私は試してもカスタムアダプタが動作しません

Question

imageviewとtextviewの画像とテキストをlistviewに表示するためのアダプタを作成しました。

私は最善を尽くしましたが、このアクティビティが呼び出されるたびにアプリケーションがクラッシュします。

ImageAdapter.java：

public class ImageAdapter extends ArrayAdapter<String> { 

    private final Activity context; 
    private final String[] filedescrptions; 
    private final Integer[] filenames; 

    public ImageAdapter(Activity context, String[] filedescrptions, Integer[] filenames) { 
    super(context, R.layout.list_item, filedescrptions); 
    this.context = context; 
    this.filedescrptions = filedescrptions; 
    this.filenames = filenames; 

    } 

    @Override 
    public View getView(int position, View view, ViewGroup parent) { 
    LayoutInflater inflater = context.getLayoutInflater(); 
    View rowView= inflater.inflate(R.layout.list_item, null, true); 
    TextView txtTitle = (TextView) rowView.findViewById(R.id.txt); 

    ImageView imageView = (ImageView) rowView.findViewById(R.id.img); 
    txtTitle.setText(filedescrptions[position]); 
    imageView.setImageResource(filenames[position]); 
    return rowView; 

    } 
} 

これは、アダプタが使用されている主な活動です。

ImageActivity.java：

public class ImageActivity extends AppCompatActivity { 

    ListView list; 

    String[] descriptions = {"Abnormal menstrual bleeding", 
     "Adverse effects of HIV drugs", 
     "Antibiotics contraindicated during pregnancy", 
     "Antiemetic drugs" 
    }; 

    Integer[] fileIds = { 
     R.drawable.abnromalmenstrualbleeding, 
     R.drawable.adverseeffectsofhivdrugs, 
     R.drawable.antibioticscontraindicatedduringpregnancy, 
     R.drawable.antiemeticdrugs 
    }; 

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


    ImageAdapter adapter = new ImageAdapter(ImageActivity.this, descriptions, fileIds); 
    list=(ListView)findViewById(R.id.listview_image); 
    list.setAdapter(adapter); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
    // Inflate the menu; this adds items to the action bar if it is present. 
    getMenuInflater().inflate(R.menu.menu_main, menu); 
    return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 
    return super.onOptionsItemSelected(item); 
    } 
} 

list_item.xml：

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> 
    <ImageView 
     android:id="@+id/img" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content"/> 

    <TextView 
     android:id="@+id/txt" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:textSize="24sp" 
     android:textColor="@android:color/black"/> 

</LinearLayout> 

logcat第38行referes list.setAdapter(adapter);に

FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vivek.pocketmedbook/com.vivek.pocketmedbook.ImageActivity}:java.lang.NullPointerException 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084) 
at android.app.ActivityThread.access$600(ActivityThread.java:130) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195) 
at android.os.Handler.dispatchMessage(Handler.java:99) 
at android.os.Looper.loop(Looper.java:137) 
at android.app.ActivityThread.main(ActivityThread.java:4745) 
at java.lang.reflect.Method.invokeNative(Native Method) 
at java.lang.reflect.Method.invoke(Method.java:511) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
at dalvik.system.NativeStart.main(Native Method) 
Caused by: java.lang.NullPointerException 
at com.vivek.pocketmedbook.ImageActivity.onCreate(ImageActivity.java:38) 
at android.app.Activity.performCreate(Activity.java:5008) 
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)  
at android.app.ActivityThread.access$600(ActivityThread.java:130)  
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)  
at android.os.Handler.dispatchMessage(Handler.java:99)  
at android.os.Looper.loop(Looper.java:137)  
at android.app.ActivityThread.main(ActivityThread.java:4745)  
at java.lang.reflect.Method.invokeNative(Native Method)  
at java.lang.reflect.Method.invoke(Method.java:511)  
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)  
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)  
at dalvik.system.NativeStart.main(Native Method)  

Answer 1

変更

1. ImageAdapterは