Android 屏幕固定

    public void showScreenPinningRequest(int taskId, boolean allowCancel) {
        mScreenPinningRequest.showPrompt(taskId, allowCancel);
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.screen_pinning_ok_button || mRequestWindow == v) {
            try {
                ActivityManagerNative.getDefault().startSystemLockTaskMode(taskId);
            } catch (RemoteException e) {}
        }
        clearPrompt();
    }

    @Override
    public void startSystemLockTaskMode(int taskId) throws RemoteException {
        enforceCallingPermission(MANAGE_ACTIVITY_STACKS, "startSystemLockTaskMode");
        // This makes inner call to look as if it was initiated by system.
        long ident = Binder.clearCallingIdentity();
        try {
            synchronized (this) {
                startLockTaskMode(taskId);
            }
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
    }

    @Override
    public void startLockTaskMode(int taskId) {
        synchronized (this) {
            final TaskRecord task = mStackSupervisor.anyTaskForIdLocked(taskId);
            if (task != null) {
                startLockTaskModeLocked(task);
            }
        }
    }

    void startLockTaskModeLocked(TaskRecord task) {
        if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, "startLockTaskModeLocked: " + task);
        if (task.mLockTaskAuth == LOCK_TASK_AUTH_DONT_LOCK) {
            return;
        }

        // isSystemInitiated is used to distinguish between locked and pinned mode, as pinned mode
        // is initiated by system after the pinning request was shown and locked mode is initiated
        // by an authorized app directly
        final int callingUid = Binder.getCallingUid();
        boolean isSystemInitiated = callingUid == Process.SYSTEM_UID;
        long ident = Binder.clearCallingIdentity();
        try {
            if (!isSystemInitiated) {
                task.mLockTaskUid = callingUid;
                if (task.mLockTaskAuth == LOCK_TASK_AUTH_PINNABLE) {
                    // startLockTask() called by app and task mode is lockTaskModeDefault.
                    if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, "Mode default, asking user");
                    StatusBarManagerInternal statusBarManager =
                            LocalServices.getService(StatusBarManagerInternal.class);
                    if (statusBarManager != null) {
                        statusBarManager.showScreenPinningRequest(task.taskId);
                    }
                    return;
                }

                final ActivityStack stack = mStackSupervisor.getFocusedStack();
                if (stack == null || task != stack.topTask()) {
                    throw new IllegalArgumentException("Invalid task, not in foreground");
                }
            }
            if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, isSystemInitiated ? "Locking pinned" :
                    "Locking fully");
            mStackSupervisor.setLockTaskModeLocked(task, isSystemInitiated ?
                    ActivityManager.LOCK_TASK_MODE_PINNED :
                    ActivityManager.LOCK_TASK_MODE_LOCKED,
                    "startLockTask", true);
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
    }

    void setLockTaskModeLocked(TaskRecord task, int lockTaskModeState, String reason,
            boolean andResume) {

        // Should have already been checked, but do it again.
        if (task.mLockTaskAuth == LOCK_TASK_AUTH_DONT_LOCK) {
            if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK,
                    "setLockTaskModeLocked: Can't lock due to auth");
            return;
        }
        if (isLockTaskModeViolation(task)) {
            Slog.e(TAG_LOCKTASK, "setLockTaskMode: Attempt to start an unauthorized lock task.");
            return;
        }

        if (mLockTaskModeTasks.isEmpty()) {
            // First locktask.
            final Message lockTaskMsg = Message.obtain();
            lockTaskMsg.obj = task.intent.getComponent().getPackageName();
            lockTaskMsg.arg1 = task.userId;
            lockTaskMsg.what = LOCK_TASK_START_MSG;
            lockTaskMsg.arg2 = lockTaskModeState;
            mHandler.sendMessage(lockTaskMsg);
        }
        // Add it or move it to the top.
        if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, "setLockTaskModeLocked: Locking to " + task +
                " Callers=" + Debug.getCallers(4));
        mLockTaskModeTasks.remove(task);
        mLockTaskModeTasks.add(task);

        if (task.mLockTaskUid == -1) {
            task.mLockTaskUid = task.effectiveUid;
        }

