Android6.0屏幕固定功能详解

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

public void startLockTaskModeOnCurrent() throws RemoteException { 
enforceCallingPermission(android.Manifest.permission.MANAGE_ACTIVITY_STACKS, 
"startLockTaskModeOnCurrent"); 
long ident = Binder.clearCallingIdentity(); 
try { 
synchronized (this) { 
ActivityRecord r = mStackSupervisor.topRunningActivityLocked(); 
if (r != null) { 
startLockTaskModeLocked(r.task); 
} 
} 
} finally { 
Binder.restoreCallingIdentity(ident); 
} 
}

ActivityRecord topRunningActivityLocked() { 
final ActivityStack focusedStack = mFocusedStack; 
ActivityRecord r = focusedStack.topRunningActivityLocked(null); 
if (r != null) { 
return r; 
} 
// Return to the home stack. 
final ArrayList stacks = mHomeStack.mStacks; 
for (int stackNdx = stacks.size() - 1; stackNdx >= 0; --stackNdx) { 
final ActivityStack stack = stacks.get(stackNdx); 
if (stack != focusedStack && isFrontStack(stack)) { 
r = stack.topRunningActivityLocked(null); 
if (r != null) { 
return r; 
} 
} 
} 
return null; 
}

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(); 
resumeTopActivitiesLocked(); 
return; 
} 
} 
if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, 
"setLockTaskModeLocked: No tasks to unlock. Callers=" + Debug.getCallers(4)); 
return; 
} 
// 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;//发送消息 
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);//加入到mLockModeTasks中 
if (task.mLockTaskUid == -1) { 
task.mLockTaskUid = task.effectiveUid; 
} 
if (andResume) { 
findTaskToMoveToFrontLocked(task, 0, null, reason);//把task放最前面 
resumeTopActivitiesLocked();//显示新的Activity 
} 
}

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;

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; 
} 
}

void setLockTaskAuth() { 
if (!mPrivileged && 
(mLockTaskMode == LOCK_TASK_LAUNCH_MODE_ALWAYS || 
mLockTaskMode == LOCK_TASK_LAUNCH_MODE_NEVER)) { 
// Non-priv apps are not allowed to use always or never, fall back to default 
mLockTaskMode = LOCK_TASK_LAUNCH_MODE_DEFAULT; 
} 
switch (mLockTaskMode) { 
case LOCK_TASK_LAUNCH_MODE_DEFAULT: 
mLockTaskAuth = isLockTaskWhitelistedLocked() &＃63; 
LOCK_TASK_AUTH_WHITELISTED : LOCK_TASK_AUTH_PINNABLE; 
break; 
case LOCK_TASK_LAUNCH_MODE_NEVER: 
mLockTaskAuth = LOCK_TASK_AUTH_DONT_LOCK; 
break; 
case LOCK_TASK_LAUNCH_MODE_ALWAYS: 
mLockTaskAuth = LOCK_TASK_AUTH_LAUNCHABLE_PRIV; 
break; 
case LOCK_TASK_LAUNCH_MODE_IF_WHITELISTED: 
mLockTaskAuth = isLockTaskWhitelistedLocked() &＃63; 
LOCK_TASK_AUTH_LAUNCHABLE : LOCK_TASK_AUTH_PINNABLE; 
break; 
} 
if (DEBUG_LOCKTASK) Slog.d(TAG_LOCKTASK, "setLockTaskAuth: task=" + this + 
" mLockTaskAuth=" + lockTaskAuthToString()); 
}

case LOCK_TASK_AUTH_PINNABLE: 
// Pinnable tasks can't be launched on top of locktask tasks. 
return !mLockTaskModeTasks.isEmpty();

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; 
// 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. 
if (getLockTaskModeState() == ActivityManager.LOCK_TASK_MODE_LOCKED && 
callingUid != lockTaskUid 
&& (lockTaskUid != 0 
|| (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); 
} 
} 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(); 
resumeTopActivitiesLocked(); 
return; 
} 
} 
if (DEBUG_LOCKTASK) Slog.w(TAG_LOCKTASK, 
"setLockTaskModeLocked: No tasks to unlock. Callers=" + Debug.getCallers(4)); 
return; 
}

public boolean onKeyLongPress(int keyCode, KeyEvent event) { 
if (keyCode == KeyEvent.KEYCODE_BACK) { 
stopLockTask(); 
} 
return false; 
}