如何通过单击按钮从android eclipse中的listview中删除列表项

Question

单击 android eclipse 中的删除按钮时，我需要从 listview 中删除一个列表项。列表值是从 mysql 数据库（JSON）中填充的，所以在删除时，我也需要从数据库中删除相同的值。

这是我的主要活动；单击列表视图中每个项目上的删除按钮时，我需要从列表视图中删除一个列表项：

    public class MainActivity extends Activity implements AsyncResponse2 {
        private ProgressDialog dialog;
        ListView l1;
         //for getting count
        TextView count;
        private static final String TAG_COUNT = "cnt";
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState); 
     requestWindowFeature(Window.FEATURE_NO_TITLE);    //to hide title bar   
            setContentView(R.layout.activity_main);  
            l1=(ListView)findViewById(R.id.listView1);
            /** Reference to the delete button of the layout main.xml */
            Button btnDel = (Button) findViewById(R.id.deleteid);
            initView();
            //str for getting count
            count=(TextView)findViewById(R.id.countid);
          //to display count while loading(so outside buttonclick)
             String key1 = "saasvaap123";
           String signupid1 = "8";
             String url2 = "http://gooffers.in/omowebservices/index.php/webservice/Public_User/saved_offers_list?";
             //http://gooffers.in/omowebservices/index.php/webservice/Public_User/saved_offers_list?key=saasvaap123&signup_id=8
             //put the below lines outside button onclick since we load the values into edittext when opening the app
           CustomHttpClient2 task2 = new CustomHttpClient2();
           task2.execute(url2,key1,signupid1);
           task2.delegate = MainActivity.this;
           //end
        }
     //str getting count
      //str customhttp2
           private class CustomHttpClient2 extends AsyncTask<String, String, String>{




        public AsyncResponse2 delegate=null;
        private String msg;




    @Override
    protected void onPostExecute(String result2) {
       // TODO Auto-generated method stub
       super.onPostExecute(result2);

       delegate.processFinish2(result2);

    }

    @Override
    protected void onPreExecute() {

       // TODO Auto-generated method stub
       super.onPreExecute();

    }



           @Override
           protected String doInBackground(String... params) {
               if(params == null) return null;

               // get url from params
               String url2 = params[0];
               String key1 = params[1];
               String signupid1 = params[2];

               ArrayList<NameValuePair> postParameters;


               postParameters = new ArrayList<NameValuePair>();

               postParameters.add(new BasicNameValuePair("key",key1));
               postParameters.add(new BasicNameValuePair("signup_id",signupid1));




               try {
                   // create http connection
                   HttpClient client = new DefaultHttpClient();
                   HttpPost httppost = new HttpPost(url2);
                   httppost.setEntity(new UrlEncodedFormEntity(postParameters));

                   // connect
                   HttpResponse response = client.execute(httppost);

                   // get response
                   HttpEntity entity = response.getEntity();

                   if(entity != null){
                       return EntityUtils.toString(entity);
                   }
                   else{
                       return "No string.";
                   }
                }
                catch(Exception e){
                    return "Network problem";
                }
           }




       }



           public void processFinish2 (String output2){

           Toast.makeText(MainActivity.this,output2, Toast.LENGTH_SHORT).show();




               try{   
                   //str
                  JSONObject jsonResponse = new JSONObject(output2);

                    JSONArray aJson = jsonResponse.getJSONArray("gen_off");

                    // create apps list


                    for(int i=0; i<aJson.length(); i++) {
                        JSONObject json = aJson.getJSONObject(i);
                   //end




                      //str

                        String strCount = json.getString(TAG_COUNT);

                        count.setText(strCount);//setting name to original name text
                      //end
                    }





                }catch (JSONException e) {
                    Toast.makeText(MainActivity.this,"Exception caught!", Toast.LENGTH_SHORT).show();
                }       

                  }

        //end getting count
        private void initView() {
            // show progress dialog
         //   dialog = ProgressDialog.show(this, "", "Loading...");
            String key="saasvaap123";
            String signup_id="8";
            String url = "http://gooffers.in/omowebservices/index.php/webservice/Public_User/saved_offers_list?";
            FetchDataTask task = new FetchDataTask();
            task.execute(url,key,signup_id);
        }



        public class FetchDataTask extends AsyncTask<String, Void, String>{
           // private final FetchDataListener listener;
            private String msg;



            @Override
            protected String doInBackground(String... params) {
                if(params == null) return null;

                // get url from params
                String url = params[0];
                String key1 = params[1];
                String signupid1 = params[2]; 
                ArrayList<NameValuePair> postParameters;


                postParameters = new ArrayList<NameValuePair>();

                postParameters.add(new BasicNameValuePair("key",key1));
                postParameters.add(new BasicNameValuePair("signup_id",signupid1));


