ajouter le bouton à listview dans android

Question

Salut dans mon application Je suis analyser l'URL json pour afficher l'image et le texte que cela fonctionne très bien.
Après que j'ajoute un bouton nommé comme ajouter à Listview il affichage dans tous les endroits correctement. Mais après le si je clique sur le bouton Ajouter je veux passer à une autre activité. Après avoir cliqué sur le bouton Ajouter, il affiche malheureusement une erreur.

Quelqu'un peut-il s'il vous plaît me dire ce que j'ai fait erreur dans mon code?

classe ListViewAdapter

public class ListViewAdapter extends BaseAdapter { 

    // Declare Variables 
    Context context; 
    LayoutInflater inflater; 
    ArrayList<HashMap<String, String>> data; 
    ImageLoader imageLoader; 
    HashMap<String, String> resultp = new HashMap<String, String>(); 

    public ListViewAdapter(Context context, ArrayList<HashMap<String, String>> arraylist) { 
     this.context = context; 
     data = arraylist; 
     imageLoader = new ImageLoader(context); 
    } 

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

    @Override 
    public Object getItem(int position) { 
     return null; 
    } 

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

    public View getView(final int position, View convertView, ViewGroup parent) { 
     // Declare Variables 
     TextView title; 

     ImageView thumb_url; 
     inflater = (LayoutInflater) context 
       .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

     View itemView = inflater.inflate(R.layout.listview_item, parent, false); 
     // Get the position 
     resultp = data.get(position); 

     // Locate the TextViews in listview_item.xml 
     title = (TextView) itemView.findViewById(R.id.rank); 

     // Locate the ImageView in listview_item.xml 
     thumb_url = (ImageView) itemView.findViewById(R.id.flag); 

     // Capture position and set results to the TextViews 
     title.setText(resultp.get(MainActivity.TITLE)); 

     // Capture position and set results to the ImageView 
     // Passes flag images URL into ImageLoader.class 
     imageLoader.DisplayImage(resultp.get(MainActivity.THUMB_URL), thumb_url); 
     // Capture ListView item click 
     Button Add = (Button) itemView.findViewById(R.id.add); 

     Add.setOnClickListener(new OnClickListener() { 

      @Override 
      public void onClick(View arg0) { 
       // Get the position 
       resultp = data.get(position); 
       Intent intent = new Intent(context, SingleItemView.class); 
       // Pass all data rank 
       intent.putExtra("title", resultp.get(MainActivity.TITLE)); 
       // Pass all data country 
        /*intent.putExtra("country", resultp.get(MainActivity.COUNTRY)); 
        // Pass all data population 
        intent.putExtra("population",resultp.get(MainActivity.POPULATION)); 
        */// Pass all data flag 
       intent.putExtra("thumb_url", resultp.get(MainActivity.THUMB_URL)); 
       // Start SingleItemView Class 
       context.startActivity(intent); 
      } 


      public void onClick(DialogInterface dialog, int which) { 
       // TODO Auto-generated method stub 
      } 
     }); 
     return itemView; 
    } 

    public void onClick(DialogInterface dialog, int which) { 
     // TODO Auto-generated method stub 
    } 
} 

classe SingleItemView

public class SingleItemView extends Activity { 
    // Declare Variables 
    String title; 
    /*String country; 
    String population; 
    */ 
    String thumb_url; 

    ImageLoader imageLoader = new ImageLoader(this); 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     // Get the view from singleitemview.xml 
     setContentView(R.layout.singleitemview); 

     Intent i = getIntent(); 
     // Get the result of rank 
     title = i.getStringExtra("title"); 
     // Get the result of country 
       /*country = i.getStringExtra("country"); 
       // Get the result of population 
       population = i.getStringExtra("population");*/ 
     // Get the result of flag 
     thumb_url = i.getStringExtra("thumb_url"); 

     // Locate the TextViews in singleitemview.xml 
     TextView txtrank = (TextView) findViewById(R.id.rank); 
       /*TextView txtcountry = (TextView) findViewById(R.id.country); 
       TextView txtpopulation = (TextView) findViewById(R.id.population); 
    */ 
     // Locate the ImageView in singleitemview.xml 
     ImageView imgflag = (ImageView) findViewById(R.id.flag); 

     // Set results to the TextViews 
     txtrank.setText(title); 
       /*txtcountry.setText(country); 
       txtpopulation.setText(population); 
    */ 
     // Capture position and set results to the ImageView 
     // Passes flag images URL into ImageLoader.class 
     imageLoader.DisplayImage(thumb_url, imgflag); 
    } 
} 

classe MainActivity

public class MainActivity extends Activity { 
    // Declare Variables 
    JSONObject jsonobject; 
    JSONArray jsonarray; 
    ListView listview; 
    ListViewAdapter adapter; 
    ProgressDialog mProgressDialog; 
    ArrayList<HashMap<String, String>> arraylist; 
    static String TITLE = "title"; 
    /*static String COUNTRY = "country"; 
    static String POPULATION = "population";*/ 
    static String THUMB_URL = "thumb_url"; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     // Get the view from listview_main.xml 
     setContentView(R.layout.listview_main); 
     // Execute DownloadJSON AsyncTask 
     new DownloadJSON().execute(); 
    } 

