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Android开发实现ListView异步加载数据的方法详解

时间：2021-01-25 10:28:26|栏目：Android代码|点击： 次

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

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