Android TV Leanback (六)（卡片视图）

使用BaseCardView和它的子类显示与媒体项相关的数据。使用ImageCardView显示显示图片和标题。

创建一个Card Presenter

Presenter根据需求生成视图并将数据对象与之绑定。
如下：

@Override
public void onLoadFinished(Loader<HashMap<String, List<Movie>>> arg0,
                       HashMap<String, List<Movie>> data) {

    mRowsAdapter = new ArrayObjectAdapter(new ListRowPresenter());
    CardPresenter cardPresenter = new CardPresenter();

    int i = 0;

    for (Map.Entry<String, List<Movie>> entry : data.entrySet()) {
        ArrayObjectAdapter listRowAdapter = new ArrayObjectAdapter(cardPresenter);
        List<Movie> list = entry.getValue();

        for (int j = 0; j < list.size(); j++) {
            listRowAdapter.add(list.get(j));
        }
        HeaderItem header = new HeaderItem(i, entry.getKey(), null);
        i++;
        mRowsAdapter.add(new ListRow(header, listRowAdapter));
    }

    HeaderItem gridHeader = new HeaderItem(i, getString(R.string.more_samples),null);

    GridItemPresenter gridPresenter = new GridItemPresenter();
    ArrayObjectAdapter gridRowAdapter = new ArrayObjectAdapter(gridPresenter);
    gridRowAdapter.add(getString(R.string.grid_view));
    gridRowAdapter.add(getString(R.string.error_fragment));
    gridRowAdapter.add(getString(R.string.personal_settings));
    mRowsAdapter.add(new ListRow(gridHeader, gridRowAdapter));

    setAdapter(mRowsAdapter);
    updateRecommendations();
}

注：每一个presenter只能创建一种视图类型，如果有多种不同视图类型就需要创建多种presenter。
创建Presenter需要实现onCreatViewHolder()方法：

@Override
public class CardPresenter extends Presenter {

    private Context mContext;
    private static int CARD_WIDTH = 313;
    private static int CARD_HEIGHT = 176;
    private Drawable mDefaultCardImage;

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent) {
        mContext = parent.getContext();
        mDefaultCardImage = mContext.getResources().getDrawable(R.drawable.movie);

...

如果卡片选中，你可以做各种操作，默认放大：

...
ImageCardView cardView = new ImageCardView(mContext) {
    @Override
    public void setSelected(boolean selected) {
        int selected_background = mContext.getResources().getColor(R.color.detail_background);
        int default_background = mContext.getResources().getColor(R.color.default_background);
        int color = selected ? selected_background : default_background;
        findViewById(R.id.info_field).setBackgroundColor(color);
        super.setSelected(selected);
    }
};
...

为了实现遥控操作需要设置 setFocusable(true)，setFocusableInTouchMode(true)：

...
cardView.setFocusable(true);
cardView.setFocusableInTouchMode(true);
return new ViewHolder(cardView);