Android从网络获取图片，并缓存到SD卡

paths=new String[5];
for(int i=0;i<5;i++){
//图片路径
paths[i]=Environment.getExternalStorageDirectory()+"/"+i+".jpg";
}

public class IndexActivity extends Activity {

private String[] paths;
private int j;
private File cache;
private String appid="";  //你的Application ID

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Bmob.initialize(this, appid);
setContentView(R.layout.activity_index);

///创建缓存目录
cache=new File(Environment.getExternalStorageDirectory(),"cache");
if(!cache.exists()){
cache.mkdirs();
}
}

public void skip(View v){
Intent intent=new Intent(this,MainActivity.class);
startActivity(intent);
}

public void upload(View v){
paths=new String[5];
for(int i=0;i<5;i++){
//图片路径
paths[i]=Environment.getExternalStorageDirectory()+"/"+i+".jpg";
}

//批量上传图片
Bmob.uploadBatch(this, paths, new UploadBatchListener() {

@Override
public void onSuccess(List<BmobFile> arg0, List<String> arg1) {
// TODO Auto-generated method stub
String strurl="";
for(String url:arg1){
strurl=url;
}
Person p=new Person();
p.setIcPath(strurl);
p.setStr("s"+j);
p.save(IndexActivity.this);
j++;
toast("第"+j+"个上传成功！");
}

@Override
public void onProgress(int curIndex, int curPercent, int total, int totalPercent) {
// TODO Auto-generated method stub

//1、curIndex--表示当前第几个文件正在上传
//2、curPercent--表示当前上传文件的进度值（百分比）
//3、total--表示总的上传文件数
//4、totalPercent--表示总的上传进度（百分比）
MyUtil.logI(curIndex+" "+curPercent+" "+total+" "+totalPercent);

}

@Override
public void onError(int arg0, String arg1) {
// TODO Auto-generated method stub
toast("error "+arg1);
MyUtil.logI("errer "+arg1);
}
});
}

// 清理缓存
public void clear(View v){
if(cache.length()!=0){
File[] files=cache.listFiles();
for(File file:files){
file.delete();
}
cache.delete();
toast("缓存清理成功");
}else{
toast("暂无缓存");
}
}

public void toast(String msg){
Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
}

}

public class MainActivity extends Activity {

private ListView lv;
private MyAdapter adapter;
private File cache;
private List<Person> list;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
}

private void initView() {
// TODO Auto-generated method stub
lv=(ListView)findViewById(R.id.listView1);
list=new ArrayList<Person>();

cache=new File(Environment.getExternalStorageDirectory(),"cache");
if(!cache.exists()){
cache.mkdirs();
}

getData();
}

private void getData() {
// TODO Auto-generated method stub
//查询数据
BmobQuery<Person> bq=new BmobQuery<Person>();
bq.setCachePolicy(CachePolicy.CACHE_ELSE_NETWORK);        //缓存查询
bq.findObjects(this, new FindListener<Person>() {

@Override
public void onSuccess(List<Person> arg0) {
// TODO Auto-generated method stub
list=arg0;
adapter=new MyAdapter(MainActivity.this, list, cache);
lv.setAdapter(adapter);
}

@Override
public void onError(int arg0, String arg1) {
// TODO Auto-generated method stub
MyUtil.logI("errer "+arg1);
}
});
}

public class MyAdapter extends BaseAdapter {
private Context context;
private List<Person> list;
private File cache;
public MyAdapter(Context context, List<Person> list, File cache) {
this.context = context;
this.list = list;
this.cache = cache;
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return list.size();
}

@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return list.get(position);
}

@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder vh;
if(convertView==null){
convertView=LayoutInflater.from(context).inflate(R.layout.item, null);
vh=new ViewHolder();
vh.tv=(TextView)convertView.findViewById(R.id.tv);
vh.iv=(ImageView)convertView.findViewById(R.id.iv);
convertView.setTag(vh);
}else{
vh=(ViewHolder)convertView.getTag();
}

final Person p=list.get(position);
vh.tv.setText(p.getStr());

// 异步的加载图片
MyUtil mu=new MyUtil();
AsyncImageTask as=new AsyncImageTask(mu,vh.iv,cache);
if(p.getIcPath()!=null){
as.execute(p.getIcPath());
}else{
vh.iv.setImageResource(R.drawable.ic_launcher);
}

return convertView;
}

class ViewHolder{
TextView tv;
ImageView iv;
}

}

public class MyUtil {
/**
* 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
* */
public Uri getImageURI(String path,File cache) throws Exception{
String name=MD5.getMD5(path)+path.substring(path.lastIndexOf("."));
logI("name"+name);
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()){
logI("cache");
return Uri.fromFile(file);
}else{
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[] b=new byte[2*1024];
int len=0;
while((len=is.read(b))!=-1){
fos.write(b,0,len);
}
is.close();
fos.close();
return Uri.fromFile(file);
}
}
return null;
}

public static void logI(String msg){
Log.i("-------", msg);
}
}

public class AsyncImageTask extends AsyncTask<String, Integer, Uri> {

private ImageView ivIcon;
private MyUtil mu;
private File cache;
public AsyncImageTask(MyUtil mu,ImageView ivIcon,File cache) {
this.mu=mu;
this.ivIcon = ivIcon
9040
;
this.cache=cache;
}

@Override
protected Uri doInBackground(String... arg0) {
// TODO Auto-generated method stub
try {
return mu.getImageURI(arg0[0], cache);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

@Override
protected void onPostExecute(Uri result) {
// TODO Auto-generated method stub
super.onPostExecute(result);
if(ivIcon!=null && result!=null){
ivIcon.setImageURI(result);
}
}
}