Android Activity 太忙无法设置 TextView 文本？

Question

我有一个函数，用 http 查询的条目填充我的 SQLite 数据库：

try {
        stringEntity = new StringEntity(SQL);
        httpPost.setEntity(stringEntity);
        httpResponse = httpClient.execute(httpPost);
        httpEntity = httpResponse.getEntity();
        bos = new ByteArrayOutputStream();
        httpEntity.writeTo(bos);

        data = bos.toString();

        reader = new BufferedReader(
                  new StringReader(data));

        try {
            //SAVE DATA IN MY DB || WORKS
        } catch(IOException e) {
          e.printStackTrace();
        }

    } catch (IOException e3) {
        // TODO Auto-generated catch block
        e3.printStackTrace();
    }

我尝试做的是在程序开始之前在我的活动上设置文本视图的文本（在第一个“try{..”前面）我发布的代码）。 但文本不会改变，因为我的活动太忙而无法获取数据（我想。我没有其他解释..）有

什么建议吗？

谢谢， prexx

更新 ''从AsyncTask获取数据''

 txtAction.setText("Loading...");

    AsyncTask<String, String, String> test = new cAsyncTask();

    try {
        data = test.execute(URL).get();

        reader = new BufferedReader(
                  new StringReader(data));

        while ((line = reader.readLine()) != null) {
            //SAVE DATA IN DB || WORKS
            }
        }

    } catch(IOException e) {
      e.printStackTrace();
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

我的异步任务：

class cAsyncTask extends AsyncTask<String, String, String> {

protected String doInBackground(String... urls) {
    int count = urls.length;
    String data = "";
    DefaultHttpClient httpClient = new DefaultHttpClient();
    HttpPost httpPost;
    StringEntity stringEntity;
    HttpResponse httpResponse;
    HttpEntity httpEntity;
    ByteArrayOutputStream bos;
    String line;
    BufferedReader reader;
    for (int i = 0; i < count; i++) {
        httpPost = new HttpPost(urls[i].toString());
        try {
            stringEntity = new StringEntity(SQL);
            httpPost.setEntity(stringEntity);
            httpResponse = httpClient.execute(httpPost);
            httpEntity = httpResponse.getEntity();
            bos = new ByteArrayOutputStream();
            httpEntity.writeTo(bos);

            data = bos.toString();

        } catch (IOException e3) {
            // TODO Auto-generated catch block
            e3.printStackTrace();
        }
    }
    return data;
}

protected void onProgressUpdate(String... progress) {

}

protected void onPostExecute(String result) {
    String test = result;
}

Answer 1

将代码的繁忙部分放入单独的线程中。

查看 AsyncTask 实用程序

调用 AsyncTask.execute()< /code> 就在 textview.setText("foo") 之后，你会没事的:)

问候

代码示例更新：

 txtAction.setText("Loading...");
 AsyncTask<String, String, String> test = new cAsyncTask();
 test.execute("http://...");

class cAsyncTask extends AsyncTask<String, String, String> {

protected String doInBackground(String... urls) {
    int count = urls.length;
    String data = "";
    DefaultHttpClient httpClient = new DefaultHttpClient();
    HttpPost httpPost;
    StringEntity stringEntity;
    HttpResponse httpResponse;
    HttpEntity httpEntity;
    ByteArrayOutputStream bos;
    String line;
    BufferedReader reader;
    for (int i = 0; i < count; i++) {
        httpPost = new HttpPost(urls[i].toString());
        try {
            stringEntity = new StringEntity(SQL);
            httpPost.setEntity(stringEntity);
            httpResponse = httpClient.execute(httpPost);
            httpEntity = httpResponse.getEntity();
            bos = new ByteArrayOutputStream();
            httpEntity.writeTo(bos);

            data = bos.toString();

        } catch (IOException e3) {
            // TODO Auto-generated catch block
            e3.printStackTrace();
        }
    }
     reader = new BufferedReader(
                  new StringReader(data));
       String line = "";
        while ((line = reader.readLine()) != null) {
            //SAVE DATA IN DB || WORKS
     }
    return data;
}


protected void onPostExecute(String result) {
    String test = result;
   textView.setText("Done!");
}

}

关键是将所有繁忙的代码放入doInBackGround 方法将在单独的线程中运行。所有 UI 修改必须在同一个 UI 线程中进行，并且可以在 onPostExecute 方法中完成，该方法将在同一个 UI 线程中执行

Answer 2

您可以尝试在 TextView 上调用 invalidate() 。但使用异步任务是重数据加载方法的最佳实践。这不会中断用户操作 UI 控件。

Answer 3

它与“太忙”无关，而是与只有在方法返回时才会设置文本这一事实有关。通过你的网络，这将会被延迟。

顺便提一句。在 UI 线程上的 Honeycomb 网络上将抛出异常并终止您的应用程序。