        if (andResume) {
            findTaskToMoveToFrontLocked(task, 0, null, reason,
                    lockTaskModeState != LOCK_TASK_MODE_NONE);
            resumeFocusedStackTopActivityLocked();
        } else if (lockTaskModeState != LOCK_TASK_MODE_NONE) {
            handleNonResizableTaskIfNeeded(task, INVALID_STACK_ID, task.stack.mStackId,
                    true /* forceNonResizable */);
        }
    }

    private final class ActivityStackSupervisorHandler extends Handler {

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case LOCK_TASK_START_MSG: {
                    // When lock task starts, we disable the status bars.
                    try {
                        if (mLockTaskNotify == null) {
                            mLockTaskNotify = new LockTaskNotify(mService.mContext);
                        }
                        mLockTaskNotify.show(true);
                        mLockTaskModeState = msg.arg2;
                        if (getStatusBarService() != null) {
                            int flags = 0;
                            if (mLockTaskModeState == LOCK_TASK_MODE_LOCKED) {
                                flags = StatusBarManager.DISABLE_MASK
                                        & (~StatusBarManager.DISABLE_BACK);
                            } else if (mLockTaskModeState == LOCK_TASK_MODE_PINNED) {
                                flags = StatusBarManager.DISABLE_MASK
                                        & (~StatusBarManager.DISABLE_BACK)
                                        & (~StatusBarManager.DISABLE_HOME)
                                        & (~StatusBarManager.DISABLE_RECENT);
                            }
                            getStatusBarService().disable(flags, mToken,
                                    mService.mContext.getPackageName());
                        }
                        mWindowManager.disableKeyguard(mToken, LOCK_TASK_TAG);
                        if (getDevicePolicyManager() != null) {
                            getDevicePolicyManager().notifyLockTaskModeChanged(true,
                                    (String)msg.obj, msg.arg1);
                        }
                    } catch (RemoteException ex) {
                        throw new RuntimeException(ex);
                    }
                } break;

            }

        }
    }

    /**
     * This API should be called by SystemUI only when user perform certain action to dismiss
     * lock task mode. We should only dismiss pinned lock task mode in this case.
     */
    @Override
    public void stopSystemLockTaskMode() throws RemoteException {
        if (mStackSupervisor.getLockTaskModeState() == ActivityManager.LOCK_TASK_MODE_PINNED) {
            stopLockTaskMode();
        } else {
            mStackSupervisor.showLockTaskToast();
        }
    }

    @Override
    public void stopLockTaskMode() {
        final TaskRecord lockTask = mStackSupervisor.getLockedTaskLocked();
        if (lockTask == null) {
            // Our work here is done.
            return;
        }

        final int callingUid = Binder.getCallingUid();
        final int lockTaskUid = lockTask.mLockTaskUid;
        final int lockTaskModeState = mStackSupervisor.getLockTaskModeState();
        if (lockTaskModeState == ActivityManager.LOCK_TASK_MODE_NONE) {
            // Done.
            return;
        } else {
            // Ensure the same caller for startLockTaskMode and stopLockTaskMode.
            // It is possible lockTaskMode was started by the system process because
            // android:lockTaskMode is set to a locking value in the application manifest
            // instead of the app calling startLockTaskMode. In this case
            // {@link TaskRecord.mLockTaskUid} will be 0, so we compare the callingUid to the
            // {@link TaskRecord.effectiveUid} instead. Also caller with
            // {@link MANAGE_ACTIVITY_STACKS} can stop any lock task.
            if (checkCallingPermission(MANAGE_ACTIVITY_STACKS) != PERMISSION_GRANTED
                    && callingUid != lockTaskUid
                    && (lockTaskUid != 0 || callingUid != lockTask.effectiveUid)) {
                throw new SecurityException("Invalid uid, expected " + lockTaskUid
                        + " callingUid=" + callingUid + " effectiveUid=" + lockTask.effectiveUid);
            }
        }
        long ident = Binder.clearCallingIdentity();
        try {
            Log.d(TAG, "stopLockTaskMode");
            // Stop lock task
            synchronized (this) {
                mStackSupervisor.setLockTaskModeLocked(null, ActivityManager.LOCK_TASK_MODE_NONE,
                        "stopLockTask", true);
            }
            TelecomManager tm = (TelecomManager) mContext.getSystemService(Context.TELECOM_SERVICE);
            if (tm != null) {
                tm.showInCallScreen(false);
            }
        } finally {
            Binder.restoreCallingIdentity(ident);
        }
    }

