Java listview的适配器出现null异常
我在用适配器实现自定义视图时遇到问题,代码没有显示任何错误,但当我运行它时,它会给我一个空点异常Java listview的适配器出现null异常,java,android,eclipse,listview,adapter,Java,Android,Eclipse,Listview,Adapter,我在用适配器实现自定义视图时遇到问题,代码没有显示任何错误,但当我运行它时,它会给我一个空点异常 01-08 12:21:43.949: E/AndroidRuntime(12646): FATAL EXCEPTION: main 01-08 12:21:43.949: E/AndroidRuntime(12646): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jp.blueoceans
01-08 12:21:43.949: E/AndroidRuntime(12646): FATAL EXCEPTION: main
01-08 12:21:43.949: E/AndroidRuntime(12646): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jp.blueoceans2/friends.ListFriendsMain}: java.lang.NullPointerException
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1837)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.ActivityThread.access$1500(ActivityThread.java:132)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1033)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.os.Handler.dispatchMessage(Handler.java:99)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.os.Looper.loop(Looper.java:143)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.ActivityThread.main(ActivityThread.java:4196)
01-08 12:21:43.949: E/AndroidRuntime(12646): at java.lang.reflect.Method.invokeNative(Native Method)
01-08 12:21:43.949: E/AndroidRuntime(12646): at java.lang.reflect.Method.invoke(Method.java:507)
01-08 12:21:43.949: E/AndroidRuntime(12646): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-08 12:21:43.949: E/AndroidRuntime(12646): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-08 12:21:43.949: E/AndroidRuntime(12646): at dalvik.system.NativeStart.main(Native Method)
01-08 12:21:43.949: E/AndroidRuntime(12646): Caused by: java.lang.NullPointerException
01-08 12:21:43.949: E/AndroidRuntime(12646): at friends.ListFriendsMain.onCreate(ListFriendsMain.java:95)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
01-08 12:21:43.949: E/AndroidRuntime(12646): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
01-08 12:21:43.949: E/AndroidRuntime(12646): ... 11 more
适配器的代码如下所示:
public class FriendsAdapter extends BaseAdapter{
private Activity activity;
ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader;
public FriendsAdapter (Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
imageLoader=new ImageLoader(activity.getApplicationContext());
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.row_friend_cell, null);
TextView surname_friend = (TextView)vi.findViewById(R.id.surname_friend);
TextView name_friend = (TextView)vi.findViewById(R.id.name_friend);
TextView relation = (TextView)vi.findViewById(R.id.relation);
ImageView avatar = (ImageView)vi.findViewById(R.id.avatar);
HashMap<String, String> friends = new HashMap<String, String>();
friends = data.get(position);
// Setting all values in listview
surname_friend.setText(friends.get(ListFriendsMain.KEY_SURNAME));
name_friend.setText(friends.get(ListFriendsMain.KEY_NAME));
relation.setText(friends.get(ListFriendsMain.KEY_RELATION));
imageLoader.DisplayImage(friends.get(ListFriendsMain.KEY_AVATAR_URL), avatar);
return vi;
}
}
问题出在onCreate()中的
ListFriendsMain类中,行号为95
<代码>由:java.lang.NullPointerException在friends.ListFriendsMain.onCreate(ListFriendsMain.java:95)引起的
如果您可以使用相关代码编辑您的问题,那么您的问题就有可能得到准确解决。您显示的调用堆栈表明错误在
列表中的某个地方。具体而言,如果您在以下位置显示代码,则会有所帮助:
friends.ListFriendsMain.onCreate(ListFriendsMain.java:95)
查看您的代码:
list=(ListView)findViewById(R.id.list);
adapter = new FriendsAdapter(this, info);
list.setAdapter(adapter);
适配器绝对不是空的。
在setContentView()中使用哪种布局?
确保布局具有id为list的ListView。如果您的跟踪是正确的,这是我能想到的唯一问题。实际上,在我将listview id从@+id/list更改为@+id/android:list之前,eclipse一直说我必须有一个id为android:list的listview,知道它为什么这么说吗?可能是因为名称列表。有时日食会把事情搞砸。最好有一个好的命名约定,以节省您在大型项目中的时间。不要给ListView列表命名,而是使用像idListViewFriends这样的名称……你是对的,这是我一直尝试做的,除非Eclipse心情不好,不允许我这么做。无论如何,谢谢你的帮助。你必须和Eclipse分手。你太棒了。此外,我知道这个很棒的IDE,我想让你认识一下。它有一个性感的黑色主题,和一个非常通融的角色。有一天给它打个电话。(只是小心别把它和它的孪生兄弟混在一起——那是一个真正的淘金者……)
friends.ListFriendsMain.onCreate(ListFriendsMain.java:95)
list=(ListView)findViewById(R.id.list);
adapter = new FriendsAdapter(this, info);
list.setAdapter(adapter);