Lifecycle是什么

• Lifecycle可以有效的避免内存泄漏和解决android生命周期的常见难题
• Livecycle 是一个表示android生命周期及状态的对象
• LivecycleOwner 用于连接有生命周期的对象，如activity,fragment
• LivecycleObserver 用于观察查LifecycleOwner
• Lifecycle框架使用观察者模式实现观察者监听被观察者的生命周期的变化

LifeCycle的各种使用方式

不使用lifecycle对生命周期的处理：

1.使用监听器

// TODO 第一个版本 监听器监听生命周期
class MainActivity : AppCompatActivity() {

    private var myListener: MyListener ? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        myListener = MyListener()
    }

    override fun onStart() {
        super.onStart()
        myListener ?.start() // 会出现人为失误，一旦出现人为失误 造成不一致性功能问题
    }

    override fun onStop() {
        super.onStop()
        myListener ?.stop() // 会出现人为失误
    }
}

class MyListener {

    private val TAG = "MyListener"

    fun start() = Log.d(TAG, "start run ...")

    fun stop() = Log.d(TAG, "stop run ...")
}

2.MVP的P层

// TODO 第二个版本 MVP 的 P层
class MainActivity : AppCompatActivity() {

    private var myPresenter: MyPresenter ? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        myPresenter = MyPresenter()
    }

    override fun onResume() {
        super.onResume()
        myPresenter ?.onResume()  // 会出现人为失误
    }

    override fun onPause() {
        super.onPause()
        myPresenter ?.onPause()  // 会出现人为失误
    }
}

class MyPresenter {

    private val TAG = "MyPresenter"

    fun onResume() = Log.d(TAG, "onResume run ...")

    fun onPause() = Log.d(TAG, "onPause run ...")
}

使用lifecycle:
1.

// TODO 第二个版本 MVP 的 P层
class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // 一般是在BaseActivity 关联注册的
        // 观察者 与 被观察者 关联的环节
        lifecycle.addObserver(MyObserver())
        lifecycle.addObserver(MyObserver2())
    }

}

// 观察者  眼睛
class MyObserver : LifecycleObserver {

    private val TAG = "MyObserver"

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) // 画面可见 就连接
    fun connectListener() = Log.d(TAG,"connectListener run ...")

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)  // 画面不可见 就断开连接
    fun disconnectListener() = Log.d(TAG,"disconnectListener run ...")

}

// DefaultLifecycleObserver 就是对 LifecycleObserver 二次封装  为了用户好用
class MyObserver2 : DefaultLifecycleObserver {

    private val TAG = "MyObserver2"

    override fun onCreate(owner: LifecycleOwner) {
        super.onCreate(owner)
        Log.d(TAG,"onCreate run ...")

        // 项目实战 给大家演示好处 可以拿到 Activity Fragment 所有环境 Toast
    }

    override fun onResume(owner: LifecycleOwner) {
        super.onResume(owner)
        Log.d(TAG,"onResume run ...")
    }

    override fun onPause(owner: LifecycleOwner) {
        super.onPause(owner)
        Log.d(TAG,"onPause run ...")
    }

}

2.使用内部类监听

// TODO 第四个版本  会内部类 监听
class MainActivity : AppCompatActivity() {

    private val TAG = "MainActivity"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // 一般是在BaseActivity 关联注册的
        lifecycle.addObserver(MyObserver())
    }

    inner class MyObserver : LifecycleObserver {

        @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
        fun onResume() {
            Log.d(TAG, "Lifecycle call onResume");
            // 逻辑
        }

        @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
        fun onPause() {
            Log.d(TAG, "Lifecycle call onPause");
        }
    }

    /*override fun onResume() {
        super.onResume()
        // 逻辑
    }*/
}

3.使用接口继承observer，再去实现接口

// TODO 第五个版本  接口监听法，设计模式的设计环节，你会见到这种写法
class MainActivity : AppCompatActivity() {

    private val TAG = "MainActivity"

    private var myPresenter : IPresenter ? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // 一般是在BaseActivity 关联注册的   (省略：工厂设计模式)
        myPresenter = MyPresenter3()

        lifecycle.addObserver(myPresenter !!)
    }
}

interface IPresenter : LifecycleObserver {

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    fun onResume()

