Question

I have a problem saving the list after edit the listview with drag and drop.

I’am using the sourche code from here:Android Drag and Drop List

The code works fine but the new list order is not save when you exit and open the app again:

The first the listview is like this

a 
b 
c 

after drag and drop

c
b
a

but if i quit this app and then start it later , it will still be -> a b c

public class DragNDropListActivity extends ListActivity {

public static String[] mNewPositions; 

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.dragndroplistview);

    ArrayList<String> content = new ArrayList<String>(mListContent.length);
    for (int i=0; i < mListContent.length; i++) {
        content.add(mListContent[i]);
    }

    setListAdapter(new DragNDropAdapter(this, new int[]{R.layout.dragitem}, new int[]{R.id.TextView01}, content));//new DragNDropAdapter(this,content)
    ListView listView = getListView();

    if (listView instanceof DragNDropListView) {
        ((DragNDropListView) listView).setDropListener(mDropListener);
        ((DragNDropListView) listView).setRemoveListener(mRemoveListener);
        ((DragNDropListView) listView).setDragListener(mDragListener);
        ((DragNDropListView) listView).setPositionListener(mPositionListener);
    }
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
    String selection = (String) getListAdapter().getItem(position);
     SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
     SharedPreferences.Editor editor = preferences.edit();
     editor.putString("selection", selection);
     editor.commit();
         Intent i = new Intent(this, DkNewsActivity.class);
         i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
         this.startActivity(i);

}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);
    return true;
}

@Override
   public boolean onOptionsItemSelected(MenuItem item) {
       switch (item.getItemId()) {
           case (R.id.Info):
              Intent intent = new Intent(Intent.ACTION_VIEW);
              intent.setData(Uri.parse("market://search?q=pub:notToSee"));
              startActivity(intent);

                 break;
           case (R.id.Rate):

           SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);
            SharedPreferences.Editor editor = preferences.edit();
            editor.putInt("rateDone", 1);
            editor.commit();

               intent = new Intent(Intent.ACTION_VIEW);
              intent.setData(Uri.parse("market://details?id=notToSee"));
              startActivity(intent);
                 break;
       }
       return true;
   }
@Override
public boolean onPrepareOptionsMenu (Menu menu) {
    SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(this);

    //set menu rate visible
    if (preferences.getInt("rateDone", 0) == 0){
        menu.getItem(1).setVisible(true);
    }
    else {
        menu.getItem(1).setVisible(false);
    }

    return true;
}

private PositionListener mPositionListener=new PositionListener(){
     public void tryToScrollInAndroid_1point5(int position) {
        ListAdapter adapter = getListAdapter();
        if (adapter instanceof DragNDropAdapter) {
            getListView().setSelection(position);  //android 1.5
        }
     }
};
private DropListener mDropListener = 
    new DropListener() {
    public void onDrop(int from, int to) {
        ListAdapter adapter = getListAdapter();
        if (adapter instanceof DragNDropAdapter) {
            ((DragNDropAdapter)adapter).onDrop(from, to);
            getListView().invalidateViews();

            //Saving dragNDropList
            mNewPositions = new String[adapter.getCount()]; //Initialize your new items storage

            for(int i=0; i < adapter.getCount(); i++) {
                //Implement here your logic for save positions
                mNewPositions[i] = adapter.getItem(i).toString();
            }               
        }
    }
};

private RemoveListener mRemoveListener =
    new RemoveListener() {
    public void onRemove(int which) {
        ListAdapter adapter = getListAdapter();
        if (adapter instanceof DragNDropAdapter) {
            ((DragNDropAdapter)adapter).onRemove(which);
            getListView().invalidateViews();
        }
    }
};

private DragListener mDragListener =
    new DragListener() {

    int backgroundColor = 0xe0103010;
    int defaultBackgroundColor;

        public void onDrag(int x, int y, ListView listView) {}

        public void onStartDrag(View itemView) {
            if (itemView != null){itemView.setVisibility(View.INVISIBLE);
            defaultBackgroundColor = itemView.getDrawingCacheBackgroundColor();
            itemView.setBackgroundColor(backgroundColor);
            ImageView iv = (ImageView)itemView.findViewById(R.id.ImageView01);
            if (iv != null) iv.setVisibility(View.INVISIBLE);
            }
        }

        public void onStopDrag(View itemView) {
            if (itemView != null){itemView.setVisibility(View.VISIBLE);
            itemView.setBackgroundColor(defaultBackgroundColor);
            ImageView iv = (ImageView)itemView.findViewById(R.id.ImageView01);
            if (iv != null) iv.setVisibility(View.VISIBLE);}
        }

};

  private static String[] mListContent={
     "Item 1", "Item 2", "Item 3", "Item 4", "Item 5", "Item 6", "Item 7","Item 8", "Item 9", "Item 10"
    ,"Item 11", "Item 12", "Item 13", "Item 14", "Item 15", "Item 16", "Item 17","Item 18", "Item 19", "Item 20"};
}

I believe I have to do something under “private DropListener mDropListener” to save the change and the I need to read the new item position onCreate?

Answer 1

Why not put the String[] into SharedPreferences using the Editor in the onPause() method of the Activity (make one if its not there) and then get it in the onCreate() method. This way you will always have the most recent version. Right now you set it to mListContent every time which is static and doesn’t change. Have that be the default one, and instead get your last one from shared preferences. I assume your new order is in mNewPositions.