android异步下载图片缓存到sdcard
2013-12-04 17:30
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http://www.cnblogs.com/gzggyy/archive/2013/05/18/3085844.html
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
service类
自定义Adapter
服务器xml文件
AsyncTask.zip AsyncTaskTest.zip
转：http://www.eoeandroid.com/thread-188411-1-1.html
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
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