    void setLockTaskModeLocked(TaskRecord task, int lockTaskModeState, String reason,
            boolean andResume) {
        if (task == null) {
            // Take out of lock task mode if necessary
            final TaskRecord lockedTask = getLockedTaskLocked();
            if (lockedTask != null) {
                removeLockedTaskLocked(lockedTask);
                if (!mLockTaskModeTasks.isEmpty()) {
                    // There are locked tasks remaining, can only finish this task, not unlock it.
                    if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK,
                            "setLockTaskModeLocked: Tasks remaining, can't unlock");
                    lockedTask.performClearTaskLocked();
                    resumeFocusedStackTopActivityLocked();
                    return;
                }
            }
            if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK,
                    "setLockTaskModeLocked: No tasks to unlock. Callers=" + Debug.getCallers(4));
            return;
        }

        -------------------------------------------------------------------
    }

    void removeLockedTaskLocked(final TaskRecord task) {
        if (!mLockTaskModeTasks.remove(task)) {
            return;
        }
        if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, "removeLockedTaskLocked: removed " + task);
        if (mLockTaskModeTasks.isEmpty()) {
            // Last one.
            if (DEBUG_LOCKTASK) Slog.d(TAG_LOCKTASK, "removeLockedTask: task=" + task +
                    " last task, reverting locktask mode. Callers=" + Debug.getCallers(3));
            final Message lockTaskMsg = Message.obtain();
            lockTaskMsg.arg1 = task.userId;
            lockTaskMsg.what = LOCK_TASK_END_MSG;
            mHandler.sendMessage(lockTaskMsg);
        }
    }

    private final class ActivityStackSupervisorHandler extends Handler {


        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
               case LOCK_TASK_END_MSG: {
                    // When lock task ends, we enable the status bars.
                    try {
                        if (getStatusBarService() != null) {
                            getStatusBarService().disable(StatusBarManager.DISABLE_NONE, mToken,
                                    mService.mContext.getPackageName());
                        }
                        mWindowManager.reenableKeyguard(mToken);
                        if (getDevicePolicyManager() != null) {
                            getDevicePolicyManager().notifyLockTaskModeChanged(false, null,
                                    msg.arg1);
                        }
                        if (mLockTaskNotify == null) {
                            mLockTaskNotify = new LockTaskNotify(mService.mContext);
                        }
                        mLockTaskNotify.show(false);
                        try {
                            boolean shouldLockKeyguard = Settings.Secure.getInt(
                                    mService.mContext.getContentResolver(),
                                    Settings.Secure.LOCK_TO_APP_EXIT_LOCKED) != 0;
                            if (mLockTaskModeState == LOCK_TASK_MODE_PINNED && shouldLockKeyguard) {
                                mWindowManager.lockNow(null);
                                mWindowManager.dismissKeyguard();
                                new LockPatternUtils(mService.mContext)
                                        .requireCredentialEntry(UserHandle.USER_ALL);
                            }
                        } catch (SettingNotFoundException e) {
                            // No setting, don't lock.
                        }
                    } catch (RemoteException ex) {
                        throw new RuntimeException(ex);
                    } finally {
                        mLockTaskModeState = LOCK_TASK_MODE_NONE;
                    }
                } break;
            }
        }
    }

    /** Can't be put in lockTask mode. */
    final static int LOCK_TASK_AUTH_DONT_LOCK = 0;
    /** Can enter app pinning with user approval. Can never start over existing lockTask task. */
    final static int LOCK_TASK_AUTH_PINNABLE = 1;
    /** Starts in LOCK_TASK_MODE_LOCKED automatically. Can start over existing lockTask task. */
    final static int LOCK_TASK_AUTH_LAUNCHABLE = 2;
    /** Can enter lockTask without user approval. Can start over existing lockTask task. */
    final static int LOCK_TASK_AUTH_WHITELISTED = 3;
    /** Priv-app that starts in LOCK_TASK_MODE_LOCKED automatically. Can start over existing
     * lockTask task. */
    final static int LOCK_TASK_AUTH_LAUNCHABLE_PRIV = 4;
    int mLockTaskAuth = LOCK_TASK_AUTH_PINNABLE;

    int mLockTaskUid = -1;  // The uid of the application that called startLockTask().


