public class FourActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
BusLogUtils.d("------AppCompatActivity onCreate() called");
testLifecycle();
}
@Override
protected void onResume() {
super.onResume();
BusLogUtils.d("------AppCompatActivity onResume() called");
}
@Override
protected void onDestroy() {
super.onDestroy();
BusLogUtils.d("------AppCompatActivity onDestroy() called");
}
private void testLifecycle() {
getLifecycle().addObserver(new LifecycleObserver() {
@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
void onCreate(){
BusLogUtils.d("------LifecycleObserver onCreate() called");
}
@OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
void onResume(){
BusLogUtils.d("------LifecycleObserver onResume() called");
}
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
void onDestroy(){
BusLogUtils.d("------LifecycleObserver onDestroy() called");
}
});
}
}//打开页面 2020-03-06 09:44:09.522 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------AppCompatActivity onCreate() called 2020-03-06 09:44:09.545 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------LifecycleObserver onCreate() called 2020-03-06 09:44:09.551 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------AppCompatActivity onResume() called 2020-03-06 09:44:09.552 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------LifecycleObserver onResume() called //关闭页面 2020-03-06 09:44:14.265 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------LifecycleObserver onStop() called 2020-03-06 09:44:14.265 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------AppCompatActivity onStop() called 2020-03-06 09:44:14.266 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------LifecycleObserver onDestroy() called 2020-03-06 09:44:14.266 11647-11647/com.ycbjie.yclivedatabus D/BusLogUtils: ------AppCompatActivity onDestroy() called
public abstract class Lifecycle {
@MainThread
public abstract void addObserver(@NonNull LifecycleObserver observer);
@MainThread
public abstract void removeObserver(@NonNull LifecycleObserver observer);
@MainThread
@NonNull
public abstract State getCurrentState();
@SuppressWarnings("WeakerAccess")
public enum Event {
ON_CREATE,
ON_START,
ON_RESUME,
ON_PAUSE,
ON_STOP,
ON_DESTROY,
ON_ANY
}
@SuppressWarnings("WeakerAccess")
public enum State {
DESTROYED,
INITIALIZED,
CREATED,
STARTED,
RESUMED;
public boolean isAtLeast(@NonNull State state) {
return compareTo(state) >= 0;
}
}
}public class ReportFragment extends Fragment {
//这个方法很关键，搜索一下那些地方用到了这个方法
public static void injectIfNeededIn(Activity activity) {
// ProcessLifecycleOwner should always correctly work and some activities may not extend
// FragmentActivity from support lib, so we use framework fragments for activities
android.app.FragmentManager manager = activity.getFragmentManager();
if (manager.findFragmentByTag(REPORT_FRAGMENT_TAG) == null) {
//把Fragment加入到Activity中
manager.beginTransaction().add(new ReportFragment(), REPORT_FRAGMENT_TAG).commit();
// Hopefully, we are the first to make a transaction.
manager.executePendingTransactions();
}
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
dispatchCreate(mProcessListener);
//分发状态
dispatch(Lifecycle.Event.ON_CREATE);
}
@Override
public void onStart() {
super.onStart();
dispatchStart(mProcessListener);
//分发状态
dispatch(Lifecycle.Event.ON_START);
}
@Override
public void onResume() {
super.onResume();
dispatchResume(mProcessListener);
//分发状态
dispatch(Lifecycle.Event.ON_RESUME);
}
@Override
public void onPause() {
super.onPause();
//分发状态
dispatch(Lifecycle.Event.ON_PAUSE);
}
@Override
public void onStop() {
//分发状态
super.onStop();
dispatch(Lifecycle.Event.ON_STOP);
}
@Override
public void onDestroy() {
super.onDestroy();
//分发状态
dispatch(Lifecycle.Event.ON_DESTROY);
// just want to be sure that we won't leak reference to an activity
mProcessListener = null;
}
//分发生命周期事件
private void dispatch(Lifecycle.Event event) {
// 获取宿主activity
Activity activity = getActivity();
if (activity instanceof LifecycleRegistryOwner) {
//后面在分析handleLifecycleEvent方法源码
((LifecycleRegistryOwner) activity).getLifecycle().handleLifecycleEvent(event);
return;
}
if (activity instanceof LifecycleOwner) {
Lifecycle lifecycle = ((LifecycleOwner) activity).getLifecycle();
if (lifecycle instanceof LifecycleRegistry) {
后面在分析handleLifecycleEvent方法源码
((LifecycleRegistry) lifecycle).handleLifecycleEvent(event);
}
}
}
//...
