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Android开发实现ListView异步加载数据的方法详解

程序员文章站 2023-01-22 09:22:08
本文实例讲述了android开发实现listview异步加载数据的方法。分享给大家供大家参考，具体如下： 1.主activity public class ma...

本文实例讲述了android开发实现listview异步加载数据的方法。分享给大家供大家参考，具体如下：

1.主activity

public class mainactivity extends activity {
  private listview listview;
  private arraylist<person> persons;
  private listadapter adapter;
  private handler handler=null;
  //xml文件的网络地址
  final string path="http://192.168.5.10:8080/fileserver/person.xml";
  @suppresslint("handlerleak")
  protected void oncreate(bundle savedinstancestate) {
    super.oncreate(savedinstancestate);
    setcontentview(r.layout.main);
    listview=(listview) super.findviewbyid(r.id.listview);
    //cache=new file(environment.getexternalstoragedirectory().getabsolutepath()+"/cache");
    //开一条子线程加载网络数据
    runnable runnable=new runnable()
    {
      public void run() 
      {
        try 
        {
          thread.sleep(2000);
          //xmlwebdata解析网络中xml中的数据
          persons=xmlwebdata.getdata(path);
          //发送消息，并把persons结合对象传递过去
          handler.sendmessage(handler.obtainmessage(0, persons));
        } 
        catch (interruptedexception e) 
        {
          e.printstacktrace();
        }
      }
    };
    try 
    {
      //开启线程
      new thread(runnable).start();
      //handler与线程之间的通信及数据处理
      handler=new handler()
      {
        public void handlemessage(message msg) 
        {
          if(msg.what==0)
          {
            //msg.obj是获取handler发送信息传来的数据
            @suppresswarnings("unchecked")
            arraylist<person> person=(arraylist<person>) msg.obj;
            //给listview绑定数据
            binderlistdata(person);
          }
        }
      };
    } 
    catch (exception e) 
    {
      e.printstacktrace();
    }
  }
  //绑定数据
  public void binderlistdata(arraylist<person> person)
  {
    //创建adapter对象
    adapter=new listviewadapter(r.layout.item,this,person);
    //将adapter绑定到listview中
    listview.setadapter(adapter);
  }
}

2.从网络中获取xml文件并解析数据

public class xmlwebdata 
{
  private static arraylist<person> persons=null; 6   public static arraylist<person> getdata(final string path)
  {
        try 
        {
          url url=new url(path);
          person person=null;
          httpurlconnection conn=(httpurlconnection) url.openconnection();
          conn.setrequestmethod("get");
          conn.setconnecttimeout(5000);
          if(conn.getresponsecode()==200)
          {
            inputstream inputstream=conn.getinputstream(); 
            xmlpullparser xml=xml.newpullparser();
            xml.setinput(inputstream, "utf-8");
            int event=xml.geteventtype();
            while(event!=xmlpullparser.end_document)
            {
              switch (event) 
              {
              //开始解析文档
              case xmlpullparser.start_document:
                persons=new arraylist<person>();
                break;
              case xmlpullparser.start_tag:
                string value=xml.getname();
                if(value.equals("person"))
                {//person对象的初始化必须在这里初始化不然可能出现为null的现象
                  person=new person();
                  //获取属性值
                  person.setid(new integer(xml.getattributevalue(0)));
                }
                else if(value.equals("name"))
                {
                  person.setname(xml.nexttext());
                }
                else if(value.equals("sex"))
                {
                  person.setsex(xml.nexttext());
                }
                else if(value.equals("age"))
                {
                  person.setage(new integer(xml.nexttext()));
                }
                else if(value.equals("path"))
                {
                  person.setpath(xml.nexttext());
                }
                break;
              case xmlpullparser.end_tag:
                if(xml.getname().equals("person"))
                {
                  persons.add(person);
                  system.out.println(person.getname());;
                  person=null;
                }
                break;
              }
              //解析下一个对象
              event=xml.next();
            }
            return persons;
          }
        } 
        catch (exception e) 
        {
          e.printstacktrace();
        } 
    return null;
  }
}

