Android：适配器(Adapter)的使用

Posted 2021-08-07 Z|Star

一、什么是适配器

在常见软件中，往往能看到列表一样的信息流，例如：

如果在xml中将信息写死，那显然是不合适的，无法做到上拉刷新的效果。
这个时候，就需要用到适配器。

二、Adapter基本概念和继承关系

三、自定义适配器实例

1.文件结构

2.xml内容

main.xml:

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/listview"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical">
</ListView>

listview_item.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="100dp"
    android:gravity="center_vertical"
    android:orientation="horizontal"
    android:padding="15dp">
    <ImageView
        android:id="@+id/img_icon"
        android:layout_width="130dp"
        android:layout_height="80dp"
        android:src="@mipmap/news"/>
    <RelativeLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_weight="1">
        <TextView
            android:id="@+id/tv_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:text="我是一个新闻标题---- 1"
            android:textColor="#000000"
            android:textSize="18dp" />
        <TextView
            android:id="@+id/tv_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:text="我是新闻内容---- 1"
            android:textColor="#000000"
            android:textSize="14dp" />
    </RelativeLayout>
</LinearLayout>

3.java内容

MainActivity

package cn.edu.cdut.testadapter;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.Toast;

import java.util.LinkedList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private List<News> mData = null;
    private Context mContext;
    private NewsAdapter mAdapter = null;
    private ListView listView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        listView = (ListView) findViewById(R.id.listview);
        mData = new LinkedList<News>();
        for (int i = 0; i < 10; i++) {
            mData.add(new News("我是一个新闻标题---- " + i, "我是一个新闻内容---- " + i, R.mipmap.news));
        }
        mAdapter = new NewsAdapter(mData, mContext);
        listView.setAdapter(mAdapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int
                    position, long id) {
                Toast.makeText(mContext, "点击了第" + position + "条数据",
                        Toast.LENGTH_SHORT).show();
            }
        });
    }
}

News.java

package cn.edu.cdut.testadapter;

public class News {
    private String title;
    private String content;
    private int aIcon;
    public News() {
    }
    public News(String title, String content, int aIcon) {
        this.title = title;
        this.content = content;
        this.aIcon = aIcon;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public String getContent() {
        return content;
    }
    public void setContent(String content) {
        this.content = content;
    }
    public int getaIcon() {
        return aIcon;
    }
    public void setaIcon(int aIcon) {
        this.aIcon = aIcon;
    }
}

NewsAdapter

package cn.edu.cdut.testadapter;

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;

public class NewsAdapter extends BaseAdapter {
    private List<News> mData;
    private Context mContext;
    public NewsAdapter(List<News> mData, Context mContext) {
        this.mData = mData;
        this.mContext = mContext;
    }
    @Override
    public int getCount() {
        return mData.size();
    }
    @Override
    public Object getItem(int position) {
        return mData.get(position);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        convertView =
                LayoutInflater.from(mContext).inflate(R.layout.listview_item,
                        parent, false);
        ImageView img_icon = (ImageView)
                convertView.findViewById(R.id.img_icon);
        TextView title = (TextView)
                convertView.findViewById(R.id.tv_title);
        TextView content = (TextView)
                convertView.findViewById(R.id.tv_content);
        img_icon.setBackgroundResource(mData.get(position).getaIcon());
        title.setText(mData.get(position).getTitle());
        content.setText(mData.get(position).getContent());
        return convertView;
    }
}

四、参考资料

https://gitee.com/hwdroid/HelloWorld