Androidアプリケーションでエラーが発生しました

Question

私のアプリにビルド中にコンソールでこのエラーが発生しました "java.lang.RuntimeException：アクティビティを開始できませんComponentInfo {com.example.cassieleong.delishcart/com.example.cassieleong.delishcart.FruitMain }：java.lang.NullPointerException：NULLオブジェクト参照に仮想メソッド 'void android.widget.ListView.setAdapter（android.widget.ListAdapter）'を呼び出そうとしました。

私はリストビューを含むアクティビティを構築しようとしていますcheckboxtextviewを使って

このエラーの解決方法はわかりません。助けてください。どうもありがとう。

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

あなたはリストビュー

代わりの

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

を取得するために間違ったIDを使用しています210

これを試してください：

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