android UI控件之ListView详解之一listView+BaseAdpater

android UI控件之ListView详解之一listView+BaseAdpater

BaseAdpater是一个抽象类，也是自定义ListView时，自定义的适配器要继承BaseAdpater，也是ArrayAdpater,SimpleAdpater的父类。

baseAdpater的抽象方法。

public int getCount()

得到Item条目的总数
public Object getItem(int i)

根据i（位置）得到某个Item的对象
public long getItemId(int i)

根据i（位置）得到某个Item的id
public View getView(int i,View view, ViewGroup viewGroup)

得到相应i对应的Item视图，i是当前Item的位置，view用于复用旧视图，viewGroup用于加载XML布局

由于Android Studio的更新，方法提示变了，i对应着position（下标），view对应着convertView，viewGroup对应着parent。

自定义ListView，一个MainActivity.java、Info.java(Item的封装类)、main_activity.xml(包含ListView控件的布局)、item_simple_adpater.xml(自定义的布局)

代码MainActivity.java：

package momo.yuan.com.listviewdemo;

import android.icu.text.IDNA;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

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

public class MainActivity extends AppCompatActivity {
    private ListView LV;
    private List<Info> data;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        LV=(ListView)findViewById(R.id.LV);
        //准备集合数据
        data=new ArrayList<Info>();
        data.add(new Info(R.drawable.m1, "name>>>>1", "content----1"));
        data.add(new Info(R.drawable.m2, "name>>>>2", "content----2"));
        data.add(new Info(R.drawable.m3, "name>>>>3", "content----3"));
        data.add(new Info(R.drawable.m4, "name>>>>4", "content----4"));
        data.add(new Info(R.drawable.m5, "name>>>>5", "content----5"));
        data.add(new Info(R.drawable.m6, "name----6", "content----6"));
        data.add(new Info(R.drawable.m7, "name----7", "content----7"));
        data.add(new Info(R.drawable.m8, "name----8", "content----8"));
        data.add(new Info(R.drawable.m9, "name----9", "content----9"));
        //准备BaseAdapter对象
        MyAdpater adpater=new MyAdpater();
        //设置Adapter显示列表\
        LV.setAdapter(adpater);

    }
    class MyAdpater extends BaseAdapter{
        @Override
        //返回集合数据的数量,data
        public int getCount() {
            return data.size();
        }
        @Override
        //返回指定下标对应的数据对象
        public Object getItem(int i) {
            return data.get(i);
        }
        @Override
        public long getItemId(int i) {
            return 0;
        }
        @Override
        /**
         * 返回指定下标所对应的item的View对象
         * position : 下标
         * convertView : 可复用的缓存Item视图对象, 前n+1个为null
         * parent : ListView对象
         */
        public View getView(int i, View view, ViewGroup viewGroup) {
            //如果没有复用的
            if(view==null) {//涉及到ListView的优化（内存的益处），此处必须有这么一个判断
                //加载item的布局, 得到View对象
                view = View.inflate(MainActivity.this, R.layout.item_simple_adapter, null);
            }
            //根据position设置对应的数据
            //得到当前行的数据对象
            Info shopInfo = data.get(i);
            //得到子View对象，一定要注意，此时的findviewbyid不是mian_activity.xml中的id，而是item_simple_adapter中的
            ImageView imageView = (ImageView) view.findViewById(R.id.icon);
            TextView nameTV = (TextView) view.findViewById(R.id.tv_name);
            TextView contentTV = (TextView) view.findViewById(R.id.tv_content);
            //设置数据，给相应的id对应的控件添加数据
            imageView.setImageResource(shopInfo.getIcon());
            nameTV.setText(shopInfo.getName());
            contentTV.setText(shopInfo.getContent());

            return view;//返回视图
        }
    }
}

Info.java:写三个属性，对应要显示的icon、name、content

package momo.yuan.com.listviewdemo;

/**
 * 对每行的Item数据进行封装
 */

class Info {
    private int icon;
    private String name;
    private String content;
    public Info(int icon, String name, String content) {
        super();
        this.icon = icon;
        this.name = name;
        this.content = content;
    }
    public int getIcon() {
        return icon;
    }

    public String getName() {
        return name;
    }

    public String getContent() {
        return content;
    }

    public void setIcon(int icon) {
        this.icon = icon;
    }

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

    public void setContent(String content) {
        this.content = content;
    }

    @Override
    public String toString() {
        return "Info{" + "icon=" + icon + ", name='" + name + '\'' + ", content='" + content + '\'' + '}';
    }


}

item_simple_adpater.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="wrap_content"
    android:orientation="horizontal" >

    <ImageView
        android:id="@+id/icon"
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:src="@drawable/m1" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" 
        android:gravity="center_vertical"
        android:layout_marginLeft="10dp">

        <TextView
            android:id="@+id/tv_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView" />

        <TextView
            android:id="@+id/tv_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView" />

    </LinearLayout>

</LinearLayout>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="momo.yuan.com.listviewdemo.MainActivity">
    <ListView
        android:id="@+id/LV"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        ></ListView>
</RelativeLayout>