Fragement生命周期是和Activity生命周期相关的。
Activity生命周期由ActivityThread发起的，ActivityThread成员对象ApplictionThread接受AMS远程调用数据，然后调用Handler发起主线程启动。
ActivityThread :: private class H extends Handler {
public void handleMessage(Message msg) {
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;
....
}
}
这个内部类很长就不全贴了，大家可以自己看看。Activity是事件驱动行的，上面LAUNCH_ACTIVITY就是一个事件
public class Activity extends ContextThemeWrapper
implements LayoutInflater.Factory2,
Window.Callback, KeyEvent.Callback,
OnCreateContextMenuListener, ComponentCallbacks2,
Window.OnWindowDismissedCallback, WindowControllerCallback {
...
final FragmentController mFragments = FragmentController.createController(new HostCallbacks());
}
public void onLowMemory() {
if (DEBUG_LIFECYCLE) Slog.v(TAG, "onLowMemory " + this);
mCalled = true;
mFragments.dispatchLowMemory();
}
public void onTrimMemory(int level) {
if (DEBUG_LIFECYCLE) Slog.v(TAG, "onTrimMemory " + this + ": " + level);
mCalled = true;
mFragments.dispatchTrimMemory(level);
}
public void onBackPressed() {
...
if (!mFragments.getFragmentManager().popBackStackImmediate()) {
finishAfterTransition();
}
}
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) {
attachBaseContext(context);
mFragments.attachHost(null /*parent*/);
...
}
}
Activity最初会初始化一个FragmentController，来做所有生命周期的转换。另外几个不是生命周期，但有时候会参与调用回收。
attach()来自ActivityThread::performLaunchActivity()调用mInstrumentation对象来启动的。后面有。
protected void onCreate(@Nullable Bundle savedInstanceState) {//【create ： 1】
if (mLastNonConfigurationInstances != null) {
mFragments.restoreLoaderNonConfig(mLastNonConfigurationInstances.loaders);
}
....
if (savedInstanceState != null) {
Parcelable p = savedInstanceState.getParcelable(FRAGMENTS_TAG);
mFragments.restoreAllState(p, mLastNonConfigurationInstances != null
? mLastNonConfigurationInstances.fragments : null);
}
mFragments.dispatchCreate();
getApplication().dispatchActivityCreated(this, savedInstanceState);
}
final void performCreateCommon() {//【create ： 1】
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mFragments.dispatchActivityCreated();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
}
final void performCreate(Bundle icicle) {
restoreHasCurrentPermissionRequest(icicle);
onCreate(icicle); //【create ： 1】
mActivityTransitionState.readState(icicle);
performCreateCommon();
}
Activity::performCreate()来自ActivityThread::performLaunchActivity()
private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
Activity activity = null;
try {
java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
activity = mInstrumentation.newActivity(
cl, component.getClassName(), r.intent); //【这里面启动，先做反射，弄个空壳，一般做Test】
StrictMode.incrementExpectedActivityCount(activity.getClass());
r.intent.setExtrasClassLoader(cl);
r.intent.prepareToEnterProcess();
if (r.state != null) {
r.state.setClassLoader(cl);
}
} catch (Exception e) {
}
...
try {
Application app = r.packageInfo.makeApplication(false, mInstrumentation);
if (activity != null) {
Context appContext = createBaseContextForActivity(r, activity);
CharSequence title = r.activityInfo.loadLabel(appContext.getPackageManager());
Configuration config = new Configuration(mCompatConfiguration);
if (r.overrideConfig != null) {
config.updateFrom(r.overrideConfig);
}
activity.attach(appContext, this, getInstrumentation(), r.token, // 【这里面启动前面Activity::attach()】
r.ident, app, r.intent, r.activityInfo, title, r.parent,
r.embeddedID, r.lastNonConfigurationInstances, config,
r.referrer, r.voiceInteractor, window);
...
activity.mCalled = false;
if (r.isPersistable()) { //【create ： 2】
mInstrumentation.callActivityOnCreate(activity, r.state, r.persistentState);
} else {
mInstrumentation.callActivityOnCreate(activity, r.state); //【create ： 2】
}
...
