提供一个Card视图
最后更新于:2022-04-01 01:42:38
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。
![app-browse](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2015-07-28_55b724744c928.png)
### 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。
![card-view](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2015-07-28_55b7247463cf9.png)