Android - custom ArrayAdapter

Question

Could anybody help me solve my problem. I still trying work with DraggingListView and ArrayAdapter. Now i want realize delete element from listview by click, but when i making :

StableArrayAdapter.this.notifyDataSetChanged();

i get nullPointer Exception ...

here is my adapter:

public class StableArrayAdapter extends ArrayAdapter<Product> {

    final int INVALID_ID = -1;
    LayoutInflater lInflater;
    Context ctx;
    public static final String PREFS_NAME = "com.shvedchenko.skleroshop";
    public static final String PREFS_THEME = "theme";

    HashMap<Product, Integer> mIdMap = new HashMap<Product, Integer>();

    public StableArrayAdapter(Context context, int textViewResourceId, List<Product> prod) {
        super(context, textViewResourceId, /*objects*/prod);
        lInflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        ctx = context;
        for (int i = 0; i < prod.size(); ++i) {
            mIdMap.put(prod.get(i), i);
        }
    }


    // пункт списка
    @Override
    public View getView(final int position, View convertView, final ViewGroup parent) {
        // используем созданные, но не используемые view
        View view = convertView;
        if (view == null) {
            view = lInflater.inflate(R.layout.item, parent, false);
        }

        Product p = getItem(position);

        SharedPreferences pref = ctx.getSharedPreferences(PREFS_NAME, ctx.MODE_PRIVATE);
        int theme = pref.getInt(PREFS_THEME, 0);             // getting Integer

        if(theme == 0)
            ((TextView) view.findViewById(R.id.tvDescr)).setTextColor(Color.WHITE);
        else
            ((TextView) view.findViewById(R.id.tvDescr)).setTextColor(Color.BLACK);

        ((TextView) view.findViewById(R.id.tvDescr)).setText(p.getProductName());
        ((ImageView) view.findViewById(R.id.ivImage)).setImageResource(p.getProductImage());

        ImageView iv = (ImageView)view.findViewById(R.id.ivImage);
        iv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                mIdMap.remove(getItem(position));
                System.out.println("FROM CLICK -- " + mIdMap.size() );
                /*for( Product p : mIdMap.keySet() ) {
                    System.out.println( p.getProductName() );
                }*/
                //StableArrayAdapter.this.notifyDataSetChanged();
            }
        });

        return view;
    }

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


    @Override
    public long getItemId(int position) {
        if (position < 0 || position >= mIdMap.size()) {
            return INVALID_ID;
        }
        Product item = (Product) getItem(position);
        return mIdMap.get(item);
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }

}

here is the error:

08-26 08:50:58.902 2167-2167/com.shvedchenko.skleroshop E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.NullPointerException at com.shvedchenko.skleroshop.StableArrayAdapter.getItemId(StableArrayAdapter.java:104) at android.widget.AdapterView.rememberSyncState(AdapterView.java:1195) at android.widget.AdapterView$AdapterDataSetObserver.onChanged(AdapterView.java:810) at android.widget.AbsListView$AdapterDataSetObserver.onChanged(AbsListView.java:5958) at android.database.DataSetObservable.notifyChanged(DataSetObservable.java:37) at android.widget.BaseAdapter.notifyDataSetChanged(BaseAdapter.java:50) at android.widget.ArrayAdapter.notifyDataSetChanged(ArrayAdapter.java:286) at com.shvedchenko.skleroshop.StableArrayAdapter$1.onClick(StableArrayAdapter.java:85) at android.view.View.performClick(View.java:4204) at android.view.View$PerformClick.run(View.java:17355) at android.os.Handler.handleCallback(Handler.java:725) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method)

/UPDATED/

My adapter now:

public class StableArrayAdapter extends ArrayAdapter<Product> {

    final int INVALID_ID = -1;
    LayoutInflater lInflater;
    Context ctx;
    public static final String PREFS_NAME = "com.shvedchenko.skleroshop";
    public static final String PREFS_THEME = "theme";

    HashMap<Product, Integer> mIdMap = new HashMap<Product, Integer>();
    ArrayList<Product> prods = new ArrayList<Product>();

    public StableArrayAdapter(Context context, int textViewResourceId, List<Product> prod) {
        super(context, textViewResourceId, /*objects*/prod);
        lInflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        ctx = context;
        for (int i = 0; i < prod.size(); ++i) {
            mIdMap.put(prod.get(i), i);
            prods.add(i,prod.get(i));
        }
    }


    // пункт списка
    @Override
    public View getView(final int position, View convertView, final ViewGroup parent) {
        // используем созданные, но не используемые view
        View view = convertView;
        if (view == null) {
            view = lInflater.inflate(R.layout.item, parent, false);
        }

        Product p = getItem(position);

