[英]Android ListView throws NullPointer exception on click
I have the following code which correctly adds the series name to aName and link to aLink so both ArrayLists hold values. 我有以下代码,可以正确地将系列名称添加到aName并链接到aLink,以便两个ArrayList都保存值。 When run the ListView correctly displays aName, but when one of the items in the listview is clicked the app throws the NullPointer exeption. 运行ListView时,正确显示aName,但是单击listview中的一项时,应用程序将抛出NullPointer异常。
public class MainActivity extends ListActivity {
ArrayAdapter<String> adapter;
ArrayList aName;
ArrayList aLink;
ListView view;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
view = getListView();
view.setTextFilterEnabled(true);
//CONNECT CODE//
Document main = Jsoup.parse("<html> </html>");
try {
main = Jsoup.connect("http://www.animeseason.com/anime-list/").get();
} catch (IOException e) {
AlertDialog alertDialog;
alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle("Connection Error");
alertDialog.setMessage("Could not Connect.");
alertDialog.show();
e.printStackTrace();
}
//PARSE HTML CODE//
aName = new ArrayList();
aLink = new ArrayList();
main = Jsoup.parse(main.getElementsByClass("series_col").toString());
Elements seriesL = main.getElementsByTag("li");
for(Element anime: seriesL){
Elements link = anime.getElementsByTag("a");
aName.add(link.text());
aLink.add(link.attr("href"));
}
//SET VIEW//
adapter = new ArrayAdapter<String>(this, R.layout.list_item, aName);
setListAdapter(adapter);
//ONCLICK
view.setOnItemClickListener(
new OnItemClickListener(){
public void onItemClick(AdapterView<?> arg0, View view, int position, long arg3) {
Intent myIntent = new Intent(view.getContext(), EpisodeListActivity.class);
String name = (String) aName.get(position).toString();
String link = (String) aLink.get(position).toString();
myIntent.putExtra("Anime", name);
myIntent.putExtra("Link", link);
startActivity(myIntent);
}
});
}
Here's the log- 这是日志
07-04 15:08:15.382: W/dalvikvm(3489): threadid=1: thread exiting with uncaught exception (group=0x40a3c1f8)
07-04 15:08:15.406: E/AndroidRuntime(3489): FATAL EXCEPTION: main
07-04 15:08:15.406: E/AndroidRuntime(3489): java.lang.NullPointerException
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.AbsListView.obtainView(AbsListView.java:2035)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.ListView.makeAndAddView(ListView.java:1772)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.ListView.fillDown(ListView.java:672)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.ListView.fillFromTop(ListView.java:732)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.ListView.layoutChildren(ListView.java:1625)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.AbsListView.onLayout(AbsListView.java:1865)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.View.layout(View.java:11278)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.View.layout(View.java:11278)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1628)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1486)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.LinearLayout.onLayout(LinearLayout.java:1399)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.View.layout(View.java:11278)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.widget.FrameLayout.onLayout(FrameLayout.java:431)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.View.layout(View.java:11278)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.ViewGroup.layout(ViewGroup.java:4224)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1489)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2442)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.os.Handler.dispatchMessage(Handler.java:99)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.os.Looper.loop(Looper.java:137)
07-04 15:08:15.406: E/AndroidRuntime(3489): at android.app.ActivityThread.main(ActivityThread.java:4424)
07-04 15:08:15.406: E/AndroidRuntime(3489): at java.lang.reflect.Method.invokeNative(Native Method)
07-04 15:08:15.406: E/AndroidRuntime(3489): at java.lang.reflect.Method.invoke(Method.java:511)
07-04 15:08:15.406: E/AndroidRuntime(3489): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
07-04 15:08:15.406: E/AndroidRuntime(3489): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
07-04 15:08:15.406: E/AndroidRuntime(3489): at dalvik.system.NativeStart.main(Native Method)
You are extending ListActivity, override the method onListItemClick() in Activity instead of view.setOnItemClickListener that you are doing in onCreate() 您正在扩展ListActivity,覆盖Activity中的onListItemClick()方法,而不是您在onCreate()中执行的view.setOnItemClickListener
EDIT: 编辑:
in your layout xml: 在您的布局xml中:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />
</LinearLayout>
in your activity that uses the layout: 在使用布局的活动中:
in class: public class MyActivity extends ListActivity
在类中:公共类MyActivity extends ListActivity
getting the list view: ListView list = getListView();
获取列表视图: ListView list = getListView();
setting the list adapter: setListAdapter(adapter);
设置列表适配器: setListAdapter(adapter);
inside MyActivity class override the onListItemClick: 在MyActivity类中,重写onListItemClick:
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
//do your thing
}
documentation: http://developer.android.com/reference/android/app/ListActivity.html 文档: http : //developer.android.com/reference/android/app/ListActivity.html
You could also create a "normal" Activity instead of a ListActivity. 您也可以创建一个“普通”活动而不是一个ListActivity。
public class MainActivity extends Activity {
...
Change the ListViews id in your xml layout to "@+id/list". 将您的xml布局中的ListViews id更改为“ @ + id / list”。
<ListView
android:id="@+id/list"
...
Or create your list view in your onCreate method: 或在onCreate方法中创建列表视图:
ListView listView = new ListView(this);
setContentView(listView);
Get the ListView and you can use the OnItemClickListener. 获取ListView,然后可以使用OnItemClickListener。
ListView listView = (ListView) findViewById(R.id.list); // only needed if you have a xml layout
listView.setAdapter(adapter);
listView.setOnItemClickListener( ...
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