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    fun onPause()

}

class MyPresenter3 : IPresenter {
    private val TAG = "test"

    override fun onResume() {
        Log.d(TAG, "Lifecycle call onResume")
    }

    override fun onPause() {
        Log.d(TAG, "Lifecycle call onPause")
    }
}

LifeCycle的源码解析

通过追溯源码可以发现，当前Activity继承的是androidx.core.app.Component-Activity，而ComponentActivity实现了LifecycleOwner接口，所以开发者可以直接调用getLifecycle方法。

/**
 * A class that has an Android lifecycle. These events can be used by custom components to
 * handle lifecycle changes without implementing any code inside the Activity or the Fragment.
 *
 * @see Lifecycle
 */
@SuppressWarnings({"WeakerAccess", "unused"})
public interface LifecycleOwner {
    /**
     * Returns the Lifecycle of the provider.
     *
     * @return The lifecycle of the provider.
     */
    @NonNull
    Lifecycle getLifecycle();
}

除了ComponentActivity之外，在ComponentActivity的子类androidx.fragment.app.FragmentActivity、androidx.appcompat.app.AppCompatActivity以及androidx.fragment.app.Fragment中都是可以直接使用Lifecycle的，这是AndroidX帮助开发者完成的。

在ComponentActivity的onCreate的函数中，使用了一个ReportFragment，ReportFragment是一个无页面的Fragment，它是用来协助Activity处理任务的。代码如下：

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mSavedStateRegistryController.performRestore(savedInstanceState);
        ReportFragment.injectIfNeededIn(this);
        if (mContentLayoutId != 0) {
            setContentView(mContentLayoutId);
        }
    }

（这里可以看到高于29的版本做了单独的处理，后面会提到）

    public static void injectIfNeededIn(Activity activity) {
        if (Build.VERSION.SDK_INT >= 29) {
            // On API 29+, we can register for the correct Lifecycle callbacks directly
            activity.registerActivityLifecycleCallbacks(
                    new LifecycleCallbacks());
        }
        // Prior to API 29 and to maintain compatibility with older versions of
        // ProcessLifecycleOwner (which may not be updated when lifecycle-runtime is updated and
        // need to support activities that don't extend from FragmentActivity from support lib),
        // use a framework fragment to get the correct timing of Lifecycle events
        android.app.FragmentManager manager = activity.getFragmentManager();
        if (manager.findFragmentByTag(REPORT_FRAGMENT_TAG) == null) {
            manager.beginTransaction().add(new ReportFragment(), REPORT_FRAGMENT_TAG).commit();
            // Hopefully, we are the first to make a transaction.
            manager.executePendingTransactions();
        }
    }

通过源码注释可以看出，引入ReportFragment是为了兼容那些并不是直接继承自FragmentActivity的页面，这样它们就可以正常使用Lifecycle了。在Report-Fragment中可以看到对应生命周期的方法中都会执行dispatch方法，代码如下：

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        dispatchCreate(mProcessListener);
        dispatch(Lifecycle.Event.ON_CREATE);
    }

    @Override
    public void onStart() {
        super.onStart();
        dispatchStart(mProcessListener);
        dispatch(Lifecycle.Event.ON_START);
    }

    @Override
    public void onResume() {
        super.onResume();
        dispatchResume(mProcessListener);
        dispatch(Lifecycle.Event.ON_RESUME);
    }

    @Override
    public void onPause() {
        super.onPause();
        dispatch(Lifecycle.Event.ON_PAUSE);
    }

    @Override
    public void onStop() {
        super.onStop();
        dispatch(Lifecycle.Event.ON_STOP);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        dispatch(Lifecycle.Event.ON_DESTROY);
        // just want to be sure that we won't leak reference to an activity
        mProcessListener = null;
    }

