在ListView上显示进度条

Question

问最简单的问题，我搜索了很多与我的问题相关但没有找到任何解决方案。我在Android应用程序中有一个布局，我使用listview和progressbar。在 AsyncTask 类中执行的所有任务。我想在加载列表之前在活动的中心显示进度条。谁能告诉我哪里出错或者这个解决方案需要哪些更改。在此先感谢。

我是怎么做的

activity_main：          

<ProgressBar
    android:id="@+id/progressBar1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_gravity="center_horizontal"
    android:visibility="invisible" />

<ListView
    android:id="@android:id/list"
    android:layout_width="match_parent"
    android:layout_height="fill_parent" >
</ListView>

MainActivity：

public class GettingAlerts extends ListActivity {

// Initialization
IPAddress ipAddressObject = new IPAddress();
public static String GETTING_ALERTS_URL = "http://"
        + IPAddress.IP_Address.toString()
        + "/MyServices/Alerts/AlertService.svc/gettingAllAlerts";

// TAGS
public static String TAG_NAME = "GetAllAlertsResult";
public static String TAG_ALERT_TITLE = "alertTitle";
public static String TAG_ALERT_DESCRIPTION = "alertDescription";
public static String TAG_ALERT_OWNER = "alertOwner";
public static String TAG_ALERT_DEADLINE = "alertDeadline";
static String Serv_Response = "";

ArrayList<Alerts> alertsList;
ProgressBar pg;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.alert_activity_list);

    pg = (ProgressBar) findViewById(R.id.progressBar1);
    // requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
    // setProgressBarIndeterminateVisibility(true);

    alertsList = new ArrayList<Alerts>();
    ListView lv = getListView();

    // setProgressBarIndeterminateVisibility(false);

    new GettingAlertsList().execute();
}

private class GettingAlertsList extends AsyncTask<Void, Void, Void> {

    @Override
    protected Void doInBackground(Void... params) {
        // TODO Auto-generated method stub

        // LinearLayout linlaHeaderProgress = (LinearLayout)
        // findViewById(R.id.linlaHeaderProgress);
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(GETTING_ALERTS_URL);
        HttpResponse httpResponse = null;
        try {
            httpResponse = httpClient.execute(httpGet);

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

        HttpEntity httpEntity = httpResponse.getEntity();
        try {
            Serv_Response = EntityUtils.toString(httpEntity);
        } catch (ParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        try {
            if (Serv_Response != null) {
                JSONObject jsonObj = new JSONObject(Serv_Response);
                JSONArray quiz = jsonObj.getJSONArray(TAG_NAME);

                for (int i = 0; i < quiz.length(); i++) {
                    JSONObject c = quiz.getJSONObject(i);
                    String alert_title = c.getString(TAG_ALERT_TITLE);
                    String alert_owner = c.getString(TAG_ALERT_OWNER);
                    String alert_desc = c.getString(TAG_ALERT_DESCRIPTION);
                    String alert_dealdine = c.getString(TAG_ALERT_DEADLINE);

                    Alerts alertObject = new Alerts();
                    alertObject.setAlertTitle(alert_title);
                    alertObject.setAlertDescription(alert_desc);
                    alertObject.setAlertDeadline(alert_dealdine);
                    alertObject.setAlertOwner(alert_owner);

                    alertsList.add(alertObject);
                }

            }

        } catch (JSONException e) {
            // TODO: handle exception
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);

        CustomAlertListAdapter adapter = new CustomAlertListAdapter(
                GettingAlerts.this, alertsList);
        setListAdapter(adapter);

        pg.setVisibility(View.GONE);
    }

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
        super.onPreExecute();
        pg.setVisibility(View.VISIBLE);
    }

}

}

图片

正如您所见，进度条位于活动的顶部。在加载List之前，我想在活动的center中使用进度条。

Answer 1

试试这个..

删除android:layout_alignParentTop="true"和android:layout_gravity="center_horizontal"并添加android:layout_centerInParent="true"

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <ProgressBar
        android:id="@+id/progressBar1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:visibility="invisible" />

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="fill_parent" >
    </ListView>

</RelativeLayout>

Answer 2

更改可见性以显示/隐藏进度条。您可能需要设置更改某些属性，如样式：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <RelativeLayout
        android:id="@+id/progress_bar_wrapper"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:background="@null"
        android:visibility="gone">

        <ProgressBar
            android:id="@+id/progress_bar"
            android:layout_width="100dp"
            android:layout_height="30dp"
            android:progress="0"
            android:layout_centerHorizontal="true"
            android:layout_centerInParent="true"
            android:layout_centerVertical="true"/>

    </RelativeLayout>

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</RelativeLayout>

Answer 3

我假设您目前使用了LinearLayout，而是在XML中获取RelativeLayout并更改小部件的顺序，如下所示，并从ProgressBar中删除android:layout_alignParentTop="true"。

<RelativeLayout
  ...
  ...>

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="fill_parent" >
    </ListView>

    <ProgressBar
        android:id="@+id/progressBar1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"/>

</RelativeLayout>