1

I am struggling with a memory leak associated with a ListView. I have created the following small program which exhibits this behavior.

What I do is create 2 LinearLayouts. The first has a Button and a GListView control. The code for GListView is below, but it just sub-classes ListView, and implements the ListAdapter interface. When the GListView is created, it sets it's adapter to itself.

Now when you press the button I switch to the second LinearLayout. This layout has only a single button. When you press this button, I create a new 1st layout with a new GListView and set it as the active view.

Run the program, and switch between the two views 20 times. Then bring up the DDMS and force a garbage collection. Then Dump the memory, and use the Memory Analyzer and you will find 21 GListView objects remaining. That is, the 20 GListViews that are not longer connected to anything have NOT been freed.

If I do a memory dump and take a look at one of the GListViews that should have been recycled, and list the incomming references using the Memory Analyzer, I get the following:

Class Name                                                              | Shallow Heap | Retained Heap 
-------------------------------------------------------------------------------------------------------
com.gabysoft.memoryleak.GListView @ 0x43e72270 Unknown                  |          672 |         3,528 
|- host android.view.View$ScrollabilityCache @ 0x43e72560               |           80 |           584 
|- this$0 android.widget.AbsListView$RecycleBin @ 0x43e72830            |           40 |           160 
|- mCallback android.graphics.drawable.StateListDrawable @ 0x43e728a8   |           64 |         1,464 
|- this$0 android.widget.AdapterView$AdapterDataSetObserver @ 0x43e730b8|           16 |            16 
-------------------------------------------------------------------------------------------------------

Now if I comment out the 'setAdapter(this)' function in the GListView constructor and repeat the above, I find that there is only 1 GListView that remains. That is, in this case, all of the unused GListViews have been properly recycled.

Someone suggested that I create a private class within my GListView to handle the ListAdapter interface, and I tried that, but it did not help. I have also tried creating a completely separate public class to handle the ListAdapter, but, alas, that doesn't seem to work either.

Surely there is some way to make these objects go away when they are no longer used anywhere. (Isn't that what garbage collection is all about?)

Any help would be appreciated. I am really pulling my hair out on this one.

Thanks.

/*
 * Activity
 */

package com.gabysoft.memoryleak;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.ListView;

public class MemoryLeak extends Activity implements android.view.View.OnClickListener 
{
    LinearLayout ll2;
    boolean page2 = false;

    private LinearLayout CreateLayout()
    {
        LinearLayout ll = new LinearLayout(this);

        Button btn1 = new Button(this);
        ListView    lv    = new GListView(this);

        btn1.setText("Press");
        btn1.setLayoutParams(new LinearLayout.LayoutParams(100, 40));
        btn1.setOnClickListener(this);

        ll.addView(btn1);
        ll.addView(lv);

        return(ll);
    }

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);

        CreateLayout();

        LinearLayout ll = CreateLayout();
        ll2 = new LinearLayout(this);

        Button btn2 = new Button(this);

        btn2.setText("Back");
        btn2.setLayoutParams(new LinearLayout.LayoutParams(100, 40));
        btn2.setOnClickListener(this);

        ll2.addView(btn2);

        setContentView(ll);
    }

    @Override
    public void onClick(View v) 
    {
        if (page2)
        {
            LinearLayout ll = CreateLayout();

            setContentView(ll);

            page2 = false;
        }
        else
        {
            setContentView(ll2);
            page2 = true;
        }
    }

}

/*
 * GListView
 */
package com.gabysoft.memoryleak;

import android.content.Context;
import android.database.DataSetObserver;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class GListView extends ListView implements ListAdapter
{
    Context m_context;
    DataSetObserver m_observer = null;

    public GListView(Context context) 
    {
        super(context);

        m_context    = context;

        setAdapter(this);

        setChoiceMode(CHOICE_MODE_SINGLE);
    }

    /*
     * ListAdapter 
     */


    @Override
    public boolean areAllItemsEnabled() 
    {
        return true;
    }

    @Override
    public boolean isEnabled(int position) 
    {
        return true;
    }