接下来看看dispatch方法的主要代码，具体如下：

    private void dispatch(@NonNull Lifecycle.Event event) {
        if (Build.VERSION.SDK_INT < 29) {
            // Only dispatch events from ReportFragment on API levels prior
            // to API 29. On API 29+, this is handled by the ActivityLifecycleCallbacks
            // added in ReportFragment.injectIfNeededIn
            dispatch(getActivity(), event);
        }
    }

对于高于29的版本：

    // this class isn't inlined only because we need to add a proguard rule for it. (b/142778206)
    static class LifecycleCallbacks implements Application.ActivityLifecycleCallbacks {
        @Override
        public void onActivityCreated(@NonNull Activity activity,
                @Nullable Bundle bundle) {
        }

        @Override
        public void onActivityPostCreated(@NonNull Activity activity,
                @Nullable Bundle savedInstanceState) {
            dispatch(activity, Lifecycle.Event.ON_CREATE);
        }

        @Override
        public void onActivityStarted(@NonNull Activity activity) {
        }

        @Override
        public void onActivityPostStarted(@NonNull Activity activity) {
            dispatch(activity, Lifecycle.Event.ON_START);
        }

        @Override
        public void onActivityResumed(@NonNull Activity activity) {
        }

        @Override
        public void onActivityPostResumed(@NonNull Activity activity) {
            dispatch(activity, Lifecycle.Event.ON_RESUME);
        }

        @Override
        public void onActivityPrePaused(@NonNull Activity activity) {
            dispatch(activity, Lifecycle.Event.ON_PAUSE);
        }

        @Override
        public void onActivityPaused(@NonNull Activity activity) {
        }

        @Override
        public void onActivityPreStopped(@NonNull Activity activity) {
            dispatch(activity, Lifecycle.Event.ON_STOP);
        }

        @Override
        public void onActivityStopped(@NonNull Activity activity) {
        }

        @Override
        public void onActivitySaveInstanceState(@NonNull Activity activity,
                @NonNull Bundle bundle) {
        }

        @Override
        public void onActivityPreDestroyed(@NonNull Activity activity) {
            dispatch(activity, Lifecycle.Event.ON_DESTROY);
        }

        @Override
        public void onActivityDestroyed(@NonNull Activity activity) {
        }
    }

    static void dispatch(@NonNull Activity activity, @NonNull Lifecycle.Event event) {
        if (activity instanceof LifecycleRegistryOwner) {
            ((LifecycleRegistryOwner) activity).getLifecycle().handleLifecycleEvent(event);
            return;
        }

        if (activity instanceof LifecycleOwner) {
            Lifecycle lifecycle = ((LifecycleOwner) activity).getLifecycle();
            if (lifecycle instanceof LifecycleRegistry) {
                ((LifecycleRegistry) lifecycle).handleLifecycleEvent(event);
            }
        }
    }

dispatch方法最终都会进入handleLifecycleEvent方法中，通过handleLifecycle-Event设置状态并通知观察者，Activity便能监听到生命周期的变化了。
dispatch()方法则会判断Activity是否实现了LifecycleOwner接口，如果实现了该接口就调用LifecycleRegister的handleLifecycleEvent()
这样生命周期的状态就会借由LifecycleRegistry通知给各个LifecycleObserver从而调用其中对应Lifecycle.Event的方法。这种通过Fragment来感知Activity生命周期的方法其实在Glide的中也是有体现的。

接下来我们看一下handleLifecycleEvent方法：

    /**
     * Sets the current state and notifies the observers.
     * <p>
     * Note that if the {@code currentState} is the same state as the last call to this method,
     * calling this method has no effect.
     *
     * @param event The event that was received
     */
    public void handleLifecycleEvent(@NonNull Lifecycle.Event event) {
        State next = getStateAfter(event);
        moveToState(next);
    }