        SharedPreferences pref = ctx.getSharedPreferences(PREFS_NAME, ctx.MODE_PRIVATE);
        int theme = pref.getInt(PREFS_THEME, 0);             // getting Integer

        if(theme == 0)
            ((TextView) view.findViewById(R.id.tvDescr)).setTextColor(Color.WHITE);
        else
            ((TextView) view.findViewById(R.id.tvDescr)).setTextColor(Color.BLACK);

        ((TextView) view.findViewById(R.id.tvDescr)).setText(p.getProductName());
        ((ImageView) view.findViewById(R.id.ivImage)).setImageResource(p.getProductImage());

        ImageView iv = (ImageView)view.findViewById(R.id.ivImage);
        iv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                prods.remove(position);
                StableArrayAdapter.this.notifyData(prods);

            }
        });

        return view;
    }

    public void notifyData(List<Product> prod) {

        //First of all Clear Map
        mIdMap.clear();
        for (int i = 0; i < prod.size(); ++i) {
            mIdMap.put(prod.get(i), i);
        }

        notifyDataSetChanged();
    }


    @Override
    public long getItemId(int position) {
        if (position < 0 || position >= mIdMap.size()) {
            return INVALID_ID;
        }
        Product item = (Product) getItem(position);
        return mIdMap.get(item);
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }

}

/ERROR/

08-26 09:53:19.270 2530-2530/com.shvedchenko.skleroshop E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.NullPointerException at com.shvedchenko.skleroshop.StableArrayAdapter.getItemId(StableArrayAdapter.java:122) at android.widget.AdapterView.rememberSyncState(AdapterView.java:1195) at android.widget.AdapterView$AdapterDataSetObserver.onChanged(AdapterView.java:810) at android.widget.AbsListView$AdapterDataSetObserver.onChanged(AbsListView.java:5958) at android.database.DataSetObservable.notifyChanged(DataSetObservable.java:37) at android.widget.BaseAdapter.notifyDataSetChanged(BaseAdapter.java:50) at android.widget.ArrayAdapter.notifyDataSetChanged(ArrayAdapter.java:286) at com.shvedchenko.skleroshop.StableArrayAdapter.notifyData(StableArrayAdapter.java:112) at com.shvedchenko.skleroshop.StableArrayAdapter$1.onClick(StableArrayAdapter.java:91)

What i am doing wrong?

TNX in advance!

Answer 1

Correct code for adapter:

public class StableArrayAdapter extends ArrayAdapter<Product> {

    final int INVALID_ID = -1;
    LayoutInflater lInflater;
    Context ctx;
    public static final String PREFS_NAME = "com.shvedchenko.skleroshop";
    public static final String PREFS_THEME = "theme";

    HashMap<Product, Integer> mIdMap = new HashMap<Product, Integer>();

    public StableArrayAdapter(Context context, int textViewResourceId, List<Product> prod) {
        super(context, textViewResourceId, /*objects*/prod);
        lInflater = (LayoutInflater) context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        ctx = context;
        for (int i = 0; i < prod.size(); i++) {
            mIdMap.put(prod.get(i), i);
        }
    }


    // пункт списка
    @Override
    public View getView(final int position, View convertView, final ViewGroup parent) {
        // используем созданные, но не используемые view
        View view = convertView;
        if (view == null) {
            view = lInflater.inflate(R.layout.item, parent, false);
        }

        Product p = getItem(position);

        SharedPreferences pref = ctx.getSharedPreferences(PREFS_NAME, ctx.MODE_PRIVATE);
        int theme = pref.getInt(PREFS_THEME, 0);             // getting Integer

        if(theme == 0)
            ((TextView) view.findViewById(R.id.tvDescr)).setTextColor(Color.WHITE);
        else
            ((TextView) view.findViewById(R.id.tvDescr)).setTextColor(Color.BLACK);

        ((TextView) view.findViewById(R.id.tvDescr)).setText(p.getProductName());
        ((ImageView) view.findViewById(R.id.ivImage)).setImageResource(p.getProductImage());

        ImageView iv = (ImageView)view.findViewById(R.id.ivImage);
        iv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                StableArrayAdapter.this.remove(getItem(position));
                StableArrayAdapter.this.notifyDataSetChanged();
            }
        });

        return view;
    }


    @Override
    public long getItemId(int position) {
        if (position < 0 || position >= mIdMap.size()) {
            return INVALID_ID;
        }
        Product item = (Product) getItem(position);
        return mIdMap.get(item);
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }

}

Answer 2

Remove item from list

  list.remove(position);

Then call below method using adapter object.

  stableAdapter.notifyData(list);

Write a method in your Adapter class.

  public void notifyData(List<Product> prod)
  {

      //First of all Clear Map
      mIdMap.clear();
      for (int i = 0; i < prod.size(); ++i) {
          mIdMap.put(prod.get(i), i);
      }   

      notifyDataSetChanged();
  }

Call this method using adpater object