第七天ListView与BaseAdapter适配器混合运用

最新推荐文章于 2022-03-15 09:14:33 发布

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最新推荐文章于 2022-03-15 09:14:33 发布

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分类专栏：学习博客文章标签：运用于新闻显示等 listview 布局

本文链接：https://blog.youkuaiyun.com/youzi749/article/details/52107364

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创建主布局文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.jeredu.administrator.classday7application.listdemo.List3Activity">
    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/lv3"></ListView>
</RelativeLayout>

其中在ListView标签当中还这些标签

listSelector 背景颜色
scrollbars  是否显示有侧边滑动条；有三个属性，不显示为none
dividerHeight  ListView布局中的分割线效果可以设置宽度

用来创建Activity主布局文件用来显示ListView

创建BaseAdapter调用布局，用在主布局上显示新闻所需要的标签图片等

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="我是标题"
        android:id="@+id/title"
        android:layout_centerHorizontal="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:id="@+id/from"
        android:text="未来网"
        android:layout_below="@+id/iv"
        android:layout_alignParentStart="true" />
    <ImageView
            android:layout_width="60dp"
            android:layout_height="60dp"
            android:src="@mipmap/ic_launcher"
            android:id="@+id/iv"
            android:scaleType="centerCrop"
            android:layout_below="@+id/title"
            android:layout_alignParentEnd="true" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="今天  "
        android:id="@+id/pubDate"
        android:gravity="center"
        android:layout_alignEnd="@+id/iv"
        android:layout_below="@+id/iv"
        android:layout_alignStart="@+id/iv" />
</RelativeLayout>

这就是新闻的一条，然后通过BaseAdapter方法调用在主布局ListView实现多条新闻

编写BaseAdapter方法首先创建新闻类

<span style="font-size:12px;">package com.jeredu.administrator.classday7application.entity;

/**
 * Created by Administrator on 2016/8/3.
 */
public class News {
    private  String title;
    private  String pubDate;
    private String newID;
    private int img;
    private  String from;
    public News (){}
    public News(String title, String pubDate, String newID, int img, String from) {
        this.title = title;
        this.pubDate = pubDate;
        this.newID = newID;
        this.img = img;
        this.from = from;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getPubDate() {
        return pubDate;
    }

    public void setPubDate(String pubDate) {
        this.pubDate = pubDate;
    }

    public String getNewID() {
        return newID;
    }

    public void setNewID(String newID) {
        this.newID = newID;
    }

    public int getImg() {
        return img;
    }

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

    public String getFrom() {
        return from;
    }

    public void setFrom(String from) {
        this.from = from;
    }</span>
<span style="font-size:12px;">}</span>

新闻类当中包含新闻布局里面的标题时间图片来源布局中所用的标签

编写BaseAdapter方法

package com.jeredu.administrator.classday7application.entity;

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 android.widget.Toast;

import com.jeredu.administrator.classday7application.R;

import java.util.List;

/**
 * Created by Administrator on 2016/8/3.
 */
public class MyListAdaper extends BaseAdapter{
    private List<News>myDate;
    private Context context;
    public  MyListAdaper(Context context,List<News>myDate){
        this.myDate=myDate;
        this.context=context;
    }
    @Override
    public int getCount() {
        return myDate.size();
    }

    @Override
    public Object getItem(int i) {
        return myDate.get(i);
    }

    @Override
    public long getItemId(int i) {
        return 0;
    }

    @Override
    public View getView(final int i, View view, ViewGroup viewGroup) {
<span style="color:#FF6666;">//        View view= LayoutInflater.from(context).inflate(R.layout.list3_layout_base,null);
//        TextView title= (TextView) view.findViewById(R.id.title);
//        TextView pubDate= (TextView) view.findViewById(R.id.pubDate);
//        TextView from= (TextView) view.findViewById(R.id.from);
//        ImageView img = (ImageView) view.findViewById(R.id.iv);
//        News news =myDate.get(i);
//        title.setText(news.getTitle());
//        pubDate.setText(news.getPubDate());
//        from.setText(news.getFrom());
//        img.setImageResource(news.getImg());</span>
        ViewHolder vh ;
        if(view == null){
            vh = new ViewHolder();
            view = LayoutInflater.from(context).inflate(R.layout.list3_layout_base,null);
            vh.title= (TextView)view.findViewById(R.id.title);
            vh.img = (ImageView) view.findViewById(R.id.iv);
            vh.pubDate= (TextView) view.findViewById(R.id.pubDate);
            vh.from= (TextView) view.findViewById(R.id.from);
            view.setTag(vh);
        }else{
            vh=(ViewHolder) view.getTag();
        }
        vh.img.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(context,"点击了图片"+i,Toast.LENGTH_SHORT).show();
            }
        });
        News news =myDate.get(i);
        vh.title.setText(news.getTitle());
        vh.pubDate.setText(news.getPubDate());
        vh.from.setText(news.getFrom());
        vh.img.setImageResource(news.getImg());
        return view;
    }

    public class ViewHolder{
        TextView title;
        ImageView img;
        TextView pubDate;
        TextView from;

    }
}

方法中红色字体写的是不考虑资源占用等因素直接编写的方法，而另一种采用ViewHolder这种方法资源占有少，只用创建一次或是说调用一次布局文件，之后执行else之后的内容进行往主布局里面写新闻

主布局编写代码调用方法，并把所要添加的新闻

<span style="font-size:12px;">package com.jeredu.administrator.classday7application.listdemo;

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

import com.jeredu.administrator.classday7application.R;
import com.jeredu.administrator.classday7application.entity.MyListAdaper;
import com.jeredu.administrator.classday7application.entity.News;

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

public class List3Activity extends AppCompatActivity {
 private ListView lv3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list3);
        lv3= (ListView) findViewById(R.id.lv3);
        List<News> list = new ArrayList();
        News ns =new News("新闻1","刚刚","n001",R.mipmap.ic_launcher,"新浪网");
        list.add(ns);
        ns =new News("新闻2","今天","n002",R.mipmap.ic_launcher,"腾讯网");
        list.add(ns);
        ns =new News("新闻3","昨天","n003",R.mipmap.ic_launcher,"百度网");
        list.add(ns);
        ns =new News("新闻4","刚刚","n004",R.mipmap.ic_launcher,"新浪网");
        list.add(ns);
        ns =new News("新闻5","刚刚","n005",R.mipmap.ic_launcher,"新浪网");
        list.add(ns);
        ns =new News("新闻6","刚刚","n006",R.mipmap.ic_launcher,"新浪网");
        list.add(ns);
        ns =new News("新闻7","刚刚","n007",R.mipmap.ic_launcher,"新浪网");
        list.add(ns);
        ns =new News("新闻8","刚刚","n008",R.mipmap.ic_launcher,"新浪网");
        list.add(ns);
        lv3.setAdapter(new MyListAdaper(this,list));
    }
}</span>
一共写了8条新闻在运行之后可以在ListView里面看到8条新闻