问题来源

在进行新Settings App 核心功能取代旧Settings App的尾声阶段，碰到的问题就是，有一些服务不得不调用到旧Settings的功能、服务。在保留旧Settings App的情况下（毕竟有的功能、服务，新Settings App无法取代），最大化减少新、旧Settings App带来的突兀感，一是隐藏掉旧Settings App的桌面图标，二是在一的基础上，从Recents（最近使用列表）不显示旧Settings App的相关Activity。

第一个方法很好解决，只需在framework/base/package/Settings/AndroidManifest.xml中，将Settings注册的activity中，把 <category android:name="android.intent.category.LAUNCHER" />注释掉即可，这样子桌面就不会有Settings图标了。

第二个方法也很好解决，只需在framework/base/package/Settings/AndroidManifest.xml中，将注册的Activity加上android:excludeFromRecents="true"即可。

可是问题在于，AndroidManifest.xml中，注册的Activity数量过于多，如果我们一行一行加上上述代码，虽然需求很简单解决，但实在过于浪费时间。

于是，我们可以想到，从Recents源码下手，来解决我们的需求。

问题解析

当我们点击导航栏的Recents时候，根据Log，我们会发现，触发了framework/base/package/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java中的onRecentsTouch(View v, MotionEvent event)事件

java

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// additional optimization when we have software system buttons - start loading the recent
// tasks on touch down
private boolean onRecentsTouch(View v, MotionEvent event) {
    int action = event.getAction() & MotionEvent.ACTION_MASK;
    if (action == MotionEvent.ACTION_DOWN) {
        mCommandQueue.preloadRecentApps();
    } else if (action == MotionEvent.ACTION_CANCEL) {
        mCommandQueue.cancelPreloadRecentApps();
    } else if (action == MotionEvent.ACTION_UP) {
        if (!v.isPressed()) {
            mCommandQueue.cancelPreloadRecentApps();
        }
    }
    return false;
}

上述代码中，调用了mCommandQueue.preloadRecentApps();

framework/base/package/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java

java

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case MSG_PRELOAD_RECENT_APPS:
	for (int i = 0; i < mCallbacks.size(); i++) {
    	mCallbacks.get(i).preloadRecentApps();
	}
	break;

java

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public interface Callbacks {
    preloadRecentApps();
}

很显然，子类实现了CommandQueue.Callback接口，调用了preloadRecentApps();

查找哪些类实现该接口

shell

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find ./ -name "*.java" | xargs grep "CommandQueue.Callbacks"

结果：

shell

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find ./ -iname "*.java" | xargs grep "CommandQueue.Callbacks"
./SystemUI/tests/src/com/android/systemui/statusbar/CommandQueueTest.java:import com.android.systemui.statusbar.CommandQueue.Callbacks;
./SystemUI/src/com/android/systemui/pip/PipUI.java:public class PipUI extends SystemUI implements CommandQueue.Callbacks {
./SystemUI/src/com/android/systemui/recents/Recents.java:        implements RecentsComponent, CommandQueue.Callbacks {
./SystemUI/src/com/android/systemui/qs/QSFragment.java:public class QSFragment extends Fragment implements QS, CommandQueue.Callbacks {
./SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarPolicy.java:import com.android.systemui.statusbar.CommandQueue.Callbacks;
./SystemUI/src/com/android/systemui/statusbar/phone/CollapsedStatusBarFragment.java:public class CollapsedStatusBarFragment extends Fragment implements CommandQueue.Callbacks {
./SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java:import com.android.systemui.statusbar.CommandQueue.Callbacks;
./SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java:    // ----- CommandQueue Callbacks -----
./SystemUI/src/com/android/systemui/statusbar/phone/StatusBarIconControllerImpl.java:        ConfigurationListener, Dumpable, CommandQueue.Callbacks, StatusBarIconController {
./SystemUI/src/com/android/systemui/statusbar/phone/StatusBar.java:        OnHeadsUpChangedListener, CommandQueue.Callbacks, ZenModeController.Callback,
./SystemUI/src/com/android/systemui/statusbar/phone/LightBarTransitionsController.java:import com.android.systemui.statusbar.CommandQueue.Callbacks;
./SystemUI/src/com/android/systemui/statusbar/tv/TvStatusBar.java:import com.android.systemui.statusbar.CommandQueue.Callbacks;
./SystemUI/src/com/android/systemui/statusbar/policy/Clock.java:public class Clock extends TextView implements DemoMode, Tunable, CommandQueue.Callbacks,
./SystemUI/src/com/android/systemui/globalactions/GlobalActionsComponent.java:import com.android.systemui.statusbar.CommandQueue.Callbacks;
./SystemUI/src/com/android/systemui/globalactions/GlobalActionsImpl.java:public class GlobalActionsImpl implements GlobalActions, CommandQueue.Callbacks {
./SystemUI/src/com/android/systemui/fingerprint/FingerprintDialogImpl.java:public class FingerprintDialogImpl extends SystemUI implements CommandQueue.Callbacks {
./SystemUI/src/com/android/systemui/util/Utils.java:    public static class DisableStateTracker implements CommandQueue.Callbacks,
./SystemUI/src/com/android/systemui/util/Utils.java:         * {@link com.android.systemui.statusbar.CommandQueue.Callbacks#disable(int, int)}.