    @SuppressWarnings("WeakerAccess")
    public enum Event {
        /**
         * Constant for onCreate event of the {@link LifecycleOwner}.
         */
        ON_CREATE,
        /**
         * Constant for onStart event of the {@link LifecycleOwner}.
         */
        ON_START,
        /**
         * Constant for onResume event of the {@link LifecycleOwner}.
         */
        ON_RESUME,
        /**
         * Constant for onPause event of the {@link LifecycleOwner}.
         */
        ON_PAUSE,
        /**
         * Constant for onStop event of the {@link LifecycleOwner}.
         */
        ON_STOP,
        /**
         * Constant for onDestroy event of the {@link LifecycleOwner}.
         */
        ON_DESTROY,
        /**
         * An {@link Event Event} constant that can be used to match all events.
         */
        ON_ANY
    }

    /**
     * Lifecycle states. You can consider the states as the nodes in a graph and
     * {@link Event}s as the edges between these nodes.
     */
    @SuppressWarnings("WeakerAccess")
    public enum State {
        /**
         * Destroyed state for a LifecycleOwner. After this event, this Lifecycle will not dispatch
         * any more events. For instance, for an {@link android.app.Activity}, this state is reached
         * <b>right before</b> Activity's {@link android.app.Activity#onDestroy() onDestroy} call.
         */
        DESTROYED,

        /**
         * Initialized state for a LifecycleOwner. For an {@link android.app.Activity}, this is
         * the state when it is constructed but has not received
         * {@link android.app.Activity#onCreate(android.os.Bundle) onCreate} yet.
         */
        INITIALIZED,

        /**
         * Created state for a LifecycleOwner. For an {@link android.app.Activity}, this state
         * is reached in two cases:
         * <ul>
         *     <li>after {@link android.app.Activity#onCreate(android.os.Bundle) onCreate} call;
         *     <li><b>right before</b> {@link android.app.Activity#onStop() onStop} call.
         * </ul>
         */
        CREATED,

        /**
         * Started state for a LifecycleOwner. For an {@link android.app.Activity}, this state
         * is reached in two cases:
         * <ul>
         *     <li>after {@link android.app.Activity#onStart() onStart} call;
         *     <li><b>right before</b> {@link android.app.Activity#onPause() onPause} call.
         * </ul>
         */
        STARTED,

        /**
         * Resumed state for a LifecycleOwner. For an {@link android.app.Activity}, this state
         * is reached after {@link android.app.Activity#onResume() onResume} is called.
         */
        RESUMED;

        /**
         * Compares if this State is greater or equal to the given {@code state}.
         *
         * @param state State to compare with
         * @return true if this State is greater or equal to the given {@code state}
         */
        public boolean isAtLeast(@NonNull State state) {
            return compareTo(state) >= 0;
        }
    }

handleLifecycleEvent方法中State next = getStateAfter(event);事件发生的时候，先得到当前activity应该出现的下一个状态。moveToState(next);mState = next;更新现在的状态sync();backwardPass(lifecycleOwner);逆推forwardPass(lifecycleOwner);正推，从图表上分析 ：

//如果状态和原本的一致 就直接return了
    private void moveToState(State next) {
        if (mState == next) {
            return;
        }
        mState = next;
        if (mHandlingEvent || mAddingObserverCounter != 0) {
            mNewEventOccurred = true;
            // we will figure out what to do on upper level.
            return;
        }
        mHandlingEvent = true;
        sync();
        mHandlingEvent = false;
    }

    private void sync() {
        LifecycleOwner lifecycleOwner = mLifecycleOwner.get();
        if (lifecycleOwner == null) {
            throw new IllegalStateException("LifecycleOwner of this LifecycleRegistry is already"
                    + "garbage collected. It is too late to change lifecycle state.");
        }
        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(lifecycleOwner);
            }
            Entry<LifecycleObserver, ObserverWithState> newest = mObserverMap.newest();
            if (!mNewEventOccurred && newest != null
                    && mState.compareTo(newest.getValue().mState) > 0) {
                forwardPass(lifecycleOwner);
            }
        }
        mNewEventOccurred = false;
    }