}class LifecycleDispatcher {
static void init(Context context) {
if (sInitialized.getAndSet(true)) {
return;
}
((Application) context.getApplicationContext())
.registerActivityLifecycleCallbacks(new DispatcherActivityCallback());
}
@SuppressWarnings("WeakerAccess")
@VisibleForTesting
static class DispatcherActivityCallback extends EmptyActivityLifecycleCallbacks {
private final FragmentCallback mFragmentCallback;
DispatcherActivityCallback() {
mFragmentCallback = new FragmentCallback();
}
@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
if (activity instanceof FragmentActivity) {
((FragmentActivity) activity).getSupportFragmentManager()
.registerFragmentLifecycleCallbacks(mFragmentCallback, true);
}
ReportFragment.injectIfNeededIn(activity);
}
}
}public void handleLifecycleEvent(@NonNull Lifecycle.Event event) {
State next = getStateAfter(event);
moveToState(next);
}@RestrictTo(LIBRARY_GROUP)
public class ComponentActivity extends Activity implements LifecycleOwner {
private LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);
@Override
@SuppressWarnings("RestrictedApi")
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ReportFragment.injectIfNeededIn(this);
}
@CallSuper
@Override
protected void onSaveInstanceState(Bundle outState) {
mLifecycleRegistry.markState(Lifecycle.State.CREATED);
super.onSaveInstanceState(outState);
}
@Override
public Lifecycle getLifecycle() {
return mLifecycleRegistry;
}
}
public class LifecycleRegistry extends Lifecycle {}
public abstract class Lifecycle {}@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface OnLifecycleEvent {
Lifecycle.Event value();
}public void handleLifecycleEvent(Lifecycle.Event event) {
mState = getStateAfter(event);
if (mHandlingEvent || mAddingObserverCounter != 0) {
mNewEventOccurred = true;
// we will figure out what to do on upper level.
return;
}
mHandlingEvent = true;
sync();
mHandlingEvent = false;
}static State getStateAfter(Event event) {
switch (event) {
case ON_CREATE:
case ON_STOP:
return CREATED;
case ON_START:
case ON_PAUSE:
return STARTED;
case ON_RESUME:
return RESUMED;
case ON_DESTROY:
return DESTROYED;
case ON_ANY:
break;
}
throw new IllegalArgumentException("Unexpected event value " + event);
}private void sync() {
while (!isSynced()) {
mNewEventOccurred = false;
// no need to check eldest for nullability, because isSynced does it for us.
if (mState.compareTo(mObserverMap.eldest().getValue().mState) < 0) {
backwardPass();
}
Entry<LifecycleObserver, ObserverWithState> newest = mObserverMap.newest();
if (!mNewEventOccurred && newest != null
&& mState.compareTo(newest.getValue().mState) > 0) {
forwardPass();
}
}
mNewEventOccurred = false;
}private void backwardPass(LifecycleOwner lifecycleOwner) {
Iterator<Entry<LifecycleObserver, ObserverWithState>> descendingIterator =
mObserverMap.descendingIterator();
while (descendingIterator.hasNext() && !mNewEventOccurred) {
Entry<LifecycleObserver, ObserverWithState> entry = descendingIterator.next();
ObserverWithState observer = entry.getValue();
while ((observer.mState.compareTo(mState) > 0 && !mNewEventOccurred
&& mObserverMap.contains(entry.getKey()))) {
//调用 downEvent 获取更前面的 Event
Event event = downEvent(observer.mState);
pushParentState(getStateAfter(event));
//分发 Event
observer.dispatchEvent(lifecycleOwner, event);
popParentState();
}
}
}
private static Event downEvent(State state) {
switch (state) {
case INITIALIZED:
throw new IllegalArgumentException();
case CREATED:
return ON_DESTROY;
case STARTED:
return ON_STOP;
case RESUMED:
return ON_PAUSE;
case DESTROYED:
throw new IllegalArgumentException();
}
throw new IllegalArgumentException("Unexpected state value " + state);
