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du...@google.com
Can you please describe exactly what method call you're making on ExifInterface? I would expect this to work for exifInterface.setAttribute(TAG_EXPOSURE_TIME, "1/1600") but not exifInterface.setAttribute(TAG_EXPOSURE_TIME, "0.000625").
du...@google.com
ta...@gmail.com
```
val sourceExif = ExifInterface(sourceFilePath)
val destinationExif = ExifInterface(destinationFilePath)
exifTagsList
.associateWith { sourceExif.getAttribute(it) }
.forEach { (tag, value) ->
destinationExif.setAttribute(tag, value)
}
destinationExif.saveAttributes()
```
Where exifTagsList contains the tags I need, e.g. ExifInterface.TAG_EXPOSURE_TIME.
I'm not sure if it's okay to simply read all attributes as String and write them as String, but it worked fine for all tags, except this one.
The attribute value I get for `getAttribute(TAG_EXPOSURE_TIME)` is a String `6.25E-4`. This should be parsed correctly as double value of `0,000625`, which is equal to the actual photo exposure time of `1/1600`.
The problem here is IMO the lack of precision - for higher exposure times like 1/100, 1/50, etc. it works fine. It doesn't for smaller values like 1/1600 or 1/3200.
When you run this code, you will get 1/1666 instead of 1/1600, which I suppose is lack of precision, as 1/1666 = 0,0006:
`exifInterface.setAttribute(TAG_EXPOSURE_TIME, "6.25E-4")`
I tried `exifInterface.setAttribute(TAG_EXPOSURE_TIME, "1/1600")` but it didn't work for me. Probably the interface expects a value that it can parse as double. According to ExifInterface documentation:
> TAG_EXPOSURE_TIME
> Type is double.
ap...@google.com
Thanks, I think part of the cause of the problem you're seeing is that exifInterface.getAttribute(TAG_EXPOSURE_TIME) is returning "6.25E-4" while setAttribute(TAG_EXPOSURE_TIME, value) is ideally expecting "1/1600".
Turns out there is code to handle the case of passing a decimal string to setAttribute, by converting it to a Rational representation of { int numerator, int denominator }, but it (arbitrarily)
Rational(double value) {
this(/* numerator= */ (long) (value * 10000), /* denominator */ 10000);
}
It looks like this code has been present for a long time, seems it was present in ExifInterface added in 2016
So I think there's an obvious improvement we can make here:
-
Fix the
double->Rationalconversion to support more precision. Ideally we would first try a denominator of1 / value(since this would give an exact result in the case of this bug, and probably most other cases since shutter speeds that are less than 1 are usually1/something), something like:Rational createRationalFromDouble(double value) { double inverse = 1 / value; if (isMathematicalInteger(value)) { return new Rational(1, (long) inverse); } // Not sure what we can do here }For the
elsecase, maybe we could do something clever with continued fractions:https://en.wikipedia.org/wiki/Continued_fraction
It feels like we should also align the format that getAttribute returns with the format setAttribute expects, in order to explicitly support the copying use-case you've described. That would mean changing getAttribute to return "1/1600" in this case. Unfortunately that is a breaking change for any existing code that is doing Double.parseDouble(exifInterface.getAttribute(TAG_EXPOSURE_TIME)), so not feasible. If we were to introduce this it would need to be a separate method.
Description
Version used: 3.0.0-alpha08 or 3.0.0-alpha09
Devices/Android versions reproduced on: Samsung Galaxy S8 / Android 9
Starting with version 3.0.0-alpha08 of the Paging library, the MediatorResult.Success(false) value returned from a RemoteMediator.load(LoadType.REFRESH, state) call doesn’t trigger a RemoteMediator.load(LoadType.APPEND, state) call and doesn’t update PagingDataAdapter.loadStateFlow to notify that the refresh state has changed from LoadState.Loading to LoadState.NotLoading.
This bug can be reproduced by means of the following project, if you’ve changed the version of the Paging library it uses so that it’s equal to 3.0.0-alpha08 or 3.0.0-alpha09: