Android学习第二天

• recyclerView的学习 (和iOS的UITableView控制作用类似，都是展示很多数据的列表)

• 引入recyclerView类

  • 在build.gradle文件中引入该类。

    api 'com.android.support:recyclerview-v7:28.0.0'

• activity的布局文件中 activity_main

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        >
        <android.support.v7.widget.RecyclerView
            android:id="@+id/my_recycler_view"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scrollbars="vertical">
        </android.support.v7.widget.RecyclerView>
    </LinearLayout>
  

• 在activity中

   /*
      * 初始化数据
      * */
      private void initData(){
          myAdapter = new MyAdapter(getData());
      }
      /*
       * 初始化界面
       * */
      private void initView(){
          recyclerView  = (RecyclerView) findViewById(R.id.my_recycler_view);
          LinearLayoutManager mlayouotManager = new LinearLayoutManager(this,LinearLayoutManager.VERTICAL,false);
          recyclerView.setLayoutManager(mlayouotManager);
          recyclerView.setAdapter(myAdapter);
      }
  
      /*
      *
      * 获取数据
      * */
      private ArrayList<String> getData(){
          ArrayList<String> data = new ArrayList<>();
          String temp = "item";
          for (int i = 0; i < 20; i++){
              data.add(i + temp);
          }
          return data;
      }
  

• 声明一个适配器

  • 新建一个适配器类，叫MyAdapter.java

    package com.example.songhongkang.recyclerview;
    
    import android.support.annotation.NonNull;
    import android.support.v7.widget.RecyclerView;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.TextView;
    
    import java.util.ArrayList;
    
    public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
    
        private ArrayList<String> mData;
    
        public MyAdapter(ArrayList<String> data){
            this.mData = data;
        }
    
        @NonNull
        @Override
        public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
    
            // 实例化展示的view
            View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.view_rv_item, viewGroup, false);
            // 实例化viewholder
            ViewHolder viewHolder = new ViewHolder(v);
            return viewHolder;
    
        }
    
        @Override
        public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
                viewHolder.et.setText(mData.get(i));
        }
    
    
        @Override
        public int getItemCount() {
            return mData == null ?  0 : mData.size();
        }
    
        public static class ViewHolder extends RecyclerView.ViewHolder {
            TextView et;
            public ViewHolder(@NonNull View itemView) {
                super(itemView);
               et = (TextView)itemView.findViewById(R.id.item_tv);
            }
        }
    }
    

运行的结果如下 图片

• 总结几个知识点

  • ArrayList 类似于iOS的可变数组，简单用法如下

    ArrayList<String> data = new ArrayList<>();
    String temp = "item";
    for (int i = 0; i < 20; i++){
        data.add(i + temp);
    }
    

  • 获取ArrayList的长度

    data.size()
    

• 把xml文件转换成View

          View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.view_rv_item, viewGroup, false);
  

更多recyclerView的用法 参考博客