java - 使用接口(interface)从异步任务 onpostexecute 获取数据

Question

您好，我正在尝试从异步任务类获取数据数组列表到另一个主类:

我一直在关注下面的答案，但我有点迷茫:

How to get the result of OnPostExecute() to main activity because AsyncTask is a separate class?

所以我的类扩展异步任务并调用数据库以获取我的对象数组:

public class GetVideoInfoFromDataBase extends AsyncTask {

    // Paginated list of results for song database scan
    static PaginatedScanList<AlarmDynamoMappingAdapter> results;

    // The DynamoDB object mapper for accessing DynamoDB.
    private final DynamoDBMapper mapper;

    public interface AlarmsDataBaseAsyncResponse {
        void processFinish(PaginatedScanList<AlarmDynamoMappingAdapter> output);
    }

    public AlarmsDataBaseAsyncResponse delegate = null;

    public GetVideoInfoFromDataBase(AlarmsDataBaseAsyncResponse delegate){
        mapper = AWSMobileClient.defaultMobileClient().getDynamoDBMapper();
        this.delegate = delegate;
    }

    @Override
    protected Object doInBackground(Object[] params) {

        DynamoDBScanExpression scanExpression = new DynamoDBScanExpression();
        results = mapper.scan(AlarmDynamoMappingAdapter.class, scanExpression);
        return results;
    }

    @Override
    public void onPostExecute(Object obj) {

        delegate.processFinish(results);

    }
}

没有错误，但我认为我在其中做错了什么导致了我的错误。

所以在我调用结果的主要 Activity 中:

GetVideoInfoFromDataBase asyncTask =new GetVideoInfoFromDataBase(new GetVideoInfoFromDataBase.AlarmsDataBaseAsyncResponse(){


    @Override
    public void processFinish(PaginatedScanList<AlarmDynamoMappingAdapter> output) {

    }
}).execute();

这里有两个问题

1. 我收到错误:
   “不兼容的类型:AsyncTask 无法转换为 GetVideoInfoFromDataBase”

在我的主要 Activity 中:

`new GetVideoInfoFromDataBase(new GetVideoInfoFromDataBase.AlarmsDataBaseAsyncResponse()`

它要我这样投它:

(GetVideoInfoFromDataBase) new GetVideoInfoFromDataBase(new GetVideoInfoFromDataBase.AlarmsDataBaseAsyncResponse()

这似乎不对，但我想我会检查一下。

1. 我不确定在覆盖 onprocessfinished 时如何返回结果。

预先感谢您的帮助

Answer 1

首先创建一个接口(interface)

public interface AsyncInterface {
    void response(String response);
}

在 asynctask 类中分配它，如下所示:-

Context context;
Private AsyncInterface asyncInterface;

AsyncClassConstructor(Context context){
    this.context = context;
    this.asyncInterface = (AsyncInterface) context;
}

然后在 asynctask 类的 onPostExecute 方法中:-

@Override
protected void onPostExecute(String s) {
    super.onPostExecute(s);
    asyncInterface.response(s);
}

然后在你的 Activity 中实现这个接口(interface):-

class MainActivity extends AppCompatActivity implements AsyncInterface {

然后引入asyncInterface的方法

@Override
public void response(String response) {
    //Here you get your response
    Log.e(TAG, response);
}