搜索到的结果比较多，通过猜测，个人第一反应觉得**./SystemUI/src/com/android/systemui/recents/Recents.java: implements RecentsComponent, CommandQueue.Callbacks {** 是我们要找的类了。

java

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public class Recents extends SystemUI implements RecentsComponent, CommandQueue.Callbacks {
    
    private RecentsImpl mImpl;
    
    @Override
    public void preloadRecentApps() {
        // Ensure the device has been provisioned before allowing the user to interact with
        // recents
        if (!isUserSetup()) {
            return;
        }

        if (mOverviewProxyService.getProxy() != null) {
            // TODO: Proxy to Launcher
            return;
        }

        int currentUser = sSystemServicesProxy.getCurrentUser();
        if (sSystemServicesProxy.isSystemUser(currentUser)) {
            mImpl.preloadRecents();
        } else {
            if (mSystemToUserCallbacks != null) {
                IRecentsNonSystemUserCallbacks callbacks =
                    mSystemToUserCallbacks.getNonSystemUserRecentsForUser(currentUser);
                if (callbacks != null) {
                    try {
                        callbacks.preloadRecents();
                    } catch (RemoteException e) {
                        Log.e(TAG, "Callback failed", e);
                    }
                } else {
                    Log.e(TAG, "No SystemUI callbacks found for user: " + currentUser);
                }
            }
        }
    }   

}

通过日志打印，发现调用了mImpl.preloadRecents();

查看framework/base/package/SystemUI/src/com/android/systemui/recents/RecentsImpl.java

java

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public void preloadRecents() {
    if (ActivityManagerWrapper.getInstance().isScreenPinningActive()) {
        return;
    }

    // Skip preloading recents when keyguard is showing
    final StatusBar statusBar = getStatusBar();
    if (statusBar != null && statusBar.isKeyguardShowing()) {
        return;
    }

    // Preload only the raw task list into a new load plan (which will be consumed by the
    // RecentsActivity) only if there is a task to animate to.  Post this to ensure that we
    // don't block the touch feedback on the nav bar button which triggers this.
    mHandler.post(() -> {
        SystemServicesProxy ssp = Recents.getSystemServices();
        if (!ssp.isRecentsActivityVisible(null)) {
            ActivityManager.RunningTaskInfo runningTask =
                ActivityManagerWrapper.getInstance().getRunningTask();
            if (runningTask == null) {
                return;
            }

            RecentsTaskLoader loader = Recents.getTaskLoader();
            sInstanceLoadPlan = new RecentsTaskLoadPlan(mContext);
            loader.preloadTasks(sInstanceLoadPlan, runningTask.id);
            TaskStack stack = sInstanceLoadPlan.getTaskStack();
            if (stack.getTaskCount() > 0) {
                preloadIcon(runningTask.id);
                updateHeaderBarLayout(stack, null /* window rect override*/);
            }
        }
    });
}

调用了loader.preloadTasks(sInstanceLoadPlan, runningTask.id);

查看framework/base/package/SystemUI/shared/src/com/android/systemui/shared/recents/model/RecentsTaskLoader.java

java

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/** Preloads recents tasks using the specified plan to store the output. */
public synchronized void preloadTasks(RecentsTaskLoadPlan plan, int runningTaskId) {
    preloadTasks(plan, runningTaskId, ActivityManagerWrapper.getInstance().getCurrentUserId());
}

/** Preloads recents tasks using the specified plan to store the output. */
public synchronized void preloadTasks(RecentsTaskLoadPlan plan, int runningTaskId,
                                      int currentUserId) {
    try {
        Trace.beginSection("preloadPlan");
        plan.preloadPlan(new PreloadOptions(), this, runningTaskId, currentUserId);
    } finally {
        Trace.endSection();
    }
}