    @Override
    public int getCount() 
    {
        return(0);
    }    

    @Override
    public Object getItem(int position) 
    {
        return null;
    }

    @Override
    public long getItemId(int position) 
    {
        return(position);
    }

    @Override
    public int getItemViewType(int position) 
    {
        return 0;
    } 

    @Override
    public View getView(int position, View convertView, ViewGroup parent) 
    {
        TextView tv = new TextView(m_context);

        tv.setText("Item");

        return(tv);
    }

    @Override
    public int getViewTypeCount() 
    {
        return 1;
    }

    @Override
    public boolean hasStableIds() 
    {
        return false;
    }

    @Override
    public boolean isEmpty() 
    {
        return false;
    }

    @Override
    public void registerDataSetObserver(DataSetObserver observer) 
    {
        m_observer    = observer;
    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) 
    {
        m_observer    = null;
    }
}
6
  • @John Gaby: Post a link to a ZIP file containing a complete project with this code, that I can download and play with, and I'll take a look at it. Commented Oct 22, 2010 at 15:44
  • Thanks for taking a look. I couldn't see how I can post a file along with this comment, so I uploaded it to my website. You can download it at gabysoft.com/download/memoryleak.zip. I am running it on the emulator (although I believe that it happens on a real device as well) using Android 2.2 Commented Oct 22, 2010 at 16:21
  • @John Gaby: Yeah, you can't attach files to SO questions, so what you did there was fine. Give me a few hours, as I have a book update I would like to get out the door first. Commented Oct 22, 2010 at 16:26
  • Thanks, I really appreciate the help. I have tried a lot of different things, and it seems that no matter what I do, I cannot get my GListView objects to recycle. Commented Oct 22, 2010 at 16:34
  • Also note that real application is much more complex, and does things a bit differently than in this simple example. What I tried to do here was create as simple a program that I can which exhibits the behavior I am seeing in my full application. Commented Oct 22, 2010 at 16:39

1 Answer 1

1

Your GListView objects are being garbage collected. Leastways, they are called with finalize() when a manual GC is done from DDMS. Unfortunately, the DDMS HPROF file seems incompatible with my version of jhat, and I'm not an Eclipse user so I do not have ready access to MAT.

Sign up to request clarification or add additional context in comments.

15 Comments

Strange, that is not the behavior that I am seeing. I added an override finalize method to my GListView class, and I only ever see it called one time, even though I create many GListView objects that need to be recycled. I uploaded the version with the log to gabysoft.com/download/MemoryLeak.zip. Is it possible that I am seeing this because I am using Eclipse and you are not?
@John Gaby: I downloaded your latest ZIP, compiled and installed it into a 2.2 emulator, clicked the button 40 times, did a manual GC from DDMS, and got 21 finalize debug messages. You might want to try running the test from outside of Eclipse once. To do this, go to your project directory, and run android update project -p . (assumes your SDK tools/ directory is in your PATH). Install Apache Ant if you don't have it, start an emulator via the android command, and run ant clean install. Run DDMS via ddms.
Thanks again for you help. I will have to track down Apache Ant and give it a try. I can tell you that the GListView is the source of my problem even in my real app. I have a page which contains a GListView has a large graphic as a background. If I reload that page enough times, the program crashes with an out of memory error. I fixed it so that I remove the GListView from it parent ViewGroup, and, although the GListView is not freed, the parent is. After this change, I can load the page many times without a crash. I do not understand why I see this with Eclipse.
@John Gaby: "If I reload that page enough times, the program crashes with an out of memory error." -- my guess is that is tied to your "large graphic as a background". Try not to recreate that Bitmap every time.
Thanks, I know that. The problem is that the old page was not being freed by the GC. I tracked it down to the fact that the GListView was not being freed. If, after I am through with that page, I remove the GListView from the ViewGroup, then the page does get freed, and I no longer see the Out Of Memory condition. However, using the Memory Analyzer, I can see that the GListViews are still not being freed. I am trying to get Ant to work so that I can investigate the problem from that direction. It is very strange.
|

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.