1.生命周期
Activity個狀態(tài)生命周期流程圖
20140810102151522.png
由上圖可知：
1.Starting -> Running，執(zhí)行的生命周期順序 onCreate()->onstart()->onResume()，
此activity所處于任務棧的top中，可以與用戶進行交互。
2.Running -> Paused ，執(zhí)行Activity生命周期中的onPause()，
該Activity已失去了焦點但仍然是可見的狀態(tài)(包括部分可見)。就比如彈出DialogActivity
3.Paused -> Running,執(zhí)行Activity生命周期中的onResume()，
此情況用戶操作[home鍵]，然后重新回到當前activity界面，還有就是關閉DialogActivity
1.1Activity1 跳轉至 Activity2 執(zhí)行的生命周期：
Activity1:onPause
Activity2:onCreate
Activity2:onStart
Activity2:onResume
Activity1:onStop
1.2Activity2回到Activity1 執(zhí)行的生命周期：
Activity2:onPause
Activity1:onRestart
Activity1:onStart
Activity1:onResume
Activity2:onStop
Activity2:onDestory
2.1 LifeCycleActivity彈出DialogActivity 執(zhí)行的生命周期：
LifeCycleActivity:onPause
DialogActivity:onCreate
DialogActivity:onStart
DialogActivity:onResume
值得注意的是：這里 LifeCycleActivity不會進入onStop，因為彈出DialogActivity時LifeCycleActivity還處于可見，
這里上文也有說到。
2.2.DialogActivity返回鍵到LifeCycleActivity執(zhí)行的生命周期：
DialogActivity:onPause
LifeCycleActivity:onResume
DialogActivity:onStop
DialogActivity:onDestroy
3.LifeCycleActivity旋轉屏幕執(zhí)行的生命周期：
LifeCycleActivity:onPause
LifeCycleActivity:onStop
LifeCycleActivity:onDestroy
LifeCycleActivity:onCreate
LifeCycleActivity:onStart
LifeCycleActivity:onResume
這里相當于重新創(chuàng)建了Activity
4.Activity橫豎屏切換狀態(tài)保存：
問題：當前ViewPager有三個Fragment，在豎屏時選擇的Fragment為第二個，如何在切換橫屏后選中第二個Fragment并且Fragment保持之前的狀態(tài)?
解答：由于onCreate可以拿到保持狀態(tài)的Bundle，而每次onPause以及onStop都會回調onSaveInstanceState(Bundle outState)方法，詳情見上圖。
所以可在該方法就行保存狀態(tài)，大體代碼如下：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 初始化主頁fragment
if (savedInstanceState != null) {
//系統(tǒng)回收后重新進入當前頁面恢復數(shù)據(jù)
resumeFragment(getSupportFragmentManager(), savedInstanceState);
resumeIndex(savedInstanceState);
showSelectFragmentOnly(getSupportFragmentManager());
mTabLayout.setCurrentItem(mIndex);
} else {
//正常初始化
mTabLayout.setCurrentItem(0);
showFragment(getSupportFragmentManager(), 0);
mIndex=0;
}
}
private void resumeFragment(FragmentManager fragmentManager, Bundle savedInstanceState) {
Fragment[] fragments = new Fragment[fragmentTab.length];
for (int i = 0; i < fragments.length; i++) {
fragments[i] = fragmentManager.getFragment(savedInstanceState, fragmentTab[i].getSimpleName());
}
mFragments = fragments;
}
private void resumeIndex(Bundle savedInstanceState) {
mIndex = savedInstanceState.getInt(CURRENT_INDEX, 0);
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
for (Fragment fragment : mFragments) {
if (fragment != null) {
getSupportFragmentManager().putFragment(outState, fragment.getClass().getName(), fragment);
}
}
outState.putInt(CURRENT_INDEX, mIndex);
}
下圖概括了android生命周期的各個環(huán)節(jié)，描述了activity從生成到銷毀的過程
0_1314838777He6C.gif
創(chuàng)建：onCreate():
|---可用于初始化工作，如setContentView界面資源、初始化數(shù)據(jù)
啟動：onStart():
|---可見但無法交互
恢復:onResume():
|---恢復播放動畫、音樂、視頻等
暫停:onPause():
|---可做數(shù)據(jù)存儲、停止動畫、音樂、視頻等
停止:onStop():
|---此時Activity不可見,可做視情況做些重量級回收工作，避免被Killed
銷毀:onDestroy():
|---回收工作、資源釋放
重現(xiàn)：onRestart():
|---可做一些恢復工作
2.源碼淺析
Activty是如何創(chuàng)建？ActivityThread 便是這關鍵
public final class ActivityThread {
Instrumentation mInstrumentation;
......
final ApplicationThread mAppThread = new ApplicationThread();
// Looper類創(chuàng)建
final Looper mLooper = Looper.myLooper();
// H是繼承Handler類 在AcivityThread創(chuàng)建時就創(chuàng)建了
final H mH = new H();
......