3.person对象类

public class person 
{
  private int id;
  private string name;
  private string sex;
  private string path;
  public string getpath() {
    return path;
  }
  public void setpath(string path) {
    this.path = path;
  }
  private int age;
  public int getid() {
    return id;
  }
  public void setid(int id) {
    this.id = id;
  }
  public string getname() {
    return name;
  }
  public void setname(string name) {
    this.name = name;
  }
  public string getsex() {
    return sex;
  }
  public void setsex(string sex) {
    this.sex = sex;
  }
  public int getage() {
    return age;
  }
  public void setage(int age) {
    this.age = age;
  }
  public person(){
  }
}

4.adapter数据适配器类

public class listviewadapter extends baseadapter implements listadapter 
{
  private arraylist<person> data;
  private int id;
  private context context;
  private layoutinflater inflater;
  public listviewadapter(int item, mainactivity mainactivity,arraylist<person> data) 
  {
    this.data=data;
    this.context=mainactivity;
    this.id=item;
    inflater=layoutinflater.from(context);
  }
  @override
  public int getcount() 
  {
    return data.size();
  }
  @override
  public object getitem(int position) 
  {
    return data.get(position);
  }
  @override
  public long getitemid(int position)
  {
    return position;
  }
  @override
  public view getview(int position, view view, viewgroup arg2)
  {
    textview name=null;
    textview sex=null;
    textview age=null;
    imageview img=null;
    if(view==null)
    {
      view=inflater.inflate(id, null);
      name=(textview) view.findviewbyid(r.id.personname);
      sex=(textview) view.findviewbyid(r.id.personsex);
      age=(textview) view.findviewbyid(r.id.personage);
      img=(imageview) view.findviewbyid(r.id.personimage);
      //保存view对象到objectclass类中
      view.settag(new objectclass(name,sex,age,img));
    }
    else
    {
      //得到保存的对象
      objectclass objectclass=(objectclass) view.gettag();
      name=objectclass.name;
      sex=objectclass.sex;
      age=objectclass.age;
      img=objectclass.img;
    }
    person person=(person) data.get(position);
    //帮数据绑定到控件上
    name.settext(person.getname().tostring());
    sex.settext("性别："+person.getsex().tostring());
    age.settext("年龄："+string.valueof(person.getage()));
    //加载图片资源
    loadimage(img,person.getpath());
    return view;
  }
  private void loadimage(imageview img, string path) 
  {
    //异步加载图片资源
    asynctaskimageload async=new asynctaskimageload(img);
    //执行异步加载，并把图片的路径传送过去
    async.execute(path);
  }
  private final class objectclass
  {
    textview name=null;
    textview sex=null;
    textview age=null;
    imageview img=null;
    public objectclass(textview name, textview sex, textview age,imageview img) 
    {
      this.name=name;
      this.sex=sex;
      this.age=age;
      this.img=img;
    }
  }
}

5.异步加载图片类

public class asynctaskimageload extends asynctask<string, integer, bitmap> {
  private imageview image=null;
  public asynctaskimageload(imageview img) 
  {
    image=img;
  }
  //运行在子线程中
  protected bitmap doinbackground(string... params) {
    try 
    {
      url url=new url(params[0]);
      httpurlconnection conn=(httpurlconnection) url.openconnection();
      conn.setrequestmethod("post");
      conn.setconnecttimeout(5000);
      if(conn.getresponsecode()==200)
      {
        inputstream input=conn.getinputstream();
        bitmap map=bitmapfactory.decodestream(input);
        return map;
      }
    } catch (exception e) 
    {
      e.printstacktrace();
    }
    return null;
  }
  protected void onpostexecute(bitmap result)
  {
    if(image!=null && result!=null)
    {
      image.setimagebitmap(result);
    }
    super.onpostexecute(result);
  }
}

