安卓高手之路之 应用篇

安卓高手之路之 应用篇 - 修补C++ - ITeye技术网站

1. 安装应用流程：

     PackageManagerService的installPackage 调用 InstallArgs的copyAPK完成了安装。如果在SD卡中，那么调用SdInstallArgs的copyApk完成安装。

2. 应用启动流程：

  首先，直接从ActivityManagerService入手，首先调用startActivity这个函数：

     public final int startActivity(IApplicationThread caller,
            Intent intent, String resolvedType, Uri[] grantedUriPermissions,
            int grantedMode, IBinder resultTo,
            String resultWho, int requestCode, boolean onlyIfNeeded, boolean debug,
            String profileFile, ParcelFileDescriptor profileFd, boolean autoStopProfiler) {
        return mMainStack.startActivityMayWait(caller, -1, intent, resolvedType,
                grantedUriPermissions, grantedMode, resultTo, resultWho,
                requestCode, onlyIfNeeded, debug, profileFile, profileFd, autoStopProfiler,
                null, null);
    }

下面看AcitivityStack，

  final int startActivityMayWait(IApplicationThread caller, int callingUid,
            Intent intent, String resolvedType, Uri[] grantedUriPermissions,
            int grantedMode, IBinder resultTo,
            String resultWho, int requestCode, boolean onlyIfNeeded,
            boolean debug, String profileFile, ParcelFileDescriptor profileFd,
            boolean autoStopProfiler, WaitResult outResult, Configuration config) {

这个函数比较长，下面只看关键部位：

  
        // Collect information about the target of the Intent.
        ActivityInfo aInfo = resolveActivity(intent, resolvedType, debug,
                profileFile, profileFd, autoStopProfiler);

 这个调到了PackageManager里面的resolveActivity方法里面。这里既暂时不说了。后面再讨论。

  往下继续看：

 看到一个重量级app的含义，经分析，这样的app会在状态栏，发送一个如下的图标：

    

 

所以那段代码直接忽略。往下看，看到如下一句话：

 int res = startActivityLocked(caller, intent, resolvedType,
                    grantedUriPermissions, grantedMode, aInfo,
                    resultTo, resultWho, requestCode, callingPid, callingUid,
                    onlyIfNeeded, componentSpecified, null);

这个方法比较长，要有耐性:

  ProcessRecord callerApp = null;
        if (caller != null) {
            callerApp = mService.getRecordForAppLocked(caller);
            if (callerApp != null) {
                callingPid = callerApp.pid;
                callingUid = callerApp.info.uid;
            } else {
                Slog.w(TAG, "Unable to find app for caller " + caller
                      + " (pid=" + callingPid + ") when starting: "
                      + intent.toString());
                err = START_PERMISSION_DENIED;
            }
        }
这段话找出调用者的ProcessRecord

        ActivityRecord sourceRecord = null;
        ActivityRecord resultRecord = null;
        if (resultTo != null) {
            int index = indexOfTokenLocked(resultTo);
            if (DEBUG_RESULTS) Slog.v(
                TAG, "Will send result to " + resultTo + " (index " + index + ")");
            if (index >= 0) {
                sourceRecord = mHistory.get(index);
                if (requestCode >= 0 && !sourceRecord.finishing) {
                    resultRecord = sourceRecord;
                }
            }
        }

这段话，找出一个resultRecord。

 然后是这句话

 final int perm = mService.checkComponentPermission(aInfo.permission, callingPid,
                callingUid, aInfo.applicationInfo.uid, aInfo.exported); 这个是权限检测，后面再说。

下面这句话

  if (mMainStack) {
            if (mService.mController != null) {
                boolean abort = false;
                try {
                    // The Intent we give to the watcher has the extra data
                    // stripped off, since it can contain private information.
                    Intent watchIntent = intent.cloneFilter();
                    abort = !mService.mController.activityStarting(watchIntent,
                            aInfo.applicationInfo.packageName);
                } catch (RemoteException e) {
                    mService.mController = null;
                }
   
                if (abort) {
                    if (resultRecord != null) {
                        sendActivityResultLocked(-1,
                            resultRecord, resultWho, requestCode,
                            Activity.RESULT_CANCELED, null);
                    }
                    // We pretend to the caller that it was really started, but
                    // they will just get a cancel result.
                    mDismissKeyguardOnNextActivity = false;
                    return START_SUCCESS;
                }
            }
        }