}
H類源碼如下：
private class H extends Handler {
........
public void handleMessage(Message msg) {
if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
switch (msg.what) {
case LAUNCH_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo, r.compatInfo);
handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case RELAUNCH_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityRestart");
ActivityClientRecord r = (ActivityClientRecord)msg.obj;
handleRelaunchActivity(r);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case PAUSE_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
SomeArgs args = (SomeArgs) msg.obj;
handlePauseActivity((IBinder) args.arg1, false,
(args.argi1 & USER_LEAVING) != 0, args.argi2,
(args.argi1 & DONT_REPORT) != 0, args.argi3);
maybeSnapshot();
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case PAUSE_ACTIVITY_FINISHING: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityPause");
SomeArgs args = (SomeArgs) msg.obj;
handlePauseActivity((IBinder) args.arg1, true, (args.argi1 & USER_LEAVING) != 0,
args.argi2, (args.argi1 & DONT_REPORT) != 0, args.argi3);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case STOP_ACTIVITY_SHOW: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");
SomeArgs args = (SomeArgs) msg.obj;
handleStopActivity((IBinder) args.arg1, true, args.argi2, args.argi3);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case STOP_ACTIVITY_HIDE: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStop");
SomeArgs args = (SomeArgs) msg.obj;
handleStopActivity((IBinder) args.arg1, false, args.argi2, args.argi3);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
case SHOW_WINDOW:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityShowWindow");
handleWindowVisibility((IBinder)msg.obj, true);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case HIDE_WINDOW:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityHideWindow");
handleWindowVisibility((IBinder)msg.obj, false);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case RESUME_ACTIVITY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityResume");
SomeArgs args = (SomeArgs) msg.obj;
handleResumeActivity((IBinder) args.arg1, true, args.argi1 != 0, true,
args.argi3, "RESUME_ACTIVITY");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case SEND_RESULT:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDeliverResult");
handleSendResult((ResultData)msg.obj);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
case DESTROY_ACTIVITY:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityDestroy");
handleDestroyActivity((IBinder)msg.obj, msg.arg1 != 0,
msg.arg2, false);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
.........
}
}
那么H類handleMessage是怎么被調用的呢？其實是通過ApplicationThread的scheduleLaunchActivity來完成的，這里ApplicationThread是ActivtyThread的內部類
ApplicationThread部分源碼如下：
private class ApplicationThread extends IApplicationThread.Stub {
........省略......
public final void schedulePauseActivity(IBinder token, boolean finished,
boolean userLeaving, int configChanges, boolean dontReport) {
int seq = getLifecycleSeq();
if (DEBUG_ORDER) Slog.d(TAG, "pauseActivity " + ActivityThread.this
+ " operation received seq: " + seq);
sendMessage(
finished ? H.PAUSE_ACTIVITY_FINISHING : H.PAUSE_ACTIVITY,
token,
(userLeaving ? USER_LEAVING : 0) | (dontReport ? DONT_REPORT : 0),
configChanges,
seq);
}
public final void scheduleStopActivity(IBinder token, boolean showWindow,
int configChanges) {
int seq = getLifecycleSeq();
if (DEBUG_ORDER) Slog.d(TAG, "stopActivity " + ActivityThread.this
+ " operation received seq: " + seq);
sendMessage(
showWindow ? H.STOP_ACTIVITY_SHOW : H.STOP_ACTIVITY_HIDE,
token, 0, configChanges, seq);
}
public final void scheduleWindowVisibility(IBinder token, boolean showWindow) {
sendMessage(
showWindow ? H.SHOW_WINDOW : H.HIDE_WINDOW,
token);
}
public final void scheduleSleeping(IBinder token, boolean sleeping) {
sendMessage(H.SLEEPING, token, sleeping ? 1 : 0);
}
public final void scheduleResumeActivity(IBinder token, int processState,
boolean isForward, Bundle resumeArgs) {
int seq = getLifecycleSeq();
if (DEBUG_ORDER) Slog.d(TAG, "resumeActivity " + ActivityThread.this
+ " operation received seq: " + seq);
