提供一个Card视图

编写:[huanglizhuo](https://github.com/huanglizhuo) - 原文:[http://developer.android.com/training/tv/playback/card.html](http://developer.android.com/training/tv/playback/card.html) 在前面的课程中，我们创建一个目录浏览器，实现了浏览 fragment，显示了媒体项目的列表。在本课程中，我们将创建该卡视图的媒体项目，并在浏览fragment中呈现出来。 [BaseCardView](http://developer.android.com/reference/android/support/v17/leanback/widget/BaseCardView.html)类以及子类显示与媒体项目相关联的元数据。在本节课程中使用的[ImageCardView](http://developer.android.com/reference/android/support/v17/leanback/widget/ImageCardView.html)类显示随着媒体项目的标题内容的图像。 这节课介绍了GitHub上 [ Android Leanback sample app](https://github.com/googlesamples/androidtv-Leanback)的示例应用程序代码。使用该示例代码，开始你自己的应用程序。  ### 创建一个卡片呈现者 [Presenter](http://developer.android.com/reference/android/support/v17/leanback/widget/Presenter.html)生成视图并把类和它们绑定起来。在你的浏览 fragment 中将内容呈现给用户,你为内容卡片创建[Presenter](http://developer.android.com/reference/android/support/v17/leanback/widget/Presenter.html)并把它传给适配器然后将内容呈现在屏幕上。在下面的代码中,CardPresenter在[ LoaderManager](http://developer.android.com/reference/android/support/v4/app/LoaderManager.html)的[onLoadFinished](http://developer.android.com/reference/android/support/v4/app/LoaderManager.LoaderCallbacks.html#onLoadFinished(android.support.v4.content.Loader<D>, D))方法中被创建。 ~~~ @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(); } ~~~ ### 创建一个卡片视图 在这步中,你将用view holder创建一个卡片presenter来为卡片视图呈现媒体项目。注意,每个presenter只能创建一个view类别。如果你有俩个不同的卡片视图,你就得创建俩个不同的presenter 在[presenter](http://developer.android.com/reference/android/support/v17/leanback/widget/Presenter.html)实现[onCreateViewHolder](http://developer.android.com/reference/android/support/v17/leanback/widget/Presenter.html#onCreateViewHolder(android.view.ViewGroup))时创建一个可以呈现内容项目的view holder。 ~~~ @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); ... ~~~ 在[onCreateViewHolder](http://developer.android.com/reference/android/support/v17/leanback/widget/Presenter.html#onCreateViewHolder(android.view.ViewGroup))方法中,创建呈现内容的卡片视图。下面的例子用的是[ImageCardView](http://developer.android.com/reference/android/support/v17/leanback/widget/ImageCardView.html) 当卡片被选中时,默认的行为是放大展开。如果你想创建不同颜色的卡片可以向下面这样调用[setSelected](http://developer.android.com/reference/android/support/v17/leanback/widget/BaseCardView.html#setSelected(boolean))方法中实现。 ~~~ ... 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); } }; ... ~~~ 当用户打开你的应用时,[Presenter.ViewHolder ](http://developer.android.com/reference/android/support/v17/leanback/widget/Presenter.ViewHolder.html)为内容项目显示了卡片视图。你需要调用[setFocusable(true) ](http://developer.android.com/reference/android/view/View.html#setFocusable(boolean))和[setFocusableInTouchMode(true)](http://developer.android.com/reference/android/view/View.html#setFocusableInTouchMode(boolean))方法设置接收来自D-pad的焦点控制。 ~~~ ... cardView.setFocusable(true); cardView.setFocusableInTouchMode(true); return new ViewHolder(cardView); } ~~~ 当用户选中[ImageCardView](http://developer.android.com/reference/android/support/v17/leanback/widget/ImageCardView.html)时,它用你制定的颜色背景展开文字内容,就像下面这样。