android-将图像从url加载到recyclerview,而无需第三方库

概述一位潜在的雇主要求我制作一个简单的应用程序,该应用程序将从JSON数据加载到recyclerview.问题是：我不能使用任何第三方库来加载图像.有谁知道我可以使用的当前教程.我在网上搜索过,但似乎有不同的方法,但是很遗憾,到目前为止,我一直非常依赖Picasso和Glide.我的代码基本上是设置

一位潜在的雇主要求我制作一个简单的应用程序,该应用程序将从JSON数据加载到recyclervIEw.

问题是：我不能使用任何第三方库来加载图像.

有谁知道我可以使用的当前教程.我在网上搜索过,但似乎有不同的方法,但是很遗憾,到目前为止,我一直非常依赖Picasso和GlIDe.

我的代码基本上是设置为从AsyncTask加载程序获取JsON数据,并在加载程序的onLoadFinish()中设置recyclervIEw和适配器.

理想情况下,我想通过调用AsyncTask从适配器的onBindVIEwHolder中获取url图像.那可行吗？还是我应该另辟do径.

谢谢你的帮助.

解决方法:

我找到了解决方案,您可以查看此链接以获取更多详细描述
Android Hive – Load images from URL-HTTP

清单权限：

    <!-- Internet Permissions -->    <uses-permission androID:name="androID.permission.INTERNET" />    <!-- Permission to write to external storage -->    <uses-permission androID:name="androID.permission.WRITE_EXTERNAL_STORAGE" />

MainActivity代码：

        // Loader image - will be shown before loading image        int loader = R.drawable.loader;        // ImagevIEw to show        ImageVIEw image = (ImageVIEw) findVIEwByID(R.ID.image);        // Image url        String image_url = "https://API.androIDhive.info/images/sample.jpg";        // ImageLoader class instance        ImageLoader imgLoader = new ImageLoader(getApplicationContext());        // whenever you want to load an image from url        // call displayImage function        // url - image url to load        // loader - loader image, will be displayed before getting image        // image - ImageVIEw         imgLoader.displayImage(image_url, loader, image);

ImageLoader类：

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 url, int loader, ImageVIEw imageVIEw)    {        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;        //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;        }    }    //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;        }        @OverrIDe        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();    }}

文件缓存类：

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();    }}

记忆类别：

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();    }}

实用程序类：

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){}    }}

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