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POAndroid: EfficientAdapter with two different Views
 

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  1. POAndroid: EfficientAdapter with two different Views
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    <p>I'm using an extended version of BaseAdapter based on the <a href="http://developer.android.com/guide/samples/ApiDemos/src/com/example/android/apis/view/List14.html" rel="noreferrer">EfficientAdapter example</a> from the SDK demo samples.</p> <p>My data is basically an object (<code>ListPlaces</code>) which holds an <code>ArrayList</code> with the actual list of places, accessible via <code>listPlaces.getValues()</code>. This ArrayList data is sorted by range and the <code>ArrayList</code> consist of some special items (separators), with no data, but a <code>separator</code> flag set to <code>true</code>. </p> <p>Now whenever my <code>EfficientAdapter</code> gets a data object which is a separator it returns <code>false</code> for <code>public boolean isEnabled(int position)</code> and <code>public View getView(int position, View convertView, ViewGroup parent)</code> inflates two different layouts depending on if the current data object consists of real data or is just a separator dummy.</p> <p>This works great, if I inflate the layout every time. However, inflating the layout every time and calling <code>findViewById</code> makes the <code>ListView</code> almost unusabely slow.</p> <p>So I tried to use the EfficientAdapter with <code>ViewHolder</code> approach. But that didn't work right out of the box, because of the two different views I try to access. So whenever my <code>convertView != null</code> (the else-case) accesses the items on the layout via our <code>ViewHolder</code> and when the previous View was a separator it of course doesn't work to access a TextView there which is only available on the "real" items layout.</p> <p>So I also force my <code>getView()</code> to inflate the layout not only when <code>convertView == null</code>, but also when the previous listRow is different than the current one: <code>if (convertView == null || (listRow != listRow_previous)) { [....] }</code></p> <p>This seems to almost work now. Or at least it doesn't crash right from the beginning. But it still crashes and I don't know what I've to do different. I've tried to look into <code>convertView.getID()</code> and <code>convertView.getResources()</code>, but that wasn't really helpful so far. Maybe someone else has an idea how I can check whether my current <code>convertView</code> matches with the list item layout or the list separator layout. Thanks.</p> <p>Here's the code. Where ever there is a [...] I took out some less important code to make it easier to read and understand:</p> <pre><code>private class EfficientAdapter extends BaseAdapter { private LayoutInflater mInflater; private ListPlaces listPlaces; private ListRow listRow; private ListRow listRow_previous; public EfficientAdapter(Context context, ListPlaces listPlaces) { // Cache the LayoutInflate to avoid asking for a new one each time. mInflater = LayoutInflater.from(context); // Data this.listPlaces = listPlaces; } /** * The number of items in the list is determined by the number of items * in our ArrayList * * @see android.widget.ListAdapter#getCount() */ public int getCount() { return listPlaces.getValues().size(); } /** * Since the data comes from an array, just returning the index is * sufficent to get at the data. If we were using a more complex data * structure, we would return whatever object represents one row in the * list. * * @see android.widget.ListAdapter#getItem(int) */ public Object getItem(int position) { return position; } /** * Use the array index as a unique id. * * @see android.widget.ListAdapter#getItemId(int) */ public long getItemId(int position) { return position; } @Override public boolean isEnabled(int position) { // return false if item is a separator: if(listPlaces.getValues().get(position).separator &gt;= 0) return false; else return true; } @Override public boolean areAllItemsEnabled() { return false; } /** * Make a view to hold each row. * * @see android.widget.ListAdapter#getView(int, android.view.View, * android.view.ViewGroup) */ public View getView(int position, View convertView, ViewGroup parent) { // Get the values for the current list element ListPlacesValues curValues = listPlaces.getValues().get(position); if (curValues.separator &gt;= 0) listRow = ListRow.SEPARATOR; else listRow = ListRow.ITEM; Log.i(TAG,"Adapter: getView("+position+") " + listRow + " (" + listRow_previous + ") -&gt; START"); // A ViewHolder keeps references to children views to avoid unneccessary calls // to findViewById() on each row. ViewHolder holder; // When convertView is not null, we can reuse it directly, there is no need // to reinflate it. We only inflate a new View when the convertView supplied // by ListView is null. if (convertView == null || (listRow != listRow_previous)) { Log.i(TAG, "--&gt; (convertView == null) at position: " + position); // Creates a ViewHolder and store references to the two children views // we want to bind data to. holder = new ViewHolder(); if (listRow == ListRow.SEPARATOR) { convertView = mInflater.inflate(R.layout.taxonomy_list_separator, null); holder.separatorText = (TextView) convertView.findViewById(R.id.separatorText); convertView.setTag(holder); Log.i(TAG,"\tCREATE SEPARATOR: convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources()); } else { convertView = mInflater.inflate(R.layout.taxonomy_listitem, null); holder.name = (TextView) convertView.findViewById(R.id.name); holder.category = (TextView) convertView.findViewById(R.id.category); // [...] convertView.setTag(holder); Log.i(TAG,"\tCREATE ITEM: convertView ID: " + convertView.getId() + " Resource: " + convertView.getResources()); } } else { // Get the ViewHolder back to get fast access to the TextView // and the ImageView. Log.i(TAG,"\tconvertView ID: " + convertView.getId() + " Resource: " + convertView.getResources()); holder = (ViewHolder) convertView.getTag(); convertView.setAnimation(null); } /* Bind the data efficiently