Android的UI开发——ListView

效果如下：

1. 新建fruit_xml文件，意为列表存放的格式。

2. MainActivity.java中代码

   public class MainActivity extends AppCompatActivity {
       //第一步：定义对象
       ListView listView;
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           //第二步：绑定控件
           listView = (ListView) findViewById(R.id.list_view);
           //第三步：创建一个列表 准备数据（数据源）
           List fruitlist = new ArrayList<>();
           for (int i = 0; i <5 ; i++) {//列表整体重复次数
               Fruit pineapple=new Fruit(R.drawable.pic1,"菠萝","¥16.9 元/KG");
               fruitlist.add(pineapple);
               Fruit mango = new Fruit(R.drawable.pic2, "芒果","¥29.9 元/kg");
               fruitlist.add(mango);
               Fruit pomegranate = new Fruit(R.drawable.pic3, "石榴","¥15元/kg");
               fruitlist.add(pomegranate);
               Fruit grape = new Fruit(R.drawable.pic4, "葡萄","¥19.9 元/kg");
               fruitlist.add(grape);
           }
           //第四步：设计每一个列表项的子布局 即fruit_item.xml文件
           //第五步：定义适配器 控件-桥梁-数据源
           FruitAdapter adapter=new FruitAdapter(MainActivity.this,R.layout.fruit_item,
                   fruitlist);
           listView.setAdapter(adapter);//将适配器加载到控件中
           //列表点击事件
           listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
               @Override
               public void onItemClick(AdapterView parent ,View view, int position,long id) {
                   Fruit fruit = fruitlist.get(position);
                   Toast.makeText(MainActivity.this,fruit.getName(),Toast.LENGTH_LONG).show();
               }//通过position判断用户点击的是哪一个子项 
           });
       }
   }

3. 新建一个类Fruit

   public class Fruit {
       private int imageID;
       private String name;
       private String price;
       public int getImageID() {
           return imageID;
       }
       public String getName() {
           return name;
       }
       public String getPrice() {
           return price;
       }
       public Fruit(int imageID, String name, String price) {
           this.imageID = imageID;
           this.name = name;
           this.price = price;
       }
   }

4. 新建一个类FruitAdapter                                                                                                                                 用于将上下文、listview 子项布局的 id 和数据都传递过来

   public class FruitAdapter extends ArrayAdapter {
       public FruitAdapter(@NonNull Context context, int resource, @NonNull List objects) {
           super(context, resource, objects);
       }
       //每个子项被滚动到屏幕内的时候会被调用
       @NonNull
       @Override
       public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
           Fruit fruit=getItem(position);//得到当前项的 Fruit 实例
           //为每一个子项加载设定的布局
           View view=LayoutInflater.from(getContext()).inflate(R.layout.fruit_item,parent,false);
           //分别获取 image view 和 textview 的实例
           ImageView fruitimage =view.findViewById(R.id.fruit_image);
           TextView fruitname =view.findViewById(R.id.fruit_name);
           TextView fruitprice =view.findViewById(R.id.fruit_price);
           // 设置要显示的图片和文字
           fruitimage.setImageResource(fruit.getImageID());
           fruitname.setText(fruit.getName());
           fruitprice.setT