android - 在 AsyncTask 中压缩位图时抛出异常不会停止执行

Question

我有一个用 Kotlin 编写的 AsyncTask，它处理位图并将其存储到内部存储器中的文件中。我的手机没有用于新位图的可用空间，因此在写入期间抛出 IOException，这应该会导致应用程序崩溃。

这是我的doInBackground() 函数:

override fun doInBackground(vararg params: Int?): Exception? {
    if(params[0] == null)
        throw IllegalArgumentException();
    Log.d("PhotoEditTask", "start")
    var bitmap : Bitmap? = null
        val degrees = if(params.size == 0) 0 else params[0] ?: 0
        bitmap = BitmapProcessing.getBitmapFromUri(sourceUri, resolver)
        if (bitmap != null) {
            bitmap = BitmapProcessing.rotateBitmap(bitmap, degrees)
            var destFile = File(destPath)
            destFile.delete()
            BitmapFile.saveBitmapToFile(bitmap, destFile, 85)
            Log.d("PhotoEditTask", "save successfull!")
            return null
        }
        bitmap?.recycle()

    return Exception("Write failed")

}

将文件写入位图的函数是:

fun saveBitmapToFile(source: Bitmap, dest: File, quality: Int) {
        var fout : FileOutputStream? = null
        fout = FileOutputStream(dest)
        source.compress(Bitmap.CompressFormat.PNG, quality, fout)
        fout.flush()
        fout.close()
        Log.d("BitmapProcessing", "fout is closed")

    }

这应该会崩溃，或者至少会返回带有“写入失败”消息的异常，但它永远不会返回 null，因为我的手机无法写入文件。但是日志显示不同:

09-09 12:16:40.824 26074-26805/com.criptext.uisample D/skia: jpeg_decoder finish successfully, L:1881!!!
09-09 12:16:40.833 26074-26805/com.criptext.uisample W/System.err: java.io.IOException: write failed: ENOSPC (No space left on device)
09-09 12:16:40.836 26074-26805/com.criptext.uisample W/System.err:     at libcore.io.IoBridge.write(IoBridge.java:499)
09-09 12:16:40.836 26074-26805/com.criptext.uisample W/System.err:     at java.io.FileOutputStream.write(FileOutputStream.java:187)
09-09 12:16:40.837 26074-26805/com.criptext.uisample W/System.err:     at android.graphics.Bitmap.nativeCompress(Native Method)
09-09 12:16:40.837 26074-26805/com.criptext.uisample W/System.err:     at android.graphics.Bitmap.compress(Bitmap.java:1013)
09-09 12:16:40.837 26074-26805/com.criptext.uisample W/System.err:     at com.criptext.monkeykitui.util.BitmapFile.saveBitmapToFile(BitmapFile.java:18)
09-09 12:16:40.837 26074-26805/com.criptext.uisample W/System.err:     at com.criptext.monkeykitui.input.photoEditor.PhotoEditTask.doInBackground(PhotoEditTask.kt:42)
09-09 12:16:40.838 26074-26805/com.criptext.uisample W/System.err:     at com.criptext.monkeykitui.input.photoEditor.PhotoEditTask.doInBackground(PhotoEditTask.kt:17)
09-09 12:16:40.838 26074-26805/com.criptext.uisample W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:288)
09-09 12:16:40.838 26074-26805/com.criptext.uisample W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
09-09 12:16:40.839 26074-26805/com.criptext.uisample W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
09-09 12:16:40.840 26074-26805/com.criptext.uisample W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
09-09 12:16:40.840 26074-26805/com.criptext.uisample W/System.err:     at java.lang.Thread.run(Thread.java:848)
09-09 12:16:40.840 26074-26805/com.criptext.uisample W/System.err: Caused by: libcore.io.ErrnoException: write failed: ENOSPC (No space left on device)
09-09 12:16:40.842 26074-26805/com.criptext.uisample W/System.err:     at libcore.io.Posix.writeBytes(Native Method)
09-09 12:16:40.842 26074-26805/com.criptext.uisample W/System.err:     at libcore.io.Posix.write(Posix.java:202)
09-09 12:16:40.843 26074-26805/com.criptext.uisample W/System.err:     at libcore.io.BlockGuardOs.write(BlockGuardOs.java:197)
09-09 12:16:40.843 26074-26805/com.criptext.uisample W/System.err:     at libcore.io.IoBridge.write(IoBridge.java:494)
09-09 12:16:40.843 26074-26805/com.criptext.uisample W/System.err:  ... 11 more
09-09 12:16:40.843 26074-26805/com.criptext.uisample D/skia: ------- write threw an exception
09-09 12:16:40.844 26074-26805/com.criptext.uisample D/BitmapToFile: fout is closed
09-09 12:16:40.844 26074-26805/com.criptext.uisample D/PhotoEditTask: save successfull!
09-09 12:16:40.844 26074-26074/com.criptext.uisample D/PhotoEditTask: result: null

根据Log，抛出IOException，并在某处被捕获，但执行从未中断，所以总是返回null。到底是怎么回事？我该如何处理 IOException？？

Answer 1

Bitmap 类 compress() method有意不在失败时抛出异常。

文档没有列出此方法的异常，而是将预期的返回值列为:

Returns: boolean true if successfully compressed to the specified stream.

这就是为什么您会看到 “fout is closed” 的日志输出行，因为没有抛出异常并且没有检查 bool 结果。

调用 compress() 的代码行需要检查 bool 结果:

if (!source.compress(Bitmap.CompressFormat.PNG, quality, fout)) {
    throw IOException("compression failure")
}