Why does the bitmap from the cache in the folllowing code return null?

Question

The following code should be caching image into the memory but every time I run it the cache always return null. What could be the issue? I have used the code as exactly as it is on the Android Developer website.

private lateinit var memoryCache: LruCache<String, Bitmap>

fun load(imageUrl: String, imageView: ImageView) {

    val maxMemory = (Runtime.getRuntime().maxMemory() / 1024).toInt()

    val cacheSize = maxMemory / 8

    memoryCache = object : LruCache<String, Bitmap>(cacheSize) {

        override fun sizeOf(key: String, bitmap: Bitmap): Int {

            return bitmap.byteCount / 1024

        }
    }

    CoroutineScope(IO).launch {

        loadBitmap(imageUrl, imageView)

    }

}

suspend fun loadBitmap(imageUrl: String, imageView: ImageView) {

    val bitmap: Bitmap? = memoryCache[imageUrl]

    if (bitmap != null) {
        withContext(Dispatchers.Main) {
            imageView.setImageBitmap(bitmap)
        }
    } else {
        val url = URL(imageUrl)
        val image = BitmapFactory.decodeStream(url.openConnection().getInputStream())

        withContext(Dispatchers.Main) {
            imageView.setImageBitmap(image)
        }
        memoryCache.put(imageUrl, image)
    }
}

@blackapps https://developer.android.com/topic/performance/graphics/cache-bitmap#kotlin this — ronnieotieno, Jan 03 '20 at 12:12
`memoryCache.put(imageUrl, image)` Isnt there a return value? — blackapps, Jan 03 '20 at 12:13
@blackapps apparently no. I even added .also to display the value after putting it in the cache and it displayed nothing — ronnieotieno, Jan 03 '20 at 12:15
Quote: `Note: In this example, one eighth of the application memory is allocated for our cache. On a normal/hdpi device this is a minimum of around 4MB (32/8). A full screen GridView filled with images on a device with 800x480 resolution would use around 1.5MB (800*480*4 bytes), so this would cache a minimum of around 2.5 pages of images in memory.` Check the size of your bitmap. — blackapps, Jan 03 '20 at 12:16
Please first tell if that was the problem. And if it was then allocate more. But... memory caches for bitmaps are a bad idea as it takes so much memory. If you need a memory cache then save .jpgs in it instead of bitmaps. But you could use a file cache too. — blackapps, Jan 03 '20 at 12:19
Is that the size of the cache or the bitmap? You should tell both of course. Only then we can see if the bitmap would fit in the cache. — blackapps, Jan 03 '20 at 12:33
Also determine how many elements are in your cache right after putting one in. — blackapps, Jan 03 '20 at 12:35
@blackapps that's the size of one bitmap to be cached. I am afraid Idk how to determine the size of the cache. — ronnieotieno, Jan 03 '20 at 12:38
`max size` ? was that cacheSize or maxMemory? (Please be exact). — blackapps, Jan 03 '20 at 12:46
@blackapps after removing the divide by 1024 the size is 536870912 and still it doesnt show — ronnieotieno, Jan 03 '20 at 12:46
Quote: `// Get max available VM memory, exceeding this amount will throw an // OutOfMemory exception.` , You have that exception? — blackapps, Jan 03 '20 at 12:51
@blackapps I have no exception its just doesn't show even with max memory allocated — ronnieotieno, Jan 03 '20 at 12:53
Sorry i see now that that exception will come at creating the cache. Not at putting something in it. But then... no warning if the cache is full or to small at put() is no good. — blackapps, Jan 03 '20 at 12:57
Cache size is 65 MB and your bitmap was an unreadable 96000000 or better 96.000.000 hence 96 MB. Does not fit indeed. You can easily enlarge the cache size to hold that bitmap. — blackapps, Jan 03 '20 at 12:59

Why does the bitmap from the cache in the folllowing code return null?

0 Answers0