performance
TRANSCRIPT
Yonatan Levin
Android Academy
How to create great apps
that also working well
OutOfMemory - Bitmap memory usageImage 1080X1920pixels, 124KB .png compressed Bitmap size = Width * Height * depth(4 bytes) = 8 MB!!!!
Reduce the size before loading it to the memory.BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(getResources(), R.id.myimage, options);
int imageHeight = options.outHeight;
int imageWidth = options.outWidth;
String imageType = options.outMimeType;
OutOfMemory - Garbage collectorA large number of small allocations can also cause heap fragmentation
List<Object> mTempObjects = new ArrayList<Object>(); for(int i=0; i<10000; i++){ mTempObjects.add(new Object());}
OutOfMemory - Garbage collector for(int i=0; i<mTempObjects.size(); i++){ Object c = mTempObjects.get(i); Log.d(TAG, "Object data:" + c.getValue()); }
10,000 references waiting to be collected by GC
OutOfMemory - Garbage collector“To improve is to change; to be perfect is to change often.” – Winston Churchill
Object c; for(int i=0; i<mTempObjects.size(); i++){ c = mTempObjects.get(i); Log.d(TAG, "Object data:" + c.getValue());}
OutOfMemory - Garbage collectorReuse of the same objectprivate StringBuilder buildSomething(StringBuilder sb){ sb.append(readString(fileStream)); sb.append(readOrderDetails(AnotheFileStream)); return sb; }No short term temporary object for String
Memory overheadObject with just one int take 16 bytes at minimum
Class Integer {private int value;
}Object overhead (8 bytes ) + Overhead of dlmalloc(8 bytes) + data (n bytes) = >16 bytes
Memory overheadclass HashMap$HashMapEntry<K,V> {
K key;V value;int hash;HashMapEntry<K,V> next;
}Total: 8 bytes (Object) + 8(dlmalloc) + 4*4(members) = 32 bytes
Primitive Type vs ObjectInteger (16 bytes) vs int(4 bytes)Boolean(16 bytes) vs boolean(4 bytes)
or bit-field(1 bit) //even
better!
Enums vs IntsVery simple - don’t use Enumspublic final static enum Things {
THING_1,THING_2,
}; == + 1,112 bytes
Enums vs IntsUse final static variable:public static int THING_1 = 1;public static int THING_2 = 2;------------------------128 bytes
Discover by yourselfimport java.lang.instrument.Instrumentation;
public class ObjectSizeFetcher {
private static Instrumentation instrumentation;
public static void premain(String args, Instrumentation inst) { instrumentation = inst; }
public static long getObjectSize(Object o) { return instrumentation.getObjectSize(o); } }
Use getObjectSize:
public class C { private int x; private int y;
public static void main(String [] args) {
System.out.println(ObjectSizeFetcher.getObjectSize(new C())); } }
Anonymous and Inner Classes~500 bytes of codebutton.setOnClickListener(new Runnable() {
public void run(){//do some stuff
}});unregister as soon as possible
Service- Very usefull, but overused.- Bind to Lifecycle
- Stop it when no need.- Use IntentService instead (will stop when job is
done)
- Release memory when your activity no longer visible
- Don’t hold direct references. Use WeakReference
- Stop all your handlers, threads in onPause/onStop
- Configuration changes
Memory Leak
ProguardTool to shrink, optimize and obfuscate the code.
Very usefull, hard to configure.