updateProcessState(processState, false);
sendMessage(H.RESUME_ACTIVITY, token, isForward ? 1 : 0, 0, seq);
}
public final void scheduleSendResult(IBinder token, List<ResultInfo> results) {
ResultData res = new ResultData();
res.token = token;
res.results = results;
sendMessage(H.SEND_RESULT, res);
}
// AMS通過調用此方法啟動Activity
@Override
public final void scheduleLaunchActivity(Intent intent, IBinder token, int ident,
ActivityInfo info, Configuration curConfig, Configuration overrideConfig,
CompatibilityInfo compatInfo, String referrer, IVoiceInteractor voiceInteractor,
int procState, Bundle state, PersistableBundle persistentState,
List<ResultInfo> pendingResults, List<ReferrerIntent> pendingNewIntents,
boolean notResumed, boolean isForward, ProfilerInfo profilerInfo) {
updateProcessState(procState, false);
ActivityClientRecord r = new ActivityClientRecord();
r.token = token;
r.ident = ident;
r.intent = intent;
r.referrer = referrer;
r.voiceInteractor = voiceInteractor;
r.activityInfo = info;
r.compatInfo = compatInfo;
r.state = state;
r.persistentState = persistentState;
r.pendingResults = pendingResults;
r.pendingIntents = pendingNewIntents;
r.startsNotResumed = notResumed;
r.isForward = isForward;
r.profilerInfo = profilerInfo;
r.overrideConfig = overrideConfig;
updatePendingConfiguration(curConfig);
sendMessage(H.LAUNCH_ACTIVITY, r);
}
........省略......
}
問題1：那么ActivtyThread是如何初始化的?
答案：通過主入口函數(shù)main方法進行初始化：
public static void main(String[] args) {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "ActivityThreadMain");
SamplingProfilerIntegration.start();
CloseGuard.setEnabled(false);
Environment.initForCurrentUser();
EventLogger.setReporter(new EventLoggingReporter());
final File configDir = Environment.getUserConfigDirectory(UserHandle.myUserId());
TrustedCertificateStore.setDefaultUserDirectory(configDir);
Process.setArgV0("<pre-initialized>");
Looper.prepareMainLooper();
// 初始化ActivityThread
ActivityThread thread = new ActivityThread();
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
// End of event ActivityThreadMain.
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
Looper.loop();
throw new RuntimeException("Main thread loop unexpectedly exited");
}
問題2：ApplicationThread的scheduleLaunchActivity是如何被調用的?
答案：在上述代碼中我們看到ActivtyThread初始化后調用了attach方法，答案就在attach方法。
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
if (!system) {
ViewRootImpl.addFirstDrawHandler(new Runnable() {
@Override
public void run() {
ensureJitEnabled();
}
});
android.ddm.DdmHandleAppName.setAppName("<pre-initialized>",
UserHandle.myUserId());
RuntimeInit.setApplicationObject(mAppThread.asBinder());
final IActivityManager mgr = ActivityManager.getService();
try {
// 調用scheduleLaunchActivity的關鍵代碼
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
// Watch for getting close to heap limit.
BinderInternal.addGcWatcher(new Runnable() {
@Override public void run() {
if (!mSomeActivitiesChanged) {
return;
}
Runtime runtime = Runtime.getRuntime();
long dalvikMax = runtime.maxMemory();
long dalvikUsed = runtime.totalMemory() - runtime.freeMemory();
if (dalvikUsed > ((3*dalvikMax)/4)) {
if (DEBUG_MEMORY_TRIM) Slog.d(TAG, "Dalvik max=" + (dalvikMax/1024)
+ " total=" + (runtime.totalMemory()/1024)
+ " used=" + (dalvikUsed/1024));
mSomeActivitiesChanged = false;
try {
mgr.releaseSomeActivities(mAppThread);
} catch (RemoteException e) {
throw e.rethrowFromSystemServer();
}
}
}
});
} else {
// 這里是系統(tǒng)服務初始化的，在SystemServer類中main方法進行調用
android.ddm.DdmHandleAppName.setAppName("system_process",
UserHandle.myUserId());
try {
mInstrumentation = new Instrumentation();
ContextImpl context = ContextImpl.createAppContext(
this, getSystemContext().mPackageInfo);
mInitialApplication = context.mPackageInfo.makeApplication(true, null);
mInitialApplication.onCreate();
} catch (Exception e) {
throw new RuntimeException(
"Unable to instantiate Application():" + e.toString(), e);
}
}
// add dropbox logging to libcore
DropBox.setReporter(new DropBoxReporter());
ViewRootImpl.ConfigChangedCallback configChangedCallback
= (Configuration globalConfig) -> {
synchronized (mResourcesManager) {
// We need to apply this change to the resources immediately, because upon returning
// the view hierarchy will be informed about it.
