Android新手开发之旅-BaseAdapter的使用

liu

BaseAdapter的使用



相比较于ArrayAdapter和SimpleAdapter，使用BaseAdapter会更加的灵活，使用时先自定义一个MyAdapter(名字随便起)继承BaseAdapter，并实现其中的方法





举例：


先写主布局，就放入一个ListView

activity_main.xml:

[XML] 纯文本查看 复制代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical">

    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
</LinearLayout>

接下来写item布局，用来显示每条数据的样式

item布局：

[XML] 纯文本查看 复制代码

<?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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:gravity="center_vertical"
        android:orientation="horizontal">

        <ImageView
            android:id="@+id/iv"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:layout_marginLeft="10dp" />

        <TextView
            android:id="@+id/tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="20dp"
            android:textColor="@android:color/black"
            android:textSize="16sp" />
    </LinearLayout>
</LinearLayout>

创建实体类

实体类：

[Java] 纯文本查看 复制代码

package com.company.helloworld.firstapplication;

/**
 * Created by Administrator on 2018/12/13.
 */

public class WeaponBean {
    public int img;       //图片
    public String name;   //名字

    public WeaponBean(int img, String name) {
        this.img = img;
        this.name = name;
    }

    public int getImg() {
        return img;
    }

    public void setImg(int img) {
        this.img = img;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

然后写适配器，用于绑定数据

MyAdapter:

[Java] 纯文本查看 复制代码

package com.company.helloworld.firstapplication;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

/**
 * Created by Administrator on 2018/12/13.
 */

public class MyAdapter extends BaseAdapter {
    private Context context;         //上下文对象
    private List<WeaponBean> list;   //数据

    /**
     * @param context 上下文对象
     * @param list    要绑定的数据
     */
    public MyAdapter(Context context, List<WeaponBean> list) {
        this.context = context;
        this.list = list;
    }

    //返回数据的总数
    @Override
    public int getCount() {
        return list.size();
    }

    //返回 在list中指定位置的数据内容
    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    //返回数据在list中的位置
    @Override
    public long getItemId(int position) {
        return position;
    }

    //设置ListView每一行的布局和数据绑定
    @Override
    public View getView(int position, View convertView, ViewGroup viewGroup) {
        ViewHolder holder;
        //判断convertView，为空则创建，并设置tag，不为空则通过tag取出ViewHolder,减少findViewById次数，达到优化的目的
        if (convertView == null) {
            holder = new ViewHolder();
            //将布局文件转化为View对象
            convertView = LayoutInflater.from(context).inflate(R.layout.item_weapon, null);
            //初始化控件
            holder.iv = (ImageView) convertView.findViewById(R.id.iv);
            holder.tv = (TextView) convertView.findViewById(R.id.tv);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        //将数据绑定到指定控件
        holder.iv.setImageResource(list.get(position).img);
        holder.tv.setText(list.get(position).name);
        return convertView;
    }

    //用于缓存控件
    public class ViewHolder {
        private ImageView iv;
        private TextView tv;
    }
}

最后主页面中给ListView设置适配器

MainActivity：

[Java] 纯文本查看 复制代码

package com.company.helloworld.firstapplication;

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

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

public class MainActivity extends AppCompatActivity {
    String[] data = {"M416", "AWM", "M24", "AK47", "平底锅"};
    private ListView mListView;
    private List<WeaponBean> list;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        addData();
        initView();
    }

    //创建数据
    private void addData() {
        list = new ArrayList<>();
        WeaponBean weaponBean = new WeaponBean(R.drawable.m4, "M416");
        WeaponBean weaponBean2 = new WeaponBean(R.drawable.awm, "AWM");
        WeaponBean weaponBean3 = new WeaponBean(R.drawable.m24, "M24");
        WeaponBean weaponBean4 = new WeaponBean(R.drawable.ak, "AK47");
        WeaponBean weaponBean5 = new WeaponBean(R.drawable.pdg, "神器平底锅");
        list.add(weaponBean);
        list.add(weaponBean2);
        list.add(weaponBean3);
        list.add(weaponBean4);
        list.add(weaponBean5);
    }

    private void initView() {
        mListView = (ListView) findViewById(R.id.lv);
        MyAdapter adapter = new MyAdapter(this, list);
        //listview设置适配器
        mListView.setAdapter(adapter);
    }

}

看下效果：


        

站长苏飞

我只是路过打酱油的。

惜

激动人心，无法言表！

竹林风

真是难得给力的帖子啊。

Amy

真是难得给力的帖子啊。