2

我FragmentActivity用来交换两个标签。那是选项卡 A 和选项卡 B。在选项卡 B 中，我使用ListViewLoadmore 按钮，假设单击加载更多按钮时，我只是调用了背景线程。

private class loadMoreListView extends AsyncTask<Void, Void, Void> {
    @Override
    protected void onPreExecute() {
        // Showing progress dialog before sending http request
        pDialog = new ProgressDialog (
                getActivity());
        pDialog.setMessage("Please wait..");
        pDialog.setIndeterminate(true);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    protected Void doInBackground(Void... unused) {
        try {
            //service url to fectch data..
            //xml parsing
        } catch (Exception e) {
            response = "failure";
            System.out.println(" sec XML Pasing Excpetion = " + e);
        }

        int currentPosition = listViewattlist.getFirstVisiblePosition();

        // Appending new data to menuItems ArrayList
        adapter = new CustomAdapter(getActivity(), R.layout.att_list, R.id.title, data);
        listViewattlist.setAdapter(adapter);

        // Setting new scroll position
        listViewattlist.setSelectionFromTop(currentPosition + 1, 0);
        return (null);
    }

    protected void onPostExecute(Void unused) {
        // closing progress dialog
        pDialog.dismiss();
    }
}

当我交换并单击该按钮时，我可以看到进度条，但它显示如下错误：

07-13 11:42:29.386: E/AndroidRuntime(894): FATAL EXCEPTION: AsyncTask #2
07-13 11:42:29.386: E/AndroidRuntime(894): java.lang.RuntimeException: An error occured while executing doInBackground()
07-13 11:42:29.386: E/AndroidRuntime(894): at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.lang.Thread.run(Thread.java:856)
07-13 11:42:29.386: E/AndroidRuntime(894): Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:4607)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.ViewRootImpl.invalidateChildInParent(ViewRootImpl.java:867)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.ViewGroup.invalidateChild(ViewGroup.java:4066)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.View.invalidate(View.java:10250)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.View.invalidate(View.java:10205)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.widget.ImageView.invalidateDrawable(ImageView.java:190)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.graphics.drawable.Drawable.invalidateSelf(Drawable.java:350)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.graphics.drawable.Drawable.setVisible(Drawable.java:546)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.widget.ImageView.onDetachedFromWindow(ImageView.java:1173)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.View.dispatchDetachedFromWindow(View.java:11789)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.ViewGroup.dispatchDetachedFromWindow(ViewGroup.java:2532)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.view.ViewGroup.removeAllViewsInLayout(ViewGroup.java:3819)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.widget.AbsListView.resetList(AbsListView.java:1936)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.widget.ListView.resetList(ListView.java:502)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.widget.ListView.setAdapter(ListView.java:442)

07-13 11:42:29.386: E/AndroidRuntime(894): at com.owentech.testswipeab.TabTwo$loadMoreListView.doInBackground(TabTwo.java:372)
07-13 11:42:29.386: E/AndroidRuntime(894): at com.owentech.testswipeab.TabTwo$loadMoreListView.doInBackground(TabTwo.java:1)
07-13 11:42:29.386: E/AndroidRuntime(894): at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-13 11:42:29.386: E/AndroidRuntime(894): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-13 11:42:29.386: E/AndroidRuntime(894): ... 5 more

------------------------------------------------------------------------
4

3 回答 3

4

doInBackground()在其他线程中执行。在doInBackground()您尝试更新listViewattlist时，它是在 UI 线程中创建的。这是一个错误，您应该更新listViewattlist您的onPostExecute()方法。

于 2012-07-13T06:51:41.660 回答
1

您不能View从单独的线程中触摸您的对象，并且您知道它doInBackground()在单独的线程中运行。因此，对 的调用ListView将导致抛出异常。将所有View接触代码移至onPostExecute(). 希望这可以帮助。

于 2012-07-13T06:50:42.763 回答
0

您正在尝试从后台线程更改 UI，这是不可能的。

  1. 您可以看到进度条，因为 preExceute 工作正常
  2. 在 doInBackground 中，您尝试在主活动 UI 上设置适配器，这是错误的。doInBackground 用于后台进程，请注释函数（@Override）
  3. 关于调试的一些事情：-请参阅日志中的错误消息“原因：android.view.ViewRootImpl$CalledFromWrongThreadException：只有创建视图层次结构的原始线程才能触摸其视图”..这一行实际上应该告诉你你是什么做错事
于 2012-07-13T06:51:41.080 回答