调用了plan.preloadPlan(new PreloadOptions(), this, runningTaskId, currentUserId);

查看framework/base/package/SystemUI/shared/src/com/android/systemui/shared/recents/model/RecentsTaskLoaderPlan.java

java

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public void preloadPlan(PreloadOptions opts, RecentsTaskLoader loader, int runningTaskId,
                        int currentUserId) {
    Resources res = mContext.getResources();
    ArrayList<Task> allTasks = new ArrayList<>();
    if (mRawTasks == null) {
        mRawTasks = ActivityManagerWrapper.getInstance().getRecentTasks(
            ActivityManager.getMaxRecentTasksStatic(), currentUserId);

        // Since the raw tasks are given in most-recent to least-recent order, we need to reverse it
        Collections.reverse(mRawTasks);
    }

    int taskCount = mRawTasks.size();
    for (int i = 0; i < taskCount; i++) {
        ActivityManager.RecentTaskInfo t = mRawTasks.get(i);

        // Compose the task key
        final ComponentName sourceComponent = t.origActivity != null
            // Activity alias if there is one
            ? t.origActivity
            // The real activity if there is no alias (or the target if there is one)
            : t.realActivity;
        final int windowingMode = t.configuration.windowConfiguration.getWindowingMode();
        TaskKey taskKey = new TaskKey(t.persistentId, windowingMode, t.baseIntent,
                                      sourceComponent, t.userId, t.lastActiveTime);

        boolean isFreeformTask = windowingMode == WINDOWING_MODE_FREEFORM;
        boolean isStackTask = !isFreeformTask;
        boolean isLaunchTarget = taskKey.id == runningTaskId;

        ActivityInfo info = loader.getAndUpdateActivityInfo(taskKey);
        if (info == null) {
            continue;
        }

        // Load the title, icon, and color
        String title = opts.loadTitles
            ? loader.getAndUpdateActivityTitle(taskKey, t.taskDescription)
            : "";
        String titleDescription = opts.loadTitles
            ? loader.getAndUpdateContentDescription(taskKey, t.taskDescription)
            : "";
        Drawable icon = isStackTask
            ? loader.getAndUpdateActivityIcon(taskKey, t.taskDescription, false)
            : null;
        ThumbnailData thumbnail = loader.getAndUpdateThumbnail(taskKey,
                                                               false /* loadIfNotCached */, false /* storeInCache */);
        int activityColor = loader.getActivityPrimaryColor(t.taskDescription);
        int backgroundColor = loader.getActivityBackgroundColor(t.taskDescription);
        boolean isSystemApp = (info != null) &&
            ((info.applicationInfo.flags & ApplicationInfo.FLAG_SYSTEM) != 0);

        // TODO: Refactor to not do this every preload
        if (mTmpLockedUsers.indexOfKey(t.userId) < 0) {
            mTmpLockedUsers.put(t.userId, mKeyguardManager.isDeviceLocked(t.userId));
        }
        boolean isLocked = mTmpLockedUsers.get(t.userId);

        // Add the task to the stack
        Task task = new Task(taskKey, icon,
                             thumbnail, title, titleDescription, activityColor, backgroundColor,
                             isLaunchTarget, isStackTask, isSystemApp, t.supportsSplitScreenMultiWindow,
                             t.taskDescription, t.resizeMode, t.topActivity, isLocked);

        allTasks.add(task);
    }

    // Initialize the stacks
    mStack = new TaskStack();
    mStack.setTasks(allTasks, false /* notifyStackChanges */);
}

可以注意到，在for循环中，遍历了任务栈，将符合条件的最近添加到allTasks中，于是我们就找到了我们需要改动的地方，通过添加条件筛选，过滤掉我们不需要的旧Settings App

java

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public void preloadPlan(PreloadOptions opts, RecentsTaskLoader loader, int runningTaskId,
                        int currentUserId) {
    int taskCount = mRawTasks.size();
    for (int i = 0; i < taskCount; i++) {
        ActivityManager.RecentTaskInfo t = mRawTasks.get(i);

        ActivityInfo info = loader.getAndUpdateActivityInfo(taskKey);
        if (info == null) {
            continue;
        }
        
+       /// M: modify by wayhoi, hidden Settings App 
+       if (info.packageName.equals("com.android.settings")) {
+           continue;
+       }

    }
}