6.网络中的person.xml文件内容为

<?xml version="1.0" encoding="utf-8"?>
<persons>
  <person id="1">
    <name>张三</name>
    <sex>男</sex>
    <age>25</age>
    <path>http://192.168.5.10:8080/fileserver/chengjisihan.jpg</path>
  </person>
  <person id="2">
    <name>李斯</name>
    <sex>男</sex>
    <age>78</age>
    <path>http://192.168.5.10:8080/fileserver/laozi.jpg</path>
  </person>
  <person id="3">
    <name>王五</name>
    <sex>男</sex>
    <age>22</age>
    <path>http://192.168.5.10:8080/fileserver/lilongji.jpg</path>
  </person>
  <person id="4">
    <name>庞聪</name>
    <sex>男</sex>
    <age>31</age>
    <path>http://192.168.5.10:8080/fileserver/lishimin.jpg</path>
  </person>
  <person id="5">
    <name>孙膑</name>
    <sex>男</sex>
    <age>48</age>
    <path>http://192.168.5.10:8080/fileserver/lisi.jpg</path>
  </person>
  <person id="6">
    <name>孙武</name>
    <sex>男</sex>
    <age>58</age>
    <path>http://192.168.5.10:8080/fileserver/liyuan.jpg</path>
  </person>
  <person id="7">
    <name>成吉思汗</name>
    <sex>男</sex>
    <age>40</age>
    <path>http://192.168.5.10:8080/fileserver/sunbiin.jpg</path>
  </person>
  <person id="8">
    <name>李渊</name>
    <sex>男</sex>
    <age>36</age>
    <path>http://192.168.5.10:8080/fileserver/sunwu.jpg</path>
  </person>
  <person id="9">
    <name>李隆基</name>
    <sex>男</sex>
    <age>32</age>
    <path>http://192.168.5.10:8080/fileserver/wangwu.jpg</path>
  </person>
  <person id="10">
    <name>武则天</name>
    <sex>女</sex>
    <age>55</age>
    <path>http://192.168.5.10:8080/fileserver/wuzetian.jpg</path>
  </person>
</persons>
<?xml version="1.0" encoding="utf-8"?>
<persons>
  <person id="1">
    <name>张三</name>
    <sex>男</sex>
    <age>25</age>
    <path>http://192.168.5.10:8080/fileserver/chengjisihan.jpg</path>
  </person>
  <person id="2">
    <name>李斯</name>
    <sex>男</sex>
    <age>78</age>
    <path>http://192.168.5.10:8080/fileserver/laozi.jpg</path>
  </person>
  <person id="3">
    <name>王五</name>
    <sex>男</sex>
    <age>22</age>
    <path>http://192.168.5.10:8080/fileserver/lilongji.jpg</path>
  </person>
  <person id="4">
    <name>庞聪</name>
    <sex>男</sex>
    <age>31</age>
    <path>http://192.168.5.10:8080/fileserver/lishimin.jpg</path>
  </person>
  <person id="5">
    <name>孙膑</name>
    <sex>男</sex>
    <age>48</age>
    <path>http://192.168.5.10:8080/fileserver/lisi.jpg</path>
  </person>
  <person id="6">
    <name>孙武</name>
    <sex>男</sex>
    <age>58</age>
    <path>http://192.168.5.10:8080/fileserver/liyuan.jpg</path>
  </person>
  <person id="7">
    <name>成吉思汗</name>
    <sex>男</sex>
    <age>40</age>
    <path>http://192.168.5.10:8080/fileserver/sunbiin.jpg</path>
  </person>
  <person id="8">
    <name>李渊</name>
    <sex>男</sex>
    <age>36</age>
    <path>http://192.168.5.10:8080/fileserver/sunwu.jpg</path>
  </person>
  <person id="9">
    <name>李隆基</name>
    <sex>男</sex>
    <age>32</age>
    <path>http://192.168.5.10:8080/fileserver/wangwu.jpg</path>
  </person>
  <person id="10">
    <name>武则天</name>
    <sex>女</sex>
    <age>55</age>
    <path>http://192.168.5.10:8080/fileserver/wuzetian.jpg</path>
  </person>
</persons>

运行结果如下

Android开发实现ListView异步加载数据的方法详解

更多关于android相关内容感兴趣的读者可查看本站专题：《android控件用法总结》、《android开发入门与进阶教程》、《android视图view技巧总结》、《android编程之activity操作技巧总结》、《android数据库操作技巧总结》及《android资源操作技巧汇总》

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