if (mResourcesManager.applyConfigurationToResourcesLocked(globalConfig,
null /* compat */)) {
updateLocaleListFromAppContext(mInitialApplication.getApplicationContext(),
mResourcesManager.getConfiguration().getLocales());
// This actually changed the resources! Tell everyone about it.
if (mPendingConfiguration == null
|| mPendingConfiguration.isOtherSeqNewer(globalConfig)) {
mPendingConfiguration = globalConfig;
sendMessage(H.CONFIGURATION_CHANGED, globalConfig);
}
}
}
};
ViewRootImpl.addConfigCallback(configChangedCallback);
}
上述代碼中IActivityManager是一個接口而他的實現(xiàn)類就是大名鼎鼎的ActivityManagerService(AMS)，我們來看AMS中對attachApplication的實現(xiàn):
@Override
public final void attachApplication(IApplicationThread thread) {
// ApplicationThread 實現(xiàn)了IApplicationThread的接口
synchronized (this) {
int callingPid = Binder.getCallingPid();
final long origId = Binder.clearCallingIdentity();
attachApplicationLocked(thread, callingPid);
Binder.restoreCallingIdentity(origId);
}
}
attachApplicationLocked方法中調用了ActivityStackSupervisor中的attachApplicationLocked方法，而該方法中調用了ApplicationThread中scheduleLaunchActivity，有興趣的可以去看下源碼。
我們可以發(fā)現(xiàn)其實不管是scheduleLaunchActivity還是其他的schedule...方法都調用了ApplicationThread中的sendMessage方法，該方法如下：
private void sendMessage(int what, Object obj) {
sendMessage(what, obj, 0, 0, false);
}
private void sendMessage(int what, Object obj, int arg1) {
sendMessage(what, obj, arg1, 0, false);
}
private void sendMessage(int what, Object obj, int arg1, int arg2) {
sendMessage(what, obj, arg1, arg2, false);
}
private void sendMessage(int what, Object obj, int arg1, int arg2, boolean async) {
if (DEBUG_MESSAGES) Slog.v(
TAG, "SCHEDULE " + what + " " + mH.codeToString(what)
+ ": " + arg1 + " / " + obj);
Message msg = Message.obtain();
msg.what = what;
msg.obj = obj;
msg.arg1 = arg1;
msg.arg2 = arg2;
if (async) {
msg.setAsynchronous(true);
}
mH.sendMessage(msg);
}
我們方法轉了一圈依舊回到了handler.sendMessage()方法，可見handler在Android中的重要性，后面也會陸續(xù)講解Handler的源碼。
問題1：H類中是如何處理Handler發(fā)送的消息呢?
答案：通過handleMessage進行處理，所有的生命周期其實都是通過該方法處理的，源碼如下：
public void handleMessage(Message msg) {
......省略.....
if (DEBUG_MESSAGES) Slog.v(TAG, ">>> handling: " + codeToString(msg.what));
switch (msg.what) {
case LAUNCH_ACTIVITY: {
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "activityStart");
final ActivityClientRecord r = (ActivityClientRecord) msg.obj;
r.packageInfo = getPackageInfoNoCheck(
r.activityInfo.applicationInfo, r.compatInfo);
handleLaunchActivity(r, null, "LAUNCH_ACTIVITY");
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
} break;
}
......省略.....
