[android] Detect application heap size in Android

How do you programmatically detect the application heap size available to an Android app?

I heard there's a function that does this in later versions of the SDK. In any case, I'm looking for solution that works for 1.5 and upwards.

This returns max heap size in bytes:

Runtime.getRuntime().maxMemory()

I was using ActivityManager.getMemoryClass() but on CyanogenMod 7 (I didn't test it elsewhere) it returns wrong value if the user sets heap size manually.

Some operations are quicker than java heap space manager. Delaying operations for some time can free memory space. You can use this method to escape heap size error:

waitForGarbageCollector(new Runnable() {
  @Override
  public void run() {
    // Your operations.
  }
});

/**
 * Measure used memory and give garbage collector time to free up some
 * of the space.
 *
 * @param callback Callback operations to be done when memory is free.
 */
public static void waitForGarbageCollector(final Runnable callback) {

  Runtime runtime;
  long maxMemory;
  long usedMemory;
  double availableMemoryPercentage = 1.0;
  final double MIN_AVAILABLE_MEMORY_PERCENTAGE = 0.1;
  final int DELAY_TIME = 5 * 1000;

  runtime =
    Runtime.getRuntime();

  maxMemory =
    runtime.maxMemory();

  usedMemory =
    runtime.totalMemory() -
    runtime.freeMemory();

  availableMemoryPercentage =
    1 -
    (double) usedMemory /
    maxMemory;

  if (availableMemoryPercentage < MIN_AVAILABLE_MEMORY_PERCENTAGE) {
    try {
      Thread.sleep(DELAY_TIME);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
    waitForGarbageCollector(
      callback);
  } else {
    // Memory resources are available, go to next operation:
    callback.run();
  }
}

The official API is:

This was introduced in 2.0 where larger memory devices appeared. You can assume that devices running prior versions of the OS are using the original memory class (16).

Do you mean programatically, or just while you're developing and debugging? If the latter, you can see that info from the DDMS perspective in Eclipse. When your emulator (possibly even physical phone that is plugged in) is running, it will list the active processes in a window on the left. You can select it and there's an option to track the heap allocations.

Debug.getNativeHeapSize() will do the trick, I should think. It's been there since 1.0, though.

The Debug class has lots of great methods for tracking allocations and other performance concerns. Also, if you need to detect a low-memory situation, check out Activity.onLowMemory().

Here's how you do it:

Getting the max heap size that the app can use:

Runtime runtime = Runtime.getRuntime();
long maxMemory=runtime.maxMemory();

Getting how much of the heap your app currently uses:

long usedMemory=runtime.totalMemory() - runtime.freeMemory();

Getting how much of the heap your app can now use (available memory) :

long availableMemory=maxMemory-usedMemory;

And, to format each of them nicely, you can use:

String formattedMemorySize=Formatter.formatShortFileSize(context,memorySize); 

Asus Nexus 7 (2013) 32Gig: getMemoryClass()=192 maxMemory()=201326592

I made the mistake of prototyping my game on the Nexus 7, and then discovering it ran out of memory almost immediately on my wife's generic 4.04 tablet (memoryclass 48, maxmemory 50331648)

I'll need to restructure my project to load fewer resources when I determine memoryclass is low.
Is there a way in Java to see the current heap size? (I can see it clearly in the logCat when debugging, but I'd like a way to see it in code to adapt, like if currentheap>(maxmemory/2) unload high quality bitmaps load low quality

Runtime rt = Runtime.getRuntime();
rt.maxMemory()

value is b

ActivityManager am = (ActivityManager) getSystemService(ACTIVITY_SERVICE);
am.getMemoryClass()

value is MB