                 //str
                try {
                    // create http connection
                    HttpClient client = new DefaultHttpClient();
                    HttpPost httppost = new HttpPost(url);
                    httppost.setEntity(new UrlEncodedFormEntity(postParameters));

                    // connect
                    HttpResponse response = client.execute(httppost);

                    // get response
                    HttpEntity entity = response.getEntity();

                    if(entity != null){
                        return EntityUtils.toString(entity);
                    }
                    else{
                        return "No string.";
                    }
                 }
                 catch(Exception e){
                     return "Network problem";
                 }
            }
                //end


    //         
            @Override
            protected void onPostExecute(String sJson) {




                try {

                    JSONObject jsonResponse = new JSONObject(sJson);

                    JSONArray aJson = jsonResponse.getJSONArray("gen_off");
                   Toast.makeText(MainActivity.this, aJson.toString(),Toast.LENGTH_SHORT).show();

                    // create apps list
                    List<SavedOffers> apps = new ArrayList<SavedOffers>();

                    for(int i=0; i<aJson.length(); i++) {
                        JSONObject json = aJson.getJSONObject(i);
                        SavedOffers app = new SavedOffers();
                        app.setTitle(json.getString("title"));
                        app.setOriginalRate(json.getString("price"));
                        app.setOfferRate(json.getString("off_price"));  
                        app.setPercentage(json.getString("percent"));  
                        app.setSavings(json.getString("savings"));  
                        app.setUrl(json.getString("image")); 

                        // add the app to apps list
                        apps.add(app);


                    }

                    SavedOffersAdapter adapter = new SavedOffersAdapter(MainActivity.this, apps);
    //               set the adapter to list
                 l1.setAdapter(adapter);   
                  //for delete
      //   adapter.notifyDataSetChanged();
         /** Defining a click event listener for the button "Delete" */
         Button btnDel = (Button) findViewById(R.id.deleteid);

         OnClickListener listenerDel = new OnClickListener() {

             @Override
             public void onClick(View v) {
                 /** Getting the checked items from the listview */
                 SparseBooleanArray checkedItemPositions = l1.getCheckedItemPositions();
                 int itemCount = l1.getCount();

                 for(int i=itemCount-1; i >= 0; i--){
                     if(checkedItemPositions.get(i)){
                         adapter.remove(l1.get(i));
                     }
                 }
                 checkedItemPositions.clear();
                 adapter.notifyDataSetChanged();
             }
         };
         /** Setting the event listener for the delete button */
         btnDel.setOnClickListener(listenerDel);

         /** Setting the adapter to the ListView */
         l1.setAdapter(adapter);              //end delete
                    //notify the activity that fetch data has been complete
                  //  if(listener != null) listener.onFetchComplete(apps);
                } catch (JSONException e) {
    //                msg = "Invalid response";
    //                if(listener != null) listener.onFetchFailure(msg);
    //                return;


                }        
            }

            /**
             * This function will convert response stream into json string
             * @param is respons string
             * @return json string
             * @throws IOException
             */
            public String streamToString(final InputStream is) throws IOException{
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                StringBuilder sb = new StringBuilder(); 
                String line = null;

                try {
                    while ((line = reader.readLine()) != null) {
                        sb.append(line + "\n");
                    }
                } 
                catch (IOException e) {
                    throw e;
                } 
                finally {           
                    try {
                        is.close();
                    } 
                    catch (IOException e) {
                        throw e;
                    }
                }

                return sb.toString();
            }
        }
    }

// this is my adapter class ,  I think change is only needed in main activity
// , I need to delete a specific list item from listview on clicking the delete button
public class SavedOffersAdapter extends ArrayAdapter<SavedOffers>{
    private List<SavedOffers> items;
    Bitmap bitmap;
    ImageView image;
    public SavedOffersAdapter(Context context, List<SavedOffers> items) {
        super(context, R.layout.app_custom_list, items);
        this.items = items;
    }

    @Override
    public int getCount() {
        return items.size();
    }
    private class ViewHolder {
        //TextView laptopTxt;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
    //   ViewHolder holder;//added
        View v = convertView;

        if(v == null) {
            LayoutInflater li = LayoutInflater.from(getContext());
            v = li.inflate(R.layout.app_custom_list, null);           
        }

