android异步下载图片缓存到sdcard

从网络上加载XML资源，其中包括图片，我们要做的解析XML里面的数据，并且把图片缓存到本地一个cache目录里面，并且用一个自定义的Adapter去填充到LIstView：
对象类

public class Contact {
        int id;
        String image;
        String name;
         
        public Contact() {
                super();
        }
        public Contact(int id, String image, String name) {
                this.id = id;
                this.image = image;
                this.name = name;
        }
        public int getId() {
                return id;
        }
        public void setId(int id) {
                this.id = id;
        }
        public String getImage() {
                return image;
        }
        public void setImage(String image) {
                this.image = image;
        }
        public String getName() {
                return name;
        }
        public void setName(String name) {
                this.name = name;
        }
         
}

service类

public class ContactService {
 
        /*
         * 从服务器上获取数据
         */
        public List<Contact> getContactAll() throws Exception {
                List<Contact> contacts = null;
                String Parth = "http://10.0.2.2:8080/AsyncTaskTest/list.xml";
                URL url = new URL(Parth);
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setConnectTimeout(30000);
                conn.setReadTimeout(30000);
                conn.setRequestMethod("GET");
                if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
                        InputStream is = conn.getInputStream();
                        // 这里获取数据直接放在XmlPullParser里面解析
                        contacts = xmlParser(is);
                        return contacts;
                } else {
                        return null;
                }
        }
 
        // 这里并没有下载图片下来，而是把图片的地址保存下来了
        private List<Contact> xmlParser(InputStream is) throws Exception {
                List<Contact> contacts = null;
                Contact contact = null;
                XmlPullParser parser = Xml.newPullParser();
                parser.setInput(is, "UTF-8");
                int eventType = parser.getEventType();
                while ((eventType = parser.next()) != XmlPullParser.END_DOCUMENT) {
                        switch (eventType) {
                        case XmlPullParser.START_TAG:
                                if (parser.getName().equals("contacts")) {
                                        contacts = new ArrayList<Contact>();
                                } else if (parser.getName().equals("contact")) {
                                        contact = new Contact();
                                        contact.setId(Integer.valueOf(parser.getAttributeValue(0)));
                                } else if (parser.getName().equals("name")) {
                                        contact.setName(parser.nextText());
                                } else if (parser.getName().equals("image")) {
                                        contact.setImage(parser.getAttributeValue(0));
                                }
                                break;
 
                        case XmlPullParser.END_TAG:
                                if (parser.getName().equals("contact")) {
                                        contacts.add(contact);
                                }
                                break;
                        }
                }
                return contacts;
        }
 
        /*
         * 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
         * 这里的path是图片的地址
         */
        public Uri getImageURI(String path, File cache) throws Exception {
                String name = MD5.getMD5(path) + path.substring(path.lastIndexOf("."));
                File file = new File(cache, name);
                // 如果图片存在本地缓存目录，则不去服务器下载 
                if (file.exists()) {
                        return Uri.fromFile(file);//Uri.fromFile(path)这个方法能得到文件的URI
                } else {
                        // 从网络上获取图片
                        URL url = new URL(path);
                        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                        conn.setConnectTimeout(5000);
                        conn.setRequestMethod("GET");
                        conn.setDoInput(true);
                        if (conn.getResponseCode() == 200) {
 
                                InputStream is = conn.getInputStream();
                                FileOutputStream fos = new FileOutputStream(file);
                                byte[] buffer = new byte[1024];
                                int len = 0;
                                while ((len = is.read(buffer)) != -1) {
                                        fos.write(buffer, 0, len);
                                }
                                is.close();
                                fos.close();
                                // 返回一个URI对象
                                return Uri.fromFile(file);
                        }
                }
                return null;
        }
}

自定义Adapter

public class ImageAdapter extends BaseAdapter {
 
        protected static final int SUCCESS_GET_IMAGE = 0;
        private Context context;
        private List<Contact> contacts;
        private File cache;
        private LayoutInflater mInflater;
 
        // 自己定义的构造函数
        public ImageAdapter(Context context, List<Contact> contacts, File cache) {
                this.context = context;
                this.contacts = contacts;
                this.cache = cache;
 
                mInflater = (LayoutInflater) context
                                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        }
 
        @Override
        public int getCount() {
                return contacts.size();
        }
 
        @Override
        public Object getItem(int position) {
                return contacts.get(position);
        }
 
        @Override
        public long getItemId(int position) {
                return position;
        }
 
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
                // 1获取item,再得到控件
                // 2 获取数据
                // 3绑定数据到item
                View view = null;
                if (convertView != null) {
                        view = convertView;
                } else {
                        view = mInflater.inflate(R.layout.item, null);
                }
 
                ImageView iv_header = (ImageView) view.findViewById(R.id.imageView);
                TextView tv_name = (TextView) view.findViewById(R.id.textView);
 
                Contact contact = contacts.get(position);
                 
                // 异步的加载图片 (线程池 + Handler ) ---> AsyncTask
                asyncloadImage(iv_header, contact.image);
                 
                tv_name.setText(contact.name);
 
                return view;
        }
         
        private void asyncloadImage(ImageView iv_header, String path) {
                ContactService service = new ContactService();
                AsyncImageTask task = new AsyncImageTask(service, iv_header);
                task.execute(path);
        }
 
        private final class AsyncImageTask extends AsyncTask<String, Integer, Uri> {
 
                private ContactService service;
                private ImageView iv_header;
 
                public AsyncImageTask(ContactService service, ImageView iv_header) {
                        this.service = service;
                        this.iv_header = iv_header;
                }
 
