深入浅出学习Android ListView基础

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

<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>

2、新建一个javabean

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;
  }
}

3、新建icon_item.xml 用于 listview 每个元素的视图

<?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>

4、新建一个class iconadapter 继承自 arrayadapter

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;
  }
}

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

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);
  }


}

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。