如何从Android中的ListView中正确删除项目？

Question

我已经尝试在ListView中为我的项目实现删除过程，当我调用 adapter.remove（itemToRemove）; itemToRemove为null时，不显示删除项目... 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) {


            }
          }

        });
      }
}

这是我的 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;
    }
}

这是我的 CommentArrayAdapter.java

package com.bandweb.ordinefornitore.datastructure;

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

这是我的 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*/
}

这是我的 CustomAppContext.java

Answer 1

您可以在列表中调用.remove来填充您的视图。之后，您需要notifyDataSetChanged到"refresh" the ArrayAdapter

因此，如果您有一个array名为mylist的填充listView

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

Answer 2

您可以尝试以下操作：

替换adapter.remove(itemToRemove);

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

这样你的代码就变成了：

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;
                }

在您的代码中ArrayList<CommentObject> commentList是CommentObject的集合，因此您必须使用commentList.remove(itemToRemove)从集合中删除该项，然后调用adapter.notifyDataSetChanged()，但您正在调用{{ 1}} remove(itemToRemove)。