Fehler in Android App

Question

Im Aufbau auf meiner App und ich habe diesen Fehler auf der Konsole "java.lang.RuntimeException: Kann nicht starten ComponentInfo {com.beispiel.cassieleong.delishcart/com.example.cassieleong.delishcart.FruitMain }: java.lang.NullPointerException: Der Versuch, auf einer null-Objekt Referenz“

virtuelle Methode‚Leeren android.widget.ListView.setAdapter (android.widget.ListAdapter)‘aufzurufen

ich versuche, eine Aktivität zu erstellen, die Listview enthalten mit checkboxtextview.

Ich weiß nicht, wie man diesen Fehler löst. Bitte helfen Sie. Danke vielmals.

Java.

public class FruitMain extends AppCompatActivity { 
ListView listView; 
String[] fruit; 
Context context; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_fruit_main); 
    context = this; 
    listView = (ListView) findViewById(R.id.listView4); 
    String [] fruit = {"Apple","Applesauce","Apricot","Banana","Barlett Pears","Blackberries","Blueberries","Cantaloupe","Cherry","Citron","Coconut","Cranberry", 
    "Currants","Dates","Dried Fruit","Fig","Fruit Cocktail","Fruit Sauce","Grape","Grapefruit","Green Grapes","Honeydew Melon","Juniper Berries","Kiwi", 
    "Kumquat","Lemon","Lime","Lime Juice","Mango","Nectarines","Orange","Papaya","Passion Fruit","Peach","Pear","Persimmon", 
      "Pineapple","Plantain","Plum","Plum Tomatoes","Pomegranate","Prunes","Raison","Raspberry","Red Grapes","Strawberry","Sweet Cherries","Tangerine", 
      "Watermelon"}; 

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.fruititem_list, fruit); 
    listView.setAdapter(adapter); 
    listView.setItemsCanFocus(false); 
    listView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE); 
} 
@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    //Inflate the menu; this adds item to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.menu_ingredient_choices, menu); 
    return true; 
} 

}

XML.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:app="http://schemas.android.com/apk/res-auto" 
xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:paddingBottom="@dimen/activity_vertical_margin" 
android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
app:layout_behavior="@string/appbar_scrolling_view_behavior" 
tools:context="com.example.cassieleong.delishcart.FruitMain" 
tools:showIn="@layout/activity_fruit_main"> 

<TextView 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:textAppearance="?android:attr/textAppearanceLarge" 
    android:text="   Fruit Product   " 
    android:id="@+id/textView6" 
    android:textSize="35dp" 
    android:background="#f97c7c" 
    android:layout_alignParentTop="true" 
    android:layout_alignParentStart="true" /> 

<ListView 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:id="@+id/listView5" 
    android:layout_below="@+id/textView6" 
    android:layout_alignParentStart="true" 
    android:layout_above="@+id/button2" 
    android:layout_alignParentEnd="true"/> 

<Button 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:text="Submit" 
    android:id="@+id/button3" 
    android:layout_alignParentBottom="true" 
    android:layout_centerHorizontal="true" /> 

XML

<CheckedTextView xmlns:android="http://schemas.android.com/apk/res/android" 
android:id="@+id/checkedTextView4" 
android:orientation="vertical" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:text="" 
android:gravity="center" 
android:drawableLeft="?android:attr/listChoiceIndicatorMultiple" 
android:textSize="25dp"> 

Answer 1

Sie sind die falsche ID mit dem Listview

statt

listView = (ListView) findViewById(R.id.listView4); 

zu erhalten 210

versuchen Sie dies:

listView = (ListView) findViewById(R.id.listView5);