从URL的Android ocasionally下载图片(Android ocasionally d

2019-11-01 07:28发布

站内文章 / 前沿技术
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我的应用程序的一部分是从URL下载图像，并分析它们对ListView和单imgaview。 Generaly这是行不通的，但有些图像偶尔出现。 

public class ImageLoader {

    MemoryCache memoryCache=new MemoryCache();
    FileCache fileCache;
    private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
    ExecutorService executorService; 

    public ImageLoader(Context context){
        fileCache=new FileCache(context);
        executorService=Executors.newFixedThreadPool(5);
    }

    int stub_id = R.drawable.ic_launcher;
    public void DisplayImage(String uurl, int loader, ImageView imageView)
    {
        String url = uurl.replaceAll(" ", "%20");
        url = url.replaceAll("\n", "%20");
        stub_id = loader;
        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);
        if(bitmap!=null)
            imageView.setImageBitmap(bitmap);
        else
        {
            queuePhoto(url, imageView);
            imageView.setImageResource(loader);
        }
    }

    private void queuePhoto(String url, ImageView imageView)
    {
        PhotoToLoad p=new PhotoToLoad(url, imageView);
        executorService.submit(new PhotosLoader(p));
    }

    private Bitmap getBitmap(String url)
    {
        File f=fileCache.getFile(url);

        //from SD cache
        Bitmap b = decodeFile(f);
        if(b!=null)
            return b;
        return downloadBitmap(url);

        //from web
        /*try {
            Bitmap bitmap=null;
            URL imageUrl = new URL(url);
            HttpURLConnection conn = (HttpURLConnection)imageUrl.openConnection();
            conn.setConnectTimeout(30000);
            conn.setReadTimeout(30000);
            conn.setInstanceFollowRedirects(true);
            InputStream is=conn.getInputStream();
            OutputStream os = new FileOutputStream(f);
            Utils.CopyStream(is, os);
            os.close();
            bitmap = decodeFile(f);
            return bitmap;
        } catch (Exception ex){
           ex.printStackTrace();
           return null;
        }*/
    }
    Bitmap downloadBitmap(String url){
        Bitmap bmp = null;
        URL url_1 = null;
        try {
            url_1 = new URL(url);
             bmp = BitmapFactory.decodeStream(url_1.openConnection().getInputStream());
        } catch (Exception e) {
            Log.v("Error while downloading bitmap from url", e.getMessage());
        }
        return bmp;
    }

    //decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f){
        try {
            //decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f),null,o);

            //Find the correct scale value. It should be the power of 2.
            final int REQUIRED_SIZE=70;
            int width_tmp=o.outWidth, height_tmp=o.outHeight;
            int scale=1;
            while(true){
                if(width_tmp/2<REQUIRED_SIZE || height_tmp/2<REQUIRED_SIZE)
                    break;
                width_tmp/=2;
                height_tmp/=2;
                scale*=2;
            }

            //decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize=scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {}
        return null;
    }

    //Task for the queue
    private class PhotoToLoad
    {
        public String url;
        public ImageView imageView;
        public PhotoToLoad(String u, ImageView i){
            url=u;
            imageView=i;
        }
    }

    class PhotosLoader implements Runnable {
        PhotoToLoad photoToLoad;
        PhotosLoader(PhotoToLoad photoToLoad){
            this.photoToLoad=photoToLoad;
        }

        public void run() {
            if(imageViewReused(photoToLoad))
                return;
            Bitmap bmp=getBitmap(photoToLoad.url);
            memoryCache.put(photoToLoad.url, bmp);
            if(imageViewReused(photoToLoad))
                return;
            BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad);
            Activity a=(Activity)photoToLoad.imageView.getContext();
            a.runOnUiThread(bd);
        }
    }

    boolean imageViewReused(PhotoToLoad photoToLoad){
        String tag=imageViews.get(photoToLoad.imageView);
        if(tag==null || !tag.equals(photoToLoad.url))
            return true;
        return false;
    }

    //Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable
    {
        Bitmap bitmap;
        PhotoToLoad photoToLoad;
        public BitmapDisplayer(Bitmap b, PhotoToLoad p){bitmap=b;photoToLoad=p;}
        public void run()
        {
            if(imageViewReused(photoToLoad))
                return;
            if(bitmap!=null)
                photoToLoad.imageView.setImageBitmap(bitmap);
            else
                photoToLoad.imageView.setImageResource(stub_id);
        }
    }

    public void clearCache() {
        memoryCache.clear();
        fileCache.clear();
    }

}

filecash 

public class FileCache {

    private File cacheDir;

    public FileCache(Context context){
        //Find the dir to save cached images
        if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
            cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"TempImages");
        else
            cacheDir=context.getCacheDir();
        if(!cacheDir.exists())
            cacheDir.mkdirs();
    }

    public File getFile(String url){
        String filename=String.valueOf(url.hashCode());
        File f = new File(cacheDir, filename);
        return f;