r.activity = activity;
r.stopped = true;
if (!r.activity.mFinished) {//【start : 2】
activity.performStart(); //【start : 2】
r.stopped = false;//【start : 2】
}
}
}
接着Instrumentation::callActivityOnCreate()就调用Activity::performCreate()
public void callActivityOnCreate(Activity activity, Bundle icicle,
PersistableBundle persistentState) {
prePerformCreate(activity);
activity.performCreate(icicle, persistentState);
postPerformCreate(activity);
}
可以看出：
- mFragments.dispatchActivityCreated()在Activity::onCreate()之后，从【create ：1】可以看出
- mFragments.dispatchCreate()在Activity::onCreate()之中
final void performStart() {
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
mFragments.noteStateNotSaved();
mCalled = false;
mFragments.execPendingActions();
mInstrumentation.callActivityOnStart(this); //【start：1】
...
mFragments.dispatchStart();//【start：1】
mFragments.reportLoaderStart();
...
mActivityTransitionState.enterReady(this);
}
final void performRestart() {
mFragments.noteStateNotSaved();
if (mStopped) {
mStopped = false;
...
mCalled = false;
mInstrumentation.callActivityOnRestart(this);
if (!mCalled) {
throw new SuperNotCalledException(
"Activity " + mComponent.toShortString() +
" did not call through to super.onRestart()");
}
performStart();
}
}
Activity::performStart()来自ActivityThread::performLaunchActivity(),前面有,//【start : 2】
Activity::performRestart()来自ActivityThread::performRestartActivity()
可以看出：
- performRestart()中mFragments没有干活。
- mFragments.dispatchStart()在Instrumentation::performStart()之后，从【start：1】可以看出
final void performResume() {
performRestart();
mFragments.execPendingActions();
mLastNonConfigurationInstances = null;
// mResumed is set by the instrumentation
mInstrumentation.callActivityOnResume(this); // 【resume ： 1】
...
mFragments.dispatchResume(); // 【resume ： 1】
mFragments.execPendingActions();
onPostResume();
}
Activity::performResume()来自ActivityThread::performResumeActivity()
可以看出：
- mFragments.dispatchResume()在Instrumentation::callActivityOnResume()之后， 从【resume ： 1】可以看出
final void performPause() {
mDoReportFullyDrawn = false;
mFragments.dispatchPause(); // 【pause ： 1】
mCalled = false;
onPause();// 【pause ： 1】
mResumed = false;
if (!mCalled && getApplicationInfo().targetSdkVersion
>= android.os.Build.VERSION_CODES.GINGERBREAD) {
throw new SuperNotCalledException(
"Activity " + mComponent.toShortString() +
" did not call through to super.onPause()");
}
mResumed = false;
}
Activity::performPause()来自ActivityThread::performPauseActivityIfNeeded()然后调用Instrumentation.callActivityOnPause()
可以看出：
- mFragments.dispatchPause()在Activity::onPause()之前， 从【pause ： 1】可以看出
final void performStop(boolean preserveWindow) {
mDoReportFullyDrawn = false;
mFragments.doLoaderStop(mChangingConfigurations /*retain*/);
if (!mStopped) {
...
mFragments.dispatchStop(); // 【stop ： 1】
mCalled = false;
mInstrumentation.callActivityOnStop(this); // 【stop ： 1】
...
mStopped = true;
}
mResumed = false;
}
Activity::performStop()来自ActivityThread::performStopActivityInner()它会先检查是否pause
可以看出：
- mFragments.dispatchStop()在Instrumentation::callActivityOnStop()之前， 从【stop ： 1】可以看出
final void performDestroy() {
mDestroyed = true;
mWindow.destroy();
mFragments.dispatchDestroy(); // 【destroy ： 1】
onDestroy(); // 【destroy ： 1】
mFragments.doLoaderDestroy();
if (mVoiceInteractor != null) {
mVoiceInteractor.detachActivity();
}
}
Activity::performDestroy()来自ActivityThread::performDestroyActivity()它会去先检查是否stop
可以看出：
- mFragments.dispatchDestroy()在Activity::onDestroy()之前， 从【destroy ： 1】可以看出
好了先看一波图：
图是我网上抄的
大致所我所描述，细节需要自己看。
FragmentController里面有FragmentManagerImpl，核心方法：
void moveToState(Fragment f, int newState, int transit, int transitionStyle,
boolean keepActive) {
if (DEBUG && false) Log.v(TAG, "moveToState: " + f
+ " oldState=" + f.mState + " newState=" + newState
+ " mRemoving=" + f.mRemoving + " Callers=" + Debug.getCallers(5));
// Fragments that are not currently added will sit in the onCreate() state.
