我正在尝试运行以下代码:
public class MyListActivity extends ListActivity {
private static class MyListLoadingCallback implements Handler.Callback {
private ListActivity activity;
private MyListManager myListManager;
public MyListLoadingCallback(ListActivity activity,
MyListManager articleListManager) {
this.activity = activity;
this.myListManager = myListManager;
}
@Override
public boolean handleMessage(Message message) {
throw new NotYetImplementedException();
}
}
private MyListManager myListManager;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
myListManager.fetchArticles(new Handler(
new MyListLoadingCallback(this, MyListManager)));
}
我在articleListManager.fetchArticles(new Handler(new MyListLoadingCallback(this,MyListManager)))处获得了一个空指针
我的其他课程如下所示:
public class MyListManager {
public void fetchArticles(final Handler handler) {
}
}
有人可以步行给我/用这段代码帮助我,以便更好地理解。我似乎不太了解。
最佳答案
该错误似乎很明显:)。
抛出异常(myListManager.fetchArticles(new Handler(new MyListLoadingCallback(this, MyListManager)));
)的行中只有一个“引用”被访问,并且它是myListManager
,因此它必须是NULL
。看一下代码,您永远不会将其初始化为任何东西,因此它的确是NULL
:)