    private void forwardPass(LifecycleOwner lifecycleOwner) {
        Iterator<Entry<LifecycleObserver, ObserverWithState>> ascendingIterator =
                mObserverMap.iteratorWithAdditions();
        while (ascendingIterator.hasNext() && !mNewEventOccurred) {
            Entry<LifecycleObserver, ObserverWithState> entry = ascendingIterator.next();
            ObserverWithState observer = entry.getValue();
            while ((observer.mState.compareTo(mState) < 0 && !mNewEventOccurred
                    && mObserverMap.contains(entry.getKey()))) {
                pushParentState(observer.mState);
                observer.dispatchEvent(lifecycleOwner, upEvent(observer.mState));
                popParentState();
            }
        }
    }

    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()))) {
                Event event = downEvent(observer.mState);
                pushParentState(getStateAfter(event));
                observer.dispatchEvent(lifecycleOwner, event);
                popParentState();
            }
        }
    }

forwardPass(lifecycleOwner)方法中的细节ObserverWithState observer = entry.getValue();找到ObserverWithState 类。调用mLifecycleObserver = Lifecycling.lifecycleEventObserver(observer);生成观察者适配器。接下来就是调用onStateChanged(),来通知 实现了 LifecycleObserver的类，生命周期发生了变化；

        void dispatchEvent(LifecycleOwner owner, Event event) {
            State newState = getStateAfter(event);
            mState = min(mState, newState);
            mLifecycleObserver.onStateChanged(owner, event);
            mState = newState;
        }

/**
 * Class that can receive any lifecycle change and dispatch it to the receiver.
 * <p>
 * If a class implements both this interface and
 * {@link androidx.lifecycle.DefaultLifecycleObserver}, then
 * methods of {@code DefaultLifecycleObserver} will be called first, and then followed by the call
 * of {@link LifecycleEventObserver#onStateChanged(LifecycleOwner, Lifecycle.Event)}
 * <p>
 * If a class implements this interface and in the same time uses {@link OnLifecycleEvent}, then
 * annotations will be ignored.
 */
public interface LifecycleEventObserver extends LifecycleObserver {
    /**
     * Called when a state transition event happens.
     *
     * @param source The source of the event
     * @param event The event
     */
    void onStateChanged(@NonNull LifecycleOwner source, @NonNull Lifecycle.Event event);
}

查看实现类ReflectiveGenericLifecycleObserver。onStateChanged()
ReflectiveGenericLifecycleObserver的构造方法中就把presenter中的方法和注解保存了下来，再通过onStateChanged()进行生命周期的方法的调用

class ReflectiveGenericLifecycleObserver implements LifecycleEventObserver {
    private final Object mWrapped;
    private final CallbackInfo mInfo;

    ReflectiveGenericLifecycleObserver(Object wrapped) {
        mWrapped = wrapped;
        mInfo = ClassesInfoCache.sInstance.getInfo(mWrapped.getClass());
    }

    @Override
    public void onStateChanged(@NonNull LifecycleOwner source, @NonNull Event event) {
        mInfo.invokeCallbacks(source, event, mWrapped);
    }
}

ClassInfoCache中使用map来保存我们的反射拿到的类信息，这样第一次通过反射创建，第二次可以直接从缓存里面拿：

class ClassesInfoCache {
private final Map<Class<?>, CallbackInfo> mCallbackMap = new HashMap<>();
    private CallbackInfo createInfo(Class<?> klass, @Nullable Method[] declaredMethods) {
        Class<?> superclass = klass.getSuperclass();
        Map<MethodReference, Lifecycle.Event> handlerToEvent = new HashMap<>();
        if (superclass != null) {
            CallbackInfo superInfo = getInfo(superclass);
            if (superInfo != null) {
                handlerToEvent.putAll(superInfo.mHandlerToEvent);
            }
        }

