Bolts-Android
如果你已經在用 RxJava ，那這應該僅供參考。
Bolts 是一款 promise 的實現。由 Parse.com 主持。Facebook 在收購 Parse.com 後，也整合 bolts 了。
Bolts.Task<T> 相當於Observable<T>
Bolts.Task.continueWith() 相當於 Observable.map()
Task<ParseObject> saveAsync;
...
// .map(o -> null);
saveAsync(obj).continueWith(new Continuation<ParseObject, Void>() {
public Void then(Task<ParseObject> task) throws Exception {
if (task.isCancelled()) {
// 取消
} else if (task.isFaulted()) {
// 失敗
Exception error = task.getError();
} else {
// 成功
ParseObject object = task.getResult();
}
return null;
}
});
Bolts.Task.continueWithTask() 相當於 Observable.flatMap()
// .flatMap(o -> saveObs(o)).map(o -> null);
query.findInBackground().continueWithTask(new Continuation<List<ParseObject>, Task<ParseObject>>() {
public Task<ParseObject> then(Task<List<ParseObject>> task) throws Exception {
if (task.isFaulted()) {
return null;
}
List<ParseObject> students = task.getResult();
students.get(1).put("salutatorian", true);
return saveAsync(students.get(1));
}
}).onSuccess(new Continuation<ParseObject, Void>() {
public Void then(Task<ParseObject> task) throws Exception {
return null;
}
});
Task.forResult() 相當於 Observable.just()
Task<String> successful = Task.forResult("The good result.");
Task.create() 相當於 Observable.create()
public Task<ParseObject> fetchAsync(ParseObject obj) {
final Task<ParseObject>.TaskCompletionSource tcs = Task.create();
obj.fetchInBackground(new GetCallback() {
public void done(ParseObject object, ParseException e) {
if (e == null) {
tcs.setResult(object);
} else {
tcs.setError(e);
}
}
});
return tcs.getTask();
}
Task.callInBackground() 相當於 Observable.defer()/Observable.fromCallbable():
Task<Void> Task.callInBackground(new Callable<Void>() {
public Void call() {
// Do a bunch of stuff.
}
});
Task.waitForCompletion() 相當於 Observable.toBlocking():
Tasks.java:
public static <T> T wait(Task<T> task) {
try {
task.waitForCompletion();
if (task.isFaulted()) {
Exception error = task.getError();
if (error instanceof RuntimeException) {
throw (RuntimeException) error;
}
throw new RuntimeException(error);
} else if (task.isCancelled()) {
throw new RuntimeException(new CancellationException());
}
return task.getResult();
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
RxBolts - Task2Observable
Task 轉 Observable
範例：
TaskObservable.defer(() -> Task.forResult("Hello, world!")).subscribe(it -> {
System.out.println(it);
});
實現：
ref. yongjhih/RxBolts/.../TaskObservable.java
public static <R> Observable<R> defer(Task<R> task) {
return Observable.create(sub -> {
task.continueWith(t -> {
if (t.isCancelled()) {
sub.unsubscribe(); //sub.onCompleted();?
} else if (t.isFaulted()) {
sub.onError(t.getError());
} else {
R r = t.getResult();
if (r != null) sub.onNext(r);
sub.onCompleted();
}
return null;
});
});
}