从分析类创建对象的列表视图
应用程序崩溃时，我尝试将对象从解析列表视图，请注意，对象是作为吐司会循环并提供名称，只是不能把它放在列表视图中。 这里是我的代码，关于创建方法，请帮助，我可以错过什么？
我的日志错误
03-03 12：20：52.352 27230-27230 / com.parse.starter E / AndroidRuntime：致命异常：主进程：com.parse.starter，PID：27230 java.lang.NullPointerException：尝试调用虚拟方法'java。在android.widget.ArrayAdapter.createViewFromResource（ArrayAdapter.java:401）上的空对象引用上的android.widget.ArrayAdapter.getView（ArrayAdapter.java:369）android上的lang.String java.lang.Object.toString（） .widget.AbsListView.obtainView（AbsListView.java:2474）at android.widget.ListView.makeAndAddView（ListView.java:1920）at android.widget.ListView.fillDown（ListView.java:717）at android.widget.ListView。在android.view.View.layout（View.java）android.widget.AbsListView.onLayout（AbsListView.java:2235）android.widget.ListView.layoutChildren（ListView.java:1715）fillFromTop（ListView.java:778） ：16961）at android.view.ViewGroup.layout（ViewGroup.java:5606）at android.widget.RelativeLayout.onLayout（RelativeLayout.java:1189）at android.view.View.layout（View.java:16961）at android .view.Vie wGroup.layout（ViewGroup.java:5606）在android.widget.FrameLayout.layoutChildren（FrameLayout.java:396）在android.widget.FrameLayout.onLayout（FrameLayout.java:333）在android.view.View.layout（查看的.java：16961）在android.view.ViewGroup.layout（ViewGroup.java:5606）在android.support.v7.widget.ActionBarOverlayLayout.onLayout（ActionBarOverlayLayout.java:435）在android.view.View.layout（查看。的java：16961）在android.view.ViewGroup.layout（ViewGroup.java:5606）在android.widget.FrameLayout.layoutChildren（FrameLayout.java:396）在android.widget.FrameLayout.onLayout（FrameLayout.java:333）在在android.widget.LinearLayout上的android.widget.LinearLayout.setChildFrame（LinearLayout.java:2001）上的android.view.ViewGroup.layout（ViewGroup.java:5606）上的android.view.View.layout（View.java:16961） .layoutVertical（LinearLayout.java:1844）在android.view.ViewGroup.layout（ViewGroup。）的android.view.View.layout（View.java:16961）android.widget.LinearLayout.onLayout（LinearLayout.java:1753）。 java：5606）在android.widge t.FrameLayout.layoutChildren（FrameLayout.java:396）at android.widget.FrameLayout.onLayout（FrameLayout.java:333）at com.android.internal.policy.PhoneWindow $ DecorView.onLayout（PhoneWindow.java:2742）at android .view.View.layout（View.java:16961）at android.view.ViewGroup.layout（ViewGroup.java:5606）at android.view.ViewRootImpl.performLayout（ViewRootImpl.java:2552）at android.view.ViewRootImpl。在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1321）处的android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6708）上的performTraversals（ViewRootImpl.java:2255）android.view.Choreographer $ CallbackRecord.run （Choreographer.java:894）在android.view.Choreographer.doCallbacks（Choreographer.java:696）在android.view.Choreographer.doFrame（Choreographer.java:631）在android.view.Choreographer $ FrameDisplayEventReceiver.run（编导。 java：880）在android.os.Handler.handleCallback（Handler.java:815）在android.os.Handler.dispatchMessage（Handler.java:104）在android.os.Looper.loop（循环 er.java:207）at android.app.ActivityThread.main（ActivityThread.java:5728）at java.lang.reflect.Method.invoke（Native Method）at com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ ZygoteInit.java:789）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:679）
这里是代码
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Users home
Toast.makeText(this, "USERS", Toast.LENGTH_SHORT).show();
//Populating listview with values from created parse object
final ArrayList<String> jusernames = new ArrayList<String>();
final ListView userListView = (ListView) findViewById(R.id.listview);
final ArrayAdapter arrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, jusernames);
ParseQuery <ParseObject> query = ParseQuery.getQuery("Help");
//Picking all the users without deleted tag
query.whereNotEqualTo("username", "Deleted");
//Making the list in ascending order
query.addAscendingOrder("username");
query.findInBackground(new FindCallback<ParseObject>() {
@Override
public void done(List<ParseObject> objects, ParseException e) {
if( e == null){
if(objects.size() > 0){
for(ParseObject object : objects){
String user = object.getString("Username");
String category = object.getString("Category");
Toast.makeText(MainActivity.this, category, Toast.LENGTH_SHORT).show();
String description = object.getString("Description");
String price = object.getString("Price");
//Adding the value to listview
jusernames.add(category);
}
userListView.setAdapter(arrayAdapter);
}
}else
{
Toast.makeText(MainActivity.this, "Fail", Toast.LENGTH_SHORT).show();
e.printStackTrace();
}
}
});
ParseAnalytics.trackAppOpenedInBackground(getIntent());
}
}