Android学习——控件ListView的使用

Posted 2020-09-28 会飞的咸鱼

一、ListView的简单用法

首先新建一个ListViewTest项目，并让android Studio自动创建好活动。然后修改activity_main.xml中的代码，如下：

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent">
 5 
 6    <ListView
 7        android:id="@+id/list_view"
 8        android:layout_width="match_parent"
 9        android:layout_height="match_parent">
10    </ListView>
11 </LinearLayout>

接下来修改MainActivity中的代码：

 1 public class MainActivity extends AppCompatActivity {
 2 
 3     private String[] data={"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry","Mango","Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry","Mango"};
 4     @Override
 5     protected void onCreate(Bundle savedInstanceState) {
 6         super.onCreate(savedInstanceState);
 7         setContentView(R.layout.activity_main);
 8 
 9         ArrayAdapter<String> adapter=new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
10         ListView listview=(ListView)findViewById(R.id.list_view);
11         listview.setAdapter(adapter);
12     }
13 }

数组中的数据无法直接传递给ListView，需要借助适配器来实现。

ArrayAdapter的构造函数中依次传入当前上下文，ListView子项布局的id，以及要适配的数据；

调用ListView的setAdapter()方法，将构建好的适配器对象传递进去，这样ListView和数据之间的关联就建立完成。

运行程序，可以通过滚动的方式来查看屏幕外的数据。

二、定制ListView的界面

首先准备一组图片，分别对应上面提供的每一种水果（注意图片大小尽量一致），放在drawable目录下，注意命名不能出现大写字母（比如Apple不合法）；

在com.example.administrator.listviewtest下新建.java文件，定义一个实体类Fruit，作为ListView适配器的适配类型。

 1 public class Fruit{
 2     private String name;
 3     private int imageId;
 4     public Fruit(String name,int imageId){
 5         this.name=name;
 6         this.imageId=imageId;
 7     }
 8     public String getName(){
 9         return name;
10     }
11     public int getImageId(){
12         return imageId;
13     }
14 }

然后为ListView的子项指定一个自定义布局，在layout目录下新建fruit_item.xml。

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="match_parent"
 4     android:layout_height="wrap_content">
 5 
 6     <ImageView
 7         android:id="@+id/fruit_image"
 8         android:layout_width="wrap_content"
 9         android:layout_height="wrap_content" />
10 
11     <TextView
12         android:id="@+id/fruit_name"
13         android:layout_width="wrap_content"
14         android:layout_height="wrap_content"
15         android:layout_gravity="center_vertical"
16         android:layout_marginLeft="10dp"
17         />
18 </LinearLayout>

接下来创建一个自定义的适配器，同样在com.example.administrator.listviewtest下新建.java文件，重写了父类的一组构造函数，用于将上下文、ListView子项布局的id和数据都传递进来，命名为FruitAdapter，代码如下：

 1 public class FruitAdapter extends ArrayAdapter<Fruit> {
 2     private int resourceId;
 3     public FruitAdapter(Context context, int textViewResourceId, List<Fruit> objects){
 4         super(context,textViewResourceId,objects);
 5         resourceId=textViewResourceId;
 6     }
 7     @Override
 8     public View getView(int position,View convertView,ViewGroup parent){
 9         Fruit fruit=getItem(position);           //获取当前项的实例
10         View view= LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
11         ImageView fruitImage=(ImageView)view.findViewById(R.id.fruit_image);
12         TextView fruitName=(TextView) view.findViewById(R.id.fruit_name);
13         fruitImage.setImageResource(fruit.getImageId());
14         fruitName.setText(fruit.getName());
15         return view;
16     }
17 }

下面修改MainActivity中的代码：

 1 package com.example.administrator.listviewtest;
 2 
 3 import android.support.v7.app.AppCompatActivity;
 4 import android.os.Bundle;
 5 import android.widget.ArrayAdapter;
 6 import android.widget.ListView;
 7 
 8 import java.util.ArrayList;
 9 import java.util.List;
10 
11 public class MainActivity extends AppCompatActivity {
12     private List<Fruit> fruitList=new ArrayList<>();
13 
14 //  private String[] data={"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry","Mango","Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry","Mango"};
15     @Override
16     protected void onCreate(Bundle savedInstanceState) {
17         super.onCreate(savedInstanceState);
18         setContentView(R.layout.activity_main);
19         initFruits();                 //初始化水果数据
20         FruitAdapter adapter=new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
21 
22 //      ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_list_item_1, data);
23         ListView listview = (ListView) findViewById(R.id.list_view);
24         listview.setAdapter(adapter);
25     }
26 
27     private void initFruits(){
28         for(int i=0;i<2;i++){
29             Fruit apple=new Fruit("Apple",R.drawable.apple);
30             fruitList.add(apple);
31             Fruit orange=new Fruit("Orange",R.drawable.orange);
32             fruitList.add(orange);
33             Fruit banana=new Fruit("Banana",R.drawable.banana);
34             fruitList.add(banana);
35             Fruit waterlenmo=new Fruit("Waterlemon",R.drawable.waterlemon);
36             fruitList.add(waterlenmo);
37             Fruit pear=new Fruit("Pear",R.drawable.pear);
38             fruitList.add(pear);
39             Fruit grape=new Fruit("Grape",R.drawable.grape);
40             fruitList.add(grape);
41             Fruit pineapple=new Fruit("Pineapple",R.drawable.pineapple);
42             fruitList.add(pineapple);
43             Fruit strawberry=new Fruit("Strawberry",R.drawable.straw);
44             fruitList.add(strawberry);
45             Fruit cherry=new Fruit("Cherry",R.drawable.cherry);
46             fruitList.add(cherry);
47             Fruit mango=new Fruit("mango",R.drawable.mango);
48             fruitList.add(mango);
49         }
50     }
51 }

运行程序后，效果图如下（图片大小后来才意识到，懒得换了……）：