}
問題1：H類中handleMessage是如何被調用的呢？
答案：Looper會循環(huán)獲取messageQueue隊列中的message，并通過dispatchMessage多消息進行分發(fā)，源碼如下：
public void dispatchMessage(Message msg) {
if (msg.callback != null) {
handleCallback(msg);
} else {
if (mCallback != null) {
if (mCallback.handleMessage(msg)) {
return;
}
}
// 這里其實是調用了H類的handleMessage方法
handleMessage(msg);
}
}
上述代碼可以看到handleMessage中的handleLaunchActivity是關鍵，handleLaunchActivity代碼如下：
private void handleLaunchActivity(ActivityClientRecord r, Intent customIntent, String reason) {
unscheduleGcIdler();
mSomeActivitiesChanged = true;
if (r.profilerInfo != null) {
mProfiler.setProfiler(r.profilerInfo);
mProfiler.startProfiling();
}
handleConfigurationChanged(null, null);
if (localLOGV) Slog.v(
TAG, "Handling launch of " + r);
WindowManagerGlobal.initialize();
// 在這里創(chuàng)建了application以及activity
Activity a = performLaunchActivity(r, customIntent);
if (a != null) {
r.createdConfig = new Configuration(mConfiguration);
reportSizeConfigurations(r);
Bundle oldState = r.state;
handleResumeActivity(r.token, false, r.isForward,
!r.activity.mFinished && !r.startsNotResumed, r.lastProcessedSeq, reason);
if (!r.activity.mFinished && r.startsNotResumed) {
performPauseActivityIfNeeded(r, reason);
if (r.isPreHoneycomb()) {
r.state = oldState;
}
}
} else {
try {
ActivityManager.getService()
.finishActivity(r.token, Activity.RESULT_CANCELED, null,
Activity.DONT_FINISH_TASK_WITH_ACTIVITY);
} catch (RemoteException ex) {
throw ex.rethrowFromSystemServer();
}
}
}
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
// System.out.println("##### [" + System.currentTimeMillis() + "] ActivityThread.performLaunchActivity(" + r + ")");
ActivityInfo aInfo = r.activityInfo;
if (r.packageInfo == null) {
r.packageInfo = getPackageInfo(aInfo.applicationInfo, r.compatInfo,
Context.CONTEXT_INCLUDE_CODE);
}
ComponentName component = r.intent.getComponent();
if (component == null) {
component = r.intent.resolveActivity(
mInitialApplication.getPackageManager());
r.intent.setComponent(component);
}
if (r.activityInfo.targetActivity != null) {
component = new ComponentName(r.activityInfo.packageName,
r.activityInfo.targetActivity);
}
// 創(chuàng)建context
ContextImpl appContext = createBaseContextForActivity(r);
Activity activity = null;
try {
java.lang.ClassLoader cl = appContext.getClassLoader();
// activty的創(chuàng)建
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent);
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to instantiate activity " + component
+ ": " + e.toString(), e);
}
}
try {
// application的創(chuàng)建
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (localLOGV) Slog.v(TAG, "Performing launch of " + r);
if (localLOGV) Slog.v(
TAG, r + ": app=" + app
+ ", appName=" + app.getPackageName()
+ ", pkg=" + r.packageInfo.getPackageName()
+ ", comp=" + r.intent.getComponent().toShortString()
+ ", dir=" + r.packageInfo.getAppDir());
if (activity != null) {
// 從配置文件獲取label作為Activity默認title
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {
config.updateFrom(r.overrideConfig);
}
if (DEBUG_CONFIGURATION) Slog.v(TAG, "Launching activity "
+ r.activityInfo.name + " with config " + config);
// window的創(chuàng)建
Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
window = r.mPendingRemoveWindow;
r.mPendingRemoveWindow = null;
r.mPendingRemoveWindowManager = null;
}
appContext.setOuterContext(activity);
activity.attach(appContext, this, getInstrumentation(), r.token,
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window, r.configCallback);
if (customIntent != null) {
activity.mIntent = customIntent;
}
r.lastNonConfigurationInstances = null;
checkAndBlockForNetworkAccess();
activity.mStartedActivity = false;
int theme = r.activityInfo.getThemeResource();
if (theme != 0) {
activity.setTheme(theme);
}
activity.mCalled = false;
if (r.isPersistable()) {
// 觸發(fā)onCreate回調
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
// 觸發(fā)onCreate回調
mInstrumentation.callActivityOnCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onCreate()");
}
r.activity = activity;
