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从URL加载Android位图

javaandroidbitmap
86

我有一个关于从网站加载图像的问题。我使用的代码是：

Display display = getWindowManager().getDefaultDisplay(); 
int width = display.getWidth();
int height = display.getHeight();
Bitmap bit=null;
try {
    bit = BitmapFactory.decodeStream((InputStream)new URL("http://www.mac-wallpapers.com/bulkupload/wallpapers/Apple%20Wallpapers/apple-black-logo-wallpaper.jpg").getContent());
} catch (Exception e) {}
Bitmap sc = Bitmap.createScaledBitmap(bit,width,height,true);
canvas.drawBitmap(sc,0,0,null);

但它总是返回一个空指针异常并导致程序崩溃。 URL 是有效的，似乎对其他人也有效。 我使用的是 2.3.1 版本。

1
你收到了什么崩溃信息？堆栈跟踪是什么？你知道哪一行导致了崩溃吗？ - zeh
createScalesBitmap 抛出了 NullPointerException 异常，因为 bit 为空。 - Tyeomans
1
需要网络权限... 在 AndroidManifest.xml 中添加 <uses-permission android:name="android.permission.INTERNET" /> - Tyeomans
20个回答
1
public static Bitmap getImgBitmapFromUri(final String url, final Activity context, final CropImageView imageView, final File file) {
    final Bitmap bitmap = null;
    AsyncTask.execute(new Runnable() {
        @Override
        public void run() {
            try {
                Utils.image = Glide.with(context)
                        .load(url).asBitmap()
                        .into(100, 100).get();
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
            context.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    if (imageView != null)
                        imageView.setImageBitmap(Utils.image);
                }
            });
        }
    });
    return Utils.image;
}

使用Glide库，在工作线程中运行以下代码，如下所示。
请编辑以包括一条注释，以便其他用户了解此答案的含义。 - Thomas Smyth - Treliant
1
Glide.with(context)
    .load("http://test.com/yourimage.jpg")  
    .asBitmap()  // переводим его в нужный формат
    .fitCenter()
    .into(new SimpleTarget<Bitmap>(100,100) {
          @Override
          public void onResourceReady(Bitmap bitmap, GlideAnimation<? super Bitmap> glideAnimation) {

           // do something with you bitmap 

                bitmap

          }
    });
1
欢迎来到stackoverflow。请阅读如何回答的说明（https://stackoverflow.com/help/how-to-answer）。 - Axel
1

试试这个：

AQuery aq = new AQuery(getActivity());
            aq.id(view.findViewById(R.id.image)).image(imageUrl, true, true, 0,  0,
                    new BitmapAjaxCallback() {
                        @Override
                        public void callback(String url, ImageView iv, Bitmap bm, AjaxStatus status){
                            iv.setImageBitmap(bm);
                        }
                    }.header("User-Agent", "android"));
1
  private class AsyncTaskRunner extends AsyncTask<String, String, String> {
    String Imageurl;

    public AsyncTaskRunner(String Imageurl) {
        this.Imageurl = Imageurl;
    }

    @Override
    protected String doInBackground(String... strings) {

        try {

            URL url = new URL(Imageurl);
            thumbnail_r = BitmapFactory.decodeStream(url.openConnection().getInputStream());


        } catch (IOException e) {
        }
        return null;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);


        imgDummy.setImageBitmap(thumbnail_r);
        UtilityMethods.tuchOn(relProgress);
    }
}

像这样调用asynctask：

 AsyncTaskRunner asyncTaskRunner = new AsyncTaskRunner(uploadsModel.getImages());
        asyncTaskRunner.execute();
0
请尝试以下步骤：
1）在类或适配器中创建AsyncTask（如果您想更改列表项图像）。
public class AsyncTaskLoadImage extends AsyncTask<String, String, Bitmap> {
        private final static String TAG = "AsyncTaskLoadImage";
        private ImageView imageView;

        public AsyncTaskLoadImage(ImageView imageView) {
            this.imageView = imageView;
        }

        @Override
        protected Bitmap doInBackground(String... params) {
            Bitmap bitmap = null;
            try {
                URL url = new URL(params[0]);
                bitmap = BitmapFactory.decodeStream((InputStream) url.getContent());
            } catch (IOException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return bitmap;
        }

