android - 如何将数组列表从 AsyncTask 返回到 Main Activity？

Question

我正在尝试在我的应用中显示保管箱帐户中的文件列表。我的问题是，如何将列表 (fnames) 返回到我的 MainActivity 中，以便我可以在 ListView 中显示它。以及如何在 MainActivity 中调用它？Android 开发新手，如有任何其他提示，我们将不胜感激!

谢谢!

public class DbFileExplorer extends AsyncTask<Void, Long, Boolean> {

    private Context mContext;
    private final ProgressDialog mDialog;
    private DropboxAPI<?> mApi;
    private String mPath;

    private FileOutputStream mFos;

    private boolean mCanceled;
    private Long mFileLen;
    private String mErrorMsg;
    protected String[] fnames;

    public DbFileExplorer(Context context, DropboxAPI<?> api,
            String dropboxPath, String[] efnames){
        // We set the context this way so we don't accidentally leak activities
        mContext = context.getApplicationContext();
        fnames = efnames;
        mApi = api;
        mPath = dropboxPath;

        mDialog = new ProgressDialog(context);
        mDialog.setMessage("Opening Directory");
        mDialog.show();
    }

    @Override
    protected Boolean doInBackground(Void... params){
        // Get the metadata for a directory
        int i = 0;
        try{
            fnames = null;
            Entry dirent = mApi.metadata(mPath, 1000, null, true, null);
            ArrayList<Entry> files = new ArrayList<Entry>();
            ArrayList<String> dir = new ArrayList<String>();

            for (Entry ent: dirent.contents){
                //Add it to the list of thumbs we can choose from
                files.add(ent);
                dir.add(new String(files.get(i++).path));
            }
            i=0;
            fnames = dir.toArray(new String[dir.size()]);


            return true;
        } catch (DropboxUnlinkedException e) {
            // The AuthSession wasn't properly authenticated or user unlinked.
        } catch (DropboxPartialFileException e) {
            // We canceled the operation
            mErrorMsg = "Download canceled";
        } catch (DropboxServerException e) {
            // Server-side exception.  These are examples of what could happen,
            // but we don't do anything special with them here.
            if (e.error == DropboxServerException._304_NOT_MODIFIED) {
                // won't happen since we don't pass in revision with metadata
            } else if (e.error == DropboxServerException._401_UNAUTHORIZED) {
                // Unauthorized, so we should unlink them.  You may want to
                // automatically log the user out in this case.
            } else if (e.error == DropboxServerException._403_FORBIDDEN) {
                // Not allowed to access this
            } else if (e.error == DropboxServerException._404_NOT_FOUND) {
                // path not found (or if it was the thumbnail, can't be
                // thumbnailed)
            } else if (e.error == DropboxServerException._406_NOT_ACCEPTABLE) {
                // too many entries to return
            } else if (e.error == DropboxServerException._415_UNSUPPORTED_MEDIA) {
                // can't be thumbnailed
            } else if (e.error == DropboxServerException._507_INSUFFICIENT_STORAGE) {
                // user is over quota
            } else {
                // Something else
            }
            // This gets the Dropbox error, translated into the user's language
            mErrorMsg = e.body.userError;
            if (mErrorMsg == null) {
                mErrorMsg = e.body.error;
            }
        } catch (DropboxIOException e) {
            // Happens all the time, probably want to retry automatically.
            mErrorMsg = "Network error.  Try again.";
        } catch (DropboxParseException e) {
            // Probably due to Dropbox server restarting, should retry
            mErrorMsg = "Dropbox error.  Try again.";
        } catch (DropboxException e) {
            // Unknown error
            mErrorMsg = "Unknown error.  Try again.";
        }
        return false;   
    }

    @Override
    protected void onProgressUpdate(Long... progress){
        int percent = (int)(100.0*(double)progress[0]/mFileLen + 0.5);
        mDialog.setProgress(percent);
        }

    @Override
    protected void onPostExecute(Boolean result){
        mDialog.dismiss();
    }


    private void showToast(String msg){
        Toast error = Toast.makeText(mContext, msg, Toast.LENGTH_LONG);
        error.show();
    }
}

Answer 1

AsyncTask 模板的第三个参数是任务的结果类型。将其从 Boolean 更改为 ArrayList 或类似结构。然后从您的 doInBackground 方法返回该值。然后它将传递给 AsyncTask 的 onPostExecute 方法，该方法将在 UI 线程上执行(因此您可以根据需要使用数据来操作 UI)。