来自Assets的BitmapFactory.decodeStream在Android 7上返回null [英] BitmapFactory.decodeStream from Assets returns null on Android 7

问题描述

如何在Android 7中解码Asset目录中的位图?

How to decode bitmaps from Asset directory in Android 7?

我的应用"在高达棉花糖的Android版本上运行良好.使用Android 7时，无法从Asset目录加载图像.

My App is running well on Android versions up to Marshmallow. With Android 7 it fails to load images from the Asset directory.

我的代码:

private Bitmap getImage(String imagename) {
    // Log.dd(logger, "AsyncImageLoader: " + ORDNER_IMAGES + imagename);

    AssetManager asset = context.getAssets();
    InputStream is = null;
    try {
        is = asset.open(ORDNER_IMAGES + imagename);
    } catch (IOException e) {
        // Log.de(logger, "image konnte nicht gelesen werden: " + ORDNER_IMAGES + imagename);
        return null;
    }


    // First decode with inJustDecodeBounds=true to check dimensions
    final BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeStream(is, null, options);

    // Calculate inSampleSize
    options.inSampleSize = calculateInSampleSize(options, PW, PH);

    // Decode bitmap with inSampleSize set
    options.inJustDecodeBounds = false;

    // Lesen des Bitmaps in der optimierten Groesse
    return BitmapFactory.decodeStream(is, null, options);

}

结果(仅适用于Android 7) BitmapFactory.decodeStream 为空.它可以在较旧的Android API上正常工作.

As a result (only Android 7) BitmapFactory.decodeStream is null. It works correctly an older Android APIs.

在调试模式下，我看到以下消息:

In debug mode I see the following Message:

09-04 10:10:50.384 6274-6610/myapp D/skia:--SkAndroidCodec :: NewFromStream返回null

09-04 10:10:50.384 6274-6610/myapp D/skia: --- SkAndroidCodec::NewFromStream returned null

有人可以告诉我原因以及如何纠正编码吗?

Can someone tell me the reason and how to correct the coding?

同时，我发现使用inJustDecodeBounds = true删除第一个BitmapFactory.decodeStream会导致之后使用inJustDecodeBounds = false的BitmapFactory.decodeStream成功.不知道原因，也不知道如何替代位图​​大小的度量.

Meanwhile i found, that removing of the first BitmapFactory.decodeStream with inJustDecodeBounds=true leads to a successful BitmapFactory.decodeStream afterwards with inJustDecodeBounds=false. Don't know the reason and don't know how to substitute the measurement of bitmap size.

推荐答案

我认为我们在同一条船上.我的团队像您一样在这个问题上停留了一段时间.

I think we are in the same boat. My team stuck in this problem for a while like you.

BitmapFactory.cpp(

It seems be a problem in BitmapFactory.cpp (https://android.googlesource.com/platform/frameworks/base.git/+/master/core/jni/android/graphics/BitmapFactory.cpp) Some code was added in Android 7.0 and made the problem occurred.

// Create the codec.
NinePatchPeeker peeker;
std::unique_ptr<SkAndroidCodec> codec(SkAndroidCodec::NewFromStream(streamDeleter.release(), &peeker));
if (!codec.get()) {
    return nullObjectReturn("SkAndroidCodec::NewFromStream returned null");
}

当我设置 inJustDecodeBounds = false 后，我发现 BitmapFactory.decodeStream 方法没有创建位图，但是当我尝试创建没有绑定解码的位图时.其作品！问题与BitmapOptions有关，因为当我们再次调用 BitmapFactory.decodeStream 时，InputStream不会更新.

And I found out the BitmapFactory.decodeStream method didn't create the bitmap after we set inJustDecodeBounds=false but when I try to create bitmap without bound decoding. It's works! The problem is about BitmapOptions in that InputStream doesn't updated when we called BitmapFactory.decodeStream again.

所以我先重置InputStream，然后再进行解码

So I reset that InputStream before decode again

private Bitmap getBitmapFromAssets(Context context, String fileName, int width, int height) {
    AssetManager asset = context.getAssets();
    InputStream is;
    try {
        is = asset.open(fileName);
    } catch (IOException e) {
        return null;
    }
    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inJustDecodeBounds = true;
    BitmapFactory.decodeStream(is, null, options);
    try {
        is.reset();
    } catch (IOException e) {
        return null;
    }
    options.inSampleSize = calculateInSampleSize(options, width, height);
    options.inJustDecodeBounds = false;
    return BitmapFactory.decodeStream(is, null, options);
}

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
    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;
        while ((halfHeight / inSampleSize) >= reqHeight
                && (halfWidth / inSampleSize) >= reqWidth) {
            inSampleSize *= 2;
        }
    }
    return inSampleSize;
}

似乎我们每次都必须重置InputStream才能重新使用它.

It's looks like we have to reset InputStream every time before reuse it.

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