    // DownloadJSON AsyncTask 
    private class DownloadJSON extends AsyncTask<Void, Void, Void> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      // Create a progressdialog 
      mProgressDialog = new ProgressDialog(MainActivity.this); 
      // Set progressdialog title 
      mProgressDialog.setTitle("Loading..."); 
      // Set progressdialog message 
      mProgressDialog.setMessage("Loading..."); 
      mProgressDialog.setIndeterminate(false); 
      // Show progressdialog 
      mProgressDialog.show(); 
     } 

     @Override 
     protected Void doInBackground(Void... params) { 
      // Create an array 
      arraylist = new ArrayList<HashMap<String, String>>(); 
      // Retrieve JSON Objects from the given URL address 
      jsonobject = JSONfunction 
        .getJSONfromURL("http://indianpoliticalleadersmap.com/android/DemoSchool/json/json_item.php"); 

      try { 
       // Locate the array name in JSON 
       jsonarray = jsonobject.getJSONArray("veg_food"); 

       for (int i = 0; i < jsonarray.length(); i++) { 
        HashMap<String, String> map = new HashMap<String, String>(); 
        jsonobject = jsonarray.getJSONObject(i); 
        // Retrive JSON Objects 
        map.put("title", jsonobject.getString("title")); 
          /*map.put("country", jsonobject.getString("country")); 
          map.put("population", jsonobject.getString("population"));*/ 
        map.put("thumb_url", jsonobject.getString("thumb_url")); 
        // Set the JSON Objects into the array 
        arraylist.add(map); 
       } 
      } catch (JSONException e) { 
       Log.e("Error", e.getMessage()); 
       e.printStackTrace(); 
      } 
      return null; 
     } 

     @Override 
     protected void onPostExecute(Void args) { 
      // Locate the listview in listview_main.xml 
      listview = (ListView) findViewById(R.id.listview); 
      // Pass the results into ListViewAdapter.java 
      adapter = new ListViewAdapter(MainActivity.this, arraylist); 
      // Set the adapter to the ListView 
      listview.setAdapter(adapter); 
      // Close the progressdialog 
      mProgressDialog.dismiss(); 
     } 
    } 
} 

singleitemview.xml

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" > 

    <ImageView 
     android:id="@+id/flag" 
     android:layout_width="80dp" 
     android:layout_height="80dp" 
     android:layout_centerVertical="true" 
     android:layout_margin="5dp" 
     android:background="#444" 
     android:padding="3dp" /> 
    <TextView 
     android:id="@+id/rank" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:layout_marginTop="5dip" 

     android:layout_toRightOf="@+id/flag" 
     android:maxLines="1" 
     android:textSize="15dip" 
     android:textStyle="bold" /> 


    <!-- <TextView 
     android:id="@+id/ranklabel" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     /> 

    <TextView 
     android:id="@+id/rank" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     /> 
--> 

    <!-- <ImageView 
     android:id="@+id/flag" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentRight="true" 
     android:background="#000000" 
     android:layout_toRightOf="@+id/flag" 
     android:padding="1dp" /> 
--> 

    <Button 
     android:id="@+id/add" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:layout_alignParentRight="true" 
     android:layout_below="@+id/rank" 
     android:text="Add" /> 

</RelativeLayout> 

listview_item.xml

<?xml version="1.0" encoding="utf-8"?> 
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
     android:layout_width="fill_parent" 
     android:layout_height="fill_parent" > 

     <ImageView 
      android:id="@+id/flag" 
      android:layout_width="80dp" 
      android:layout_height="80dp" 
      android:layout_centerVertical="true" 
      android:layout_margin="5dp" 
      android:background="#444" 
      android:padding="3dp" /> 
     <TextView 
      android:id="@+id/rank" 
      android:layout_width="fill_parent" 
      android:layout_height="wrap_content" 
      android:layout_marginTop="5dip" 

      android:layout_toRightOf="@+id/flag" 
      android:maxLines="1" 
      android:textSize="15dip" 
      android:textStyle="bold" /> 


     <!-- <TextView 
      android:id="@+id/ranklabel" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      /> 

     <TextView 
      android:id="@+id/rank" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      /> 
    --> 

     <!-- <ImageView 
      android:id="@+id/flag" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_alignParentRight="true" 
      android:background="#000000" 
      android:layout_toRightOf="@+id/flag" 
      android:padding="1dp" /> 
    --> 

