更改android中位图的大小以避免OOM

时间：2016-08-19 03:20:48

标签： java android bitmap scale bitmapfactory

我一直在努力改变从服务器下载的位图的大小，因为我知道这是我遇到的OOM错误的问题。我已经尝试过跟随其他示例以及此示例https://developer.android.com/training/displaying-bitmaps/load-bitmap.html，但我不能就如何使用它以及在何处使用它做出正面或反面。我想将我的位图缩放到屏幕分辨率，但无法解决这个问题。感谢您对此提供任何帮助。

如果这有所不同，也不是在AsyncTask中完成。

以下是我设置位图的代码：

public class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {

BitmapFactory.Options options = new BitmapFactory.Options();

private final WeakReference<ImageView> imageViewReference;
Resources resources;

public ImageDownloaderTask(ImageView imageView) {
    imageViewReference = new WeakReference<ImageView>(imageView);
}


@Override
protected Bitmap doInBackground(String... params)
{
    return downloadBitmap(params[0]);
}
@Override
protected void onPostExecute(Bitmap bitmap) {
    if (isCancelled()) {
        bitmap = null;
        Log.d("HTTPS No go", bitmap.toString());
    }

    if (imageViewReference != null) {
        ImageView imageView = imageViewReference.get();
        if (imageView != null) {
            if (bitmap != null) {
                //Scale the bitmap to a smaller size
                imageView.setImageBitmap(bitmap);
            } else {
                Log.d("Downloading the image: ", "No Image found");
            }
        }

    }
}

//URL connection to download the image
private Bitmap downloadBitmap(String url) {

    HttpURLConnection urlConnection = null;
            try{
            URL uri = new URL(url);
            urlConnection = (HttpURLConnection) uri.openConnection();
            urlConnection.setRequestMethod("GET");
            int statusCode = urlConnection.getResponseCode();
            //check if the HTTP status code is equal to 200, which means that it is ok
            if (statusCode != 200) {
                return null;
            }

            InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {

                /*
                options.inJustDecodeBounds = true;
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, options);
                int imageHeight = options.outHeight;
                int imageWidth = options.outWidth;
                String imageType = options.outMimeType;
                int sampleSize = calculateInSampleSize(options, imageWidth, imageHeight);
                */
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                return bitmap;
            }
            }catch (ProtocolException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } {}

    return null;
}

public static int calculateInSampleSize(
        BitmapFactory.Options options, int reqWidth, int reqHeight) {
    // Raw height and width of image
    final int height = options.outHeight;
    final int width = options.outWidth;
    int inSampleSize = 1;

    if (height > reqHeight || width > reqWidth) {

        final int halfHeight = height / 2;
        final int halfWidth = width / 2;

        // Calculate the largest inSampleSize value that is a power of 2 and keeps both
        // height and width larger than the requested height and width.
        while ((halfHeight / inSampleSize) >= reqHeight
                && (halfWidth / inSampleSize) >= reqWidth) {
            inSampleSize *= 2;
        }
    }

    return inSampleSize;
}

}

更新

这修正了一下。它允许我只注销一次，但是当我第二次注销时，它会因旧的OOM错误而崩溃。 

InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {

                BitmapFactory.Options options = new BitmapFactory.Options();
                options.inSampleSize=1; //try to decrease decoded image

                Bitmap bitmap = BitmapFactory.decodeStream(inputStream , null, options);
                return bitmap;
            }
            }catch (ProtocolException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } {}

4 个答案:

答案 0 :(得分：2)

几天前我遇到了同样的问题。从理论上讲，有两种方法可以做到这一点。您可以完全下载图像然后调整图像大小，或者您必须要求服务器执行此操作而不是应用程序。我更喜欢第二种解决方案，我发送所需的宽度，高度和所需的图像。服务器计算可能的比例，然后缩小尺寸并返回，打印图像。之后我只使用HttpURLConnection下载位图，并从我的连接的输入流创建位图，没有任何问题。

你的错误怎么样，也许你试图先从流中计算然后创建它。当然它会导致崩溃，因为你试图第二次读取输入流。您的光标已经移动到流中，同时读取图像的元数据以了解大小。现在，当它尝试创建Bitmap时，它会失败，因为它不会从流的第0个字节开始。但是在中间的某个地方，你的光标上次停止了。因此，如果需要两次读取流，则需要先将输入流复制到某处以便能够读取流两次。希望它可以帮到你。

答案 1 :(得分：1)

我使用了这段代码：

    Bitmap outBitmap;

    // Decode image size
    BitmapFactory.Options o = new BitmapFactory.Options();
    o.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(photoPath, o);

    // The new size we want to scale to ensure memory usage is optimal
    int targetWidth;
    int targetHeight;
    if (o.outHeight > o.outWidth) {
        targetWidth = getResources().getInteger(R.integer.pic_width_px);
        targetHeight = getResources().getInteger(R.integer.pic_height_px);
    } else if (o.outHeight == o.outWidth) {
        targetWidth = targetHeight = getResources().getInteger(R.integer.pic_width_px);
    } else {
        targetWidth = getResources().getInteger(R.integer.pic_width_px);
        targetHeight = getResources().getInteger(R.integer.pic_height_px);
    }

    if (o.outWidth <= targetWidth && o.outHeight <= targetHeight) {
        // Return image as is without any additional scaling
        Bitmap origBitmap = BitmapFactory.decodeFile(photoPath, null);
        outBitmap = Bitmap.createBitmap(origBitmap, 0, 0, o.outWidth, o.outHeight, m, true);
        origBitmap.recycle();

        return outBitmap;
    }

    // Find the correct scale value. It should be the power of 2.
    int scale = 1;
    while(o.outWidth / scale / 2 >= targetWidth &&
            o.outHeight / scale / 2 >= targetHeight) {
        scale *= 2;
    }

    // Decode with inSampleSize
    BitmapFactory.Options scaleOptions = new BitmapFactory.Options();
    scaleOptions.inSampleSize = scale;

    Bitmap scaledBitmap = BitmapFactory.decodeFile(photoPath, scaleOptions);
    return Bitmap.createBitmap(scaledBitmap, 0, 0, scaledBitmap.getWidth(), scaledBitmap.getHeight(), m, true);

答案 2 :(得分：1)

我认为您需要在将图像读入内存之前更改图像的大小。

private Bitmap downloadBitmap(String url) {

    HttpURLConnection urlConnection = null;
            try{
            URL uri = new URL(url);
            urlConnection = (HttpURLConnection) uri.openConnection();
            urlConnection.setRequestMethod("GET");
            int statusCode = urlConnection.getResponseCode();
            //check if the HTTP status code is equal to 200, which means that it is ok
            if (statusCode != 200) {
                return null;
            }

            InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {

                //scale down the image and load
                options.inJustDecodeBounds = true;
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream, null, options);
                options.inSampleSize = calculateInSampleSize(options, 100, 100);
                options.inJustDecodeBounds = false;
                return BitmapFactory.decodeStream(inputStream, null, options);   //I'm not sure here, because the inputStream used twice.
            }
            }catch (ProtocolException e) {
                e.printStackTrace();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } {}

    return null;
}

答案 3 :(得分：0)

感谢所有帮助过的人。我发现我的问题不是下载位图的大小，因为每当我将它们添加到我的循环视图中时，我会自动调整它们的大小。它是由我在登录页面上播放的一个gif引起的，它占用了大量的内存，一旦任何其他东西占用了内存就会杀死它。

我非常感谢大家，谢谢你。我认为自己的问题在于下载图像，因为这就是通常的culperat。

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