BaseAdapter.getView() for ListActivty using ViewHolder - Android

Question

This was my original getView method for the ListView BaseAdapter:

    // create a new ImageView for each item referenced by the Adapter
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {  // if it's not recycled, initialize some attributes
                imageView = new ImageView(mContext);
                imageView.setLayoutParams(new GridView.LayoutParams(150, 150));
                imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
                imageView.setPadding(8, 8, 8, 8);
            } else {
                imageView = (ImageView) convertView;
            }

            ImageHelper ih = new ImageHelper();



imageView.setImageBitmap(ih.decodeSampledBitmapFromResource(mContext.getResources(), mList.get(position), 40, 40));

            return imageView;
        }

It did not make use of convertView and I had no mInflater. I read that this way is not good for memory usage, and I found a better way that uses a ViewHolder. I have changed this method to implement a viewHolder and use the convertView instead making an ImageView like I originally did:

static class ViewHolder{
        TextView text;
        ImageView icon;
    }

    public View getView(int position, View convertView, ViewGroup parent) {
              ViewHolder holder;
              ImageView imageView = new ImageView(mContext);
              ImageHelper ih = new ImageHelper();
              if (convertView == null) {
              convertView = mInflater.inflate(R.id.gridviewViewOutfits, null);

              holder = new ViewHolder();
              holder.icon = (ImageView) convertView;
              holder.icon.setLayoutParams(new GridView.LayoutParams(150, 150));
              holder.icon.setScaleType(ImageView.ScaleType.FIT_CENTER);
              holder.icon.setPadding(8, 8, 8, 8);

              convertView.setTag(holder);
              } else {
              holder = (ViewHolder) convertView.getTag();
              }

              holder.icon.setImageBitmap(ih.decodeSampledBitmapFromResource(mContext.getResources(), mList.get(position), 40, 40));

              return convertView;
              }

This line caused a nullPointerException: convertView = mInflater.inflate(R.id.gridviewViewObjects, null);

It's because I had not instantiated my mInflater. Then I did that like this: mInflater = (LayoutInflater)c.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

Because I saw that online. Then I got this error:

01-20 20:37:52.080: E/AndroidRuntime(22543): FATAL EXCEPTION: main
01-20 20:37:52.080: E/AndroidRuntime(22543): android.content.res.Resources$NotFoundException: Resource ID #0x7f04002b type #0x12 is not valid
01-20 20:37:52.080: E/AndroidRuntime(22543):    at android.content.res.Resources.loadXmlResourceParser(Resources.java:2136)
01-20 20:37:52.080: E/AndroidRuntime(22543):    at android.content.res.Resources.getLayout(Resources.java:865)
01-20 20:37:52.080: E/AndroidRuntime(22543):    at android.view.LayoutInflater.inflate(LayoutInflater.java:394)
01-20 20:37:52.080: E/AndroidRuntime(22543):    at android.view.LayoutInflater.inflate(LayoutInflater.java:352)
01-20 20:37:52.080: E/AndroidRuntime(22543):    at com.btf271.imagehelper.ChooseStickersImageAdapter.getView(ChooseObjectsImageAdapter.java:136)

What should I do to instantiate the mInflater, or am I inflating the wrong thing?

This is my XML for the ListActivity:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".ViewOutfitsActivity" >

    <ListView
        android:id="@android:id/list"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true" >
    </ListView>

    <GridView
        android:id="@+id/gridviewViewObjects"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent"
        android:columnWidth="90dp"
        android:numColumns="auto_fit"
        android:verticalSpacing="10dp"
        android:horizontalSpacing="10dp"
        android:stretchMode="columnWidth"
        android:gravity="center"
    />

</RelativeLayout>

Thank you.

Solution

Here when you have inflated view at that time you should use layout

so change from this

 convertView = mInflater.inflate(R.id.gridviewViewOutfits, null);

to

  convertView = mInflater.inflate(R.layout.gridviewViewOutfits, null);

Comments

[user3164083]

Thanks. It says "gridviewViewOutfits cannot be resolved or is not a field"

[heri.wijoyo]

then you just have to import it: import YOUR_APP_PACKAGE_NAME.R.layout.gridviewViewOutfits

[user3164083]

Thanks. This will just display images in a gridView. Do you mean I create a whole new XML file such as the file that each Activity has created automatically? I have never done this. Would I right-click the Layout folder and click new XML file?

[user3164083]

My gridViewViewOutfits is just a view inside my ListActivity layout. So do I right-click the layout folder and click new XML file, to create a new layout? Then inflate that? Thank you.

[Piyush]

Yes if you want to make custom list then you should use that one..And you'r going in right direction.

[user3164083]

Thank you :) Should I give it a root element of RelativeLayout? I am creating it now and not sure what option to choose. Or should I go for ListView?

[user3164083]

Thank you. There are a lot of root elements to choose from for my custom layout. Do I choose RelativeLayout or ListView or something else?

[Piyush]

you can use relative layout or linear layout

[user3164083]

Thanks. It works but does not reduce the heap at all :( When I exit the listActivity I want those list bitmaps out of memory which does not appear to happen. However I will mark this as the answer.

[Piyush]

are you set background image for your layout any where which has a high resolution?

[user3164083]

No. I have an ImageView in my main Activity which takes up the full screen. I set it to 500 X 500 px. This just has to be there though. However, the heap keeps growing when accessing the ListActivity and then does not go back down when I click the item which adds it to the main Activity. The item drawn to the main Activity is very small. It is the List that is doing it.

[Piyush]

and this is because you are fetching images from resource folder and that images may be high resolutions.

[user3164083]

I change their resolution with inSampleSize, to 40px X 40px to draw them to the main Activity. I can confirm their resolution. The heap is growing because of the List, which is fine, but when I exit the List by clicking on an item, they should be removed from memory :(

[Roman Black]

Yes, you should give it a root element of RelativeLayout or any other layout class

[fweigl]

Exactly, that's what you need to to. If you only want to display an Image the layout needs only to contain an ImageView. You probably want to read a tutorial like this one: vogella.com/tutorials/AndroidListView/… It's about ListViews but the adapter part is exactly the same for GridViews.

[user3164083]

Thank you. I have finished and it works. However it was all for nothing, the heap is still just as big. I am convinced it is growing from this listView and not reducing upon exiting the ListView. Oh well, my original question has been answered well :)