        @Override
        protected void onPostExecute(Bitmap bitmap) {
            try {
                int width, height;
                height = bitmap.getHeight();
                width = bitmap.getWidth();

                Bitmap bmpGrayscale = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
                Canvas c = new Canvas(bmpGrayscale);
                Paint paint = new Paint();
                ColorMatrix cm = new ColorMatrix();
                cm.setSaturation(0);
                ColorMatrixColorFilter f = new ColorMatrixColorFilter(cm);
                paint.setColorFilter(f);
                c.drawBitmap(bitmap, 0, 0, paint);
                imageView.setImageBitmap(bmpGrayscale);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

2) 从您的活动、片段或适配器(在onBindViewHolder内部)调用AsyncTask。

2.a) 对于适配器:

    String src = current.getProductImage();
    new AsyncTaskLoadImage(holder.icon).execute(src);

2.b) 对于活动和片段：

**Activity:**
  ImageView imagview= (ImageView) findViewById(R.Id.imageview);
  String src = (your image string);
  new AsyncTaskLoadImage(imagview).execute(src);

**Fragment:**
  ImageView imagview= (ImageView)view.findViewById(R.Id.imageview);
  String src = (your image string);
  new AsyncTaskLoadImage(imagview).execute(src);

3) 请运行应用程序并检查图像。

愉快的编码....:)

0
如果您在不使用AsyncTask的情况下从位图加载URL，请在setContentView(R.layout.abc)之后写两行代码。
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

try {
    URL url = new URL("http://....");
    Bitmap image = BitmapFactory.decodeStream(url.openConnection().getInputStream());
} catch(IOException e) {
    System.out.println(e);
}
0
如果您正在使用Picasso来处理图片，您可以尝试以下方法！
public static Bitmap getImageBitmapFromURL(Context context, String imageUrl){
    Bitmap imageBitmap = null;
    try {
      imageBitmap = new AsyncTask<Void, Void, Bitmap>() {
        @Override
        protected Bitmap doInBackground(Void... params) {
          try {
            int targetHeight = 200;
            int targetWidth = 200;

            return Picasso.with(context).load(String.valueOf(imageUrl))
              //.resize(targetWidth, targetHeight)
              .placeholder(R.drawable.raw_image)
              .error(R.drawable.raw_error_image)
              .get();
          } catch (IOException e) {
            e.printStackTrace();
          }
          return null;
        }
      }.execute().get();
    } catch (InterruptedException e) {
      e.printStackTrace();
    } 
  return imageBitmap;
  }
0

如果你正在使用 Glide 和 Kotlin，

Glide.with(this)
            .asBitmap()
            .load("https://...")
            .addListener(object : RequestListener<Bitmap> {
                override fun onLoadFailed(
                    e: GlideException?,
                    model: Any?,
                    target: Target<Bitmap>?,
                    isFirstResource: Boolean
                ): Boolean {
                    Toast.makeText(this@MainActivity, "failed: " + e?.printStackTrace(), Toast.LENGTH_SHORT).show()
                    return false
                }

                override fun onResourceReady(
                    resource: Bitmap?,
                    model: Any?,
                    target: Target<Bitmap>?,
                    dataSource: DataSource?,
                    isFirstResource: Boolean
                ): Boolean {
                    //image is ready, you can get bitmap here
                    var bitmap = resource
                    return false
                }

            })
            .into(imageView)
0

非常快速的方法，这种方法运行非常迅速：

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;
    }
Util.copyStream(is, os); - Even Cheng
0
fun getBitmap(url : String?) : Bitmap? {
    var bmp : Bitmap ? = null
    Picasso.get().load(url).into(object : com.squareup.picasso.Target {
        override fun onBitmapLoaded(bitmap: Bitmap?, from: Picasso.LoadedFrom?) {
            bmp =  bitmap
        }

        override fun onPrepareLoad(placeHolderDrawable: Drawable?) {}

        override fun onBitmapFailed(e: Exception?, errorDrawable: Drawable?) {}
    })
    return bmp
}

尝试使用 Picasso

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