调用方式
订阅消息
- observe 生命周期感知,不需要手动取消订阅
LiveDataBus.get()
.with("key_name", String.class)
.observe(this, new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
}
});
- observeForever 需要手动取消订阅
LiveDataBus.get()
.with("key_name", String.class)
.observeForever(observer);
LiveDataBus.get()
.with("key_name", String.class)
.removeObserver(observer);
发送消息
- setValue 在主线程发送消息
LiveDataBus.get().with("key_name").setValue(value);
- postValue 在后台线程发送消息,订阅者会在主线程收到消息
LiveDataBus.get().with("key_name").postValue(value);
Sticky模式
支持在注册订阅者的时候设置Sticky模式,这样订阅者可以接收到订阅之前发送的消息
- observeSticky 生命周期感知,不需要手动取消订阅,Sticky模式
LiveDataBus.get()
.with("sticky_key", String.class)
.observeSticky(this, new Observer<String>() {
@Override
public void onChanged(@Nullable String s) {
}
});
- observeStickyForever 需要手动取消订阅,Sticky模式
LiveDataBus.get()
.with("sticky_key", String.class)
.observeStickyForever(observer);
LiveDataBus.get()
.with("sticky_key", String.class)
.removeObserver(observer);
public final class LiveDataBus {
private final Map<String, BusMutableLiveData<Object>> bus;
private LiveDataBus() {
bus = new HashMap<>();
}
private static class SingletonHolder {
private static final LiveDataBus DEFAULT_BUS = new LiveDataBus();
}
public static LiveDataBus get() {
return SingletonHolder.DEFAULT_BUS;
}
public synchronized <T> BusMutableLiveData<T> with(String key, Class<T> type) {
if (!bus.containsKey(key)) {
bus.put(key, new BusMutableLiveData<>());
}
return (BusMutableLiveData<T>) bus.get(key);
}
public BusMutableLiveData<Object> with(String key) {
return with(key, Object.class);
}
private static class ObserverWrapper<T> implements Observer<T> {
private Observer<T> observer;
public ObserverWrapper(Observer<T> observer) {
this.observer = observer;
}
@Override
public void onChanged(@Nullable T t) {
if (observer != null) {
if (isCallOnObserve()) {
return;
}
observer.onChanged(t);
}
}
private boolean isCallOnObserve() {
StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
if (stackTrace != null && stackTrace.length > 0) {
for (StackTraceElement element : stackTrace) {
if ("android.arch.lifecycle.LiveData".equals(element.getClassName()) &&
"observeForever".equals(element.getMethodName())) {
return true;
}
}
}
return false;
}
}
public static class BusMutableLiveData<T> extends MutableLiveData<T> {
private class PostValueTask implements Runnable {
private Object newValue;
public PostValueTask(@NonNull Object newValue) {
this.newValue = newValue;
}
@Override
public void run() {
setValue((T) newValue);
}
}
private Map<Observer, Observer> observerMap = new HashMap<>();
private Handler mainHandler = new Handler(Looper.getMainLooper());
@Override
public void postValue(T value) {
mainHandler.post(new PostValueTask(value));
}
@Override
public void observe(@NonNull LifecycleOwner owner, @NonNull Observer<T> observer) {
super.observe(owner, observer);
try {
hook(observer);
} catch (Exception e) {
e.printStackTrace();
}
}
public void observeSticky(@NonNull LifecycleOwner owner, @NonNull Observer<T> observer) {
super.observe(owner, observer);
}
@Override
public void observeForever(@NonNull Observer<T> observer) {
if (!observerMap.containsKey(observer)) {
observerMap.put(observer, new ObserverWrapper(observer));
}
super.observeForever(observerMap.get(observer));
}
public void observeStickyForever(@NonNull Observer<T> observer) {
super.observeForever(observer);
}
@Override
public void removeObserver(@NonNull Observer<T> observer) {
Observer realObserver = null;
if (observerMap.containsKey(observer)) {
realObserver = observerMap.remove(observer);
} else {
realObserver = observer;
}
super.removeObserver(realObserver);
}
private void hook(@NonNull Observer<T> observer) throws Exception {
//get wrapper's version
Class<LiveData> classLiveData = LiveData.class;
Field fieldObservers = classLiveData.getDeclaredField("mObservers");
fieldObservers.setAccessible(true);
Object objectObservers = fieldObservers.get(this);
Class<?> classObservers = objectObservers.getClass();
Method methodGet = classObservers.getDeclaredMethod("get", Object.class);
methodGet.setAccessible(true);
Object objectWrapperEntry = methodGet.invoke(objectObservers, observer);
Object objectWrapper = null;
if (objectWrapperEntry instanceof Map.Entry) {
objectWrapper = ((Map.Entry) objectWrapperEntry).getValue();
}
if (objectWrapper == null) {
throw new NullPointerException("Wrapper can not be bull!");
}
Class<?> classObserverWrapper = objectWrapper.getClass().getSuperclass();
Field fieldLastVersion = classObserverWrapper.getDeclaredField("mLastVersion");
fieldLastVersion.setAccessible(true);
//get livedata's version
Field fieldVersion = classLiveData.getDeclaredField("mVersion");
fieldVersion.setAccessible(true);
Object objectVersion = fieldVersion.get(this);
//set wrapper's version
fieldLastVersion.set(objectWrapper, objectVersion);
}
}
}