android 10 后台无法 startActivity 原理分析 |
您所在的位置：网站首页 › android无activity服务 › android 10 后台无法 startActivity 原理分析 |
|
前言
Android 10 (API 级别 29) 及更高版本对后台应用可启动 Activity 的时间施加限制。这些限制有助于最大限度地减少对用户造成的中断（可以更省电），并且可以让用户更好地控制其屏幕上显示的内容。 准备事项 控制后台启动的关键函数为 ActivityStarter::shouldAbortBackgroundActivityStart 原理分析根据以往咱们对 AMS 的认识，Activity的权限校验、安全校验等，都是放在 AMS 这一块来统一处理的。所以后台启动限制也不例外。所以我们直接来看 AMS 的 startActivity。 ActivityManagerService.java @Override public int startActivity(IApplicationThread caller, String callingPackage, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) { return mActivityTaskManager.startActivity(caller, callingPackage, intent, resolvedType, resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions); }这里 AMS将 startActivity 交给了 ActivityTaskManagerService 来处理。 ActivityTaskManagerService.class @Override public final int startActivity(IApplicationThread caller, String callingPackage, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) { return startActivityAsUser(caller, callingPackage, intent, resolvedType, resultTo, resultWho, requestCode, startFlags, profilerInfo, bOptions, UserHandle.getCallingUserId()); } int startActivityAsUser(IApplicationThread caller, String callingPackage, Intent intent, String resolvedType, IBinder resultTo, String resultWho, int requestCode, int startFlags, ProfilerInfo profilerInfo, Bundle bOptions, int userId, boolean validateIncomingUser) { enforceNotIsolatedCaller("startActivityAsUser"); userId = getActivityStartController().checkTargetUser(userId, validateIncomingUser, Binder.getCallingPid(), Binder.getCallingUid(), "startActivityAsUser"); // TODO: Switch to user app stacks here. return getActivityStartController().obtainStarter(intent, "startActivityAsUser") .setCaller(caller) .setCallingPackage(callingPackage) .setResolvedType(resolvedType) .setResultTo(resultTo) .setResultWho(resultWho) .setRequestCode(requestCode) .setStartFlags(startFlags) .setProfilerInfo(profilerInfo) .setActivityOptions(bOptions) .setMayWait(userId) .execute(); }ActivityTaskManagerService 将参数准备好，然后交给 ActivityStarter 的 execute 来做真正的启动动作。 ActivityStarter setMayWait(int userId) { mRequest.mayWait = true; mRequest.userId = userId; return this; } int execute() { try { if (mRequest.mayWait) { return startActivityMayWait(mRequest.caller, mRequest.callingUid, mRequest.callingPackage, mRequest.realCallingPid, mRequest.realCallingUid, mRequest.intent, mRequest.resolvedType, mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo, mRequest.resultWho, mRequest.requestCode, mRequest.startFlags, mRequest.profilerInfo, mRequest.waitResult, mRequest.globalConfig, mRequest.activityOptions, mRequest.ignoreTargetSecurity, mRequest.userId, mRequest.inTask, mRequest.reason, mRequest.allowPendingRemoteAnimationRegistryLookup, mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart); } else { return startActivity(mRequest.caller, mRequest.intent, mRequest.ephemeralIntent, mRequest.resolvedType, mRequest.activityInfo, mRequest.resolveInfo, mRequest.voiceSession, mRequest.voiceInteractor, mRequest.resultTo, mRequest.resultWho, mRequest.requestCode, mRequest.callingPid, mRequest.callingUid, mRequest.callingPackage, mRequest.realCallingPid, mRequest.realCallingUid, mRequest.startFlags, mRequest.activityOptions, mRequest.ignoreTargetSecurity, mRequest.componentSpecified, mRequest.outActivity, mRequest.inTask, mRequest.reason, mRequest.allowPendingRemoteAnimationRegistryLookup, mRequest.originatingPendingIntent, mRequest.allowBackgroundActivityStart); } } finally { onExecutionComplete(); } }上面调用 ActivityStarter 前，会执行 ActivityStarter::setMayWait 方法，这里会将mRequest.mayWait的值设置成 true ,所以 execute 会走 startActivityMayWait 方法。这里我们需要注意变量 mRequest.allowBackgroundActivityStart，这个也是控制是否可以后台启动的一个标志，但我们正常的启动流程，这个变量一直为 false。 startActivityMayWait经过层层调用，会来到 startActivity 方法 private int startActivity(IApplicationThread caller, Intent intent, Intent ephemeralIntent, String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo, IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor, IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid, String callingPackage, int realCallingPid, int realCallingUid, int startFlags, SafeActivityOptions options, boolean ignoreTargetSecurity, boolean componentSpecified, ActivityRecord[] outActivity, TaskRecord inTask, boolean allowPendingRemoteAnimationRegistryLookup, PendingIntentRecord originatingPendingIntent, boolean allowBackgroundActivityStart) { ··· boolean abort = !mSupervisor.checkStartAnyActivityPermission(intent, aInfo, resultWho, requestCode, callingPid, callingUid, callingPackage, ignoreTargetSecurity, inTask != null, callerApp, resultRecord, resultStack); abort |= !mService.mIntentFirewall.checkStartActivity(intent, callingUid, callingPid, resolvedType, aInfo.applicationInfo); abort |= !mService.getPermissionPolicyInternal().checkStartActivity(intent, callingUid, callingPackage); boolean restrictedBgActivity = false; if (!abort) { try { Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "shouldAbortBackgroundActivityStart"); //1 restrictedBgActivity = shouldAbortBackgroundActivityStart(callingUid, callingPid, callingPackage, realCallingUid, realCallingPid, callerApp, originatingPendingIntent, allowBackgroundActivityStart, intent); } finally { Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER); } } ··· //2 if (abort) { if (resultRecord != null) { resultStack.sendActivityResultLocked(-1, resultRecord, resultWho, requestCode, RESULT_CANCELED, null); } // We pretend to the caller that it was really started, but // they will just get a cancel result. ActivityOptions.abort(checkedOptions); return START_ABORTED; } ... //3 final int res = startActivity(r, sourceRecord, voiceSession, voiceInteractor, startFlags, true /* doResume */, checkedOptions, inTask, outActivity, restrictedBgActivity); mSupervisor.getActivityMetricsLogger().notifyActivityLaunched(res, outActivity[0]); return res; }abort 这个变量来控制当前的启动是否要中止。检查后台状态，需要在不中止的情况下进行检查。在注释2中，如果abort 为true,直接跳出函数，则不会对Activity进行真正的启动。接下来我们分析 注释1 关键函数 shouldAbortBackgroundActivityStart boolean shouldAbortBackgroundActivityStart(int callingUid, int callingPid, final String callingPackage, int realCallingUid, int realCallingPid, WindowProcessController callerApp, PendingIntentRecord originatingPendingIntent, boolean allowBackgroundActivityStart, Intent intent) { ··· // don't abort if the callingUid has a visible window or is a persistent system process final int callingUidProcState = mService.getUidState(callingUid); final boolean callingUidHasAnyVisibleWindow = mService.mWindowManager.mRoot.isAnyNonToastWindowVisibleForUid(callingUid); final boolean isCallingUidForeground = callingUidHasAnyVisibleWindow || callingUidProcState == ActivityManager.PROCESS_STATE_TOP || callingUidProcState == ActivityManager.PROCESS_STATE_BOUND_TOP; final boolean isCallingUidPersistentSystemProcess = callingUidProcState |
今日新闻 |
推荐新闻 |
| CopyRight 2018-2019 办公设备维修网 版权所有 豫ICP备15022753号-3 |