 有时候可以设置一个Controller到AcitivytManagerservice中。具体AM.java文件中有引用。例如，从命令行启动Acitivity。

    ActivityRecord r = new ActivityRecord(mService, this, callerApp, callingUid,
                intent, resolvedType, aInfo, mService.mConfiguration,
                resultRecord, resultWho, requestCode, componentSpecified);
        if (outActivity != null) {
            outActivity[0] = r;
        }

        if (mMainStack) {
            if (mResumedActivity == null
                    || mResumedActivity.info.applicationInfo.uid != callingUid) {
                if (!mService.checkAppSwitchAllowedLocked(callingPid, callingUid, "Activity start")) {
                    PendingActivityLaunch pal = new PendingActivityLaunch();
                    pal.r = r;
                    pal.sourceRecord = sourceRecord;
                    pal.grantedUriPermissions = grantedUriPermissions;
                    pal.grantedMode = grantedMode;
                    pal.onlyIfNeeded = onlyIfNeeded;
                    mService.mPendingActivityLaunches.add(pal);
                    mDismissKeyguardOnNextActivity = false;
                    return START_SWITCHES_CANCELED;
                }
            }
       
            if (mService.mDidAppSwitch) {
                // This is the second allowed switch since we stopped switches,
                // so now just generally allow switches.  Use case: user presses
                // home (switches disabled, switch to home, mDidAppSwitch now true);
                // user taps a home icon (coming from home so allowed, we hit here
                // and now allow anyone to switch again).
                mService.mAppSwitchesAllowedTime = 0;
            } else {
                mService.mDidAppSwitch = true;
            }
        
            mService.doPendingActivityLaunchesLocked(false);
        }

关键是红色标注的那一句话。

    final int N = mPendingActivityLaunches.size();
        if (N <= 0) {
            return;
        }
        for (int i=0; i<N; i++) {
            PendingActivityLaunch pal = mPendingActivityLaunches.get(i);
            mMainStack.startActivityUncheckedLocked(pal.r, pal.sourceRecord,
                    pal.grantedUriPermissions, pal.grantedMode, pal.onlyIfNeeded,
                    doResume && i == (N-1));
        }
        mPendingActivityLaunches.clear();

把3PendingLaunch的进行启动。

  最终进入：

 err = startActivityUncheckedLocked(r, sourceRecord,
                grantedUriPermissions, grantedMode, onlyIfNeeded, true);
        if (mDismissKeyguardOnNextActivity && mPausingActivity == null) {
            // Someone asked to have the keyguard dismissed on the next
            // activity start, but we are not actually doing an activity
            // switch...  just dismiss the keyguard now, because we
            // probably want to see whatever is behind it.
            mDismissKeyguardOnNextActivity = false;
            mService.mWindowManager.dismissKeyguard();
        }
        return err;

 err = startActivityUncheckedLocked(r, sourceRecord,
                grantedUriPermissions, grantedMode, onlyIfNeeded, true);
        if (mDismissKeyguardOnNextActivity && mPausingActivity == null) {
            // Someone asked to have the keyguard dismissed on the next
            // activity start, but we are not actually doing an activity
            // switch...  just dismiss the keyguard now, because we
            // probably want to see whatever is behind it.
            mDismissKeyguardOnNextActivity = false;
            mService.mWindowManager.dismissKeyguard();
        }
        return err;

startActivityUncheckedLocked 这个方法也是很长。

 其中FLAG_ACTIVITY_PREVIOUS_IS_TOP 说的是current不是top，之前的是top。也就是说，r不算是top。

   ActivityRecord notTop = (launchFlags&Intent.FLAG_ACTIVITY_PREVIOUS_IS_TOP)
                != 0 ? r : null;

  if (sourceRecord == null) {
            // This activity is not being started from another...  in this
            // case we -always- start a new task.
            if ((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) == 0) {
                Slog.w(TAG, "startActivity called from non-Activity context; forcing Intent.FLAG_ACTIVITY_NEW_TASK for: "
                      + intent);
                launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
            }
       

