即使更新了ArrayAdapter,AutoCompleteTextView也不显示结果

如果看不到你的代码,就很难知道会发生什么。但首先想到的是,您的网络请求发生在不同的线程上,因此 performFiltering() 可能过早返回空结果集。在那一点上, publishResults() 返回空结果,并且下拉列表为空。稍后,asynctask将返回其结果,并将结果添加到适配器的列表中,但由于某种原因,它尚未显示。

不过,我认为您可能误解了异步任务的必要性。filter对象已经在执行类似于asynctask的操作: 执行筛选() 在后台线程中完成,并且 发布结果() 在performFiltering()完成后,从UI线程调用。因此,您可以直接在performfiltering()中执行网络请求,并将结果设置为filterresults对象,这样就不必担心网络请求太慢而导致用户界面出现问题。

另一种解决方案是使用sync,它稍微复杂一些,但这是我在filter对象中所做的(由于现有的体系结构在后台执行api调用,使用异步回调而不是performfiltering()所需的阻塞/同步步骤)使用wait()/notify()将对象更新为执行跨线程监视,因此效果与直接在performfiltering()中执行网络请求相同,但它实际上发生在多个线程中:

// in Filter class..
protected FilterResults performFiltering(CharSequence constraint) {

    APIResult response = synchronizer.waitForAPI(constraint);
    // ...
}

// callback invoked after the API call finishes:
public void onAPIComplete(APIResult results) {
    synchronizer.notifyAPIDone(results);
}

private class Synchronizer {
    APIResult result;

    synchronized APIResult waitForAPI(CharSequence constraint) {
        someAPIObject.startAsyncNetworkRequest(constraint);
        // At this point, control returns here, and the network request is in-progress in a different thread.
        try {
            // wait() is a Java IPC technique that will block execution until another
            // thread calls the same object's notify() method.
            wait();
            // When we get here, we know that someone else has just called notify()
            // on this object, and therefore this.result should be set.
        } catch(InterruptedException e) { }
        return this.result;
    }

    synchronized void notifyAPIDone(APIResult result) {
        this.result = result;
        // API result is received on a different thread, via the API callback.
        // notify() will wake up the other calling thread, allowing it to continue
        // execution in the performFiltering() method, as usual.
        notify();
    }
}

但是,我认为您可能会发现,最简单的解决方案是直接在performfiltering()方法中同步地执行网络请求。如果您已经为异步/回调驱动的API调用准备好了体系结构,并且不想为了在performfiltering()中获得同步结果而更改该行为,那么上面的代码示例只是一种可能性。

我认为乔的回答是正确的。不过,我认为你应该 CountDownLatch 而不是等待/通知。

原因是,使用wait/notify,如果您的api在您开始“wait()”之前真的返回得非常快,那么您就有可能遇到竞争条件……在这种情况下,notify将不起作用,wait()将无限期地等待。 使用闩锁,代码将如下所示(从joe复制并修改):

// in Filter class..
protected FilterResults performFiltering(CharSequence constraint) {
  APIResult response = synchronizer.waitForAPI(constraint);
  // ...
}

// callback invoked after the API call finishes:
public void onAPIComplete(APIResult results) {
  synchronizer.notifyAPIDone(results);
}

private class Synchronizer {
  APIResult result;
  CountDownLatch latch;

  synchronized APIResult waitForAPI(CharSequence constraint) {
      latch = new CountDownLatch(1);
      someAPIObject.startAsyncNetworkRequest(constraint);
      // At this point, control returns here, and the network request is in-progress in a different thread.
      try {
        // Will wait till the count is 0...
        // If the count is already 0, it'll return immediately. 
        latch.await();
        // When we get here, we know that someone else has just called notify()
        // on this object, and therefore this.result should be set.
    } catch(InterruptedException e) { }
    return this.result;
  }

  synchronized void notifyAPIDone(APIResult result) {
    this.result = result;
    // API result is received on a different thread, via the API callback.
    // countDown() will wake up the other calling thread, allowing it to continue
    // execution in the performFiltering() method, as usual.
    latch.countDown();
  }
}

最后,我没有足够的信用来发表评论,否则我会…