我有这个listview，它是在片段类中编码的。选择列表视图项时，它会转到另一个片段并显示详细信息。但是加载数据需要几秒钟，因为我显示的数据是使用AsyncTask，因此从JSON和显示中获取数据需要一些时间。所以我需要在listview中单击一个项目时使用progressBar，它应该在数据准备好显示时关闭。我怎样才能做到这一点？我参考了几个教程，并尝试了很多教程。但我无法完成我正在寻找的东西。希望你们中的一些人可以帮助我。
NewsFragment class
private ListView listView;
private ArrayList<BaseElement> News;
private LazyAdapter adapter;
private Activity activity;
private CommonVariable commonVariable;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.news_fragment, container,
false);
activity = this.getActivity();
commonVariable = (CommonVariable) activity.getApplication();
listView = (ListView) view.findViewById(R.id.list);
listView.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v,
int position, long id){
android.support.v4.app.Fragment detail = new NewsDetailFragment();
android.support.v4.app.FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().add(R.id.content_frame, detail).addToBackStack("back").commit();
}
});
new BackGround().execute();
return view;
}
public class BackGround extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
News = JSONServices.getNewsDescription();
return null;
}
@Override
/* check again */
protected void onPostExecute(Void result) {
commonVariable.setNewsDescription(News);
adapter = new LazyAdapter(News, activity,Element.NEWS_LIST.getType());
listView.setAdapter(adapter);
super.onPostExecute(result);
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
}
}
}
NewsDetailFragment
public class NewsDetailFragment extends Fragment {
private View view1;
private ArrayList<BaseElement> newsdetail;
private LazyAdapter adapter;
private Activity activity;
private CommonVariable commonVariable;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.newsdetail_fragment, container,
false);
activity = this.getActivity();
commonVariable = (CommonVariable) activity.getApplication();
view1 = (View) view.findViewById(R.id.list);
new BackGround().execute();
return view;
}
public class BackGround extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
newsdetail = JSONServices.getNewsDescription();
return null;
}
@SuppressWarnings("unchecked")
@Override
/* check again */
protected void onPostExecute(Void result) {
commonVariable.setTheater(newsdetail);
adapter = new LazyAdapter(newsdetail, activity,Element.NEWS_DETAIL.getType());
((AdapterView<ListAdapter>) view1).setAdapter(adapter);
super.onPostExecute(result);
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
super.onPreExecute();
}
}
}
新闻列表布局
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@color/grey"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:background="@drawable/listview" >
<ImageView
android:id="@+id/thumb_image"
android:layout_width="150dp"
android:layout_height="120dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="1dp"
android:layout_marginBottom="1dp"
/>
<TextView
android:id="@+id/news_title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#ffffff"
android:layout_toRightOf="@+id/thumb_image"
android:layout_marginTop="10dp"
android:layout_marginLeft="7dp"
android:textStyle="bold"
android:textSize="20dp" />
<!-- <TextView
android:id="@+id/news_description"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textColor="#000000"
android:textStyle="bold"
android:layout_below="@+id/news_title"
android:textSize="15dp" /> -->
</LinearLayout>
</RelativeLayout>
NewsFragment布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="@color/grey" >
<!-- <GridView
android:id="@+id/gridView2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:numColumns="2"
android:stretchMode="columnWidth"
android:layout_margin="5dp"
android:columnWidth="100dp"/> -->
<ListView
android:id="@+id/list"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:dividerHeight="10dp"
android:layout_margin="6dp">
</ListView>
</LinearLayout>
答案 0 :(得分：1)
将ProgressBar添加到您的NewsFragment布局：
<ProgressBar
android:id="@+id/progress_bar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:indeterminate="true"
android:visibility="gone" />
然后在onItemClick方法中将其可见性更改为true progressBar.setVisibility(View.VISIBLE)以显示它，并将其可见性更改为false，以在progressBar.setVisibility(View.GONE)的AsyncTask中隐藏onPostExecute。
答案 1 :(得分：0)
好的，我现在明白了。我像这样修改了我的第二个片段。单击列表视图中的项目时，它会转到我的第二个类。所以我在第二个类中添加了一个progressBar并且它有效！
public class NewsDetailFragment extends Fragment {
private View view1;
private ArrayList<BaseElement> newsdetail;
private LazyAdapter adapter;
private Activity activity;
private CommonVariable commonVariable;
private ProgressDialog dialog;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.newsdetail_fragment, container,
false);
activity = this.getActivity();
commonVariable = (CommonVariable) activity.getApplication();
view1 = (View) view.findViewById(R.id.list);
dialog = new ProgressDialog(NewsDetailFragment.this.getActivity());
dialog.setMessage("Loading News");
dialog.setCancelable(true);
new BackGround().execute();
return view;
}
public class BackGround extends AsyncTask<Void, Void, Void> {
@Override
protected Void doInBackground(Void... params) {
newsdetail = JSONServices.getNewsDescription();
return null;
}
@SuppressWarnings("unchecked")
@Override
/* check again */
protected void onPostExecute(Void result) {
commonVariable.setTheater(newsdetail);
adapter = new LazyAdapter(newsdetail, activity,Element.NEWS_DETAIL.getType());
((AdapterView<ListAdapter>) view1).setAdapter(adapter);
dialog.dismiss();
super.onPostExecute(result);
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
dialog.show();
super.onPreExecute();
}
}
}