[英]Passing MainActivity as a parameter RecyclerView Adapter in android
I am following this android tutorial 我正在关注这个Android教程
https://github.com/udacity/ud851-Exercises/blob/student/Lesson03-Green-Recycler-View/T03.07-Solution-RecyclerViewClickHandling/app/src/main/java/com/example/android/recyclerview/MainActivity.java https://github.com/udacity/ud851-Exercises/blob/student/Lesson03-Green-Recycler-View/T03.07-Solution-RecyclerViewClickHandling/app/src/main/java/com/example/android/recyclerview/ MainActivity.java
In order to handle item clicks in the RecyclerView.Adapter which is the instance GreenAdapter in the tutorial, we create an interface to receive onclick messages from the activity. 为了处理RecyclerView.Adapter(本教程中的实例GreenAdapter)中的项目单击,我们创建了一个接口来接收来自活动的onclick消息。 We then implement the interface in the MainActivity by overriding onListItemClick.
然后,我们通过重写onListItemClick在MainActivity中实现该接口。 The code is shown below
代码如下所示
public class GreenAdapter extends RecyclerView.Adapter<GreenAdapter.NumberViewHolder> {
public interface ListItemClickListener {
void onListItemClick(int clickedItemIndex);
}
final private ListItemClickListener mOnClickListener;
public GreenAdapter(int numberOfItems, ListItemClickListener listener) {
mNumberItems = numberOfItems;
mOnClickListener = listener;
viewHolderCount = 0;
}}
and the activity 和活动
public class MainActivity extends AppCompatActivity implements GreenAdapter.ListItemClickListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAdapter = new GreenAdapter(NUM_LIST_ITEMS, this);}
The this is referring to the activity instance, but the GreenAdapter constructor takes a ListItemClickListener type. 这是指活动实例,但是GreenAdapter构造函数采用ListItemClickListener类型。
How is this possible. 这怎么可能。 How can an Activity be passed/cast as ListItemClickListener type.
如何将Activity作为ListItemClickListener类型传递/投射。
Here this
means that your MainActivity
has the implementation of the ListItemClickListener
. 在这里,
this
意味着您的MainActivity
具有ListItemClickListener
的实现。 Read the documentation of the Android from the official documentation. 从官方文档中阅读Android的文档。
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