     <Button 
      android:id="@+id/add" 
      android:layout_width="wrap_content" 
      android:layout_height="wrap_content" 
      android:layout_alignParentRight="true" 
      android:layout_below="@+id/add" 
      android:text="Add" /> 

    </RelativeLayout> 

logcat

06-17 18:22:10.146: E/AndroidRuntime(498): FATAL EXCEPTION: main 
06-17 18:22:10.146: E/AndroidRuntime(498): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.androidhive/com.example.androidhive.SingleItemView}: java.lang.NullPointerException 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.ActivityThread.access$2300(ActivityThread.java:125) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.os.Handler.dispatchMessage(Handler.java:99) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.os.Looper.loop(Looper.java:123) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.ActivityThread.main(ActivityThread.java:4627) 
06-17 18:22:10.146: E/AndroidRuntime(498): at java.lang.reflect.Method.invokeNative(Native Method) 
06-17 18:22:10.146: E/AndroidRuntime(498): at java.lang.reflect.Method.invoke(Method.java:521) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
06-17 18:22:10.146: E/AndroidRuntime(498): at dalvik.system.NativeStart.main(Native Method) 
06-17 18:22:10.146: E/AndroidRuntime(498): Caused by: java.lang.NullPointerException 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.content.ContextWrapper.getCacheDir(ContextWrapper.java:188) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.example.androidhive.FileCache.<init>(FileCache.java:15) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.example.androidhive.ImageLoader.<init>(ImageLoader.java:32) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.example.androidhive.SingleItemView.<init>(SingleItemView.java:19) 
06-17 18:22:10.146: E/AndroidRuntime(498): at java.lang.Class.newInstanceImpl(Native Method) 
06-17 18:22:10.146: E/AndroidRuntime(498): at java.lang.Class.newInstance(Class.java:1429) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577) 
06-17 18:22:10.146: E/AndroidRuntime(498): ... 11 more 

Dans mon code ci-dessus si je clique sur le bouton Ajouter ne fonctionne pas tout le monde peut s'il vous plaît, résolvez-le et aidez-moi. Merci d'avance.

Answer 1

Hai le problème est dans la ligne

itemView.setOnClickListener(new OnClickListener() { 

est en fait la vue d'ensemble, vous ne devriez pas setOnClickListener à ce sujet, au lieu de mettre un bouton dans la classe viewholder et écrire onClickListener pour ce bouton, il fonctionnera bien .

CustomAdapter public class étend BaseAdapter {

 Context context; 


     public CustomAdapter(Context context) { 
      this.context = context; 

      // this.rowItems = rowItems; 
     } 

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

     @Override 
     public Object getItem(int position) { 
      // return _data.get(position); 
      return null; 
     } 

     @Override 
     public long getItemId(int position) { 
      // return _data.indexOf(getItem(position)); 
      return position; 
     } 

     /* private view holder class */ 
     private class ViewHolder { 

      Button rl; 
     } 

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

      ViewHolder holder = null; 

      LayoutInflater mInflater = (LayoutInflater) context 
        .getSystemService(Activity.LAYOUT_INFLATER_SERVICE); 
      if (convertView == null) { 
       convertView = mInflater.inflate(R.layout.image_holder, null); 
       holder = new ViewHolder(); 
       holder.rl = (Button) convertView.findViewById(R.id.rl); 



       convertView.setTag(holder); 
      } else { 
       holder = (ViewHolder) convertView.getTag(); 
       convertView.setTag(holder); 
      } 
     try { 
    holder.rl.setOnClickListener(new OnClickListener() { 

        @Override 
        public void onClick(View v) { 
         try {       a 

          //call ur intent here 

         } catch (Exception e) { 
          // TODO Auto-generated catch block 
          e.printStackTrace(); 
        } 
        } 
       }); 
      } catch (Exception e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 

      return convertView; 
     } 
    } 

un exemple de projet u peut jeter un oeil sur le projet ici custom_list et si vous êtes à la recherche d'un chargement d'image fraîche dans l'exemple listview u peut se référer ici Universal image loader

Answer 2

06-17 18:22:10.146: E/AndroidRuntime(498): Caused by: java.lang.NullPointerException 
06-17 18:22:10.146: E/AndroidRuntime(498): at android.content.ContextWrapper.getCacheDir(ContextWrapper.java:188) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.example.androidhive.FileCache.<init>(FileCache.java:15) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.example.androidhive.ImageLoader.<init>(ImageLoader.java:32) 
06-17 18:22:10.146: E/AndroidRuntime(498): at com.example.androidhive.SingleItemView.<init>(SingleItemView.java:19) 

Vous essayez d'utiliser votre activité en tant que contexte avant onCreate() lors de l'initialisation de la variable membre ImageLoader.

Déplacez l'initialisation sur onCreate() ou plus tard dans le cycle de vie de l'activité.