Assets的BitmapFactory.decodeStream在Android 7上返回null

Question

如何从Android 7中的Asset目录解码位图？

我的应用程序在适用于Marshmallow的Android版本上运行良好.使用Android 7,无法从Asset目录加载图像.

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);

}

因此(仅限Android 7)BitmapFactory.decodeStream为空.它适用于较旧的Android API.

在调试模式下,我看到以下消息:

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

有人可以告诉我原因以及如何纠正编码？

编辑:同时我发现,删除带有inJustDecodeBounds = true的第一个BitmapFactory.decodeStream会导致一个成功的BitmapFactory.decodeStream,然后使用inJustDecodeBounds = false.不知道原因并且不知道如何替换位图大小的测量.

Answer 1

我想我们在同一条船上.我的团队像你一样坚持了这个问题.

这似乎是BitmapFactory.cpp中的一个问题(https://android.googlesource.com/platform/frameworks/base.git/+/master/core/jni/android/graphics/BitmapFactory.cpp)Android中添加了一些代码7.0并且发生了问题.

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

我发现该BitmapFactory.decodeStream方法在我们设置之后没有创建位图,inJustDecodeBounds=false但是当我尝试创建没有绑定解码的位图时.其作品!问题是关于BitmapOptions,因为当我们BitmapFactory.decodeStream再次调用时,InputStream不会更新.

所以我再次解码之前重置该InputStream

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;
}

看起来我们必须在每次重用之前重置InputStream.