with the holder */ if (listRow == ListRow.SEPARATOR) { String separatorText; switch (curValues.separator) { case 0: separatorText="case 0"; break; case 1: separatorText="case 1"; break; case 2: separatorText="case 2"; break; // [...] default: separatorText="[ERROR]"; break; } holder.separatorText.setText(separatorText); } else { // Set the name: holder.name.setText(curValues.name); // Set category String cat = curValues.classification.toString(); cat = cat.substring(1,cat.length()-1); // removing "[" and "]" if (cat.length() &gt; 35) { cat = cat.substring(0, 35); cat = cat + "..."; } holder.category.setText(cat); // [...] (and many more TextViews and ImageViews to be set) } listRow_previous = listRow; Log.i(TAG,"Adapter: getView("+position+") -&gt; DONE"); return convertView; } private class ViewHolder { TextView name; TextView category; // [...] -&gt; many more TextViews and ImageViews TextView separatorText; } } </code></pre> <p>And here my <strong>Logcat</strong> output:</p> <pre><code> 755 ListPlaces_Activity I onPostExecute: notifyDataSetChanged() 755 ListPlaces_Activity I Adapter: getView(0) SEPARATOR (null) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 0 755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(0) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(1) ITEM (SEPARATOR) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 1 755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(1) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(2) SEPARATOR (ITEM) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 2 755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(2) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(3) ITEM (SEPARATOR) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 3 755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(3) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(4) ITEM (ITEM) -&gt; START 755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(4) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(5) ITEM (ITEM) -&gt; START 755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(5) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(6) ITEM (ITEM) -&gt; START 755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(6) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(0) SEPARATOR (ITEM) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 0 755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(0) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(1) ITEM (SEPARATOR) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 1 755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(1) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(2) SEPARATOR (ITEM) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 2 755 ListPlaces_Activity I CREATE SEPARATOR: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(2) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(3) ITEM (SEPARATOR) -&gt; START 755 ListPlaces_Activity I --&gt; (convertView == null) at position: 3 755 ListPlaces_Activity I CREATE ITEM: convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(3) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(4) ITEM (ITEM) -&gt; START 755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 ListPlaces_Activity I Adapter: getView(4) -&gt; DONE 755 ListPlaces_Activity I Adapter: getView(5) ITEM (ITEM) -&gt; START 755 ListPlaces_Activity I convertView ID: 2131296317 Resource: android.content.res.Resources@437613e0 755 AndroidRuntime D Shutting down VM 755 dalvikvm W threadid=3: thread exiting with uncaught exception (group=0x4001aa28) 755 AndroidRuntime E Uncaught handler: thread main exiting due to uncaught exception 755 AndroidRuntime E java.lang.NullPointerException 755 AndroidRuntime E at com.tato.main.ListPlaces_Activity$EfficientAdapter.getView(ListPlaces_Activity.java:330) 755 AndroidRuntime E at android.widget.HeaderViewListAdapter.getView(HeaderViewListAdapter.java:191) 755 AndroidRuntime E at android.widget.AbsListView.obtainView(AbsListView.java:1255) 755 AndroidRuntime E at android.widget.ListView.makeAndAddView(ListView.java:1658) 755 AndroidRuntime E at android.widget.ListView.fillDown(ListView.java:637) 755 AndroidRuntime E at android.widget.ListView.fillFromTop(ListView.java:694) 755 AndroidRuntime E at android.widget.ListView.layoutChildren(ListView.java:1502) 755 AndroidRuntime E at android.widget.AbsListView.onLayout(AbsListView.java:1112) 755 AndroidRuntime E at android.view.View.layout(View.java:6569) 755 AndroidRuntime E at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 755 AndroidRuntime E at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998) 755 AndroidRuntime E at android.widget.LinearLayout.onLayout(LinearLayout.java:918) 755 AndroidRuntime E at android.view.View.layout(View.java:6569) 755 AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 755 AndroidRuntime E at android.view.View.layout(View.java:6569) 755 AndroidRuntime E at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 755 AndroidRuntime E at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998) 755 AndroidRuntime E at android.widget.LinearLayout.onLayout(LinearLayout.java:918) 755 AndroidRuntime E at android.view.View.layout(View.java:6569) 755 AndroidRuntime E at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 755 AndroidRuntime E at android.view.View.layout(View.java:6569) 755 AndroidRuntime E at android.view.ViewRoot.performTraversals(ViewRoot.java:979) 755 AndroidRuntime E at android.view.ViewRoot.handleMessage(ViewRoot.java:1613) 755 AndroidRuntime E at android.os.Handler.dispatchMessage(Handler.java:99) 755 AndroidRuntime E at android.os.Looper.loop(Looper.java:123) 755 AndroidRuntime E at android.app.ActivityThread.main(ActivityThread.java:4203) 755 AndroidRuntime E at java.lang.reflect.Method.invokeNative(Native Method) 755 AndroidRuntime E at java.lang.reflect.Method.invoke(Method.java:521) 755 AndroidRuntime E at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 755 AndroidRuntime E at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 755 AndroidRuntime E at dalvik.system.NativeStart.main(Native Method) </code></pre>
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