如何从Android的ListView中正确删除一个项目？

Question

我尝试在ListView中实现一个删除程序，当我调用adapter.remove（itemToRemove）; itemToRemove为空，并且没有删除项目出现... 请帮助我！，这是我的代码：

package com.bandweb.ordinefornitore;

import java.util.ArrayList; 
import java.util.Date; 
import java.util.List; 


import com.bandweb.ordinefornitore.adapter.CommentArrayAdapter; 
import com.bandweb.ordinefornitore.datastructure.CommentObject; 

import android.os.Bundle; 
import android.app.Activity; 
import android.app.AlertDialog; 
import android.app.Dialog; 
import android.content.DialogInterface; 
import android.util.Log; 
import android.view.Menu; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ListView; 
import android.widget.Spinner; 
import android.widget.TextView; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.widget.Toast; 
import android.widget.AdapterView.OnItemClickListener; 

public class MainActivity extends Activity { 

    private Spinner spin_prodotto, spin_tipo; 
    private Button btnAggiungi,btnView_order,btnNew_order; 
    private EditText EtQta; 
    private TextView tvOrder; 
    private String Order,Msg; 
    private ArrayList<CommentObject> commentList = null; 
    private ListView commentListView = null; 
    private Number Riga=0; 
    public CommentArrayAdapter adapter; 
    protected static final int DIALOG_REMOVE_CALC = 1; 
    protected static final int DIALOG_REMOVE_PERSON = 2; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main1); 

     //Prepare the Dataset 
     prepareDataList(); 

     commentListView = (ListView)findViewById(R.id.listComment); 
     TextView emptyList = (TextView)findViewById(R.id.txtEmptyList); 
     emptyList.setText("No comments to display!"); 
     commentListView.setEmptyView(emptyList); 
     adapter = new CommentArrayAdapter(this, R.id.txtLoadingList, commentList); 
     commentListView.setAdapter(adapter); 

     //Manage the onItemClick method 
     commentListView.setOnItemClickListener(new OnItemClickListener() { 

      @Override 
      public void onItemClick(AdapterView<?> parent, View view, int position, 
        long id) { 
       CommentObject currComment = (CommentObject)parent.getItemAtPosition(position); 
       int duration = Toast.LENGTH_SHORT; 
       Toast toast = Toast.makeText(MainActivity.this, 
         "You clicked on a comment by "+currComment.senderName, duration); 
       toast.show(); 

      } 
     }); 

     commentListView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener(){ 
      @Override 
      public boolean onItemLongClick(AdapterView<?> arg0, View v, int pos, long id) { 
       // TODO Auto-generated method stub 
       return onLongListItemClick(v,pos,id); 
      } 

      protected boolean onLongListItemClick(View v, final int pos, long id) { 
       final String str=commentListView.getItemAtPosition(pos).toString(); 
       Log.i("ListView", "onLongListItemClick stirng=" + str); 

       AlertDialog diaBox = AskOption(); 
       diaBox.show(); 
       CommentObject itemToRemove = (CommentObject)v.getTag(); 
       adapter.remove(itemToRemove); 
       adapter.notifyDataSetChanged(); 

       return false; 
       } 

     }); 

     addListenerOnButton(); 
    } 




    public void removeProductOnClickHandler(View v) { 

     AlertDialog diaBox = AskOption(); 
     diaBox.show(); 
     CommentObject itemToRemove = (CommentObject)v.getTag(); 
     adapter.remove(itemToRemove); 
     adapter.notifyDataSetChanged(); 
    } 

    private AlertDialog AskOption() 
    { 
     AlertDialog myQuittingDialogBox =new AlertDialog.Builder(this) 
      //set message, title, and icon 
      .setTitle("Delete") 
      .setMessage(R.string.calculation_dialog_remove_text) 
      .setIcon(R.drawable.trash_empty) 

      .setPositiveButton(R.string.calculation_dialog_button_ok, new DialogInterface.OnClickListener() { 

       public void onClick(DialogInterface dialog, int whichButton) { 
        //your deleting code 

        dialog.dismiss(); 
       } 

      }) 

      .setNegativeButton(R.string.calculation_dialog_button_cancel, new DialogInterface.OnClickListener() { 
       public void onClick(DialogInterface dialog, int which) { 

        dialog.dismiss(); 

