android-How to use CursorAdapter to fill listView and recycling them

Question

I used to fill listView with arrayAdapter and recycle them to do faster and reduce ram usage . I want to do the same with CursorAdapter ,I mean I want to read data( lots of data , about 500 rows ) with images and show them . What is the best way to do this ? What should I do and where I can learn what to do . I've searched but I'm really confuse now ,I'm a new to android.

Thanks

Answer 1

Here is an Example with comments to show you how to recycle the views in CursorAdapter that has 2 textViews as an Item in the List.

here is the class ViewHolder to hold the elements and call them once.

public class ViewHolder {

    TextView tvTitle, tvGenre;
    public ViewHolder(View row)
    {
        tvTitle = (TextView) row.findViewById(R.id.tvTitle);
        tvGenre = (TextView) row.findViewById(R.id.tvGenre);
    }


}

in your newView

@Override
public View newView(Context context, Cursor arg1, ViewGroup arg2) {
    // TODO Auto-generated method stub

    LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View row = inflater.inflate(R.layout.list_row, arg2, false);

    //create an instance of the holder
    ViewHolder holder = new ViewHolder(row);
    //add it to the Tag, so if it not null get the elements from tag.   
    row.setTag(holder);

    return row;
} 

in your bindView

Override
public void bindView(View v, Context context, Cursor c) {
    // TODO Auto-generated method stub

    //create an instance of the class and assign its value from view tag
    ViewHolder holder = (ViewHolder) v.getTag();

    //use the holder to assign values to the elements   
    holder.tvTitle.setText(c.getString(c.getColumnIndex(DatabaseHolder.TITLE_KEY)));
    holder.tvGenre.setText(c.getString(c.getColumnIndex(DatabaseHolder.GENRE_KEY)));

}

Hope this example is clear to you, change it according to your Item.

...

update: Based on demanding DatabaseHolder class

public class DatabaseHolder {

private final static String DATABASE_NAME = "MoviesDatabase";
private final static String TABLE_NAME = "MoviesTable";
private final static int VERSION = 1;

public final static String ID_KEY = "_id";
public final static String TITLE_KEY = "title";
public final static String GENRE_KEY = "genre";
public final static String DESC_KEY = "description";

public final static String[] COLUMNS = {ID_KEY, TITLE_KEY, GENRE_KEY, DESC_KEY};

private Context  context;
private SQLiteDatabase myDB;
private OpenHelper helper;

public DatabaseHolder(Context context)
{
    this.context = context;
}

public class OpenHelper extends SQLiteOpenHelper {

    Context context;

    public OpenHelper(Context context) {
        super(context, TABLE_NAME, null, VERSION);
        // TODO Auto-generated constructor stub
        this.context = context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub

        try {
            db.execSQL("CREATE TABLE "+ TABLE_NAME +" ( " +
                    ID_KEY + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                    TITLE_KEY + " TEXT(32) NOT NULL, " +
                    GENRE_KEY + " TEXT(32) NOT NULL, " +
                    DESC_KEY + " TEXT(512) NOT NULL);"
                    );
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            Message.message(context, "Failed"+e);
        }

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }


}

public DatabaseHolder open()
{
    helper = new OpenHelper(context);
    myDB = helper.getWritableDatabase();
    return this;
}

public long insertMovie(String title, String genre, String desc) {

    ContentValues cv = new ContentValues();

    cv.put(TITLE_KEY, title);
    cv.put(GENRE_KEY, genre);
    cv.put(DESC_KEY, desc);

    return myDB.insert(TABLE_NAME, null, cv);

}

public Cursor getAllRowCursor() {

    Cursor c = myDB.query(TABLE_NAME, COLUMNS, null, null, null, null, null);

    if (c != null)
        c.moveToFirst();

    return c;
}

public Cursor getSpecificRows(int id) {

    String where = ID_KEY + " = " + id;
    Cursor c = myDB.query(TABLE_NAME, COLUMNS, where, null, null, null, null);

    if (c != null)
        c.moveToFirst();

    return c;

}

public Cursor getFilteredRows(String result)
{
    result = "'" + result.trim() + "%'";
    String where = TITLE_KEY + " LIKE " + result;
    Cursor c = myDB.query(TABLE_NAME, COLUMNS, where, null, null, null, null);

    if (c != null)
        c.moveToFirst();

    return c;


}

public void truncate() {
    // TODO Auto-generated method stub

    myDB.delete(TABLE_NAME, null, null);
}
}