Question

当我尝试将对象从解析中放入List视图时，应用程序崩溃，请注意，对象存在，因为toast会遍历并提供名称，只是无法将其放在列表视图中。这是我的代码，关于创建方法，请帮助，我可能错过了什么？

我的日志错误

03-03 12：20：52.352 27230-27230 / com.parse.starter E / AndroidRuntime：FATAL EXCEPTION：main 处理：com.parse.starter，PID：27230 java.lang.NullPointerException：尝试调用虚方法＆＃39; java.lang.String java.lang.Object.toString（）＆＃39;在null对象引用上在android.widget.ArrayAdapter.createViewFromResource（ArrayAdapter.java:401）在android.widget.ArrayAdapter.getView（ArrayAdapter.java:369）在android.widget.AbsListView.obtainView（AbsListView.java:2474）在android.widget.ListView.makeAndAddView（ListView.java:1920）在android.widget.ListView.fillDown（ListView.java:717）在android.widget.ListView.fillFromTop（ListView.java:778）在android.widget.ListView.layoutChildren（ListView.java:1715）在android.widget.AbsListView.onLayout（AbsListView.java:2235）在android.view.View.layout（View.java:16961）在android.view.ViewGroup.layout（ViewGroup.java:5606）在android.widget.RelativeLayout.onLayout（RelativeLayout.java:1189）在android.view.View.layout（View.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android.view.View.layout（View.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（View.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android.view.View.layout（View.java:16961）在android.view.ViewGroup.layout（ViewGroup.java:5606）在android.widget.LinearLayout.setChildFrame（LinearLayout.java:2001）在android.widget.LinearLayout.layoutVertical（LinearLayout.java:1844）在android.widget.LinearLayout.onLayout（LinearLayout.java:1753）在android.view.View.layout（View.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com.android.internal.policy.PhoneWindow $ DecorView.onLayout（PhoneWindow.java:2742）在android.view.View.layout（View.java:16961）在android.view.ViewGroup.layout（ViewGroup.java:5606）在android.view.ViewRootImpl.performLayout（ViewRootImpl.java:2552）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:2255）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1321）在android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6708）在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（Choreographer.java:880）在android.os.Handler.handleCallback（Handler.java:815）在android.os.Handler.dispatchMessage（Handler.java:104）在android.os.Looper.loop（Looper.java:207）在android.app.ActivityThread.main（ActivityThread.java:5728） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:789）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:679）

这是代码

  @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());
  }

}

从Parse类

0 个答案: