Listenansicht macht Android App Absturz

Question

Ich arbeite an einer gesundheitsbezogenen Android App. In diesem Beispiel verwende ich in IndexPage.java die Schaltfläche "Floating Action", um zu einer anderen Aktivität "FoodEntry.java" (mit Listenansicht für Lebensmittel) zu wechseln. Immer wenn wir auf die schwebende Schaltfläche klicken, stürzt die App ab. Eine Sache, die ich herausgefunden habe, ist, dass die App aufgrund von Listview abstürzt. Bitte helfen Sie mir, eine Lösung zu finden.

Dies ist IndexPage.java

public class IndexPage extends AppCompatActivity { 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_index_page); 
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab); 
    fab.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 

      Intent in = new Intent(IndexPage.this, FoodEntry.class); 
      startActivity(in); 

     } 
    }); 
} 
} 

FoodEntry.java

public class FoodEntry extends AppCompatActivity { 

// Array of strings... 
String[] food = {"Naan","Pav bhaji","chole tikiya", "rice", "soyabean", "milk", "curd", "abc", "def", "dfadf", "fasdfa", "fsadf", "fdsfa", "fga"}; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 


    ArrayAdapter adapter = new ArrayAdapter<>(this, R.layout.activity_item, food); 
    ListView listViewFoodItems = (ListView)findViewById(R.id.listViewFood); 
    listViewFoodItems.setAdapter(adapter); 
} } 

Fehler auf logcat

03-31 15:30:58.555 13732-13732/com.praval.healthfreak W/dalvikvm: threadid=1: calling UncaughtExceptionHandler 
03-31 15:30:58.556 13732-13732/com.praval.healthfreak E/AndroidRuntime: FATAL EXCEPTION: main 
                     Process: com.praval.healthfreak, PID: 13732 
                     java.lang.RuntimeException: Unable to start activity ComponentInfo{com.praval.healthfreak/com.praval.healthfreak.FoodEntry}: java.lang.NullPointerException 
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2389) 
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441) 
                      at android.app.ActivityThread.access$900(ActivityThread.java:151) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354) 
                      at android.os.Handler.dispatchMessage(Handler.java:110) 
                      at android.os.Looper.loop(Looper.java:193) 
                      at android.app.ActivityThread.main(ActivityThread.java:5345) 
                      at java.lang.reflect.Method.invokeNative(Native Method) 
                      at java.lang.reflect.Method.invoke(Method.java:515) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644) 
                      at dalvik.system.NativeStart.main(Native Method) 
                     Caused by: java.lang.NullPointerException 
                      at com.praval.healthfreak.FoodEntry.onCreate(FoodEntry.java:20) 
                      at android.app.Activity.performCreate(Activity.java:5343) 
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088) 
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343) 
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441)  
                      at android.app.ActivityThread.access$900(ActivityThread.java:151)  
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354)  
                      at android.os.Handler.dispatchMessage(Handler.java:110)  
                      at android.os.Looper.loop(Looper.java:193)  
                      at android.app.ActivityThread.main(ActivityThread.java:5345)  
                      at java.lang.reflect.Method.invokeNative(Native Method)  
                      at java.lang.reflect.Method.invoke(Method.java:515)  
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828)  
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644)  
                      at dalvik.system.NativeStart.main(Native Method) 

Answer 1

Sie fügen vergessen zu

setContentView(R.layout.activity_layout); 

in FoodEntry Activity