Android using SQLite cursor to display next item or previous item

Question

A common Android application feature is to swipe on each detail item to get to the next item or previous item.

The database cursor contains a list of items which are displayed in the onCreate of a ListActivity:

if (cursor.moveToFirst()) {
    listThings.setAdapter(new ResourceCursorAdapter(this, R.layout.my_simple_expandable_list_item_2, cursor) {
        @Override
        public void bindView(View view, Context context, Cursor cursor) {
            TextView tvFirst = (TextView)view.findViewById(android.R.id.text1);
            TextView tvSecond = (TextView)view.findViewById(android.R.id.text2);

            tvFirst.setText(cursor.getString(1) + "  -  " + getPctString(cursor.getString(2)));
            tvSecond.setText(cursor.getString(3));
        }
    });
} else {
....

That works fine. The built-in layout resource R.layout.my_simple_expandable_list_item_2 tells the adapter to display each item in the cursor in a single text view. On click, I'm able to show the details of the item in the follow-on activity:

AdapterView.OnItemClickListener itemClickListener = new AdapterView.OnItemClickListener() {
    public void onItemClick(AdapterView listView, View v, int position, long id) {
    Intent intent = new Intent(ThingListActivity.this, ThingActivity.class);
    intent.putExtra(FollowOnActivity.EXTRA_ID, (int) id);
    startActivity(intent);
    }
};

Once in FollowOnActivity I can lookup the details and populate the view. I can also listen for and react to swipes.

Problem: I don't have access to what the next and previous items in the list are. So far, I've not come-up with what I consider a clean solution. Since this is a common requirement, there's probably a nice pattern for this. I'd like to know what that is.

I was able to get this screen slide example working, but the list in that example is fixed at five items, and those items are text in xml files instead of database items. I created ThingSlideActivity based on their ScreenSlidePagerActivity, ThingSlidePageAdapter based on their ScreenSlidePageAdapter and ThingSlideFragment based on their ScreenSlidePageFragment. But I don't know how to wire that up to the list view that I'm coming from. It might have a big list, and I'm trying not to pull details on all of them.

I'm sitting in a list view that's been populated with a cursor (the first block of code at the top of this question). The user clicks on a random one in the list and onListItemClick runs. What should it do to enable swiping left and right to see previous and next items?

Dale · Accepted Answer

This is what ended-up working. It uses the pattern found in screen-slide example from developer.android.com/training, with one difference: in ThingSlideActivity.getItem(), instead of running ThingSlideFragment.onCreate(pos), I used ThingSlideFragment.newInstance(pos). Also, I added static Cursor getCursor() which made available the original Cursor that populated the ListActivity in the first place. This allowed me to translate from the position within the list to the database key. If there are any faults with this pattern, please advise.

The initial activity This activity has a list from the database and a cursor left open until the list is destroyed :

public class ThingListActivity extends ListActivity {
    private SQLiteDatabase db;
    private static Cursor cursor;

    static Cursor getCursor() {
        return cursor;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ListView listThings = getListView();
        int position = getIntent().getIntExtra("POSITION", 0);

        try {
            SQLiteOpenHelper tableDatabaseHelper = new TableDatabaseHelper(this);
            db = tableDatabaseHelper.getReadableDatabase();
            cursor = db.query("TABLE", pullFields, selectionFields, selectionArgs, null, null, null); // you define your own query

            if (cursor.moveToFirst()) {
                listThings.setAdapter(new ResourceCursorAdapter(this, R.layout.my_simple_expandable_list_item_2, cursor) { //built-in layout
                    @Override
                    public void bindView(View view, Context context, Cursor cursor) {
                        TextView tvFirst = (TextView)view.findViewById(android.R.id.text1);
                        TextView tvSecond = (TextView)view.findViewById(android.R.id.text2);
                        tvFirst.setText(cursor.getString(1) + "  -  " + getPctString(cursor.getString(2)));
                        tvSecond.setText(cursor.getString(3));
                    }
                });
            } else {
                Toast toast = Toast.makeText(this, "The list was empty.", Toast.LENGTH_SHORT);
                toast.show();
            }
        } catch (SQLiteException e) {
            Toast toast = Toast.makeText(this, "Database Unavailable", Toast.LENGTH_SHORT);
            toast.show();
        } finally {
            //Not closing cursor.  Will do in onDestroy()
        }
    }

