Google Maps Android API v2 SupportMapFragment memory leak

Question

Using 2 simple activities. First Activity which only holds a button to start the 2nd Activity which holds the map:

Main Activity:

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}

public void goToMap(View view){ //This is just the onClick method for the button
    Intent intent=new Intent( this, BigMapTest.class);
    startActivity(intent);
}

The map activity:

public class BigMapTest extends FragmentActivity {
SupportMapFragment mapFragment;
GoogleMap map;

@Override
protected void onCreate(Bundle arg0) {
    // TODO Auto-generated method stub
    super.onCreate(arg0);

    setContentView(R.layout.travel_diary_big_map);

    mapFragment=(SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.big_map);
    map=mapFragment.getMap();

}

The XML Layout for the map activity:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >

<fragment
        android:id="@+id/big_map"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        class="com.google.android.gms.maps.SupportMapFragment"  
        />

Now when I run this code, pressing the button to move to the Activity with the map, and pressing back to get to the first activity...then repeating the process, I can see the heap increasing in size each time, until it reaches it's limits and then it starts clamping. If you mess around a bit more with map(i.e. zooming) I can get an OOM Exception at this point.

01-25 16:10:13.931: D/dalvikvm(21578): GC_FOR_ALLOC freed 1898K, 7% free 45859K/49187K, paused 204ms
01-25 16:10:14.671: I/dalvikvm-heap(21578): Clamp target GC heap from 52.724MB to 48.000MB
01-25 16:10:14.671: D/dalvikvm(21578): GC_CONCURRENT freed 2534K, 6% free 46554K/49187K, paused 3ms+14ms
01-25 16:10:15.372: I/dalvikvm-heap(21578): Clamp target GC heap from 52.979MB to 48.000MB
01-25 16:10:15.382: D/dalvikvm(21578): GC_CONCURRENT freed 2273K, 5% free 46815K/49187K, paused 3ms+15ms
01-25 16:10:15.622: I/dalvikvm-heap(21578): Clamp target GC heap from 52.604MB to 48.000MB
01-25 16:10:15.622: D/dalvikvm(21578): GC_FOR_ALLOC freed 657K, 6% free 46431K/49187K, paused 202ms
01-25 16:10:16.203: I/dalvikvm-heap(21578): Clamp target GC heap from 52.959MB to 48.000MB
01-25 16:10:16.203: D/dalvikvm(21578): GC_FOR_ALLOC freed 1469K, 5% free 46796K/49187K, paused 217ms
01-25 16:10:16.203: I/dalvikvm-heap(21578): Forcing collection of SoftReferences for 278744-byte allocation
01-25 16:10:16.423: I/dalvikvm-heap(21578): Clamp target GC heap from 52.952MB to 48.000MB
01-25 16:10:16.423: D/dalvikvm(21578): GC_BEFORE_OOM freed 9K, 5% free 46786K/49187K, paused 219ms
01-25 16:10:16.423: E/dalvikvm-heap(21578): Out of memory on a 278744-byte allocation.

Any suggestions/help would be appreciated.

Answer 1

Near as I can tell from some basic MAT sleuthing, what you are seeing is a cache maintained by Maps V2 of downloaded map data. The cache seems to be bigger if you pan and zoom a lot. The cache shrinks if you leave the map and return to a fresh map later on. I could not get N caches from N times launching the map activity of your sample app, and the cache size ebbed and flowed depending upon what the user did.

Alas, this cache is unconfigurable, AFAIK, in terms of how big it is, when it gets cleared out, does it spill over to disk, etc.

So, by default, all you can do is leave aside a healthy chunk of your heap space for Maps V2 to play with, and take steps to stay within this smaller subset of heap.

If you wanted to experiment, you could try calling clear() on GoogleMap, or onLowMemory() on your SupportMapFragment, to see if any help reduce this cache size.