从网络获取图片，并缓存到SD卡
16lz
2021-01-23
效果图：
图片存在bmob(http://www.bmob.com )后台，所以下载Demo运行的话要到官网申请 Application ID。
先点击上传图片，再点击缓存图片，不然没数据。
代码：
- paths=new String[5];
- for(int i=0;i<5;i++){
- //图片路径
- paths[i]=Environment.getExternalStorageDirectory()+"/"+i+".jpg";
- }
主要代码：
IndexActivity
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(); }} MainActivity
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); } }); }
MyAdapter
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); }}
AsyncImageTask
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; 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); } }} 更多相关文章
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