Question

I am developing an Android app and one of its use cases is to display the following situation.

1. I have a list of links (L). Each of these links is the URL for a
   picture in the Internet;
2. I have to download each picture of (L) and display it in a ListView. There should be two rows in the ListView(s), where I can insert the pictures. I want to do something similar to this app;
3. I have to display the pictures in a HorizontalScrollView;
4. The pictures have to be downloaded on demand, in other words, I just
   download the picture using a Thread when the HorizontalScrollView is
   in a position that shows this picture (similar to this
   situation).

My questions:

1. Is it possible to insert an ListView in a HorizontalScrollView? (If yes, how do I do it?)

2. How do I use HorizontalScrollView? I mean, is there any difference on how I use a ListView inside a ScrollView?

3. Do you know any plugin/project that has the same purposes?

Answer 1

Question 1 – Perhaps you should re-think your design to use a list of HorizonzalListView.
Question 2 – You can created a list of HorizontialListView programmatically, place them inside a LinearLayout wrapped by a vertical scroll view.

Your myhlist.xml layout:

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent">

  <LinearLayout android:id="@+id/list_of_hlist_placeholder"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_gravity="center_horizontal"/>

</ScrollView>

You activity:

public class ListOfHListlActivity extends Activity {

/** List of ArrayAdapter with each bind to a HorizontialListView created programmatically */
private List<MyAdapter> myAdapters = new ArrayList<MyAdapter>();
/** List of your data model */
private List<Object> myDataList;

/**
 * Worker thread running in background doing dirty job.
 */
private class DoDirtyJobAsyncTask extends AsyncTask<Void, MyAdapter, Void> {

    @Override
    protected Void doInBackground(Void... params) {
    // do your dirty job here, to populate myDataList
        for (Object myData : myDataList) {
            MyAdapter myAdapter = new MyAdapter(myData);
            myAdapters.add(myAdapter);
            publishProgress(myAdapter);
        }
        return null;
    }

    @Override
    protected void onProgressUpdate(MyAdapter... myAdapters) {
        int currViewId = 1;
        for (final MyAdapter myAdapter: myAdapters) {
            HorizontialListView listview = new HorizontialListView(getApplicationContext(), null);
            listview.setId(currViewId);
            listview.setAdapter(myAdapter);
            listview.setOnItemClickListener(new OnItemClickListener() {
                public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
                // I am clickable.
                }
            });

            RelativeLayout listOfHListLayout = (RelativeLayout) findViewById(R.id.list_of_hlist_placeholder);
            // don't forget set height here, you know the height issue in HorizontialListView
            RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
                    RelativeLayout.LayoutParams.FILL_PARENT, 40);
            listOfHListLayout.addView(listview, layoutParams);
            currViewId++;
        }
    }

}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    new DoDirtyJobAsyncTask().execute();
    setContentView(R.layout.myhlist);
}

}