    @Override
    public void onDestroy(){
        super.onDestroy();
        if (cursor != null) cursor.close();
        if (db != null) db.close();
    }

    @Override
    protected void onListItemClick(ListView listView, View view, int position, long id) {
        Intent intent = new Intent(ThingListActivity.this, ThingSlideActivity.class);
        intent.putExtra(ThingSlideActivity.EXTRA_POSITION, (int) position);
        startActivity(intent);
    }
}

The follow-on FragmentActivity. This activity has an inner class ThingSlidePageAdapter. Notice setCurrentItem, which places you in the right spot within the list. :

public class ThingSlideActivity extends FragmentActivity{

    public static final String EXTRA_POSITION = "extra_position";

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_screen_slide);
        ViewPager mPager = (ViewPager)findViewById(R.id.pager);
        PagerAdapter mPagerAdapter = new ThingSlidePageAdapter(getSupportFragmentManager());
        mPager.setAdapter(mPagerAdapter);
        mPager.setCurrentItem((Integer)getIntent().getExtras().get(EXTRA_POSITION));
    }

    private static class ThingSlidePageAdapter extends FragmentStatePagerAdapter {

        int count;

        public ThingSlidePageAdapter(FragmentManager fm){
            super(fm);
            this.count = ThingListActivity.getCursor().getCount();
        }

        @Override
        public int getCount() {
            return this.count;
        }

        @Override
        public Fragment getItem(int position) {
            return ThingSlideFragment.newInstance(position); // onCreate() doesn't work well.
        }
    }
}

**The Fragment we are paging through. This is where we use the Cursor from the original ListView in order to get the database key (_id). Then a fresh query is executed, pulling details for only for one item. But under the covers, the previous and next items are also pulled.

public class ThingSlideFragment extends Fragment {

    private static final String ARG_POSITION = "position";

    public static ThingSlideFragment create(int position) {
        ThingSlideFragment fragment = new ThingSlideFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_POSITION, position);
        fragment.setArguments(args);
        return fragment;
    }

    public static ThingSlideFragment newInstance(int position) {
        ThingSlideFragment fragment = new ThingSlideFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_POSITION, position);
        fragment.setArguments(args);
        return fragment;
    }

    public ThingSlideFragment() {
    }

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.activity_thing, container, false);
        TextView tv = (TextView)rootView.findViewById(R.id.thingname);
        Cursor mCursor = ThingListActivity.getCursor();
        if (mCursor != null) {
            mCursor.moveToPosition(getArguments().getInt(ARG_POSITION));
            int id = Integer.parseInt(mCursor.getString(0));
            populateView(id, rootView);
        }
        return rootView;
    }

    private void populateView(int id, View rootView) {
        Cursor cursor = null;
        SQLiteDatabase db = null;
        try {
            SQLiteOpenHelper tableDatabaseHelper = new TableDatabaseHelper(this.getContext()) ;
            db = tableDatabaseHelper.getReadableDatabase();
            cursor = db.query("TABLE", new String[] {"NAME", "DESCRIPTION", "DETAIL1", "DETAIL2", "DETAIL3", "DETAIL4"}, "_id = ?", new String[] {Integer.toString(id)}, null, null, null);

            //Move to first record in the cursor (should be just one since our query used database key "CREATE TABLE TABLE (_id INTEGER PRIMARY KEY AUTOINCREMENT, ...."
            if (cursor.moveToFirst()) {
                // Get thing details from the cursor
                String nameText = cursor.getString(0);
                String descriptionText = cursor.getString(1);
                // ........ continue with other fields  

                // Populate TextView items
                ((TextView)rootView.findViewById(R.id.thingname)).setText(nameText);
                ((TextView)rootView.findViewById(R.id.description)).setText(descriptionText);
                // ........ continue with other fields
            }
        } catch (SQLiteException e) {
            Toast toast = Toast.makeText(this.getContext(), "Database unavailable. "+ e.getMessage(), Toast.LENGTH_LONG)   ;
        } finally {
            try {cursor.close();} catch (Throwable t) {}
            try {db.close();} catch (Throwable t) {}
        }
    }
}

And, left out of many of the examples here, the contents of the supporting xml files!

I hope this works for you and hope a lot of people are able to find it and benefit from it, because I spent a couple of days fiddling around with this until I got it working to my satisfaction. Possibly an easy one for the more highly experienced here, but helpful for those at a certain level of experience.

Android using SQLite cursor to display next item or previous item

Answers (2)

Related Questions