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照片没有出现在我的应用程序中。我的加载代码如下：

private static final String TAG = "ERROR";
private static final int IO_BUFFER_SIZE = 4 * 1024;
public static Bitmap loadBitmap(String url) {
    Bitmap bitmap = null;
    InputStream in = null;
    BufferedOutputStream out = null;

    try {
        Log.e(TAG, "OK0");

        in = new BufferedInputStream(new URL(url).openStream(), IO_BUFFER_SIZE);
        Log.e(TAG, "OK1");

        final ByteArrayOutputStream dataStream = new ByteArrayOutputStream();
        out = new BufferedOutputStream(dataStream, IO_BUFFER_SIZE);
        copy(in, out);
        out.flush();

        final byte[] data = dataStream.toByteArray();
        BitmapFactory.Options options = new BitmapFactory.Options();
        //options.inSampleSize = 1;

        bitmap = BitmapFactory.decodeByteArray(data, 0, data.length,options);
    } catch (IOException e) {
        Log.e(TAG, "Could not load Bitmap from: " + url);
    } finally {
        closeStream(in);
        closeStream(out);
    }

    return bitmap;
}

问题出在尝试的第一行：

in = new BufferedInputStream(new URL(url).openStream(), IO_BUFFER_SIZE);

和 php 文件：

    $objQuery = mysql_query("SELECT * FROM Photos WHERE 1");

    $intNumField = mysql_num_fields($objQuery);
    $resultArray = array();
    while($obResult = mysql_fetch_array($objQuery))
    {
            $arrCol = array();
            for($i=0;$i<$intNumField;$i++)
            {
                    $arrCol[mysql_field_name($objQuery,$i)] = $obResult[$i];
            }
            array_push($resultArray,$arrCol);
    }

    mysql_close($con);

    echo json_encode($resultArray);

Android 中的输出是正确的 url，但不会显示到 Imageview 中：

E/ERROR﹕ Could not load Bitmap from:xxxxx

我从其他页面获得了代码，因为我尝试了一些示例，但从未奏效。仅当我将 url 放入 Android 时，但当我可以从 Mysql 获得多个时，永远不会只显示正确的 url 的照片，所以我认为问题是当我尝试将 url 转换为位图时。

感谢你的回答。

4

2 回答 2

0

我假设您正在使用 mysql 中的链接位置并且不加载存储在数据库中的图像（因为这非常低效）如果您使用链接路由是加载这些图像的最佳方式。请注意，这可用于一次加载多个图像而不会减慢您的应用程序的速度。就像在新闻源上加载一堆个人资料图片一样。

我有一个约会应用程序，它可以加载多张个人资料图片并将图像发布到同一个活动中。为了做到这一点，最好的方法（而且几乎是唯一的方法）是缓存图像。这是一些带有注释的详细代码，可帮助您执行此操作。请务必阅读评论，因为如果您需要编辑我的代码以优化您的应用程序，它们会为您提供帮助。

首先，您需要将此代码作为单独的类复制到您的应用中

ImageLoader.java——除非你真的需要，否则你不需要对此做任何改变。

    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.FileOutputStream;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.Collections;
    import java.util.Map;
    import java.util.WeakHashMap;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import android.app.Activity;
    import android.content.Context;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.widget.ImageView;


public class ImageLoader {

    Context context;

    MemoryCache memoryCache=new MemoryCache();//this is another java file you will have to create
    FileCache fileCache;
    private Map<ImageView, String> imageViews=Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
    ExecutorService executorService; 

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


   // final int stub_id = com.swiftkaytech.simdate.R.drawable.ic_launcher;//set this equal to a drawable resource if you want a placeholder for while your images are loading.
    public void DisplayImage(String url, ImageView imageView)
    {


        imageViews.put(imageView, url);
        Bitmap bitmap=memoryCache.get(url);

        if(bitmap!=null){
            imageView.setImageBitmap(bitmap);