                // 后台运行的子线程子线程
                @Override
                protected Uri doInBackground(String... params) {
                        try {
                                return service.getImageURI(params[0], cache);
                        } catch (Exception e) {
                                e.printStackTrace();
                        }
                        return null;
                }
 
                // 这个放在在ui线程中执行
                @Override
                protected void onPostExecute(Uri result) {
                        super.onPostExecute(result);
                        // 完成图片的绑定
                        if (iv_header != null && result != null) {
                                iv_header.setImageURI(result);
                        }
                }
        }
}

public class MainActivity extends Activity {
        protected static final int SUCCESS_GET_CONTACT = 0;
        private ListView mListView;
        private ImageAdapter mAdapter;
        private File cache;
         
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         
        mListView = (ListView) findViewById(R.id.listView);
         
        //创建缓存目录，系统一运行就得创建缓存目录的，
        cache = new File(Environment.getExternalStorageDirectory(), "cache");
         
        if(!cache.exists()){
                cache.mkdirs();
        }
         
        //获取数据，主UI线程是不能做耗时操作的，所以启动子线程来做
        new Thread(){
                public void run() {
                        ContactService service = new ContactService();
                        List<Contact> contacts = null;
                                try {
                                        contacts = service.getContactAll();
                                } catch (Exception e) {
                                        e.printStackTrace();
                                }
                                //子线程通过Message对象封装信息，并且用初始化好的，
                                //Handler对象的sendMessage()方法把数据发送到主线程中，从而达到更新UI主线程的目的
                        Message msg = new Message();
                        msg.what = SUCCESS_GET_CONTACT;
                        msg.obj = contacts;
                        mHandler.sendMessage(msg);
                };
        }.start();
    }
     
    private Handler mHandler = new Handler(){
                public void handleMessage(android.os.Message msg) {
                        if(msg.what == SUCCESS_GET_CONTACT){
                                List<Contact> contacts = (List<Contact>) msg.obj;
                                mAdapter = new ImageAdapter(getApplicationContext(),contacts,cache);
                                mListView.setAdapter(mAdapter);
                        }
                };
        };
     
    @Override
    protected void onDestroy() {
            super.onDestroy();
            //清空缓存
            File[] files = cache.listFiles();
            for(File file :files){
                    file.delete();
            }
            cache.delete();
    }
}

服务器xml文件

<?xml version="1.0" encoding="UTF-8"?>
<contacts>
        <contact id="1">
                <name>图标1</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/1.png" />
        </contact>
        <contact id="2">
                <name>图标2</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/2.png" />
        </contact>
        <contact id="3">
                <name>图标3</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/3.png" />
        </contact>
        <contact id="4">
                <name>图标4</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/4.png" />
        </contact>
        <contact id="5">
                <name>图标5</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/5.png" />
        </contact>
        <contact id="6">
                <name>图标6</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/6.png" />
        </contact>
        <contact id="7">
                <name>图标7</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/7.png" />
        </contact>
        <contact id="8">
                <name>图标8</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/8.png" />
        </contact>
        <contact id="9">
                <name>图标9</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/9.png" />
        </contact>
        <contact id="10">
                <name>图标10</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/10.png" />
        </contact>
        <contact id="11">
                <name>图标11</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/11.png" />
        </contact>
        <contact id="12">
                <name>图标12</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/12.png" />
        </contact>
 
        <contact id="13">
                <name>图标13</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/13.png" />
        </contact>
        <contact id="14">
                <name>图标14</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/14.png" />
        </contact>
        <contact id="15">
                <name>图标15</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/15.png" />
        </contact>
        <contact id="16">
                <name>图标16</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/16.png" />
        </contact>
        <contact id="17">
                <name>图标17</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/17.png" />
        </contact>
        <contact id="18">
                <name>图标18</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/18.png" />
        </contact>
        <contact id="19">
                <name>图标19</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/19.png" />
        </contact>
        <contact id="20">
                <name>图标20</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/20.png" />
        </contact>
         
        <contact id="21">
                <name>图标21</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/1.png" />
        </contact>
        <contact id="22">
                <name>图标22</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/2.png" />
        </contact>
        <contact id="23">
                <name>图标23</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/3.png" />
        </contact>
        <contact id="24">
                <name>图标24</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/4.png" />
        </contact>
        <contact id="25">
                <name>图标25</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/5.png" />
        </contact>
        <contact id="26">
                <name>图标26</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/6.png" />
        </contact>
        <contact id="27">
                <name>图标27</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/7.png" />
        </contact>
        <contact id="28">
                <name>图标28</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/8.png" />
        </contact>
        <contact id="29">
                <name>图标29</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/9.png" />
        </contact>
        <contact id="30">
                <name>图标30</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/10.png" />
        </contact>
        <contact id="31">
                <name>图标31</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/11.png" />
        </contact>
        <contact id="32">
                <name>图标32</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/12.png" />
        </contact>
 
        <contact id="33">
                <name>图标33</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/13.png" />
        </contact>
        <contact id="34">
                <name>图标34</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/14.png" />
        </contact>
        <contact id="35">
                <name>图标35</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/15.png" />
        </contact>
        <contact id="36">
                <name>图标36</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/16.png" />
        </contact>
        <contact id="37">
                <name>图标37</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/17.png" />
        </contact>
        <contact id="38">
                <name>图标38</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/18.png" />
        </contact>
        <contact id="39">
                <name>图标39</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/19.png" />
        </contact>
        <contact id="40">
                <name>图标40</name>
                <image src="http://192.168.34.20:8080/AsyncTaskTest/image/20.png" />
        </contact>
</contacts>

AsyncTask.zip  AsyncTaskTest.zip

转：http://www.eoeandroid.com/thread-188411-1-1.html