java - 每当我调用Activity时，应用程序崩溃并给出错误

Question

public class MainActivity extends AppCompatActivity {

FirebaseDatabase firebaseDatabase = FirebaseDatabase.getInstance ();
DatabaseReference databaseReference = firebaseDatabase.getReference ();
ListView listView;
List<String> ListString = new ArrayList<String> ();
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate (savedInstanceState);
    setContentView (R.layout.activity_main22);
    ListString.add ("Hello");
    databaseReference.addValueEventListener (new ValueEventListener () {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            DataSnapshot snapshot = dataSnapshot.child ("User");
            for(DataSnapshot s: snapshot.getChildren ())
                Toast.makeText (MainActivity.this, s.getKey ().toString (), Toast.LENGTH_SHORT).show ();

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    listView = (ListView) findViewById (R.id.listview);
    ListAdapter listAdapter = new ListAdapter (MainActivity.this, ListString);
    listView.setAdapter (listAdapter);
    DatabaseReference s = databaseReference.child ("User");
    DatabaseReference p = s.child ("Name");
    p.setValue (ListString.get (1));

} }

正如我所说的，每当我调用此 Activity 时，它就会使应用程序崩溃，并且logcat是

java.lang.RuntimeException: Unable to start activity ComponentInfo{lifeline.learn.com.attendencemarker/lifeline.learn.com.attendencemarker.MainActivity}: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2984) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3045) at android.app.ActivityThread.-wrap14(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1642) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6776) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1518) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1408) Caused by: java.lang.IndexOutOfBoundsException: Index: 1, Size: 1

Answer 1

这行导致错误

p.setValue (ListString.get (1));

您在ListString中只有一个值，并且访问第二个值，将其更改为以下值

p.setValue (ListString.get (0));