       } 
      }) 
      .create(); 
      return myQuittingDialogBox; 

     } 

// private Dialog createDialogRemoveConfirm(final int dialogRemove) { 
//  return new AlertDialog.Builder(getApplicationContext()) 
//  .setIcon(R.drawable.trash_empty) 
//  .setTitle(R.string.calculation_dialog_remove_text) 
//  .setPositiveButton(R.string.calculation_dialog_button_ok, new DialogInterface.OnClickListener() { 
//   public void onClick(DialogInterface dialog, int whichButton) { 
//    handleRemoveConfirm(dialogRemove); 
//   } 
//  }) 
//  .setNegativeButton(R.string.calculation_dialog_button_cancel, null) 
//  .create(); 
// } 
// 
// protected void handleRemoveConfirm(int dialogType) { 
//  if(dialogType == DIALOG_REMOVE_PERSON){ 
//   //calc.removePerson(); 
//  }else if(dialogType == DIALOG_REMOVE_CALC){ 
//   //removeCalc(); 
//  } 
// } 
// 
//// OnClickListener removeCalcButtonClickListener = new OnClickListener() { 
////  public void onClick(View v) { 
////   showDialog(DIALOG_REMOVE_CALC); 
////  } 
//// }; 
// 
// @Override 
// protected Dialog onCreateDialog(int id) { 
//  switch (id) { 
//  case DIALOG_REMOVE_CALC: 
//   return createDialogRemoveConfirm(DIALOG_REMOVE_CALC); 
//  case DIALOG_REMOVE_PERSON: 
//   return createDialogRemoveConfirm(DIALOG_REMOVE_PERSON); 
//  } 
//  return null; 
// } 

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

    private void prepareDataList(){ 
      commentList = new ArrayList<CommentObject>();  
     } 


    // get the selected dropdown list value 
     public void addListenerOnButton() { 

     spin_prodotto = (Spinner) findViewById(R.id.spin_prodotto); 
     spin_tipo = (Spinner) findViewById(R.id.spin_tipo); 
     btnAggiungi = (Button) findViewById(R.id.btn_aggiungi); 
     btnView_order = (Button) findViewById(R.id.btn_view_order); 
     btnNew_order = (Button) findViewById(R.id.btn_new_order); 
     EtQta = (EditText) findViewById(R.id.Et_qta); 
     //tvOrder = (TextView) findViewById(R.id.tv_ordine); 

     btnAggiungi.setEnabled(false); 
     btnView_order.setEnabled(false); 

     btnNew_order.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       // TODO Auto-generated method stub 
       btnAggiungi.setEnabled(true); 
       Date now = new Date(); 
       Order = "Ordine del:\n" + 
         String.valueOf(now.toString())+"\n"; 

       CommentObject comment = new CommentObject(); 
       comment.senderName = Order; 
       comment.commentText = "Aggiugere i prodotti...";   
       commentList.add(comment); 
       adapter.notifyDataSetChanged(); 
      } 

     }); 

     btnAggiungi.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { 

      try {   
       CommentObject comment = new CommentObject(); 
       comment.senderName = String.valueOf(spin_prodotto.getSelectedItem()); 
       comment.commentText = "Qtà: "+ String.valueOf(EtQta.getText())+" "+String.valueOf(spin_tipo.getSelectedItem());   
       commentList.add(comment); 
       adapter.notifyDataSetChanged(); 

      } catch (Exception e) { 


      } 
      } 

     }); 
     } 
} 

这是我MainActivity.java

package com.bandweb.ordinefornitore.adapter; 

import java.util.ArrayList; 
import java.util.List; 

import com.bandweb.ordinefornitore.R; 
import com.bandweb.ordinefornitore.R.id; 
import com.bandweb.ordinefornitore.R.layout; 
import com.bandweb.ordinefornitore.datastructure.CommentObject; 


import android.content.Context; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.view.View.OnClickListener; 
import android.widget.ArrayAdapter; 
import android.widget.ImageButton; 
import android.widget.ImageView; 
import android.widget.TextView; 
import android.widget.Toast; 


public class CommentArrayAdapter extends ArrayAdapter<CommentObject>{ 
    private Context m_context = null; 
    private ArrayList<CommentObject> m_comments = null; 
    private LayoutInflater m_inflater = null; 

    public CommentArrayAdapter(Context context, int textViewResourceId, 
      List<CommentObject> objects) { 
     super(context, textViewResourceId, objects); 

     m_context = context; 
     m_comments = (ArrayList<CommentObject>)objects; 
     m_inflater = LayoutInflater.from(m_context); 
    } 

