如何将数据添加到 listView 的自定义 BaseAdapter - Android

Question

我有一个自定义 BaseAdapter 类，它为 cmets、用户名和数字创建视图。此 BaseAdapter 从 An AsyncTask 接收此信息。当用户到达 listView 的底部时，AsyncTask 运行。问题是 BaseAdapter 不会添加新数据。当我尝试添加新数据时，它会删除列表中的当前数据，然后添加新数据。我希望它保留所有数据，并将数据添加到 listView 的底部。所有这些类都在同一个活动中。这是我当前的代码。

class CreateCommentLists extends BaseAdapter{
                Context ctx_invitation;
                String[] listComments;
                String[] listNumbers;
                String[] listUsernames;


                public CreateCommentLists(String[] comments, String[] usernames, String[] numbers, DashboardActivity context)
                {
                    super();
                    ctx_invitation = context;
                    listComments = comments;
                    listNumbers = usernames;
                    listUsernames = numbers;

                }

                @Override
                public int getCount() {
                    if(null == listComments)
                    {
                    return 0;
                    }   

                    // TODO Auto-generated method stub
                    return listComments.length;
                }

                @Override
                public Object getItem(int position) {
                    // TODO Auto-generated method stub
                    return listComments[position];
                }

                @Override
                public long getItemId(int position) {
                    // TODO Auto-generated method stub
                    return 0;
                }

                @Override
                public View getView(final int position, View convertView, ViewGroup parent) {
                    // TODO Auto-generated method stub
                    View v = null;
                    try
                    {
                        String inflater = Context.LAYOUT_INFLATER_SERVICE;
                        LayoutInflater li = (LayoutInflater)ctx_invitation.getSystemService(inflater);
                        v = li.inflate(R.layout.list_item, null);


                        TextView commentView = (TextView)v.findViewById(R.id.listComment);
                        TextView NumbersView = (TextView)v.findViewById(R.id.listNumber);
                        TextView usernamesView = (TextView)v.findViewById(R.id.listPostedBy);
                        Button usernameButton = (Button)v.findViewById(R.id.listUsernameButton);
                       Button numberButton = (Button)v.findViewById(R.id.listNumberButton);

                        commentView.setText(listComments[position]);
                        NumbersView.setText(listNumbers[position]);
                        usernamesView.setText(listUsernames[position]);




                       usernameButton.setOnClickListener(new View.OnClickListener() {

                           public void onClick(View view) {
                               Intent i = new Intent(getApplicationContext(), ProfileActivity.class);
                               i.putExtra("usernameOfProfile",listUsernames[position]);
                               startActivity(i);
                               finish();
                           }
                       });

                       numberButton.setOnClickListener(new View.OnClickListener() {

                           public void onClick(View arg0) {
                               Intent i = new Intent(getApplicationContext(), ProfileActivity.class);
                               i.putExtra("NumberProfile",listNumbers[position]);
                               startActivity(i);
                               finish();
                           }
                       });





                    }
                    catch(Exception e)
                    {
                        e.printStackTrace();
                    }
                    return v;
                }

            public void add(String[] comments, String[] usernames,
                    String[] numbers) {
                listComments = comments;
                listNumbers = usernames;
                listUsernames = numbers;
            }

            public int getCount1() {
                if(null == listComments)
                {
                return 0;
                }   

                // TODO Auto-generated method stub
                return listComments.length;
            }

            public Object getItem1(int position) {
                // TODO Auto-generated method stub
                return listComments[position];
            }

            public long getItemId1(int position) {
                // TODO Auto-generated method stub
                return 0;
            }

            public View getView1(final int position, View convertView, ViewGroup parent) {
                // TODO Auto-generated method stub
                View v = null;
                try
                {
                    String inflater = Context.LAYOUT_INFLATER_SERVICE;
                    LayoutInflater li = (LayoutInflater)ctx_invitation.getSystemService(inflater);
                    v = li.inflate(R.layout.list_item, null);


