使用AsyncTask异步加载图片

主要看看AsyncTask如何使用:

MainActivity.java

 public class MainActivity extends Activity {
     private static final String TAG = "MainActivity";
     private List<String>  datas;
     private LayoutInflater inflater;
     private Context context;
     private MyAdapter adapter;
     private ListView listview;
     private List<String> imgUrls;
     private List<TextView> list = new ArrayList<TextView>();
     private List<String> sortUrl = new ArrayList<String>();
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         requestWindowFeature(Window.FEATURE_NO_TITLE);
         setContentView(R.layout.activity_main);
         inflater = LayoutInflater.from(this);
         context = MainActivity.this;
         listview = (ListView) findViewById(R.id.listview);
         initData();
         adapter= new MyAdapter();
         listview.setAdapter(adapter);
     }

     private void initData() {
         imgUrls = new ArrayList<String>();
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/mpst/public/p2199507156.jpg");
         imgUrls.add("http://img5.douban.com/lpic/s27397768.jpg");
         imgUrls.add("http://img3.douban.com/lpic/s27505695.jpg");
         imgUrls.add("http://img3.douban.com/lpic/s27461340.jpg");
         imgUrls.add("http://img3.douban.com/lpic/s27451442.jpg");
         imgUrls.add("http://img5.douban.com/lpic/s27453059.jpg");
         imgUrls.add("http://img3.douban.com/lpic/s27452925.jpg");
         imgUrls.add("http://img5.douban.com/lpic/s27452846.jpg");
         imgUrls.add("http://img3.douban.com/lpic/s27325332.jpg");
         imgUrls.add("http://img3.douban.com/lpic/s27325315.jpg");
         imgUrls.add("http://img5.douban.com/lpic/s27389537.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/mpst/public/p2199638985.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/mpst/public/p2199637691.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2195768476.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2180002996.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2182978810.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2164841498.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2161445839.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2183221886.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2164383301.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2199638985.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2199407040.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2176900061.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2180405730.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2197059721.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2196353608.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2187391526.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2185073849.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2196328516.jpg");
         imgUrls.add("http://img5.douban.com/view/movie_poster_cover/lpst/public/p2166850749.jpg");
         imgUrls.add("http://img3.douban.com/view/movie_poster_cover/lpst/public/p2183957412.jpg");
         imgUrls.add("http://img3.douban.com/spic/s27459164.jpg");
         imgUrls.add("http://img3.douban.com/spic/s27480483.jpg");
         imgUrls.add("http://img3.douban.com/spic/s27460951.jpg");
         imgUrls.add("http://img3.douban.com/spic/s27453772.jpg");
         imgUrls.add("http://img3.douban.com/spic/s27410904.jpg");
         imgUrls.add("http://img5.douban.com/spic/s27466008.jpg");
         imgUrls.add("http://img3.douban.com/spic/s3259484.jpg");
         imgUrls.add("http://img3.douban.com/spic/s3081692.jpg");
         imgUrls.add("http://img3.douban.com/spic/s1400630.jpg");
         imgUrls.add("http://img5.douban.com/spic/s4715377.jpg");
         imgUrls.add("http://img3.douban.com/spic/s6201192.jpg");
         imgUrls.add("http://img5.douban.com/spic/s2650727.jpg");
         imgUrls.add("http://img3.douban.com/spic/s3636124.jpg");
         imgUrls.add("http://img5.douban.com/spic/s3595798.jpg");
         imgUrls.add("http://img3.douban.com/spic/s27078194.jpg");
         imgUrls.add("http://img3.douban.com/view/event_poster/large/public/2a35a85a873e8e7.jpg");
         imgUrls.add("http://img3.douban.com/view/event_poster/large/public/ce66e0569742fd7.jpg");
         imgUrls.add("http://img3.douban.com/view/event_poster/large/public/4c44752e83900d9.jpg");
         imgUrls.add("http://img3.douban.com/view/event_poster/large/public/d22f7b9e5c8c92c.jpg");
     }

    private class MyAdapter extends BaseAdapter{
         @Override
         public int getCount() {
             return imgUrls.size();
         }
         @Override
         public Object getItem(int position) {
             return imgUrls.get(position);
         }
         @Override
         public long getItemId(int position) {
             return position;
         }
         @Override
         public View getView(int position, View convertView, ViewGroup arg2) {
             ViewHolder viewHolder = null;
             if(convertView == null){
                 viewHolder = new ViewHolder();
                 convertView = inflater.inflate(R.layout.item, null);
                 viewHolder.image = (ImageView) convertView.findViewById(R.id.img);
                 convertView.setTag(viewHolder);
             }else{
                 viewHolder = (ViewHolder) convertView.getTag();
             }
             ImageTask imageTask = new ImageTask(viewHolder.image);
             iamgeTask.execute(imgUrls.get(position));
             return convertView;
         }
         class ViewHolder{
             ImageView image;
         }
     }
 }

加载图片的类：

ImageTask.java

 public class ImageTask extends AsyncTask<String, Void, Bitmap> {
     private ImageView iv;
     public ImageTask(ImageView iv){
         this.iv = iv;
     }
     @Override
     protected Bitmap doInBackground(String... param) {
         String imgUrl = param[0];
         try {
             URL url = new URL(imgUrl);
             try {
                 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                 InputStream in = conn.getInputStream();
                 Bitmap bitmap = BitmapFactory.decodeStream(in);
                 if(bitmap!=null){
                     return bitmap;
                 }
             } catch (IOException e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
             }
         } catch (MalformedURLException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return null;
     }

     @Override
     protected void onPostExecute(Bitmap result) {
         super.onPostExecute(result);
         if(result != null){
             iv.setImageBitmap(result);
         }
     }

     @Override
     protected void onPreExecute() {
         super.onPreExecute();
     }
 }