不是从Acitivity启动的话，就要加一个newTask标志。这也可以说是同一个task的一个条件吧。

  if (sourceRecord.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE) {
            // The original activity who is starting us is running as a single
            // instance...  this new activity it is starting must go on its
            // own task.
            launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;

这个说的是如果sourceActivity是一个singleton，那么也启动一个newtask。

else if (r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE
                || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
            // The activity being started is a single instance...  it always
            // gets launched into its own task.
            launchFlags |= Intent.FLAG_ACTIVITY_NEW_TASK;
        }

或者说，自己是一个singletatask或者singleinstance。那么也是newtask。

 LAUNCH_SINGLE_INSTANCE 一定是.LAUNCH_SINGLE_TASK，.LAUNCH_SINGLE_TASK 不一定是

LAUNCH_SINGLE_INSTANCE

既然是singletask，那么无法退出结果给 resultTo：

        if (r.resultTo != null && (launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0) {
            // For whatever reason this activity is being launched into a new
            // task...  yet the caller has requested a result back.  Well, that
            // is pretty messed up, so instead immediately send back a cancel
            // and let the new task continue launched as normal without a
            // dependency on its originator.
            Slog.w(TAG, "Activity is launching as a new task, so cancelling activity result.");
            sendActivityResultLocked(-1,
                    r.resultTo, r.resultWho, r.requestCode,
                Activity.RESULT_CANCELED, null);
            r.resultTo = null;
        }

下面判断很有意思，如果是一个newTask

if (((launchFlags&Intent.FLAG_ACTIVITY_NEW_TASK) != 0 &&
                (launchFlags&Intent.FLAG_ACTIVITY_MULTIPLE_TASK) == 0)
                || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK
                || r.launchMode == ActivityInfo.LAUNCH_SINGLE_INSTANCE)

找到top的task

  ActivityRecord taskTop = r.launchMode != ActivityInfo.LAUNCH_SINGLE_INSTANCE
                        ? findTaskLocked(intent, r.info)
                        : findActivityLocked(intent, r.info);

 如果是LAUNCH_SINGLE_INSTANCE，那么就全找。否则，过滤掉LAUNCH_SINGLE_INSTANCE的activity。并且，找到一个task与此相同的。也就是说是new——task，并且不是singleton，这种情况下，找所有task的顶层activity。看是否满足条件。

                    ActivityRecord curTop = topRunningNonDelayedActivityLocked(notTop);
                    if (curTop != null && curTop.task != taskTop.task) {
                        r.intent.addFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT);
                        boolean callerAtFront = sourceRecord == null
                                || curTop.task == sourceRecord.task;
                        if (callerAtFront) {
                            // We really do want to push this one into the
                            // user's face, right now.
                            moveHomeToFrontFromLaunchLocked(launchFlags);
                            moveTaskToFrontLocked(taskTop.task, r);
                        }
                    }

新任务与当前的topTask不同的时候，先把home加到前面，然后把当前的加到前面。考虑的时候，排除notTop。

 if (onlyIfNeeded) {
                        // We don't need to start a new activity, and
                        // the client said not to do anything if that
                        // is the case, so this is it!  And for paranoia, make
                        // sure we have correctly resumed the top activity.
                        if (doResume) {
                            resumeTopActivityLocked(null);
                        }
                        return START_RETURN_INTENT_TO_CALLER;
                    }

不需要启动activity。只是resumetop。

 if ((launchFlags&Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0
                                && taskTop.realActivity.equals(r.realActivity)) {
                            logStartActivity(EventLogTags.AM_NEW_INTENT, r, taskTop.task);
                            if (taskTop.frontOfTask) {
                                taskTop.task.setIntent(r.intent, r.info);
                            }
                            taskTop.deliverNewIntentLocked(callingUid, r.intent);
                        }

 调用onNewInent。如果已经在top，那么就不再启动新的activity。

if (!addingToTask && reuseTask == null) {
                        // We didn't do anything...  but it was needed (a.k.a., client
                        // don't use that intent!)  And for paranoia, make
                        // sure we have correctly resumed the top activity.
                        if (doResume) {
                            resumeTopActivityLocked(null);
                        }
                        return START_TASK_TO_FRONT;
                    }

