Question

我是android的新手。我尝试从活动中获取此信息：

i.putExtra("mlat", String.valueOf(latitude));

到这里：

public class PostDataActivity extends AsyncTask<Void, Void, Void>{
    GpsData gps;
//  double latitude = gps.getLatitude(); 
    //String mlat;

    @Override
    protected Void doInBackground(Void... params) {
        Bundle extras = getIntent().getExtras();
        String mlat = extras.getString("mlat");

        HttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost("http://test.de");
         List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);
          nameValuePairs.add(new BasicNameValuePair("lat", mlat));
          nameValuePairs.add(new BasicNameValuePair("lon", "7.358154"));
           try {
            httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
           } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
           }
           try {
            httpClient.execute(httpPost);
           } catch (ClientProtocolException e) {
            e.printStackTrace();
           } catch (IOException e) {
            e.printStackTrace();
           }
        return null;
    }

但getIntent ist undefined

Bundle extras = getIntent().getExtras();
String mlat = extras.getString("mlat");

如何在Activity和doInBackground之间传输数据？

Answer 1

execute的{{1}}方法采用一系列String参数，可用于将额外数据输入后台任务。

这是Android source documentation：

中的示例

AsyncTask

您可以通过这种方式从主线程中调用它：

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
             // Escape early if cancel() is called
             if (isCancelled()) break;
         }
         return totalSize;
     }

  ..
}

Answer 2

首先阅读我的Matt提供的教程。

对于您的情况，您必须修改您的代码，如下所示：

1.将您的参数类型从void更改为String：

public class PostDataActivity扩展AsyncTask＆lt; String ，Void，Void＆gt; {

2.将您的数据作为参数传递给AsyncTask：

new PostDataActivity（）。execute（“ mlat ”）;

Answer 3

Intent不包含任何内容，因为您正在扩展AsyncTask。我认为整个方法存在缺陷。

由于PostDataActivity是一个Activity，它不应该扩展AsyncTask。以下是我认为它应该是什么样子的想法：

public class PostDataActivity extends Activity {
GPSData gps;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.);

    Bundle extras = getIntent().getExtras();
    String mlat = extras.getString("mlat");

    MyDownloaderTask task = new MyDownloaderTask();
    task.execute(mlat);
}
    //Check docs for parameterisation of AsyncTask
private class MyDownloaderTask extends AsyncTask<String, Void, String> {
    protected String doInBackground(String params...) {
        string someResult;
        String mlat = params[0];
        //Got your variable, do whatever you want from here on
        return someResult; //Since it is no longer AsyncTask<Void, Void, Void>
    }
    protected void onPostExecute(String result) {
        //This executes after task completes successfully
    }
    protected void onCancelled(String result) {
        //This executes after task completes unsuccessfully
    }
}

//...
}

android getIntent doInBackground

3 个答案: