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

9bee
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>