不添加新的task，也不用旧的task，就什么都不干。

以上全是处理的newtask，singletask，singleinstance的东西。

 if ((launchFlags&Intent.FLAG_ACTIVITY_SINGLE_TOP) != 0
                            || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TOP
                            || r.launchMode == ActivityInfo.LAUNCH_SINGLE_TASK) {
                            logStartActivity(EventLogTags.AM_NEW_INTENT, top, top.task);
                            // For paranoia, make sure we have correctly
                            // resumed the top activity.
                            if (doResume) {
                                resumeTopActivityLocked(null);
                            }
                            if (onlyIfNeeded) {
                                // We don't need to start a new activity, and
                                // the client said not to do anything if that
                                // is the case, so this is it!
                                return START_RETURN_INTENT_TO_CALLER;
                            }
                            top.deliverNewIntentLocked(callingUid, r.intent);
                            return START_DELIVERED_TO_TOP;

如果是singletop，singletask，并且有一个在top，就直接onNewIntent。

最终进入ActivityStack的

startActivityLocked

最终进入：

    private final void startActivityLocked(ActivityRecord r, boolean newTask,
            boolean doResume, boolean keepCurTransition) {

放入activity堆栈后，调用resumeTopActivityLocked
    final boolean resumeTopActivityLocked(ActivityRecord prev)

然后调用

 startSpecificActivityLocked(next, true, true);

 这个就是如下代码

    private final void startSpecificActivityLocked(ActivityRecord r,
            boolean andResume, boolean checkConfig) {
        // Is this activity's application already running?
        ProcessRecord app = mService.getProcessRecordLocked(r.processName,
                r.info.applicationInfo.uid);
       
        if (r.launchTime == 0) {
            r.launchTime = SystemClock.uptimeMillis();
            if (mInitialStartTime == 0) {
                mInitialStartTime = r.launchTime;
            }
        } else if (mInitialStartTime == 0) {
            mInitialStartTime = SystemClock.uptimeMillis();
        }
       
        if (app != null && app.thread != null) {
            try {
                app.addPackage(r.info.packageName);
                realStartActivityLocked(r, app, andResume, checkConfig);
                return;
            } catch (RemoteException e) {
                Slog.w(TAG, "Exception when starting activity "
                        + r.intent.getComponent().flattenToShortString(), e);
            }

            // If a dead object exception was thrown -- fall through to
            // restart the application.
        }

        mService.startProcessLocked(r.processName, r.info.applicationInfo, true, 0,
                "activity", r.intent.getComponent(), false);
    }

要么调用 realStartActivityLocked(r, app, andResume, checkConfig);

要么调用 startProcessLocked

realStartActivityLocked  调用 app.thread.scheduleLaunchActivity(new Intent(r.intent), r.appToken,
                    System.identityHashCode(r), r.info,
                    new Configuration(mService.mConfiguration),
                    r.compat, r.icicle, results, newIntents, !andResume,
                    mService.isNextTransitionForward(), profileFile, profileFd,
                    profileAutoStop);

而 startProcessLocked调用

    private final void startProcessLocked(ProcessRecord app,
            String hostingType, String hostingNameStr) {

下面是一些dbug开关。

            if ("1".equals(SystemProperties.get("debug.checkjni"))) {
                debugFlags |= Zygote.DEBUG_ENABLE_CHECKJNI;
            }
            if ("1".equals(SystemProperties.get("debug.jni.logging"))) {
                debugFlags |= Zygote.DEBUG_ENABLE_JNI_LOGGING;
            }
            if ("1".equals(SystemProperties.get("debug.assert"))) {
                debugFlags |= Zygote.DEBUG_ENABLE_ASSERT;
            }

调用如下来启动进程：

  // Start the process.  It will either succeed and return a result containing
            // the PID of the new process, or else throw a RuntimeException.
            Process.ProcessStartResult startResult = Process.start("android.app.ActivityThread",
                    app.processName, uid, uid, gids, debugFlags,
                    app.info.targetSdkVersion, null);

  然后掉到ActivityThread的：

 private void attach(boolean system) 方法中

对于非系统进程就这几句话：

 ViewRootImpl.addFirstDrawHandler(new Runnable() {
                public void run() {
                    ensureJitEnabled();
                }
            });
            android.ddm.DdmHandleAppName.setAppName("<pre-initialized>");
            RuntimeInit.setApplicationObject(mAppThread.asBinder());
            IActivityManager mgr = ActivityManagerNative.getDefault();
            try {
                mgr.attachApplication(mAppThread);
            } catch (RemoteException ex) {
                // Ignore
            }

