在 Asynctask 中实现接口

Question

我不想像这样直接在 asynctask 类中实现接口：

new AsyncTask<Void, Void, Void>() {

            @Override
            protected void onPreExecute() {
                super.onPreExecute();
                swipeRefreshLayout.setRefreshing(true);
            }

            @Override
            protected Void doInBackground(Void... params) {
                retrofitCallBackUtil.getLastTenMessageCallBack(AppConfig.USER_ID, userId, offsetNumber, service, new RetrofitResponseCallBack() {
                    @Override
                    public void onSuccess(ArrayList<Message> messages) {
                        messageAdapter.insertToTheFirst(messages);
                    }

                    @Override
                    public void onFailure() {

                    }
                });
                offsetNumber += 5;
                return null;
            }

            @Override
            protected void onPostExecute(Void aVoid) {
                super.onPostExecute(aVoid);
                messageAdapter.notifyDataSetChanged();
                swipeRefreshLayout.setRefreshing(false);
            }
        }.execute();

我只是通过主类实现它并将 this 放入此参数中，如下所示：

retrofitCallBackUtil.getLastTenMessageCallBack(AppConfig.USER_ID, userId, offsetNumber, service, this);

但我不能在 asynctask 方法中做到这一点。那么有人可以给我一些解决方案吗？

Answer 1

我假设您在 MainActivity（或类似的东西）中有这些代码。

让我们通过implements RetrofitResponseCallBack {...}实现你需要在这个Activity中传入getLastTenMessageCallBack的接口

现在，在您的 Asyntask doInBackground 方法中，调用

retrofitCallBackUtil.getLastTenMessageCallBack(AppConfig.USER_ID, userId, offsetNumber, service, MainActivity.this)

瞧，您不必再在 Asyntask 中创建匿名类了。 请注意，您必须正确移动和放置fields/params，只是正确放置的问题，没什么大不了的：D

Answer 2

像这样为AsyncTask 单独创建一个类。
此AsyncTask 将处理数据并发布实现interface 在AsyncTask 中定义的数据。
在这种情况下，定义的接口是 DataDownloadListener

public class GetFoldersAsync extends AsyncTask<Integer,Boolean,Boolean> {
    Context context;
    ProgressDialog dialog;
    ArrayList mFolderDataLevel;

    public GetFoldersAsync(Context context){
        this.context=context;

    }
    public static interface DataDownloadListener {
        public void dataDownloadedSuccessfully(ArrayList data);
        public void dataDownloadFailed();
    }
    DataDownloadListener dataDownloadListener;
    public void setDataDownloadListener(DataDownloadListener dataDownloadListener) {
        this.dataDownloadListener = dataDownloadListener;
    }
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        dialog = ProgressDialog.show(context, "Please wait", "Processing.........");
    }
    @Override
    protected Boolean doInBackground(Integer... params) {
        Log.v(Constants.BLL_LOG, "ExplorerDBOperation doInBackground  ");

        mFolderDataLevel=new ArrayList();

        // Process to populate mFolderDataLevel

        return true;
    }
    @Override
    protected void onPostExecute(Boolean aBoolean) {
        super.onPostExecute(aBoolean);
        if(dialog!=null && dialog.isShowing())
        {dialog.dismiss();}
        Log.v(Constants.BLL_LOG, "ExplorerDBOperation onPostExecute  ");
        if(mFolderDataLevel!=null && mFolderDataLevel.size()>0){
            dataDownloadListener.dataDownloadedSuccessfully(mFolderDataLevel);
        }else{
            dataDownloadListener.dataDownloadFailed();
        }
    }
}

现在在调用者 Activity 中，当 AsyncTask 需要处理并取回数据给同一个 Activity 时调用此方法。

public class HomeActivity extends AppCompatActivity {

    //Other necessary methods goes here .....

    //call this method for processing AsyncTask and to get back data 
    public void getFolderData(int parentID, int callerID){
            Log.v(Constants.BLL_LOG,"parentID="+parentID+" , callerID="+callerID);
            mCallerID=callerID;
            GetFoldersAsync getFolders = new GetFoldersAsync(this);
            getFolders.setDataDownloadListener(new GetFoldersAsync.DataDownloadListener()
            {
                @SuppressWarnings("unchecked")
                @Override
                public void dataDownloadedSuccessfully(ArrayList data) {
                    Log.v(Constants.BLL_LOG,"getFolderData dataProcessSuccessfully");

                    // Success data with populated ArrayList to process further

                }
                @Override
                public void dataDownloadFailed() {
                    //Failure
                    Log.v(Constants.BLL_LOG,"getFolderData dataProcessFailed()");
                }
            });
        getFolders.execute(callerID);
    }
}