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POGridView with custom ImageAdapter doesn't update after dataset changes
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  1. POGridView with custom ImageAdapter doesn't update after dataset changes
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    copied!<p>I'm implementing a gallery of images with support for multiple item selection. The main layout is a <code>GridView</code> which uses a custom <code>Adapter</code>. Every displayed item is a combination <code>ImageView</code> + <code>CheckBox</code>. If several checkboxes are checked I want to uncheck them all simply by touching any image in the <code>GridView</code>. I'm calling <code>notifyDataSetChanged()</code> for implementing this functionality. Unfortunately this "uncheck all" feature doesn't work. I'm still a newbie so probably there is something basic that I don't understand. Could somebody tell me what is wrong with my <code>Adapter</code>? Thanks.</p> <pre><code>public class ImageAdapter extends BaseAdapter { private Context mContext; // References to our images public Integer[] mThumbIds = { R.drawable.sample_1, R.drawable.sample_2, R.drawable.sample_3, R.drawable.sample_1, R.drawable.sample_2, R.drawable.sample_3, R.drawable.sample_1, R.drawable.sample_2, R.drawable.sample_3, R.drawable.sample_1, R.drawable.sample_2, R.drawable.sample_3 }; // The layout inflater used to retrieve gallery children layouts private LayoutInflater mInflater; // Array used to update checkboxes public boolean[] checkboxesState = new boolean[getCount()]; public ImageAdapter(Context c) { mContext = c; mInflater = (LayoutInflater) c.getSystemService(Context.LAYOUT_INFLATER_SERVICE); // Define the initial checked/unchecked state of the checkboxes for(int i = 0; i &lt; getCount(); i++) { checkboxesState[i] = false; } } public int getCount() { return mThumbIds.length; } public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } /* Create a new View for each cell displayed in the GridView. * In our case a View is an instance of RelativeLayout from which * we can extract the image and checkbox to be displayed in the cell */ public View getView(int position, View convertView, ViewGroup parent) { View cell = convertView; if (cell == null) { // No View passed, create one. cell = mInflater.inflate(R.layout.galleryitem, null); // Setup the View content ImageView imageView = (ImageView)cell.findViewById(R.id.thumbImage); CheckBox checkBox = (CheckBox) cell.findViewById(R.id.itemCheckBox); checkBox.setChecked(checkboxesState[position]); checkBox.setId(position); imageView.setImageBitmap(downsample(mThumbIds[position])); // Setup the View behavior imageView.setOnClickListener(new OnClickListener() { public void onClick(View v) { // Uncheck all checked items uncheckAll(); } }); checkBox.setOnClickListener(new OnClickListener() { public void onClick(View v) { CheckBox cb = (CheckBox) v; checkboxesState[cb.getId()] = cb.isChecked(); } }); } return cell; } private Bitmap downsample(int resId){ // Some code here } private void uncheckAll() { // This code does not work. GridView is not refreshed for(int i = 0; i &lt; checkboxesState.length; i++) { checkboxesState[i] = false; } notifyDataSetChanged(); } } </code></pre> <p><strong>Update</strong></p> <p>I've realised that my initial post doesn't describe exactly how the uncheckAll method fails. What happens when I have N checked checkboxes and call the uncheckAll method is:</p> <ul> <li>the initially checked checkboxes are unchecked</li> <li>a new group of N checkboxes are checked</li> </ul> <p>This behavior made me to think that maybe the gridview items were, unexpectedly, changing their positions in the <code>GridView</code> so I added a <code>TextView</code> with a unique name to every item. My thought was correct: when I scrolled the screen the items change their position in the <code>GridView</code>. The same happens when uncheckAll is called. I've found a solution working for me <a href="https://stackoverflow.com/questions/6055730/gridview-elements-changes-their-place-dynamically-when-scroll-screen">in this thread</a>.</p> <p>Note: I didn't realise about the moving problem at the very beginning because at this stage of development I was using the same <code>ImageView</code> resource for every <code>GridView</code> item.</p>
 

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