Android中使用ListView数据异步加载与AsyncTask

package com.xushouwei.adapter; import java.io.File; import java.util.List; import com.xushouwei.asyncload.R; import com.xushouwei.bean.Contact; import com.xushouwei.service.ContactService; import android.content.Context; import android.net.Uri; import android.os.AsyncTask; import android.os.Handler; import android.os.Message; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import android.widget.TextView; /** * 自定义联系人适配器 * * @author 徐守威 * */ public class ContactAdapter extends BaseAdapter { private List<Contact> data; private int listviewItem; private File cache; private LayoutInflater layoutInflater; public ContactAdapter(Context context, List<Contact> data, int listviewItem, File cache) { // TODO Auto-generated constructor stub this.data = data; this.listviewItem = listviewItem; this.cache = cache; // 通过上下文对象取得布局填充服务 layoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } /** * 得到数据的总数 */ public int getCount() { // TODO Auto-generated method stub return data.size(); } /*** * 根据数据的索引得到集合总所对应的数据 */ public Object getItem(int position) { // TODO Auto-generated method stub return data.get(position); } public long getItemId(int position) { // TODO Auto-generated method stub return position; } /** * 当listview每显示一个条目的时候就会调用该方法 */ public View getView(int position, View convertView, ViewGroup parent) { // TODO Auto-generated method stub ImageView imageView; TextView textView; if (convertView == null) { // 得到条目的view对象 convertView = layoutInflater.inflate(listviewItem, null); // 因为每次查找的时候都要耗时因此我们可以定义一个内部类进行包装 imageView = (ImageView) convertView.findViewById(R.id.imageView); textView = (TextView) convertView.findViewById(R.id.textView); // 保存对象 convertView.setTag(new DataWrapper(imageView, textView)); } else { DataWrapper dataWrapper = (DataWrapper) convertView.getTag(); imageView = dataWrapper.imageView; textView = dataWrapper.textView; } Contact contact = data.get(position); textView.setText(contact.name); // 果如在此处直接加在图片的话容易报无响应错误 // 因此呀，我们这里需要采用异步加载数据处理的方式 asyncImageLoad(imageView, contact.image); return convertView; } private void asyncImageLoad(ImageView imageView, String path) { // TODO Auto-generated method stub AsynImageTask asynImageTask=new AsynImageTask(imageView); asynImageTask.execute(path); } private final class AsynImageTask extends AsyncTask<String,Integer,Uri> { private ImageView imageView; public AsynImageTask(ImageView imageView) { // TODO Auto-generated constructor stub this.imageView=imageView; } @Override protected void onPostExecute(Uri result) { // 从消息中取得uri if (result != null && imageView != null) { // 给imageview设置图片 imageView.setImageURI(result); } } //该方法在子线程中执行 @Override protected Uri doInBackground(String... params) { // TODO Auto-generated method stub try { return ContactService.getImage(params[0], cache); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } } /* // 异步加载图片方法(核心中的核心) private void asyncImageLoad(final ImageView imageView, final String path) { // TODO Auto-generated method stub // 在子线程中如果要想更新ui的话这里就要采用Handler技术 final Handler handler = new Handler() { @Override public void handleMessage(Message msg) {// 该方法运行在主线程 // TODO Auto-generated method stub // 从消息中取得uri Uri uri = (Uri) msg.obj; if (uri != null && imageView != null) { // 给imageview设置图片 imageView.setImageURI(uri); } } }; // 如果在内部类中要访问变量需要将变量声明成final // 这里采用匿名内部类的方式处理 Runnable runnable = new Runnable() { public void run() { // TODO Auto-generated method stub // 调用业务类中的取得图片方法(改方法通过图片路径获取，并返回图片的URI) try { Uri uri = ContactService.getImage(path, cache); handler.sendMessage(handler.obtainMessage(10, uri)); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } }; // 定义一个线程并启动 new Thread(runnable).start(); } */ private final class DataWrapper { public ImageView imageView; public TextView textView; public DataWrapper(ImageView imageView, TextView textView) { this.imageView = imageView; this.textView = textView; } } }