if ((!f.mAdded || f.mDetached) && newState > Fragment.CREATED) {
newState = Fragment.CREATED;
}
if (f.mRemoving && newState > f.mState) {
// While removing a fragment, we can't change it to a higher state.
newState = f.mState;
}
// Defer start if requested; don't allow it to move to STARTED or higher
// if it's not already started.
if (f.mDeferStart && f.mState < Fragment.STARTED && newState > Fragment.STOPPED) {
newState = Fragment.STOPPED;
}
if (f.mState < newState) {
// For fragments that are created from a layout, when restoring from
// state we don't want to allow them to be created until they are
// being reloaded from the layout.
if (f.mFromLayout && !f.mInLayout) {
return;
}
if (f.mAnimatingAway != null) {
// The fragment is currently being animated... but! Now we
// want to move our state back up. Give up on waiting for the
// animation, move to whatever the final state should be once
// the animation is done, and then we can proceed from there.
f.mAnimatingAway = null;
moveToState(f, f.mStateAfterAnimating, 0, 0, true);
}
switch (f.mState) {
case Fragment.INITIALIZING:
if (DEBUG) Log.v(TAG, "moveto CREATED: " + f);
if (f.mSavedFragmentState != null) {
f.mSavedViewState = f.mSavedFragmentState.getSparseParcelableArray(
FragmentManagerImpl.VIEW_STATE_TAG);
f.mTarget = getFragment(f.mSavedFragmentState,
FragmentManagerImpl.TARGET_STATE_TAG);
if (f.mTarget != null) {
f.mTargetRequestCode = f.mSavedFragmentState.getInt(
FragmentManagerImpl.TARGET_REQUEST_CODE_STATE_TAG, 0);
}
f.mUserVisibleHint = f.mSavedFragmentState.getBoolean(
FragmentManagerImpl.USER_VISIBLE_HINT_TAG, true);
if (!f.mUserVisibleHint) {
f.mDeferStart = true;
if (newState > Fragment.STOPPED) {
newState = Fragment.STOPPED;
}
}
}
f.mHost = mHost;
f.mParentFragment = mParent;
f.mFragmentManager = mParent != null
? mParent.mChildFragmentManager : mHost.getFragmentManagerImpl();
f.mCalled = false;
f.onAttach(mHost.getContext());
if (!f.mCalled) {
throw new SuperNotCalledException("Fragment " + f
+ " did not call through to super.onAttach()");
}
if (f.mParentFragment == null) {
mHost.onAttachFragment(f);
} else {
f.mParentFragment.onAttachFragment(f);
}
if (!f.mRetaining) {
f.performCreate(f.mSavedFragmentState);
} else {
f.restoreChildFragmentState(f.mSavedFragmentState, true);
f.mState = Fragment.CREATED;
}
f.mRetaining = false;
if (f.mFromLayout) {
// For fragments that are part of the content view
// layout, we need to instantiate the view immediately
// and the inflater will take care of adding it.
f.mView = f.performCreateView(f.getLayoutInflater(
f.mSavedFragmentState), null, f.mSavedFragmentState);
if (f.mView != null) {
f.mView.setSaveFromParentEnabled(false);
if (f.mHidden) f.mView.setVisibility(View.GONE);
f.onViewCreated(f.mView, f.mSavedFragmentState);
}
}
case Fragment.CREATED:
if (newState > Fragment.CREATED) {
if (DEBUG) Log.v(TAG, "moveto ACTIVITY_CREATED: " + f);
if (!f.mFromLayout) {
ViewGroup container = null;
if (f.mContainerId != 0) {
if (f.mContainerId == View.NO_ID) {
throwException(new IllegalArgumentException(
"Cannot create fragment "
+ f
+ " for a container view with no id"));
}
container = (ViewGroup) mContainer.onFindViewById(f.mContainerId);
if (container == null && !f.mRestored) {
String resName;
try {
resName = f.getResources().getResourceName(f.mContainerId);
} catch (NotFoundException e) {
resName = "unknown";
}
throwException(new IllegalArgumentException(
"No view found for id 0x"
+ Integer.toHexString(f.mContainerId) + " ("
+ resName
+ ") for fragment " + f));
}
}
f.mContainer = container;
f.mView = f.performCreateView(f.getLayoutInflater(
f.mSavedFragmentState), container, f.mSavedFragmentState);
if (f.mView != null) {
f.mView.setSaveFromParentEnabled(false);
if (container != null) {
Animator anim = loadAnimator(f, transit, true,
transitionStyle);
if (anim != null) {
anim.setTarget(f.mView);
setHWLayerAnimListenerIfAlpha(f.mView, anim);
anim.start();
}
container.addView(f.mView);
}
if (f.mHidden) f.mView.setVisibility(View.GONE);
f.onViewCreated(f.mView, f.mSavedFragmentState);
}
}
f.performActivityCreated(f.mSavedFragmentState);
if (f.mView != null) {
f.restoreViewState(f.mSavedFragmentState);
}
f.mSavedFragmentState = null;
}
case Fragment.ACTIVITY_CREATED:
if (newState > Fragment.ACTIVITY_CREATED) {
f.mState = Fragment.STOPPED;
}
case Fragment.STOPPED:
if (newState > Fragment.STOPPED) {
if (DEBUG) Log.v(TAG, "moveto STARTED: " + f);
f.performStart();
}
case Fragment.STARTED:
if (newState > Fragment.STARTED) {
if (DEBUG) Log.v(TAG, "moveto RESUMED: " + f);
f.performResume();
// Get rid of this in case we saved it and never needed it.
