In -depth understanding of Android supports the architecture and internal mechanism of supporting the Reyclerview framework

Android supports the architecture and internal mechanism of supporting the RecyclerView framework With the continuous evolution of Android development, Google launched the RecyclerView framework to replace the old ListView to provide more efficient and flexible list display functions.RecyclerView has strong customization capabilities, which can cope with various complex list needs, and also provide better performance.In -depth understanding of the architecture and internal mechanism of RecyclerView is essential for the development of high -quality Android applications. 1. RecyclerView architecture RecyclerView's core architecture consists of three main components: 1. LayoutManager (layout manager): Responsible for defining the layout and location of sub -items.You can choose the existing LinearLayoutManager, GridLayoutManager or StaggereDGridLidlayoutManager, or you can customize LayoutManager to meet specific needs. 2. Adapter (adapter): Responsible for binding the data with the layout, and dynamically update the list item according to the change of the data source.Adapter must inherit the RecyclerView.adapter and implement three core methods: oncreateViewHolder (Create ViewHolder), onBindViewholder, and GetiteMCount. 3. Viewholder (View Holder): The view of each list item is used to improve performance.ViewHolder must inherit RecyclerView.ViewHolder and receive the View parameter in the constructor.By calling ViewHolder's FindViewByid method, you can get the sub -views in the view. 2. RecyclerView internal mechanism RecyclerView's internal mechanism can be summarized to the following key points: 1. Reuse the view: RecyclerView will automatically recover the list item view that is no longer displayed during the scroll, and hand it over to the next list of list items.This reuse mechanism can improve performance and memory utilization.When a new list item is required, the RecyclerView calls ADAPTER's oncreateViewHolder method to create a new ViewHolder. 2. Local refresh: RecyclerView supports local refresh, that is, only a specific part of the list item, not the entire list item.The OnbindViewholder method in Adapter is used to bind data with the corresponding list items.By calling ADAPTER's NotifyItemChangeded method, you can trigger the refresh of a single column item. 3. Highly measure and layout: Recyclerview will calculate the height and layout of each list item through layoutmanager.When the adapter data is updated, Recyclerview will measure the height of each list item again and update the scroll position to maintain the user's recovery state during the scroll process. Java code example: The following is a simple review of the Java code of RecyclerView. It shows how to use the RecyclerView framework to achieve a basic list display function: 1. Create the layout file "item_layout.xml" to define the layout of the list item. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <TextView android:id="@+id/item_title" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <ImageView android:id="@+id/item_image" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout> 2. Create a custom ViewHolder class "ItemViewholder.java", which is used to cache the table item. public class ItemViewHolder extends RecyclerView.ViewHolder { public TextView titleTextView; public ImageView imageView; public ItemViewHolder(View itemView) { super(itemView); titleTextView = itemView.findViewById(R.id.item_title); imageView = itemView.findViewById(R.id.item_image); } } 3. Create a custom adapter class "itmadapter.java" and inherit RecyclerView.adapter. public class ItemAdapter extends RecyclerView.Adapter<ItemViewHolder> { private List<Item> items; public ItemAdapter(List<Item> items) { this.items = items; } @Override public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout, parent, false); return new ItemViewHolder(itemView); } @Override public void onBindViewHolder(ItemViewHolder holder, int position) { Item item = items.get(position); holder.titleTextView.setText(item.getTitle()); holder.imageView.setImageResource(item.getImageResource()); } @Override public int getItemCount() { return items.size(); } } 4. Use RecyclerView in Activity and setting LayoutManager and Adapter. public class MainActivity extends AppCompatActivity { private RecyclerView recyclerView; private ItemAdapter adapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); recyclerView = findViewById(R.id.recycler_view); recyclerView.setLayoutManager(new LinearLayoutManager(this)); List <item> itemlist = getItemlist (); // Get the data list adapter = new ItemAdapter(itemList); recyclerView.setAdapter(adapter); } private List<Item> getItemList() { // Obtain data from the data source } } Through the above steps, we can implement a simple RecyclerView list display function.Through in -depth understanding of the architecture and internal mechanism of RecyclerView, we can better use the characteristics of RecyclerView, and design high -efficiency and flexible list display functions in actual development.