更改 doInBackground 中的通用返回类型

Posted 2023-05-07

【中文标题】更改 doInBackground 中的通用返回类型

【英文标题】：Change the generic return type in doInBackground

【发布时间】：2021-07-01 12:15:27

【问题描述】：

下午好，我有一个完美运行的通用 baseAsyncTask，java 可以在 doInBackground 中定义类型，但是在 onPostExecute 我调用我的函数 doAsync，它组装为 Object，就像我在创建 Override 来定义类型时一样，所以我不要投射

类 DaoProcessorAsync

public abstract class DaoAsyncProcessor<T> 
    public interface DaoProcessCallback<T>
        void onResult(T result);
    

    private final DaoProcessCallback daoProcessCallback;

    public DaoAsyncProcessor(DaoProcessCallback daoProcessCallback) 
        this.daoProcessCallback = daoProcessCallback;
    

    protected abstract T doAsync();

    public void start()
        new DaoProcessAsyncTask().execute();
    

    private class DaoProcessAsyncTask extends AsyncTask<Void, Void, T> 

        @Override
        protected T doInBackground(Void... params) 
            return doAsync();
        

        @SuppressWarnings("unchecked")
        @Override
        protected void onPostExecute(T t) 
            if(daoProcessCallback != null)
                daoProcessCallback.onResult(t);
        
    
  

调用类

new DaoAsyncProcessor<Trabalhador>(new DaoAsyncProcessor.DaoProcessCallback() 
            @Override
            // How to make it explicit that the return is of the Worker type
            public void onResult(Object result) 
                **at that point it returns object to me, and I need to do conversion**
                Trabalhador trabalhador = (Trabalhador) result;
            
        )
            @Override
            protected Trabalhador doAsync() 
                **This worker-type return should be explicit in OnRESULT, but I can't define it**
                return trabalhadorDao.lerPorCPF(123);
            
        .start();

【参考方案1】：

我认为您在创建 DaoProcessCallback 时缺少类型。

试试

new DaoAsyncProcessor<Tabalhador>.DaoProcessCallback()