f.mSavedFragmentState = null;
f.mSavedViewState = null;
}
}
} else if (f.mState > newState) {
switch (f.mState) {
case Fragment.RESUMED:
if (newState < Fragment.RESUMED) {
if (DEBUG) Log.v(TAG, "movefrom RESUMED: " + f);
f.performPause();
}
case Fragment.STARTED:
if (newState < Fragment.STARTED) {
if (DEBUG) Log.v(TAG, "movefrom STARTED: " + f);
f.performStop();
}
case Fragment.STOPPED:
case Fragment.ACTIVITY_CREATED:
if (newState < Fragment.ACTIVITY_CREATED) {
if (DEBUG) Log.v(TAG, "movefrom ACTIVITY_CREATED: " + f);
if (f.mView != null) {
// Need to save the current view state if not
// done already.
if (mHost.onShouldSaveFragmentState(f) && f.mSavedViewState == null) {
saveFragmentViewState(f);
}
}
f.performDestroyView();
if (f.mView != null && f.mContainer != null) {
Animator anim = null;
if (mCurState > Fragment.INITIALIZING && !mDestroyed) {
anim = loadAnimator(f, transit, false,
transitionStyle);
}
if (anim != null) {
final ViewGroup container = f.mContainer;
final View view = f.mView;
final Fragment fragment = f;
container.startViewTransition(view);
f.mAnimatingAway = anim;
f.mStateAfterAnimating = newState;
anim.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator anim) {
container.endViewTransition(view);
if (fragment.mAnimatingAway != null) {
fragment.mAnimatingAway = null;
moveToState(fragment, fragment.mStateAfterAnimating,
0, 0, false);
}
}
});
anim.setTarget(f.mView);
setHWLayerAnimListenerIfAlpha(f.mView, anim);
anim.start();
}
f.mContainer.removeView(f.mView);
}
f.mContainer = null;
f.mView = null;
}
case Fragment.CREATED:
if (newState < Fragment.CREATED) {
if (mDestroyed) {
if (f.mAnimatingAway != null) {
// The fragment's containing activity is
// being destroyed, but this fragment is
// currently animating away. Stop the
// animation right now -- it is not needed,
// and we can't wait any more on destroying
// the fragment.
Animator anim = f.mAnimatingAway;
f.mAnimatingAway = null;
anim.cancel();
}
}
if (f.mAnimatingAway != null) {
// We are waiting for the fragment's view to finish
// animating away. Just make a note of the state
// the fragment now should move to once the animation
// is done.
f.mStateAfterAnimating = newState;
newState = Fragment.CREATED;
} else {
if (DEBUG) Log.v(TAG, "movefrom CREATED: " + f);
if (!f.mRetaining) {
f.performDestroy();
} else {
f.mState = Fragment.INITIALIZING;
}
f.performDetach();
if (!keepActive) {
if (!f.mRetaining) {
makeInactive(f);
} else {
f.mHost = null;
f.mParentFragment = null;
f.mFragmentManager = null;
}
}
}
}
}
}
if (f.mState != newState) {
Log.w(TAG, "moveToState: Fragment state for " + f + " not updated inline; "
+ "expected state " + newState + " found " + f.mState);
f.mState = newState;
}
}
然后外部FragmentHostCallback在Activity生命周期产生回调事件的时候会改变moveToState的值，然后实现了Fragment的生命周期。