2) {
        Log.d(LOG_TAG, "clearRecentTaskList, IllegalAccessException during use self to get the receiver");
    }

    if ( receiver != null){
        Log.d(LOG_TAG, "clearRecentTaskList, receiver is : "+receiver.toString());
    } else {
        Log.d(LOG_TAG, "clearRecentTaskList, receiver is NULL");
    }


    try {
        recentTaskList = service.getDeclaredField("mRecentTasks");
        recentTaskList.setAccessible(true);
        Log.d(LOG_TAG, "clearRecentTaskList, recentTaskList gotton"+recentTaskList.toGenericString());

        try {
            systemRecentTask = recentTaskList.get(receiver);
        } catch (IllegalArgumentException e1) {
            Log.d(LOG_TAG, "IllegalArgumentException during try to clearRecentTask");
        } catch (IllegalAccessException e1) {
            Log.d(LOG_TAG, "IllegalAccessException during try to clearRecentTask");
        }

        Log.d(LOG_TAG, "Try to print the size of recent task: "+((ArrayList<T>) systemRecentTask).size());

    } catch (SecurityException e) {
        Log.d(LOG_TAG, "SecurityException during try to clearRecentTask");
    } catch (NoSuchFieldException e) {
        Log.d(LOG_TAG, "NoSuchFieldException during try to clearRecentTask");
    }   
}

使用这个函数，我总是遇到“NullPointerException”，因为接收者是自己得到的null。我已经尝试过另一种方式(如果我删除所有 try/catch):

self = service.getDeclaredMethod("mSelf", null);
receiver = self.invoke(null, null); // mSelf is a static method which in ActivityMangerService class

同样的结果，获取不到ActivityManagerService的实例，然后获取不到mRecentTasks。任何意见表示赞赏，虽然我不知道“如何删除此列表中的所有项目”，但这可能是另一个问题。

谢谢。

Answer 1

虽然我可以编辑我之前的答案，但我在不同项目中使用的这个解决方案完全不同(而且更容易)，所以最好重新开始......

在这种情况下，我只是使用反射来访问 ActivityManager 的 removeTask() 方法，并将所有这些包装到 MyActivityManager 的便利类中，如下所示:

import java.lang.reflect.Method;

public class MyActivityManager {


    private ActivityManager mActivityManager = null;
    private Method mRemoveTask;

    public MyActivityManager(Context context) {
        try {
            Class<?> activityManagerClass = Class.forName("android.app.ActivityManager");
            mActivityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);

            mRemoveTask = activityManagerClass.getMethod("removeTask", new Class[] { int.class, int.class });
            mRemoveTask.setAccessible(true);

        }
        catch ( ClassNotFoundException e ) {
            Log.i("MyActivityManager", "No Such Class Found Exception", e);
        }
        catch ( Exception e ) {
            Log.i("MyActivityManager", "General Exception occurred", e);
        }
    }

    /**
     * If set, the process of the root activity of the task will be killed
     * as part of removing the task.
     */
    public static final int REMOVE_TASK_KILL_PROCESS = 0x0001;

    /**
     * Completely remove the given task.
     *
     * @param taskId Identifier of the task to be removed.
     * @param flags Additional operational flags.  May be 0 or
     * {@link #REMOVE_TASK_KILL_PROCESS}.
     * @return Returns true if the given task was found and removed.
     */
    public boolean removeTask(int taskId, int flags) {
        try {
            return (Boolean) mRemoveTask.invoke(mActivityManager, Integer.valueOf(taskId), Integer.valueOf(flags) );
        } catch (Exception ex) {
            Log.i("MyActivityManager", "Task removal failed", ex);
        }
        return false;
    }

    public void clearRecentTasks() {
        List<RecentTaskInfo> recents = mActivityManager.getRecentTasks(1000, ActivityManager.RECENT_IGNORE_UNAVAILABLE);
        // Start from 1, since we don't want to kill ourselves!
        for( int i=1; i < recents.size(); i++ ) {
            removeTask( recents.get(i).persistentId, 0);
        }
    }

}

然后，当我想清除最近的任务时，我会执行以下操作:

new MyActivityManager(this).clearRecentTasks();

这可能需要其中一个或两个才能起作用:

<uses-permission android:name="android.permission.GET_TASKS" />
<uses-permission android:name="android.permission.REORDER_TASKS" />

在我的例子中，应用程序是使用系统权限安装的。