开发者

Custom list adapter and different layouts for vertical/horizontal orientation

Something that puzzles me since my first steps with Android is the optimized use of a custom adapter with different layouts for different orientations. Currently I do end up in cascades of NULL checks and I would like to know if there's a better way.

Consider two different layouts for vertical orientation and horizontal orientation that do contain a different count of widg开发者_JAVA技巧ets.

Here's the vertical layout with one widget located in layout:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:orientation="horizontal" >

    <TextView
        style="@style/TextViewDefault"
        android:id="@+id/name"
        android:layout_weight="1" />
</LinearLayout>

Here's the horizontal layout with two widgets located in layout-land:

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:orientation="horizontal" >

    <TextView
        style="@style/TextViewDefault"
        android:id="@+id/name"
        android:layout_weight="1" />

    <TextView
        style="@style/TextViewDefault"
        android:id="@+id/description"
        android:layout_weight="1" />

    <TextView
        style="@style/TextViewDefault"
        android:id="@+id/date"
        android:layout_weight="1" />
</LinearLayout>

And here's the custom adapter - an extended SimpleCursorAdapter. Depending on the orientation the description and date objects are null or non-null. In my Android projetcs I do have row layouts with 10ths of objects and these null-checks become really nasty in the code. Is there a better solution? How do you guys work with custom adapters and different layouts for different orientations or sizes?

public class TestAdapter extends SimpleCursorAdapter {

    private static class ViewHolder {
        private TextView date;
        private TextView description;
        private TextView name;
    }

    private Context            context;
    private Cursor             cursor;
    private int                layout;
    private SQLiteDatabase     sqliteDatabase;
    private MySQLiteOpenHelper sqliteOpenHelper;

    public Test(final Context context, final int layout, final Cursor cursor, final String[] from, final int[] to) {
        super(context, layout, cursor, from, to);

        this.context = context;
        this.cursor = cursor;
        this.layout = layout;

        if (sqliteOpenHelper == null) {
            sqliteOpenHelper = new MySQLiteOpenHelper(context);
        }

        if (sqliteOpenHelper != null) {
            if (sqliteDatabase == null) {
                sqliteDatabase = sqliteOpenHelper.getWritableDatabase();
            }
        }
    }

    @Override
    public View getView(final int position, final View contentView, final ViewGroup viewGroup) {
        View       view = null;
        ViewHolder viewHolder = null;

        if (contentView == null) {
            LayoutInflater layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = layoutInflater.inflate(layout, null);

            if (view != null) {
                viewHolder = new ViewHolder();
                viewHolder.date = (TextView) view.findViewById(R.id.date);
                viewHolder.description = (TextView) view.findViewById(R.id.description);
                viewHolder.name = (TextView) view.findViewById(R.id.name);
                view.setTag(viewHolder);
            }
        } else {
            view = contentView;
            viewHolder = (ViewHolder) contentView.getTag();
        }

        if (viewHolder != null) {
            cursor.moveToPosition(position);

            String date = cursor.getString(cursor.getColumnIndex(Test.DATE));
            String description = cursor.getString(cursor.getColumnIndex(Test.DESCRIPTION));
            String name = cursor.getString(cursor.getColumnIndex(Test.NAME));

            if (viewHolder.date != null) {
                if (!StringUtils.isEmpty(date) && date.length() == 10) {
                    viewHolder.date.setText(Tools.formatDate(date.substring(0, 10)));
                } else {
                    viewHolder.date.setText("");
                }
            }

            if (viewHolder.description != null) viewHolder.description.setText(description);
            if (viewHolder.name != null) viewHolder.name.setText(name);
        }

        return view;
    }
}


Since you have different widget count you have to deal with the fact setting different data.
But you can get rid of following null checks:

// wouldn't you expect to have a working layout here?
View != null        

// when view != null removed this is obsolete           
viewHolder != null

// the same thing here, you would expect a name here
viewHolder.name != null

// put that under viewHolder.date != null since both are available when one of them is
viewHolder.description.setText(description);
0

上一篇:

下一篇:

精彩评论

暂无评论...
验证码 换一张
取 消

最新问答

问答排行榜