}static class ObserverWithState {
State mState;
GenericLifecycleObserver mLifecycleObserver;
ObserverWithState(LifecycleObserver observer, State initialState) {
mLifecycleObserver = Lifecycling.getCallback(observer);
mState = initialState;
}
void dispatchEvent(LifecycleOwner owner, Event event) {
State newState = getStateAfter(event);
mState = min(mState, newState);
//这里
mLifecycleObserver.onStateChanged(owner, event);
mState = newState;
}
}class ReflectiveGenericLifecycleObserver implements GenericLifecycleObserver {
//mWrapped 是 我们的 Observer
private final Object mWrapped;
//反射 mWrapped 获取被注解了的方法
private final CallbackInfo mInfo;
@SuppressWarnings("WeakerAccess")
static final Map<Class, CallbackInfo> sInfoCache = new HashMap<>();
ReflectiveGenericLifecycleObserver(Object wrapped) {
mWrapped = wrapped;
mInfo = getInfo(mWrapped.getClass());
}
@Override
public void onStateChanged(LifecycleOwner source, Event event) {
invokeCallbacks(mInfo, source, event);
}
private void invokeCallbacks(CallbackInfo info, LifecycleOwner source, Event event) {
invokeMethodsForEvent(info.mEventToHandlers.get(event), source, event);
invokeMethodsForEvent(info.mEventToHandlers.get(Event.ON_ANY), source, event);
}
private void invokeMethodsForEvent(List<MethodReference> handlers, LifecycleOwner source,
Event event) {
if (handlers != null) {
for (int i = handlers.size() - 1; i >= 0; i--) {
MethodReference reference = handlers.get(i);
invokeCallback(reference, source, event);
}
}
}
//最后走到 invokeCallback 这里
private void invokeCallback(MethodReference reference, LifecycleOwner source, Event event) {
//noinspection TryWithIdenticalCatches
try {
switch (reference.mCallType) {
case CALL_TYPE_NO_ARG:
reference.mMethod.invoke(mWrapped);
break;
case CALL_TYPE_PROVIDER:
reference.mMethod.invoke(mWrapped, source);
break;
case CALL_TYPE_PROVIDER_WITH_EVENT:
reference.mMethod.invoke(mWrapped, source, event);
break;
}
} catch (InvocationTargetException e) {
throw new RuntimeException("Failed to call observer method", e.getCause());
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
private static CallbackInfo getInfo(Class klass) {
CallbackInfo existing = sInfoCache.get(klass);
if (existing != null) {
return existing;
}
existing = createInfo(klass);
return existing;
}
//通过反射获取 method 信息
private static CallbackInfo createInfo(Class klass) {
//...
Method[] methods = klass.getDeclaredMethods();
Class[] interfaces = klass.getInterfaces();
for (Class intrfc : interfaces) {
for (Entry<MethodReference, Event> entry : getInfo(intrfc).mHandlerToEvent.entrySet()) {
verifyAndPutHandler(handlerToEvent, entry.getKey(), entry.getValue(), klass);
}
}
for (Method method : methods) {
OnLifecycleEvent annotation = method.getAnnotation(OnLifecycleEvent.class);
if (annotation == null) {
continue;
}
Class<?>[] params = method.getParameterTypes();
int callType = CALL_TYPE_NO_ARG;
if (params.length > 0) {
callType = CALL_TYPE_PROVIDER;
if (!params[0].isAssignableFrom(LifecycleOwner.class)) {
throw new IllegalArgumentException(
"invalid parameter type. Must be one and instanceof LifecycleOwner");
}
}
Event event = annotation.value();
//...
MethodReference methodReference = new MethodReference(callType, method);
verifyAndPutHandler(handlerToEvent, methodReference, event, klass);
}
CallbackInfo info = new CallbackInfo(handlerToEvent);
sInfoCache.put(klass, info);
return info;
}
@SuppressWarnings("WeakerAccess")
static class CallbackInfo {
final Map<Event, List<MethodReference>> mEventToHandlers;
final Map<MethodReference, Event> mHandlerToEvent;
CallbackInfo(Map<MethodReference, Event> handlerToEvent) {
//...