r.stopped = true;
if (!r.activity.mFinished) {
activity.performStart();
r.stopped = false;
}
if (!r.activity.mFinished) {
if (r.isPersistable()) {
if (r.state != null || r.persistentState != null) {
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state,
r.persistentState);
}
} else if (r.state != null) {
// 其實都是調用了Activity的onPostCreate方法，該方法調用了onTitleChanged方法，用于設置title欄
mInstrumentation.callActivityOnRestoreInstanceState(activity, r.state);
}
}
if (!r.activity.mFinished) {
activity.mCalled = false;
if (r.isPersistable()) {
mInstrumentation.callActivityOnPostCreate(activity, r.state,
r.persistentState);
} else {
mInstrumentation.callActivityOnPostCreate(activity, r.state);
}
if (!activity.mCalled) {
throw new SuperNotCalledException(
"Activity " + r.intent.getComponent().toShortString() +
" did not call through to super.onPostCreate()");
}
}
}
r.paused = true;
mActivities.put(r.token, r);
} catch (SuperNotCalledException e) {
throw e;
} catch (Exception e) {
if (!mInstrumentation.onException(activity, e)) {
throw new RuntimeException(
"Unable to start activity " + component
+ ": " + e.toString(), e);
}
}
return activity;
}
上述代碼中可以看到在performLaunchActivity中創(chuàng)建了上下文Context，Application，以及Activity，而后通過Activity的attach方法為Context賦值并且將Activity與Window綁定，有興趣的可以去看下其實是為ContextWrapper中的mBase對象進行了賦值，而且Activity的attach方法中實例化了Window對象，并且設定了UI線程為當前線程，這里就不做講解，貼出attach的源碼：
final void attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
Application application, Intent intent, ActivityInfo info,
CharSequence title, Activity parent, String id,
NonConfigurationInstances lastNonConfigurationInstances,
Configuration config, String referrer, IVoiceInteractor voiceInteractor,
Window window, ActivityConfigCallback activityConfigCallback) {
attachBaseContext(context);
mFragments.attachHost(null /*parent*/);
mWindow = new PhoneWindow(this, window, activityConfigCallback);
mWindow.setWindowControllerCallback(this);
mWindow.setCallback(this);
mWindow.setOnWindowDismissedCallback(this);
mWindow.getLayoutInflater().setPrivateFactory(this);
if (info.softInputMode != WindowManager.LayoutParams.SOFT_INPUT_STATE_UNSPECIFIED) {
mWindow.setSoftInputMode(info.softInputMode);
}
if (info.uiOptions != 0) {
mWindow.setUiOptions(info.uiOptions);
}
mUiThread = Thread.currentThread();
mMainThread = aThread;
mInstrumentation = instr;
mToken = token;
mIdent = ident;
mApplication = application;
mIntent = intent;
mReferrer = referrer;
mComponent = intent.getComponent();
mActivityInfo = info;
mTitle = title;
mParent = parent;
mEmbeddedID = id;
mLastNonConfigurationInstances = lastNonConfigurationInstances;
if (voiceInteractor != null) {
if (lastNonConfigurationInstances != null) {
mVoiceInteractor = lastNonConfigurationInstances.voiceInteractor;
} else {
mVoiceInteractor = new VoiceInteractor(voiceInteractor, this, this,
Looper.myLooper());
}
}
mWindow.setWindowManager(
(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),
mToken, mComponent.flattenToString(),
(info.flags & ActivityInfo.FLAG_HARDWARE_ACCELERATED) != 0);
if (mParent != null) {
mWindow.setContainer(mParent.getWindow());
}
mWindowManager = mWindow.getWindowManager();
mCurrentConfig = config;
mWindow.setColorMode(info.colorMode);
}
在所有生命周期回調中，都是調用了Instrumentation中的方法，而Instrumentation的調用都是通過Handler發(fā)送消息觸發(fā)H函數(shù)的handleMessage方法來進行的，然后Instrumentation中的方法再去調用Activity中的生命周期方法，其實我們常用的onActivityResult回調都是通過handleMessage去分發(fā)的。有興趣可以下去深入研究下，Instrumentation部分代碼如下
// 觸發(fā)onCreate
public void callActivityOnCreate(Activity activity, Bundle icicle,
PersistableBundle persistentState) {
prePerformCreate(activity);
activity.performCreate(icicle, persistentState);
postPerformCreate(activity);
}
// 觸發(fā)onResume
public void callActivityOnResume(Activity activity) {
activity.mResumed = true;
activity.onResume();
if (mActivityMonitors != null) {
synchronized (mSync) {
final int N = mActivityMonitors.size();
for (int i=0; i<N; i++) {
final ActivityMonitor am = mActivityMonitors.get(i);
am.match(activity, activity, activity.getIntent());
}
}
}
}
