CODEWITHSUNDEEP
javaandroidbitmapout-of-memoryweak-references
KDEx
KDEx

Reputation: 3667

Create weak reference in method

I have the following method which has an ImageSwitcher that the user can slide left and right. The selected image is displayed in the center of the screen. I've done some image scaling for high res images on low memory phones, but I still run into Bitmap OutOfMemoryEexception when sliding quickly left to right. I'd like to transform the line mSwitcher.setImageURI(myUri);(This is the line that is causing the OOME) to use a weak reference, so that it can be automatically garbage collected. How can I do this? Is this the best way to performance optimize this method?

Thanks

method:

    public void onItemSelected(AdapterView parent, View v, int position, long id) {

    File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
            Environment.DIRECTORY_PICTURES), "MyAppName");
    File[] cachedOnSDImages = mediaStorageDir.listFiles();
    countArray = new Integer[cachedOnSDImages.length];
    fileArray = new String[cachedOnSDImages.length];
    fileArray[position] = cachedOnSDImages[position].getAbsolutePath();
    Uri myUri = Uri.parse(fileArray[position]);
    mSwitcher.setImageURI(myUri); // weakly reference myUri in this line
    this.currentpos = position;
}

I should add the mSwitcher is instantiated here:

    private void makeSwitcher() {
    mSwitcher =  (ImageSwitcher) findViewById(R.id.switcher);
    mSwitcher.setFactory(this);
    mSwitcher.setInAnimation(AnimationUtils.loadAnimation(this,
        android.R.anim.fade_in));
    mSwitcher.setOutAnimation(AnimationUtils.loadAnimation(this,
        android.R.anim.fade_out));
}

Upvotes: 3

Views: 5165

Answers (1)

dngfng
dngfng

Reputation: 1943

import java.lang.ref.WeakReference;

public class ReferenceTest {
        public static void main(String[] args) throws InterruptedException {

            WeakReference r = new WeakReference(new String("I'm here"));
            WeakReference sr = new WeakReference("I'm here");
            System.out.println("before gc: r=" + r.get() + ", static=" + sr.get());
            System.gc();
            Thread.sleep(100);

            // only r.get() becomes null
            System.out.println("after gc: r=" + r.get() + ", static=" + sr.get());

        }
}

Taken from wiki Weak references

This is how Weak references can be used in Java - however this also means that it will not work in your case since switcher would have to explicitly accept a WeakReference Object instead of a URI.

Upvotes: 5

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