未捕获内存不足异常

Question

I have option to save Bitmap to sdcard in my app.
I am doing saving in AsyncTask method. here is what i do on background

public File saveImageToExternalStorage(Bitmap image, String name) {
 String fullPath = Environment.getExternalStorageDirectory().getAbsolutePath() + APP_PATH_SD_CARD + APP_THUMBNAIL_PATH_SD_CARD;

 try {
 File dir = new File(fullPath);
 if (!dir.exists()) {
 dir.mkdirs();
 }
 OutputStream fOut = null;
 File file = new File(fullPath, name.replaceAll("/", "").trim());
 file.createNewFile();
 fOut = new FileOutputStream(file);
 image.compress(Bitmap.CompressFormat.JPEG, 50, fOut);
 fOut.flush();
 fOut.close();
 MediaStore.Images.Media.insertImage(getApplicationContext().getContentResolver(), file.getAbsolutePath(), file.getName(), file.getName());

 return file;

 } catch (Exception e) {
 return null;
 }

I am displaying some information about failing to save and etc for user if I get null from this method. I though this should be sufficient, yet I got reported OutOfMemory crash by one user from this method. Stacktrace:

java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:299)
at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
at java.util.concurrent.FutureTask.run(FutureTask.java:137)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
at java.lang.Thread.run(Thread.java:856)
Caused by: java.lang.OutOfMemoryError
at android.graphics.BitmapFactory.nativeDecodeStream(Native Method)
at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:527)
at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:301)
at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:326)
at android.provider.MediaStore$Images$Media.insertImage(MediaStore.java:796)
at com.stancedcars.wallpapers.FullSelected.saveImageToExternalStorage(FullSelected.java:223)

I would love to solve OutOfMemory issue, but Bitmap s are heavy in size, high resolution images, I wouldn't want to reduce quality. More importantly I would like to know why the app crashed even though it was in try catch ?

Answer 1

You catch the generic Exception, while OutOfMemoryError is an Error, which is Throwable as well.

What you got

java.lang.Object
   ↳    java.lang.Throwable
       ↳    java.lang.Error
           ↳    java.lang.VirtualMachineError
               ↳    java.lang.OutOfMemoryError

What you can catch

java.lang.Object
   ↳    java.lang.Throwable
       ↳    java.lang.Exception

So to catch all possible Throwables, you need to catch

try {
     //...
} catch (Throwable e) {
    e.printStackTrace();
}

Answer 2

Use catch OutOfMemoryError not Exception!

try {
    // your code
} catch (OutOfMemoryError e) {
}

Answer 3

Once a program goes out of memory it can be hard for it to recover. You need to think carefully about how to try and clean up when that happens. For example, in your saveImageToExternalStorage, it doesn't clean up the fOut if an exception occurs inside your try/catch. So you should do things like put

OutputStream fOut = null;

outside the try/catch, and then close it in a finally block of the try/catch. And pay attention to the possibility of further exceptions in the catch of finally blocks.