        Class<?>[] interfaces = klass.getInterfaces();
        for (Class<?> intrfc : interfaces) {
            for (Map.Entry<MethodReference, Lifecycle.Event> entry : getInfo(
                    intrfc).mHandlerToEvent.entrySet()) {
                verifyAndPutHandler(handlerToEvent, entry.getKey(), entry.getValue(), klass);
            }
        }

        Method[] methods = declaredMethods != null ? declaredMethods : getDeclaredMethods(klass);
        boolean hasLifecycleMethods = false;
        for (Method method : methods) {
            OnLifecycleEvent annotation = method.getAnnotation(OnLifecycleEvent.class);
            if (annotation == null) {
                continue;
            }
            hasLifecycleMethods = true;
            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");
                }
            }
            Lifecycle.Event event = annotation.value();

            if (params.length > 1) {
                callType = CALL_TYPE_PROVIDER_WITH_EVENT;
                if (!params[1].isAssignableFrom(Lifecycle.Event.class)) {
                    throw new IllegalArgumentException(
                            "invalid parameter type. second arg must be an event");
                }
                if (event != Lifecycle.Event.ON_ANY) {
                    throw new IllegalArgumentException(
                            "Second arg is supported only for ON_ANY value");
                }
            }
            if (params.length > 2) {
                throw new IllegalArgumentException("cannot have more than 2 params");
            }
            MethodReference methodReference = new MethodReference(callType, method);
            verifyAndPutHandler(handlerToEvent, methodReference, event, klass);
        }
        CallbackInfo info = new CallbackInfo(handlerToEvent);
        mCallbackMap.put(klass, info);
        mHasLifecycleMethods.put(klass, hasLifecycleMethods);
        return info;
    }
}

        void invokeCallbacks(LifecycleOwner source, Lifecycle.Event event, Object target) {
            invokeMethodsForEvent(mEventToHandlers.get(event), source, event, target);
            invokeMethodsForEvent(mEventToHandlers.get(Lifecycle.Event.ON_ANY), source, event,
                    target);
        }

        private static void invokeMethodsForEvent(List<MethodReference> handlers,
                LifecycleOwner source, Lifecycle.Event event, Object mWrapped) {
            if (handlers != null) {
                for (int i = handlers.size() - 1; i >= 0; i--) {
                    handlers.get(i).invokeCallback(source, event, mWrapped);
                }
            }
        }

LifecycleRegistry中有带有状态的观察者：

    static class ObserverWithState {
        State mState;
        LifecycleEventObserver mLifecycleObserver;

        ObserverWithState(LifecycleObserver observer, State initialState) {
            mLifecycleObserver = Lifecycling.lifecycleEventObserver(observer);
            mState = initialState;
        }

        void dispatchEvent(LifecycleOwner owner, Event event) {
            State newState = getStateAfter(event);
            mState = min(mState, newState);
            mLifecycleObserver.onStateChanged(owner, event);
            mState = newState;
        }
    }

返回的就是ReflectiveGenericLifecycleObserver

    @NonNull
    static LifecycleEventObserver lifecycleEventObserver(Object object) {
        boolean isLifecycleEventObserver = object instanceof LifecycleEventObserver;
        boolean isFullLifecycleObserver = object instanceof FullLifecycleObserver;
        if (isLifecycleEventObserver && isFullLifecycleObserver) {
            return new FullLifecycleObserverAdapter((FullLifecycleObserver) object,
                    (LifecycleEventObserver) object);
        }
        if (isFullLifecycleObserver) {
            return new FullLifecycleObserverAdapter((FullLifecycleObserver) object, null);
        }

        if (isLifecycleEventObserver) {
            return (LifecycleEventObserver) object;
        }

        final Class<?> klass = object.getClass();
        int type = getObserverConstructorType(klass);
        if (type == GENERATED_CALLBACK) {
            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);
        }
        return new ReflectiveGenericLifecycleObserver(object);
    }