    boolean isLockTaskModeViolation(TaskRecord task) {
        return isLockTaskModeViolation(task, false);
    }

    boolean isLockTaskModeViolation(TaskRecord task, boolean isNewClearTask) {
        if (getLockedTaskLocked() == task && !isNewClearTask) {
            return false;
        }
        final int lockTaskAuth = task.mLockTaskAuth;
        switch (lockTaskAuth) {
            case LOCK_TASK_AUTH_DONT_LOCK:
                return !mLockTaskModeTasks.isEmpty();
            case LOCK_TASK_AUTH_LAUNCHABLE_PRIV:
            case LOCK_TASK_AUTH_LAUNCHABLE:
            case LOCK_TASK_AUTH_WHITELISTED:
                return false;
            case LOCK_TASK_AUTH_PINNABLE:
                // Pinnable tasks can't be launched on top of locktask tasks.
                return !mLockTaskModeTasks.isEmpty();
            default:
                Slog.w(TAG, "isLockTaskModeViolation: invalid lockTaskAuth value=" + lockTaskAuth);
                return true;
        }
    }

    private int startActivityUnchecked(final ActivityRecord r, ActivityRecord sourceRecord,
            IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
            int startFlags, boolean doResume, ActivityOptions options, TaskRecord inTask) {


        // Should this be considered a new task?
        if (mStartActivity.resultTo == null && mInTask == null && !mAddingToTask
                && (mLaunchFlags & FLAG_ACTIVITY_NEW_TASK) != 0) {
            newTask = true;
            setTaskFromReuseOrCreateNewTask(taskToAffiliate);

            if (mSupervisor.isLockTaskModeViolation(mStartActivity.task)) {
                Slog.e(TAG, "Attempted Lock Task Mode violation mStartActivity=" + mStartActivity);
                return START_RETURN_LOCK_TASK_MODE_VIOLATION;
            }
            if (!mMovedOtherTask) {
                // If stack id is specified in activity options, usually it means that activity is
                // launched not from currently focused stack (e.g. from SysUI or from shell) - in
                // that case we check the target stack.
                updateTaskReturnToType(mStartActivity.task, mLaunchFlags,
                        preferredLaunchStackId != INVALID_STACK_ID ? mTargetStack : topStack);
            }
        } else if (mSourceRecord != null) {
            if (mSupervisor.isLockTaskModeViolation(mSourceRecord.task)) {
                Slog.e(TAG, "Attempted Lock Task Mode violation mStartActivity=" + mStartActivity);
                return START_RETURN_LOCK_TASK_MODE_VIOLATION;
            }

            final int result = setTaskFromSourceRecord();
            if (result != START_SUCCESS) {
                return result;
            }
        } else if (mInTask != null) {
            // The caller is asking that the new activity be started in an explicit
            // task it has provided to us.
            if (mSupervisor.isLockTaskModeViolation(mInTask)) {
                Slog.e(TAG, "Attempted Lock Task Mode violation mStartActivity=" + mStartActivity);
                return START_RETURN_LOCK_TASK_MODE_VIOLATION;
            }

            final int result = setTaskFromInTask();
            if (result != START_SUCCESS) {
                return result;
            }
        } else {
            // This not being started from an existing activity, and not part of a new task...
            // just put it in the top task, though these days this case should never happen.
            setTaskToCurrentTopOrCreateNewTask();
        }

        mTargetStack.startActivityLocked(mStartActivity, newTask, mKeepCurTransition, mOptions);

   }

    /**
     * Sets which packages may enter lock task mode.
     *
     * <p>This function can only be called by the device owner or alternatively by the profile owner
     * in case the user is affiliated.
     *
     * @param packages The list of packages allowed to enter lock task mode.
     */
    @Override
    public void setLockTaskPackages(ComponentName who, String[] packages)
            throws SecurityException {
        Preconditions.checkNotNull(who, "ComponentName is null");
        synchronized (this) {
            ActiveAdmin deviceOwner = getActiveAdminWithPolicyForUidLocked(
                who, DeviceAdminInfo.USES_POLICY_DEVICE_OWNER, mInjector.binderGetCallingUid());
            ActiveAdmin profileOwner = getActiveAdminWithPolicyForUidLocked(
                who, DeviceAdminInfo.USES_POLICY_PROFILE_OWNER, mInjector.binderGetCallingUid());
            if (deviceOwner != null || (profileOwner != null && isAffiliatedUser())) {
                int userHandle = mInjector.userHandleGetCallingUserId();
                setLockTaskPackagesLocked(userHandle, new ArrayList<>(Arrays.asList(packages)));
            } else {
                throw new SecurityException("Admin " + who +
                    " is neither the device owner or affiliated user's profile owner.");
            }
        }
    }

    private void setLockTaskPackagesLocked(int userHandle, List<String> packages) {
        DevicePolicyData policy = getUserData(userHandle);
        policy.mLockTaskPackages = packages;