调用到

    public final void attachApplication(IApplicationThread thread) {
        synchronized (this) {
            int callingPid = Binder.getCallingPid();
            final long origId = Binder.clearCallingIdentity();
            attachApplicationLocked(thread, callingPid);
            Binder.restoreCallingIdentity(origId);
        }
    }

最终回调到ActivityThread的

private void handleBindApplication(AppBindData data)

等待调试的地方在这个地方：

 if (data.debugMode != IApplicationThread.DEBUG_OFF) {
            // XXX should have option to change the port.
            Debug.changeDebugPort(8100);
            if (data.debugMode == IApplicationThread.DEBUG_WAIT) {
                Slog.w(TAG, "Application " + data.info.getPackageName()
                      + " is waiting for the debugger on port 8100...");

                IActivityManager mgr = ActivityManagerNative.getDefault();
                try {
                    mgr.showWaitingForDebugger(mAppThread, true);
                } catch (RemoteException ex) {
                }

                Debug.waitForDebugger();

                try {
                    mgr.showWaitingForDebugger(mAppThread, false);
                } catch (RemoteException ex) {
                }

            } else {
                Slog.w(TAG, "Application " + data.info.getPackageName()
                      + " can be debugged on port 8100...");
            }
        }

 初始化context

  ContextImpl appContext = new ContextImpl();
            appContext.init(data.info, null, this);
            InstrumentationInfo ii = null;

 获得apk的信息。
            ApplicationInfo instrApp = new ApplicationInfo();
            instrApp.packageName = ii.packageName;
            instrApp.sourceDir = ii.sourceDir;
            instrApp.publicSourceDir = ii.publicSourceDir;
            instrApp.dataDir = ii.dataDir;
            instrApp.nativeLibraryDir = ii.nativeLibraryDir;
            LoadedApk pi = getPackageInfo(instrApp, data.compatInfo,
                    appContext.getClassLoader(), false, true);

ContextImpl instrContext = new ContextImpl();
            instrContext.init(pi, null, this);

初始化instrContext

如果没有instrument则

 mInstrumentation = new Instrumentation();

  // If the app is being launched for full backup or restore, bring it up in
        // a restricted environment with the base application class.
        Application app = data.info.makeApplication(data.restrictedBackupMode, null);
        mInitialApplication = app;

        // don't bring up providers in restricted mode; they may depend on the
        // app's custom Application class
        if (!data.restrictedBackupMode){
            List<ProviderInfo> providers = data.providers;
            if (providers != null) {
                installContentProviders(app, providers);
                // For process that contains content providers, we want to
                // ensure that the JIT is enabled "at some point".
                mH.sendEmptyMessageDelayed(H.ENABLE_JIT, 10*1000);
            }
        }

        try {
            mInstrumentation.callApplicationOnCreate(app);
        } catch (Exception e) {
            if (!mInstrumentation.onException(app, e)) {
                throw new RuntimeException(
                    "Unable to create application " + app.getClass().getName()
                    + ": " + e.toString(), e);
            }
        }

创造一个应用，并且调用app的 onCreate方法。

下面进入app的onCreate方法

然后

 // See if the top visible activity is waiting to run in this process...
        ActivityRecord hr = mMainStack.topRunningActivityLocked(null);
        if (hr != null && normalMode) {
            if (hr.app == null && app.info.uid == hr.info.applicationInfo.uid
                    && processName.equals(hr.processName)) {
                try {
                    if (mMainStack.realStartActivityLocked(hr, app, true, true)) {
                        didSomething = true;
                    }
                } catch (Exception e) {
                    Slog.w(TAG, "Exception in new application when starting activity "
                          + hr.intent.getComponent().flattenToShortString(), e);
                    badApp = true;
                }
            } else {
                mMainStack.ensureActivitiesVisibleLocked(hr, null, processName, 0);
            }
        }

找到toplevel Activity进行启动。这个toplevelActivity就是刚才要启动的activity。这样activity就与新创建的进程进行了关联。