        }
        else
        {
            queuePhoto(url, imageView);
           // imageView.setImageResource(stub_id);//uncomment if you are using a placeholder for while your images are loading.
        }
    }


    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 (Throwable ex){
           ex.printStackTrace();
           if(ex instanceof OutOfMemoryError)
               memoryCache.clear();
           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=160;//this value is how large the file will be. making this bigger might cause issues with memory while making it smaller will reduce image quality
            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() {
            //memoryCache.clear();


            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/*Bitmap.createScaledBitmap(bitmap, newwidth, newheight, true)*/);
            }
           // else
               // photoToLoad.imageView.setImageResource(stub_id);
        }
    }

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



}

FileCache.java 除非您真的需要，否则您不需要对此进行任何更改

import java.io.File;


import android.content.Context;

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=context.getCacheDir();//new File(android.os.Environment.getExternalStorageDirectory(),"TTImages_cache");
        else
            cacheDir=context.getCacheDir();
        if(!cacheDir.exists())
            cacheDir.mkdirs();
    }

    public File getFile(String url){
        //I identify images by hashcode. Not a perfect solution, good for the demo.
       String filename=String.valueOf(url.hashCode());
        //Another possible solution (thanks to grantland)
       // String filename = URLEncoder.encode(url);
        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();
    }

}

MemoryCache.java ---无需更改

import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import android.graphics.Bitmap;
import android.util.Log;

public class MemoryCache {

    private static final String TAG = "MemoryCache";
    private Map<String, Bitmap> cache=Collections.synchronizedMap(
            new LinkedHashMap<String, Bitmap>(10,1.5f,true));//Last argument true for LRU ordering
    private long size=0;//current allocated size
    private long limit=100000;//max memory in bytes

    public MemoryCache(){
        //use 25% of available heap size
        setLimit(Runtime.getRuntime().maxMemory()/6);
    }

    public void setLimit(long new_limit){
        limit=new_limit;
        Log.i(TAG, "MemoryCache will use up to "+limit/1024./1024.+"MB");
    }

    public Bitmap get(String id){
        try{
            if(!cache.containsKey(id))
                return null;
            //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78 
            return cache.get(id);
        }catch(NullPointerException ex){
            ex.printStackTrace();
            return null;
        }
    }

    public void put(String id, Bitmap bitmap){
        try{
            if(cache.containsKey(id))
                size-=getSizeInBytes(cache.get(id));
            cache.put(id, bitmap);
            size+=getSizeInBytes(bitmap);



            checkSize();
        }catch(Throwable th){
            th.printStackTrace();
        }
    }

    private void checkSize() {
        Log.i(TAG, "cache size="+size+" length="+cache.size());
        if(size>limit){
            Iterator<Entry<String, Bitmap>> iter=cache.entrySet().iterator();//least recently accessed item will be the first one iterated  
            while(iter.hasNext()){
                Entry<String, Bitmap> entry=iter.next();
                size-=getSizeInBytes(entry.getValue());
                iter.remove();
                if(size<=limit)
                    break;
            }
            Log.i(TAG, "Clean cache. New size "+cache.size());
        }
    }

    public void clear() {
        try{
            //NullPointerException sometimes happen here http://code.google.com/p/osmdroid/issues/detail?id=78 
            cache.clear();
            size=0;
        }catch(NullPointerException ex){
            ex.printStackTrace();
        }
    }

    long getSizeInBytes(Bitmap bitmap) {
        if(bitmap==null)
            return 0;
        return bitmap.getRowBytes() * bitmap.getHeight();
    }
}

现在在活动上（或者在适配器中，如果使用列表视图/网格视图等，请放置此代码

图像加载器图像加载器；

imageLoader = new ImageLoader(context);//根据需要将其更改为您的活动上下文

imageLoader.DisplayImage(url, imageview);//url是图片的链接，imageview是你要显示图片的imageview。

于 2014-07-29T18:18:50.440 回答
0

您只需将字节数组从数据库转换为位图....

于 2014-03-10T14:43:09.300 回答