Android Studio ImageButton参考不起作用

Question

我遇到了ArrayAdapter问题。

我有两个TabView中的两个片段列出的元素列表。

Code of the class: 


public class AdapterListaInCasa extends ArrayAdapter<String> { 

    private int layout_resource; 
    private List<String> str; 
    private Context mContext; 

    public AdapterListaInCasa(Context context, int textViewResourceId){ 
     super(context, textViewResourceId); 
     // TODO Auto-generated constructor stub 
    } 


    public AdapterListaInCasa(Context context, int layout_resource,List<String> str) { 

     super(context, layout_resource, str); 
     this.mContext = context; 
     this.str = str; 
     this.layout_resource = layout_resource; 

    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     final int mPosition = position; 
     LayoutInflater vi; 
     vi = LayoutInflater.from(getContext()); 


     if (convertView == null) { 
      convertView = vi.inflate(layout_resource, null); 
     } 



     TextView nomeElemento = (TextView)convertView.findViewById(R.id.nomeElemento); 
     nomeElemento.setText(str.get(mPosition)); 

     ImageButton btnTerminato = (ImageButton) convertView.findViewById(R.id.terminati); 
     btnTerminato.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { // bottone elimina 
       SharedPreferences preferences; 
       preferences = PreferenceManager.getDefaultSharedPreferences(getContext()); 
       SharedPreferences.Editor editor = preferences.edit(); 
       String lista = "inCasa"+mPosition; 
       editor.remove(lista); 

       str.remove(mPosition); 

       notifyDataSetChanged(); 


       int i=0; 
       String TAG = "daComprare"+i; 
       String eliminati = preferences.getString(TAG, "nonTrovato"); 
       while (eliminati != "nonTrovato"){ 
        i++; 
        TAG = "daComprare"+i; 
        eliminati = preferences.getString(TAG, "nonTrovato"); 
       } 
       editor.putString(TAG, str.get(mPosition)); 
       editor.commit(); 

      } 
     }); 


     ImageButton btnNNmiPiace = (ImageButton) convertView.findViewById(R.id.nonMiPiace); 
     btnNNmiPiace.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { // bottone elimina 
       SharedPreferences preferences; 
       preferences = PreferenceManager.getDefaultSharedPreferences(getContext()); 
       SharedPreferences.Editor editor = preferences.edit(); 
       String lista = "inCasa"+mPosition; 
       editor.remove(lista); 

       str.remove(mPosition); 

       notifyDataSetChanged(); 

       int i=0; 
       String TAG = "nonMiPiace"+i; 
       String nonMiPiace = preferences.getString(TAG, "nonTrovato"); 
       while (nonMiPiace != "nonTrovato"){ 
        i++; 
        TAG = "nonMiPiace"+i; 
        nonMiPiace = preferences.getString(TAG, "nonTrovato"); 
       } 
       editor.putString(TAG, str.get(mPosition)); 
       editor.commit(); 

      } 
     }); 
     return convertView; 
    } 
} 




Code of the xml: 

<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content"> 

    <TextView 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentLeft="true" 
     android:layout_alignParentStart="true" 
     android:layout_centerVertical="true" 
     android:layout_marginLeft="20dp" 
     android:id="@+id/nomeElemento"/> 

    <ImageButton 
     android:id="@+id/terminati" 
     android:layout_width="50dp" 
     android:layout_height="50dp" 
     android:layout_alignParentEnd="true" 
     android:layout_alignParentRight="true" 
     android:layout_margin="10dp" 
     android:src="@drawable/ic_carrello" /> 

    <ImageButton 
     android:id="@+id/nonMiPiace" 
     android:layout_width="50dp" 
     android:layout_height="50dp" 
     android:layout_margin="10dp" 
     android:layout_toLeftOf="@+id/terminati" 
     android:layout_toStartOf="@+id/terminati" 
     android:src="@drawable/ic_carrello" /> 

</RelativeLayout> 

的问题是，当我尝试使用按钮btnTerminato与

btnTerminato.setOnClickListener(new View.OnClickListener() {... 

我recive一个致命的错误，指出该变量为空：

FATAL EXCEPTION: main 
Process: com.giulio.marketrack, PID: 24457 
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setMaxWidth(int)' on a null object reference 
at com.giulio.marketrack.AdapterListaInCasa.getView(AdapterListaInCasa.java:65) 

奇怪的事实是唯一的问题可能是ID引用，但是，您如何看到ID是正确的。

任何人都看到失败？

提前感谢！

Answer 1

if (convertView == null) { 
    convertView = = inflater.inflate(R.layout.yourlayout name, null); 
}