    @Override 
    public int getCount() { 
     if(m_comments != null){ 
      return m_comments.size(); 
     } 
     return 0; 
    } 

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

     CommentViewHolder holder = null; 

     //form the view 
     if(convertView == null){ 
      holder = new CommentViewHolder(); 
      convertView = m_inflater.inflate(R.layout.order_list_row, parent, false); 
      //holder.senderImage = (ImageView)convertView.findViewById(R.id.imgUserImage); 
      holder.senderName = (TextView)convertView.findViewById(R.id.txtUserName); 
      holder.commentText = (TextView)convertView.findViewById(R.id.txtUserComment); 
      holder.removeProductButton = (ImageButton)convertView.findViewById(R.id.remove_product); 
      //holder.link = (TextView)convertView.findViewById(R.id.txtClickableLink); 

      convertView.setTag(holder); 

     }else{ 

      holder = (CommentViewHolder)convertView.getTag(); 
     } 

     //bind the data to the view 
     CommentObject comment = m_comments.get(position); 
     holder.senderName.setText(comment.senderName); 
     holder.commentText.setText(comment.commentText); 
     //final ImageButton clickableText = comment.removeProductButton; 
     //holder.link.setOnClickListener(new OnClickListener() { 
//   
//   @Override 
//   public void onClick(View v) { 
//    int duration = Toast.LENGTH_SHORT; 
//    Toast toast = Toast.makeText(m_context, clickableText, duration); 
//    toast.show();    
//   } 
//  }); 
//  holder.removeProductButton.setOnClickListener(new OnClickListener() { 
//   public void onClick(View v) { 
//    int duration = Toast.LENGTH_SHORT; 
//    Toast toast = Toast.makeText(m_context, "rimuovere", duration); 
//    toast.show(); 
// 
//   } 
//  }); 

     return convertView; 
    } 

    private class CommentViewHolder{ 
     ImageButton removeProductButton; 
     TextView senderName; 
     TextView commentText; 
    } 
} 

这是我CommentArrayAdapter.java

package com.bandweb.ordinefornitore.datastructure; 

public class CommentObject 
{  
public String senderName; 
public String commentText; 
} 

这是我CommentObject.java

package com.bandweb.ordinefornitore; 

import android.app.Application; 
import android.content.Context; 


public class CustomAppContext extends Application { 

    private static CustomAppContext context; 

    @Override 
    public void onCreate() { 
     super.onCreate(); 

     context = this; 
    } 

    public static CustomAppContext getInstance(){ 
     return context; 
    } 

    public static Context getContext(){ 
     return context.getApplicationContext(); 
    } 

    /*Add your other methods and global variables here*/ 
} 

这是我CustomAppContext.java

Answer 1

您可以将列表populats视图上调用.remove。之后，如果你有一个array称为MYLIST用于填充您的ListView，你会想notifyDataSetChanged到"refresh" the ArrayAdapter

所以

mylist.remove(int index): 
notifyDataSetChanged(); 

Answer 2

您可以尝试以下操作：

更换adapter.remove(itemToRemove);

通过adapter.remove(adapter.getItem(pos));

以便您的代码变为：

protected boolean onLongListItemClick(View v, final int pos, long id) { 
       final String str=commentListView.getItemAtPosition(pos).toString(); 
       Log.i("ListView", "onLongListItemClick stirng=" + str); 

       AlertDialog diaBox = AskOption(); 
       diaBox.show(); 
       CommentObject itemToRemove = (CommentObject)v.getTag(); 
       adapter.remove(adapter.getItem(i)); // changed this line 
       adapter.notifyDataSetChanged(); 

       return false; 
       } 

在你的代码ArrayList<CommentObject> commentList是CommentObject集，因此必须使用commentList.remove(itemToRemove)删除您的收藏该项目，然后调用adapter.notifyDataSetChanged()，但你正在呼吁adapterremove(itemToRemove)。