listview 简介
listview 是安卓里常用的控件， 本文介绍一下常用用法，以及优化等方法
1、改写activity_main.xml
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<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
<listview
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</linearlayout>
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2、新建一个javabean
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package com.example.tomchen.testlistview;
public class icon {
private int imageid;
private string name;
public icon(string name, int imageid) {
this.name = name;
this.imageid = imageid;
}
public string getname() {
return name;
}
public int getimageid() {
return imageid;
}
}
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3、新建icon_item.xml 用于 listview 每个元素的视图
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<?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="horizontal">
<textview
android:id="@+id/text"
android:layout_width="wrap_content"
android:layout_height="match_parent" />
<imageview
android:id="@+id/icon"
android:layout_width="wrap_content"
android:layout_height="match_parent" />
</linearlayout>
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4、新建一个class iconadapter 继承自 arrayadapter
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package com.example.tomchen.testlistview;
import android.content.context;
import android.view.layoutinflater;
import android.view.view;
import android.view.viewgroup;
import android.widget.arrayadapter;
import android.widget.imageview;
import android.widget.textview;
import java.util.list;
public class iconadapter extends arrayadapter<icon> {
private int resourceid;
public iconadapter(context context, int resource, list<icon> icons) {
super(context, resource, icons);
this.resourceid = resource;
}
@override
public view getview(int position, view convertview, viewgroup parent) {
icon icon = getitem(position);
view view;
if (convertview == null) {
view = layoutinflater.from(getcontext()).inflate(resourceid, null);
} else {
view = convertview;
}
imageview image = (imageview) view.findviewbyid(r.id.icon);
image.setimageresource(icon.getimageid());
textview text = (textview) view.findviewbyid(r.id.text);
text.settext(icon.getname());
return view;
}
}
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note
这儿有了一个优化, convertview 将之前的布局进行缓存, 以便之后进行重用.
所以我们判断convertview是否为空. 空的话就使用layoutinflater去加载布局, 否则的话就直接复用convertview
测试listview
mainactivity里面加入下面代码
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package com.example.tomchen.testlistview;
import android.support.v7.app.appcompatactivity;
import android.os.bundle;
import android.view.menu;
import android.view.menuitem;
import android.widget.listview;
import java.util.arraylist;
import java.util.list;
public class mainactivity extends appcompatactivity {
private listview listview;
private list<icon> icons = new arraylist<icon>();
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_main);
listview = (listview) findviewbyid(r.id.listview);
icons.add(new icon("icon_01", r.drawable.ic_01));
icons.add(new icon("icon_02", r.drawable.ic_02));
icons.add(new icon("icon_03", r.drawable.ic_03));
icons.add(new icon("icon_04", r.drawable.ic_04));
icons.add(new icon("icon_05", r.drawable.ic_05));
icons.add(new icon("icon_06", r.drawable.ic_06));
icons.add(new icon("icon_07", r.drawable.ic_07));
icons.add(new icon("icon_08", r.drawable.ic_08));
icons.add(new icon("icon_09", r.drawable.ic_09));
iconadapter adapter = new iconadapter(this, r.layout.icon_item, icons);
listview.setadapter(adapter);
}
}
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效果图如下：
以上就是本文的全部内容，希望对大家的学习android程序设计有所帮助。