        // Store the settings persistently.
        saveSettingsLocked(userHandle);
        updateLockTaskPackagesLocked(packages, userHandle);
    }

    /**
     * This function returns the list of components allowed to start the task lock mode.
     */
    @Override
    public String[] getLockTaskPackages(ComponentName who) {
        Preconditions.checkNotNull(who, "ComponentName is null");
        synchronized (this) {
            getActiveAdminForCallerLocked(who, DeviceAdminInfo.USES_POLICY_DEVICE_OWNER);
            int userHandle = mInjector.binderGetCallingUserHandle().getIdentifier();
            final List<String> packages = getLockTaskPackagesLocked(userHandle);
            return packages.toArray(new String[packages.size()]);
        }
    }

    private List<String> getLockTaskPackagesLocked(int userHandle) {
        final DevicePolicyData policy = getUserData(userHandle);
        return policy.mLockTaskPackages;
    }

    /**
     * List of packages whitelisted by DevicePolicyManager for locktask. Indexed by userId.
     */
    SparseArray<String[]> mLockTaskPackages = new SparseArray<>();

    @Override
    public void updateLockTaskPackages(int userId, String[] packages) {
        final int callingUid = Binder.getCallingUid();
        if (callingUid != 0 && callingUid != Process.SYSTEM_UID) {
            enforceCallingPermission(android.Manifest.permission.UPDATE_LOCK_TASK_PACKAGES,
                    "updateLockTaskPackages()");
        }
        synchronized (this) {
            if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, "Whitelisting " + userId + ":" +
                    Arrays.toString(packages));
            mLockTaskPackages.put(userId, packages);
            mStackSupervisor.onLockTaskPackagesUpdatedLocked();
        }
    }

    void onLockTaskPackagesUpdatedLocked() {
        boolean didSomething = false;
        for (int taskNdx = mLockTaskModeTasks.size() - 1; taskNdx >= 0; --taskNdx) {
            final TaskRecord lockedTask = mLockTaskModeTasks.get(taskNdx);
            final boolean wasWhitelisted =
                    (lockedTask.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE) ||
                    (lockedTask.mLockTaskAuth == LOCK_TASK_AUTH_WHITELISTED);
            lockedTask.setLockTaskAuth();
            final boolean isWhitelisted =
                    (lockedTask.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE) ||
                    (lockedTask.mLockTaskAuth == LOCK_TASK_AUTH_WHITELISTED);
            if (wasWhitelisted && !isWhitelisted) {
                // Lost whitelisting authorization. End it now.
                if (DEBUG_LOCKTASK) Slog.d(TAG_LOCKTASK, "onLockTaskPackagesUpdated: removing " +
                        lockedTask + " mLockTaskAuth=" + lockedTask.lockTaskAuthToString());
                removeLockedTaskLocked(lockedTask);
                lockedTask.performClearTaskLocked();
                didSomething = true;
            }
        }
        for (int displayNdx = mActivityDisplays.size() - 1; displayNdx >= 0; --displayNdx) {
            ArrayList<ActivityStack> stacks = mActivityDisplays.valueAt(displayNdx).mStacks;
            for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) {
                final ActivityStack stack = stacks.get(stackNdx);
                stack.onLockTaskPackagesUpdatedLocked();
            }
        }
        final ActivityRecord r = topRunningActivityLocked();
        final TaskRecord task = r != null ? r.task : null;
        if (mLockTaskModeTasks.isEmpty() && task != null
                && task.mLockTaskAuth == LOCK_TASK_AUTH_LAUNCHABLE) {
            // This task must have just been authorized.
            if (DEBUG_LOCKTASK) Slog.d(TAG_LOCKTASK,
                    "onLockTaskPackagesUpdated: starting new locktask task=" + task);
            setLockTaskModeLocked(task, ActivityManager.LOCK_TASK_MODE_LOCKED, "package updated",
                    false);
            didSomething = true;
        }
        if (didSomething) {
            resumeFocusedStackTopActivityLocked();
        }
    }