54 |
55 | /* |
56 | * 从网络上获取图片，如果图片在本地存在的话就直接拿，如果不存在再去服务器上下载图片 |
57 | * 这里的path是图片的地址 |
58 | */ |
59 | public Uri getImageURI(String path, File cache) throws Exception { |
60 | String name = MD5.getMD5(path) + path.substring(path.lastIndexOf(".")); |
61 | File file = new File(cache, name); |
62 | // 如果图片存在本地缓存目录，则不去服务器下载 |
63 | if (file.exists()) { |
64 | return Uri.fromFile(file);//Uri.fromFile(path)这个方法能得到文件的URI |
65 | } else { |
66 | // 从网络上获取图片 |
67 | URL url = new URL(path); |
68 | HttpURLConnection conn = (HttpURLConnection) url.openConnection(); |
69 | conn.setConnectTimeout(5000); |
70 | conn.setRequestMethod("GET"); |
71 | conn.setDoInput(true); |
72 | if (conn.getResponseCode() == 200) { |
73 |
74 | InputStream is = conn.getInputStream(); |
75 | FileOutputStream fos = new FileOutputStream(file); |
76 | byte[] buffer = new byte[1024]; |
77 | int len = 0; |
78 | while ((len = is.read(buffer)) != -1) { |
79 | fos.write(buffer, 0, len); |
80 | } |
81 | is.close(); |
82 | fos.close(); |
83 | // 返回一个URI对象 |
84 | return Uri.fromFile(file); |
85 | } |
86 | } |
87 | return null; |
88 | } |
89 | } |
Serivce类中，注意以下几点
1.HttpURLConnection conn = (HttpURLConnection) url.openConnection();获取一个链接，从而进行通讯 2.怎么利用XxmlPullPaser类去解析XML，从而把数据封装成对象
3.getImageURI(String path, File cache) 这个方法具体实现
4.Uri.fromFile(file);这个方法能够直接返回一个Uri来
下面是自定义的Adapter类，
001 | public class MyContactAdapter extends BaseAdapter { |
002 |
003 | protected static final int SUCCESS_GET_IMAGE = 0; |
004 | private Context context; |
005 | private List<Contact> contacts; |
006 | private File cache; |
007 | private LayoutInflater mInflater; |
008 |
009 | // 自己定义的构造函数 |
010 | public MyContactAdapter(Context context, List<Contact> contacts, File cache) { |
011 | this.context = context; |
012 | this.contacts = contacts; |
013 | this.cache = cache; |
014 |
015 | mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); |
016 | } |
017 |
018 | @Override |
019 | public int getCount() { |
020 | return contacts.size(); |
021 | } |
022 |
023 | @Override |
024 | public Object getItem(int position) { |
025 | return contacts.get(position); |
026 | } |
027 |
028 | @Override |
029 | public long getItemId(int position) { |
030 | return position; |
031 | } |
032 |
033 | @Override |
034 | public View getView(int position, View convertView, ViewGroup parent) { |
035 | // 1获取item,再得到控件 |
036 | // 2 获取数据 |
037 | // 3绑定数据到item |
038 | View view = null; |
039 | if (convertView != null) { |
040 | view = convertView; |
041 | } else { |
042 | view = mInflater.inflate(R.layout.item, null); |
043 | } |
044 |
045 | ImageView iv_header = (ImageView) view.findViewById(R.id.iv_header); |
046 | TextView tv_name = (TextView) view.findViewById(R.id.tv_name); |
047 |
048 | Contact contact = contacts.get(position); |
049 |
050 | // 异步的加载图片 (线程池 + Handler ) ---> AsyncTask |
051 | asyncloadImage(iv_header, contact.image); |
052 | tv_name.setText(contact.name); |
053 |
054 | return view; |
055 | } |
056 |
057 | private void asyncloadImage(ImageView iv_header, String path) { |
058 | ContactService service = new ContactService(); |
059 | AsyncImageTask task = new AsyncImageTask(service, iv_header); |
060 | task.execute(path); |
061 | } |
062 |
063 | private final class AsyncImageTask extends AsyncTask<String, Integer, Uri> { |
064 |
065 | private ContactService service; |
066 | private ImageView iv_header; |
067 |
068 | public AsyncImageTask(ContactService service, ImageView iv_header) { |
069 | this.service = service; |
070 | this.iv_header = iv_header; |
071 | } |
072 |
073 | // 后台运行的子线程子线程 |
074 | @Override |
075 | protected Uri doInBackground(String... params) { |
076 | try { |
077 | return service.getImageURI(params[0], cache); |
078 | } catch (Exception e) { |
079 | e.printStackTrace(); |
080 | } |
081 | return null; |
082 | } |
083 |
084 | // 这个放在在ui线程中执行 |
085 | @Override |
086 | protected void onPostExecute(Uri result) { |
087 | super.onPostExecute(result); |
088 | // 完成图片的绑定 |
089 | if (iv_header != null && result != null) { |
090 | iv_header.setImageURI(result); |
091 | } |
092 | } |
093 | } |