    }

    public void clear(){
        File[] files=cacheDir.listFiles();
        if(files==null)
            return;
        for(File f:files)
            f.delete();
    }

}

内存现金

public class MemoryCache {
    private Map<String, SoftReference<Bitmap>> cache=Collections.synchronizedMap(new HashMap<String, SoftReference<Bitmap>>());

    public Bitmap get(String id){
        if(!cache.containsKey(id))
            return null;
        SoftReference<Bitmap> ref=cache.get(id);
        return ref.get();
    }

    public void put(String id, Bitmap bitmap){
        cache.put(id, new SoftReference<Bitmap>(bitmap));
    }

    public void clear() {
        cache.clear();
    }
}

旧

public class Utils {
    public static void CopyStream(InputStream is, OutputStream os)
    {
        final int buffer_size=1024;
        try
        {
            byte[] bytes=new byte[buffer_size];
            for(;;)
            {
              int count=is.read(bytes, 0, buffer_size);
              if(count==-1)
                  break;
              os.write(bytes, 0, count);
            }
        }
        catch(Exception ex){}
    }
}

适配器

public class CandidateAdapter extends BaseAdapter{
    Context ctx;
    LayoutInflater lInflater;
    ArrayList<Candidate> objects;
    CandidateAdapter(Context context, ArrayList<Candidate> candidates) {
            ctx = context;
            objects = candidates;
            lInflater = (LayoutInflater) ctx
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
          }
    public int getCount() {
        return objects.size();
      }
    public Object getItem(int position) {
        return objects.get(position);
      }
    public long getItemId(int position) {
        return position;
      }
    Candidate getCandidate(int position) {
        return ((Candidate) getItem(position));
      }
    public View getView(int position, View convertView, ViewGroup parent) {
        // используем созданные, но не используемые view
        View view = convertView;
        if (view == null) {
          view = lInflater.inflate(R.layout.inbox_list_item, parent, false);
        }
        Candidate p = getCandidate(position);
        ((TextView) view.findViewById(R.id.from)).setText(p.get_name());
        ((TextView) view.findViewById(R.id.subject)).setText(p.get_office());
        ((RatingBar) view.findViewById(R.id.rateindicator)).setRating(p.get_ranking());
        int loader = R.drawable.loader;


        ImageView image = (ImageView) view.findViewById(R.id.photo);


        String image_url = p.get_photograph();


        ImageLoader imgLoader = new ImageLoader(ctx);


        imgLoader.DisplayImage(image_url, loader, image);
        return view;
    }



}

活动

public class InboxActivity extends ListActivity {

    List<Candidate> candidates;
    private DatabaseHandler db;

    public void onDestroy(){
        if (db != null)
            db.close();

        super.onDestroy();
        //db.close();
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.inbox_list);
        db = new DatabaseHandler(this);
        candidates = db.getAllCandidates(1);
        db.close();
        CandidateAdapter adapter = new CandidateAdapter(this,(ArrayList) candidates);
        ListView lvMain = getListView();
        //String numofrows = "" + candidates.size();
        //Log.d("Number of candidates", numofrows);
        lvMain.setAdapter(adapter);
        lvMain.setOnItemClickListener(new OnItemClickListener() {

            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {
                // getting values from selected ListItem
                String name = ((TextView) view.findViewById(R.id.from)).getText().toString();
                Log.d("Name ", name);

                // Starting new intent
                Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
                in.putExtra("name", name);
                Log.d("Starting activity ", "Yeah ");
                startActivity(in);

            }
        });
    }





}

logcat的警告

8月12日至16日：35：33.525：W /合子（33）：预装绘制资源＃0x1080093（RES /抽拉-HDPI / sym_def_app_icon.png），其与配置而有所不同!!

谁能帮我在这里图中的问题？

Answer 1:

我想可能是在URL问题意味着它包含在它的空白。 所以下载图像如果URL包含以下代码空白使用。 

public void DisplayImage(String uurl, int loader, ImageView imageView)
{
    String url = uurl.replaceAll(" ", "%20");
    stub_id = loader;
    imageViews.put(imageView, url);
    Bitmap bitmap=memoryCache.get(url);
    if(bitmap!=null)
        imageView.setImageBitmap(bitmap);
    else
    {
        queuePhoto(url, imageView);
        imageView.setImageResource(loader);
    }
}

使用它从指定的URL下载的位图。 

Bitmap downloadBitmap(String url)
{
    URL url_1 = null;
    try {
        url_1 = new URL(url);
        bmp = BitmapFactory.decodeStream(url_1.openConnection().getInputStream());
    } catch (Exception e) {
        Log.v("Error while downloading bitmap from url", e.getMessage());
    }
    return bmp;
}


文章来源: Android ocasionally downloads images from url
标签： android download imageview warnings
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