        SavedOffers app = items.get(position);

        if(app != null) {

            TextView productName = (TextView)v.findViewById(R.id.nameid);
            TextView originalRate = (TextView)v.findViewById(R.id.originalid);
            originalRate.setPaintFlags(originalRate.getPaintFlags() | Paint.STRIKE_THRU_TEXT_FLAG);
            TextView offerRate = (TextView)v.findViewById(R.id.offerid);
            TextView percentage = (TextView)v.findViewById(R.id.discountid);
            TextView savings = (TextView)v.findViewById(R.id.savingsid);
            image =(ImageView)v.findViewById(R.id.prctimgid);

            if(productName != null) productName.setText(app.getTitle());
            if(originalRate != null) originalRate.setText(app.getOriginalRate()); 
            if(offerRate != null) offerRate.setText(app. getOfferRate());
            if(percentage != null) percentage.setText(app. getPercentage());
            if(savings != null) savings.setText(app. getSavings());

            if(image!=null){

                new DownloadImageTask(image).execute(app.getUrl());

        }




        }

        return v;
    }

Answer 1

在您的 listviews 适配器的 getView 方法中，您链接到布局上的按钮，然后将 setOnClickListener... 附加到按钮并让它从您的适配器使用的列表或数组中删除该项目，然后 notifyDataHasChanged。

从该位置的项目中删除该项目。

所以 1. 你想从ListView 中删除该项目 2. 您想从 SQL DB 中删除该项目。

第一个非常简单，但您需要了解下划线适配器以及它如何为您的ListView 提供数据。当您为ListView 实例化BaseAdapter 时，您传入List 或数组。该数组将是您的BaseAdapter 提供给您的ListView 的数据，列表视图中的每个视图都将显示数组中的一个元素（在getView() 中完成）。如果您动态删除其中一项，则调整您的数组（或仅使用List 并且它是.remove()，最后notifyDataSetChanged(); 您的BaseAdapter 将在没有该视图的情况下刷新您的列表（或者更确切地说，该视图将是替换为新的）。例如，下面我将List<WeatherLocation>（WeatherLocation 是一个包含特定区域（城市、邮政编码、学位“Biddeford”、04005、72）的天气信息的包含类）传递给我的@987654334 @。

// Instantiate ListView
ListView lvLocations = (ListView) findViewById(R.id.lvLocations);
// Instantiate our BaseAdapter (pass in the List<WeatherLocation>)
WeatherLocationAdapter mWeatherLocationAdapter = new WeatherLocationAdapter(savedList, this, R.layout.view_weather_location);
lvLocations.setAdapter(mWeatherLocationAdapter);

这是一个常规 ListView 将 Adapter 设置为自定义 BaseAdapter 的示例。

BaseAdapter 非常简单，您真正关心的（主要）唯一方法就是getView() 方法。

R.layout.view_weather_location is just a `LinearLayout` I made, it has 3 TextViews in it that I tie (show) my data with, by attaching data to those TextViews in the `getView()` method of the `BaseAdapter`. You would put a `Button there and tie it to what you want (to delete the data item)`.

public class WeatherLocationAdapter extends BaseAdapter{
private List <WeatherLocation> mLocations;
private Context mContext;
private int rowForLocationToInflate;
private LayoutInflater inflater;

public WeatherLocationAdapter(List<WeatherLocation> mLocations, Context mContext, int rowForLocationToInflate) {
    this.mLocations = mLocations;
    this.mContext = mContext;
    this.rowForLocationToInflate = rowForLocationToInflate;
    inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

}
//TODO just built up layout now must tie to it.


private void addLocation(WeatherLocation newLocation){
    mLocations.add(newLocation);
    //TODO maybe invalidate after adding new item.

}

@Override
public int getCount() {
    return mLocations.size();
}

@Override
public WeatherLocation getItem(int position) {
    return mLocations.get(position);
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    //TODO build a viewholder

    View rowView = inflater.inflate(rowForLocationToInflate, parent, false);

    TextView tvZipcode = (TextView) rowView.findViewById(R.id.tvZipCode);
    TextView tvCity = (TextView) rowView.findViewById(R.id.tvCity);
    TextView tvTemp = (TextView) rowView.findViewById(R.id.tvDegree);

    tvZipcode.setText(mLocations.get(position).getZipcode());
    tvCity.setText(mLocations.get(position).getCity());
    tvTemp.setText(String.valueOf(mLocations.get(position).getTemperature()));


// If you had a Button in your LinearLayout you were attaching to you that you wanted to delete that view/item with, it would look something like this in my case.
Button bDel = (Button) row.findViewById(R.id.bDel);

    bDel.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mLocations.remove(position);
            }
        });

        return rowView;
    }
}

在onClick 中，您还可以从 SQL 数据库中删除该项目。我也可以证明这一点，但我觉得你有一些编码要做。