后台启动Activity的源码阅读记录（Android 12版本）
当应用处于后台时，启动Activity有诸多限制，这个主要看AOSP源码中frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java类的shouldAbortBackgroundActivityStart方法
根据源码，后台允许启动Activity的情况如下：
- 调用的UID为ROOT_UID、SYSTEM_UID或NFC_UID
if (callingUid == Process.ROOT_UID || callingAppId == Process.SYSTEM_UID
|| callingAppId == Process.NFC_UID) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed for important callingUid (" + callingUid + ")");
}
return false;
}
- 调用的APP为Home app
// Always allow home application to start activities.
if (isHomeApp(callingUid, callingPackage)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed for home app callingUid (" + callingUid + ")");
}
return false;
}
- 调用的APP为IME（输入法）
// IME should always be allowed to start activity, like IME settings.
final WindowState imeWindow = mRootWindowContainer.getCurrentInputMethodWindow();
if (imeWindow != null && callingAppId == imeWindow.mOwnerUid) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed for active ime (" + callingUid + ")");
}
return false;
}
- 持久化的系统进程或应用有可见窗口
// Normal apps with visible app window will be allowed to start activity if app switching
// is allowed, or apps like live wallpaper with non app visible window will be allowed.
final boolean appSwitchAllowedOrFg =
appSwitchState == APP_SWITCH_ALLOW || appSwitchState == APP_SWITCH_FG_ONLY;
if (((appSwitchAllowedOrFg || mService.mActiveUids.hasNonAppVisibleWindow(callingUid))
&& callingUidHasAnyVisibleWindow)
|| isCallingUidPersistentSystemProcess) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed: callingUidHasAnyVisibleWindow = " + callingUid
+ ", isCallingUidPersistentSystemProcess = "
+ isCallingUidPersistentSystemProcess);
}
return false;
}
- 真实调用方有任何可见窗口
// don't abort if the realCallingUid has a visible window
// TODO(b/171459802): We should check appSwitchAllowed also
if (realCallingUidHasAnyVisibleWindow) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed: realCallingUid (" + realCallingUid
+ ") has visible (non-toast) window");
}
return false;
}
- 真实调用方为系统进程且允许后台Activity启动
// if the realCallingUid is a persistent system process, abort if the IntentSender
// wasn't allowed to start an activity
if (isRealCallingUidPersistentSystemProcess && allowBackgroundActivityStart) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed: realCallingUid (" + realCallingUid
+ ") is persistent system process AND intent sender allowed "
+ "(allowBackgroundActivityStart = true)");
}
return false;
}
- 调用方或真实调用方和CompanionApp关联
// don't abort if the realCallingUid is an associated companion app
if (mService.isAssociatedCompanionApp(UserHandle.getUserId(realCallingUid),
realCallingUid)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Activity start allowed: realCallingUid (" + realCallingUid
+ ") is companion app");
}
return false;
}
// don't abort if the callingUid has companion device
final int callingUserId = UserHandle.getUserId(callingUid);
if (mService.isAssociatedCompanionApp(callingUserId, callingUid)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Background activity start allowed: callingUid (" + callingUid
+ ") is companion app");
}
return false;
}
- 调用方有START_ACTIVITIES_FROM_BACKGROUND权限
// don't abort if the callingUid has START_ACTIVITIES_FROM_BACKGROUND permission
if (mService.checkPermission(START_ACTIVITIES_FROM_BACKGROUND, callingPid, callingUid)
== PERMISSION_GRANTED) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG,
"Background activity start allowed: START_ACTIVITIES_FROM_BACKGROUND "
+ "permission granted for uid "
+ callingUid);
}
return false;
}
- 调用方和最近的组件有相同的uid
// don't abort if the caller has the same uid as the recents component
if (mSupervisor.mRecentTasks.isCallerRecents(callingUid)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Background activity start allowed: callingUid (" + callingUid
+ ") is recents");
}
return false;
}
- 调用方是设备拥有者
// don't abort if the callingUid is the device owner
if (mService.isDeviceOwner(callingUid)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Background activity start allowed: callingUid (" + callingUid
+ ") is device owner");
}
return false;
}
- 有 SYSTEM_ALERT_WINDOW 权限
// don't abort if the callingUid has SYSTEM_ALERT_WINDOW permission
if (mService.hasSystemAlertWindowPermission(callingUid, callingPid, callingPackage)) {
Slog.w(TAG, "Background activity start for " + callingPackage
+ " allowed because SYSTEM_ALERT_WINDOW permission is granted.");
return false;
}
- 调用方的app的进程允许从后台启动activity
// don't abort if the callerApp or other processes of that uid are allowed in any way
if (callerApp != null) {
// first check the original calling process
if (callerApp.areBackgroundActivityStartsAllowed(appSwitchState)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG, "Background activity start allowed: callerApp process (pid = "
+ callerApp.getPid() + ", uid = " + callerAppUid + ") is allowed");
}
return false;
}
// only if that one wasn't allowed, check the other ones
final ArraySet<WindowProcessController> uidProcesses =
mService.mProcessMap.getProcesses(callerAppUid);
if (uidProcesses != null) {
for (int i = uidProcesses.size() - 1; i >= 0; i--) {
final WindowProcessController proc = uidProcesses.valueAt(i);
if (proc != callerApp
&& proc.areBackgroundActivityStartsAllowed(appSwitchState)) {
if (DEBUG_ACTIVITY_STARTS) {
Slog.d(TAG,
"Background activity start allowed: process " + proc.getPid()
+ " from uid " + callerAppUid + " is allowed");
}
return false;
}
}
}
}