如何将AsyncTask的结果传递给另一个Activity？

问题描述

如何获取AsyncTask的结果以以此开始另一个活动？ 这个AsyncTask看起来非常不舒服... 现在，在onPostExecute完成之前，它将开始活动而没有结果。 那怎么能等到完成而不必重写整个代码？

public class MainFragment extends Fragment implements InsertAsyncTask.AsyncInsertTaskCompleteListener {
    private Repository mRepository;
    private String data;
    private int codeId;
    private int editMode = 0;
    private Context mContext;
    private FragmentMainBinding binding;

    
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mContext = this.getContext();
        mRepository = new Repository(mContext);

    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.mainfragment,container,false);
    }

    @Override
    public void onViewCreated(@NonNull View view,@Nullable Bundle savedInstanceState) {
        super.onViewCreated(view,savedInstanceState);
        binding = FragmentMainBinding.bind(view);
        
        binding.createFormSaveButton.setonClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String text = binding.codeCreateFormTextInput.getText().toString().trim();
            
            if (!text.equals("")){
                create("save data");
                Intent intent = new Intent(mContext.getApplicationContext(),NextActivity.class);
                intent.putExtra("code_id",codeId);
                mContext.startActivity(intent);
            }
        }
    }
    
    
    private void create(String data){
        if (editMode == 1){
            //updated data to DB
            updateCode(data);
        } else {
            //save data to DB
            save(data);
        }
    }
    
    public void save(String data){
        mRepository.insertTask(data,MainFragment.this);
    }
    
        @Override
    public void onInsertTaskComplete(long[] id) {
        if (id[0] > 0){
            codeId = (int) id[0];
        }
    }
}

Repository.java：

public void insertTask(String data,InsertAsyncTask.AsyncInsertTaskCompleteListener mListener) {
    new InsertAsyncTask(myDatabase.getCDao(),mListener).execute(data);
}

InsertAsyncTask.java：

public class InsertAsyncTask extends AsyncTask<String,Void,Long> {
    private static final String TAG = "InsertAsyncTask";
    private cDao mCDao;
    private AsyncInsertTaskCompleteListener callback;

    private long[] insertId;


    public InsertAsyncTask(CDao dao,AsyncInsertTaskCompleteListener cb) {
        mCDao = dao;
        this.callback = cb;
    }

    @Override
    protected void onPostExecute(Long aLong) {
        super.onPostExecute(aLong);
        if (callback != null) {
            callback.onInsertTaskComplete(insertId);
        }
    }

    @Override
    protected Long doInBackground(String... datas) {
        insertId = mCDao.insertCode(datas);
        return null;
    }

    public interface AsyncInsertTaskCompleteListener {
        void onInsertTaskComplete(long[] id);
    }
}
    

解决方法

codeId的初始值是

private int codeId = -1;

然后在onViewCreated内部将您的情况更改为：

if (codeId != -1){
            create("save data");
            Intent intent = new Intent(mContext.getApplicationContext(),NextActivity.class);
            intent.putExtra("code_id",codeId);
            mContext.startActivity(intent);
        }

现在应该可以正常工作。