}
}
static class MethodReference {
final int mCallType;
final Method mMethod;
MethodReference(int callType, Method method) {
mCallType = callType;
mMethod = method;
mMethod.setAccessible(true);
}
}
private static final int CALL_TYPE_NO_ARG = 0;
private static final int CALL_TYPE_PROVIDER = 1;
private static final int CALL_TYPE_PROVIDER_WITH_EVENT = 2;
}@Override
public void addObserver(@NonNull LifecycleObserver observer) {
State initialState = mState == DESTROYED ? DESTROYED : INITIALIZED;
//构造ObserverWithState
ObserverWithState statefulObserver = new ObserverWithState(observer, initialState);
//将observer对象和statefulObserver对象添加到FastSafeIterableMap数据结构中
ObserverWithState previous = mObserverMap.putIfAbsent(observer, statefulObserver);
if (previous != null) {
return;
}
LifecycleOwner lifecycleOwner = mLifecycleOwner.get();
if (lifecycleOwner == null) {
// 它是null，我们应该被摧毁。快速回退
return;
}
boolean isReentrance = mAddingObserverCounter != 0 || mHandlingEvent;
State targetState = calculateTargetState(observer);
mAddingObserverCounter++;
while ((statefulObserver.mState.compareTo(targetState) < 0
&& mObserverMap.contains(observer))) {
pushParentState(statefulObserver.mState);
statefulObserver.dispatchEvent(lifecycleOwner, upEvent(statefulObserver.mState));
popParentState();
// mState / subling may have been changed recalculate
targetState = calculateTargetState(observer);
}
if (!isReentrance) {
// we do sync only on the top level.
sync();
}
mAddingObserverCounter--;
}static class ObserverWithState {
State mState;
GenericLifecycleObserver mLifecycleObserver;
ObserverWithState(LifecycleObserver observer, State initialState) {
mLifecycleObserver = Lifecycling.getCallback(observer);
mState = initialState;
}
void dispatchEvent(LifecycleOwner owner, Event event) {
State newState = getStateAfter(event);
mState = min(mState, newState);
mLifecycleObserver.onStateChanged(owner, event);
mState = newState;
}
}@NonNull
static GenericLifecycleObserver getCallback(Object object) {
if (object instanceof FullLifecycleObserver) {
return new FullLifecycleObserverAdapter((FullLifecycleObserver) object);
}
if (object instanceof GenericLifecycleObserver) {
return (GenericLifecycleObserver) object;
}
//获取传入对象object的Class对象
final Class<?> klass = object.getClass();
//获取类型是否包含注解处理器
int type = getObserverConstructorType(klass);
if (type == GENERATED_CALLBACK) {
这里是包含注解处理器 返回SingleGeneratedAdapterObserver 或者CompositeGeneratedAdaptersObserver
List<Constructor<? extends GeneratedAdapter>> constructors =
sClassToAdapters.get(klass);
if (constructors.size() == 1) {
GeneratedAdapter generatedAdapter = createGeneratedAdapter(
constructors.get(0), object);
return new SingleGeneratedAdapterObserver(generatedAdapter);
}
GeneratedAdapter[] adapters = new GeneratedAdapter[constructors.size()];
for (int i = 0; i < constructors.size(); i++) {
adapters[i] = createGeneratedAdapter(constructors.get(i), object);
}
return new CompositeGeneratedAdaptersObserver(adapters);
}
///通过反射调用方法
return new ReflectiveGenericLifecycleObserver(object);
}@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public class SingleGeneratedAdapterObserver implements GenericLifecycleObserver {
private final GeneratedAdapter mGeneratedAdapter;
SingleGeneratedAdapterObserver(GeneratedAdapter generatedAdapter) {
mGeneratedAdapter = generatedAdapter;
}
@Override
public void onStateChanged(LifecycleOwner source, Lifecycle.Event event) {
mGeneratedAdapter.callMethods(source, event, false, null);
mGeneratedAdapter.callMethods(source, event, true, null);
}
}@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public class CompositeGeneratedAdaptersObserver implements GenericLifecycleObserver {
private final GeneratedAdapter[] mGeneratedAdapters;
CompositeGeneratedAdaptersObserver(GeneratedAdapter[] generatedAdapters) {
mGeneratedAdapters = generatedAdapters;
}
@Override
public void onStateChanged(LifecycleOwner source, Lifecycle.Event event) {
MethodCallsLogger logger = new MethodCallsLogger();
for (GeneratedAdapter mGenerated: mGeneratedAdapters) {
mGenerated.callMethods(source, event, false, logger);
}
for (GeneratedAdapter mGenerated: mGeneratedAdapters) {
mGenerated.callMethods(source, event, true, logger);
}
}
}class ReflectiveGenericLifecycleObserver implements GenericLifecycleObserver {
private final Object mWrapped;
private final CallbackInfo mInfo;
ReflectiveGenericLifecycleObserver(Object wrapped) {
mWrapped = wrapped;
mInfo = ClassesInfoCache.sInstance.getInfo(mWrapped.getClass());
}
@Override
public void onStateChanged(LifecycleOwner source, Event event) {
mInfo.invokeCallbacks(source, event, mWrapped);
}
}
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