java - onResume 中的 NullPointerException

Question

我有两个 Activity MainActivity 和 SecondActivity

Activity MainActivity.java 中的代码

public class MainActivity extends FragmentActivity implements OnMarkerClickListener {

@Override
 protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      getWindow().requestFeature(Window.FEATURE_NO_TITLE);
      setContentView(R.layout.activity_main_screen);
      databaseobj = new AppDatabase(MainActivity.this, null);
      listview = (ListView) findViewById(R.id.store_listview);
      noSavedMsg = (TextView) findViewById(R.id.no_msg);
      ..
      ..
      ..//Other code logic
      ..
 }

 @Override
 protected void onResume() {
      if (databaseobj.GetAll() != -1) { //NULL POINTER EXCEPTION
      listview.setVisibility(View.GONE);  //NULL POINTER EXCEPTION
      noSavedMsg.setVisibility(View.VISIBLE); //NULL POINTER EXCEPTION
      }
      super.onResume();
  }
}

从另一个 Activity 返回后，我收到空指针异常；

MainActivity -> SecondActivity 的新 Intent

SecondActivity->finish() 然后 MainActivity-> onResume() 空指针异常

请帮忙!

Answer 1

您的TextView名称是noSavedMsg，但您正在尝试设置名为NoSavedMsg的 View 的可见性...这两个不一样。

更改此行...

NoSavedMsg.setVisibility(View.VISIBLE);

到...

noSavedMsg.setVisibility(View.VISIBLE);