                    TextView commentView = (TextView)v.findViewById(R.id.listComment);
                    TextView NumbersView = (TextView)v.findViewById(R.id.listNumber);
                    TextView usernamesView = (TextView)v.findViewById(R.id.listPostedBy);
                    Button usernameButton = (Button)v.findViewById(R.id.listUsernameButton);
                   Button numberButton = (Button)v.findViewById(R.id.listNumberButton);

                    commentView.setText(listComments[position]);
                    NumbersView.setText(listNumbers[position]);
                    usernamesView.setText(listUsernames[position]);




                   usernameButton.setOnClickListener(new View.OnClickListener() {

                       public void onClick(View view) {
                           Intent i = new Intent(getApplicationContext(), ProfileActivity.class);
                           i.putExtra("usernameOfProfile",listUsernames[position]);
                           startActivity(i);
                           finish();
                       }
                   });

                   numberButton.setOnClickListener(new View.OnClickListener() {

                       public void onClick(View arg0) {
                           Intent i = new Intent(getApplicationContext(), ProfileActivity.class);
                           i.putExtra("NumberProfile",listNumbers[position]);
                           startActivity(i);
                           finish();
                       }
                   });





                }
                catch(Exception e)
                {
                    e.printStackTrace();
                }
                return v;






              } 




            final CreateCommentLists mycmlist = new CreateCommentLists(comments, usernames, numbers, DashboardActivity.this);

            lstComments = (ListView)findViewById(android.R.id.list);

            lstComments.setAdapter(mycmlist);

final ProgressDialog progDailog = new ProgressDialog(DashboardActivity.this);
            class loadComments extends AsyncTask<JSONObject, String, JSONObject> {



                @Override
                protected void onPreExecute() {
                    super.onPreExecute();


                    progDailog.setIndeterminate(false);
                    progDailog.setCancelable(true);
                    progDailog.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
                    progDailog.show();
                    progDailog.setContentView(R.layout.progress_circle);


                } 

                @Override
                protected void onProgressUpdate(String... values) {
                    super.onProgressUpdate(values);

                } 

                protected JSONObject doInBackground(JSONObject... params) {


                    JSONObject json2 = CollectComments.collectComments(usernameforcomments, offsetNumber);


                        return json2;



                }

                @Override
                protected void onPostExecute(JSONObject json2) {
                    try {  
                        if (json2.getString(KEY_SUCCESS) != null) { 
                            registerErrorMsg.setText("");
                            String res2 = json2.getString(KEY_SUCCESS);
                            if(Integer.parseInt(res2) == 1){ 



                                JSONArray commentArray = json2.getJSONArray(KEY_COMMENT);
                                String comments[] = new String[commentArray.length()];
                                for ( int i=0; i<commentArray.length(); i++ ) {
                                    comments[i] = commentArray.getString(i);
                                }
                                JSONArray numberArray = json2.getJSONArray(KEY_NUMBER);
                                String numbers[] = new String[numberArray.length()];
                                for ( int i=0; i<numberArray.length(); i++ ) {
                                    numbers[i] = numberArray.getString(i);
                                }
                                JSONArray usernameArray = json2.getJSONArray(KEY_USERNAME);
                                String usernames[] = new String[usernameArray.length()];
                                for ( int i=0; i<usernameArray.length(); i++ ) {
                                    usernames[i] = usernameArray.getString(i);
                                }



                                mycmlist.add(comments,usernames,numbers);
                                mycmlist.notifyDataSetChanged();








                                }//end if key is == 1
                            else{
                                // Error in registration
                                registerErrorMsg.setText(json2.getString(KEY_ERROR_MSG));
                            }//end else
                        }//end if
                    } //end try

                    catch (JSONException e) { 
                        e.printStackTrace();
                    }//end catch    
                    progDailog.dismiss();

                }


            }



            mainListView = (ListView) findViewById(android.R.id.list);



            class EndlessScrollListener implements OnScrollListener {
                private int i = 0;
                private int visibleThreshold = 5;
                private int previousTotal = 0;
                private boolean loading = true;

                public EndlessScrollListener() {
                }
                public EndlessScrollListener(int visibleThreshold) {
                    this.visibleThreshold = visibleThreshold;
                }

                @Override
                public void onScroll(AbsListView view, int firstVisibleItem,
                        int visibleItemCount, int totalItemCount) {


                       if ((firstVisibleItem + visibleItemCount) == totalItemCount) {
                           new loadComments().execute();
                        mainListView.smoothScrollToPosition(0);

