循环内的回调:如何知道一切何时结束

Question

在循环中，我需要多次调用callback方法。我怎么知道什么时候完成了?

@Override
public void onObjectsMustBeParsed(String parsableObjects) {
    String[] parsedObjects = parsableObjects.split(",");
    for (String parsedObject : parsedObjects){
        loadObject(parsedObject, new LoadObjectCallback() {
            @Override
            public void onObjectLoaded(Object object) {
                //Object Loaded
                saveObject(object, new SaveObjectCallback() {
                    @Override
                    public void onObjectSaved() {
                        // Object saved
                    }
                    @Override
                    public void onError() {
                        // Object not saved
                    }
                });
            }
            @Override
            public void onError(Throwable throwable) {
                // Object not Loaded
            }
        });
    }
}

// => do something when all processing of parsed-objects are finished
       // do something if all is ok
       // do other thing if partially ok

注意:为了操作我的数据，我使用具有本地和远程数据源的存储库。这段代码是存储库的一部分

Answer 1

添加一个volatile整数，表示正在运行的任务数量。启动任务时递增。在onObjectLoaded或onObjectSaved中进行减量。然后在每次递减之后检查任务计数器是否为空。

Answer 2

与注释类似，但使用AtomicInteger代替:

 AtomicInteger countDownLatch = null;
   @Override
   public void onObjectsMustBeParsed(String parsableObjects) {
      String[] parsedObjects = parsableObjects.split(",");
      countDownLatch = new AtomicInteger(parsedObjects.length);
      for (String parsedObject : parsedObjects){
         loadObject(parsedObject, new LoadObjectCallback() {
            @Override
            public void onObjectLoaded(Object object) {
               //Object Loaded
               saveObject(object, new SaveObjectCallback() {
                  @Override
                  public void onObjectSaved() {
                     // Object saved
                     int value = countDownLatch.decrementAndGet();
                     if ( value == 0 ) {
                        // we are done
                     }
                  }
                  @Override
                  public void onError() {
                     // Object not saved
                     int value = countDownLatch.decrementAndGet();
                     if ( value == 0 ) {
                        // we are done
                     }
                  }
               });
            }
            @Override
            public void onError(Throwable throwable) {
               // Object not Loaded
            }
         });
      }
   }