ListView的用法

一个可向下滑动的列表

main.xml

<?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"
    >
    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>


</LinearLayout>

main.java

其中使用可适配器

package com.example.listviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {
    private String[] data={"梨","苹果","沙果","海棠","野樱莓","山楂","梨","杏","樱桃","桃","李子","梅子","草莓","菠萝","橘子","橙子","柠檬","金桔","哈密瓜","香瓜","香蕉"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ArrayAdapter<String> adapter=new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data);
        ListView listView=(ListView)findViewById(R.id.listView);
        listView.setAdapter(adapter);
    }
}

ListView添加图片和优化代码

1定义实体类Fruit

public class Fruit {
    private String name;
    private int imageId;
    public Fruit(String name,int imageId){
        this.name=name;
        this.imageId=imageId;
    }
    public String getName(){
        return name;
    }
    public int getImageId(){
        return imageId;
    }
}

2添加fruit_item.xml布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginLeft="10dp"/>
</LinearLayout>

3定义适配器

package com.example.listviewtest;

import android.content.Context;
import android.support.annotation.NonNull;
import android.view.LayoutInflater;
import android.view.TextureView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

/**
 * Created by lenovo on 2019/1/25.
 */

public class FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceid;

　　//用于储存控件的实例
    class ViewHolder{
        ImageView fruitImage;
        TextView fruitName;
    }

　　//textViewRecourceId为子布局id
    public FruitAdapter(Context context, int textViewRecourceId, List<Fruit> objects){
        super(context,textViewRecourceId,objects);
        resourceid=textViewRecourceId;

    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Fruit fruit=getItem(position);
        View view;
        ViewHolder viewHolder;
        if(convertView==null) {
            view = LayoutInflater.from(getContext()).inflate(resourceid, parent, false);
            viewHolder=new ViewHolder();
            viewHolder.fruitImage=(ImageView)view.findViewById(R.id.fruit_image);
            viewHolder.fruitName=(TextView)view.findViewById(R.id.fruit_name);
            view.setTag(viewHolder);//将viewHolder放入到view中
        }else
        {
            view=convertView;
            viewHolder=(ViewHolder)view.getTag();//将viewHolder取出，此步骤避免了每次都要用find获取空间实例的问题

        }

        viewHolder.fruitImage.setImageResource(fruit.getImageId());
        viewHolder.fruitName.setText(fruit.getName());
        return view;
    }
}

4main.java

package com.example.listviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private List<Fruit> fruitList=new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits();
        FruitAdapter adapter=new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView=(ListView)findViewById(R.id.listView);
        listView.setAdapter(adapter);
    }
    private void initFruits(){
        for(int i=0;i<2;i++) {
            Fruit f1 = new Fruit("梨", R.drawable.p1);
            fruitList.add(f1);
            Fruit f2 = new Fruit("苹果", R.drawable.p2);
            fruitList.add(f2);
            Fruit f3 = new Fruit("沙果", R.drawable.p3);
            fruitList.add(f3);
            Fruit f4 = new Fruit("海棠", R.drawable.p4);
            fruitList.add(f4);
            Fruit f5 = new Fruit("野樱莓", R.drawable.p5);
            fruitList.add(f5);
            Fruit f6 = new Fruit("山楂", R.drawable.p6);
            fruitList.add(f6);
            Fruit f7 = new Fruit("杏", R.drawable.p7);
            fruitList.add(f7);
            Fruit f8 = new Fruit("樱桃", R.drawable.p8);
            fruitList.add(f8);
            Fruit f9 = new Fruit("李子", R.drawable.p9);
            fruitList.add(f9);
            Fruit f10 = new Fruit("草莓", R.drawable.p10);
            fruitList.add(f10);

        }




    }
}

添加点击事件

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initFruits();
    FruitAdapter adapter=new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
    ListView listView=(ListView)findViewById(R.id.listView);
    listView.setAdapter(adapter);
    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_SHORT).show();
        }
    });
}