                    }


                }

                @Override
                public void onScrollStateChanged(AbsListView view, int scrollState) {
                } 
            }

            mainListView.setOnScrollListener(new EndlessScrollListener());

Answer 1

你试试这个：

public class Comment {
String username;
String content;
String number;
 }

类适配器：

public class CommentAdapter extends BaseAdapter {
private List<Comment> listComment;
private Context context;

public CommentAdapter(List<Comment> listComment, Context context) {
    super();
    this.listComment = listComment;
    this.context = context;
}

@Override
public int getCount() {

    return listComment.size();
}

@Override
public Comment getItem(int position) {
    return listComment.get(position);
}

@Override
public long getItemId(int arg0) {
    return 0;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View v = convertView;
    if (v == null) {
        LayoutInflater mInflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        v = mInflater.inflate(R.layout.comment_item, null);
    }

    final TextView textViewUsername = (TextView) v
            .findViewById(R.id.comment_Username);
    final TextView textViewNumber = (TextView) v
            .findViewById(R.id.comment_number);
    final TextView textViewContent = (TextView) v
            .findViewById(R.id.comment_Content);

    final String username = listComment.get(position).getUsername();
    final String number= listComment.get(position).getNumber();
    String content = listComment.get(position).getContent();

    textViewUsername.setText(username);
    textViewNumber.setText(number);

    textViewContent.setText(content);
    return v;
}

}

当您需要向列表添加新评论时。只需创建新评论并添加到 listComment(listComment.add(newComment))，然后调用 adapter.notifyDataSetChanged();

Answer 2

package com.example.baseadapter;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

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

public class MainActivity extends Activity implements OnItemClickListener {
    public static final String[] title = new String[] {
            "image 1", "image 2", "image 3", "image 4"
    };

    public static final Integer[] images = {
            R.drawable.aa, R.drawable.bb, R.drawable.cc, R.drawable.cc, R.drawable.dd
    };

    ListView listview;

    List<RowItem> rowItems;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rowItems = new ArrayList<RowItem>();
        for (int i = 0; i < title.length; i++) {
            RowItem item = new RowItem(images[i], title[i]);
            rowItems.add(item);
        }
        listview = (ListView)findViewById(R.id.listview);
        customBaseAdapter cba = new customBaseAdapter(this, rowItems);
        listview.setAdapter(cba);
        listview.setOnItemClickListener(this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
        Toast.makeText(getApplicationContext(), "item selected", Toast.LENGTH_LONG).show();
    }

    public class customBaseAdapter extends BaseAdapter {
        Context context;

        List<RowItem> rowItem;

        public customBaseAdapter(Context context, List<RowItem> listItem) {
            this.context = context;
            rowItem = listItem;
            Log.d("const", "const");
        }

        @Override
        public int getCount() {
            Log.d("count", "count");
            return rowItem.size();
        }

        @Override
        public Object getItem(int arg0) {
            Log.d("item", "item");
            return rowItem.get(arg0);
        }

        @Override
        public long getItemId(int position) {
            Log.d("const", "item id");
            return rowItem.indexOf(getItem(position));
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            Log.d("const", "getview");
            LayoutInflater inflater = (LayoutInflater)context
                    .getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
            RowItem rowitem = (RowItem)getItem(position);
            TextView textForTitle;
            ImageView imgForImage;
            convertView = inflater.inflate(R.layout.inflate, null);
            textForTitle = (TextView)convertView.findViewById(R.id.textview);
            imgForImage = (ImageView)convertView.findViewById(R.id.imageview);
            textForTitle.setText(rowitem.getTitle());
            imgForImage.setImageResource(rowitem.getImageId());

            return convertView;
        }
    }

    public class RowItem {
        int imageId;

        String title;

        public RowItem(int imageId, String title) {
            this.imageId = imageId;
            this.title = title;
        }

        public int getImageId() {
            return imageId;
        }

        public void setImageId(int imageId) {
            this.imageId = imageId;
        }

        public String getTitle() {
            return title;
        }

        public void setStringTitle(String title) {
            this.title = title;
        }

        @Override
        public String toString() {
            return title;
        }
    }

}