Performance
Download as PPTX, PDF0 likes247 views
The document provides guidelines on handling bitmap memory usage effectively to prevent out-of-memory errors in Android applications. It emphasizes reducing image sizes before loading, managing object allocations to avoid heap fragmentation, and best practices for memory management, such as avoiding enums and using weak references. Additional tips include using ProGuard for code optimization and ensuring services are managed properly to release memory when not in use.
![Discover by yourself
import 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())); } }](https://image.slidesharecdn.com/performance-150824194137-lva1-app6892/85/Performance-13-320.jpg)
Performance
- 2. How to create great apps that also working well
- 3. OutOfMemory - Bitmap memory usage Image 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;
- 4. OutOfMemory - Garbage collector A 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()); }
- 5. 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
- 6. 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()); }
- 7. OutOfMemory - Garbage collector Reuse of the same object private StringBuilder buildSomething(StringBuilder sb){ sb.append(readString(fileStream)); sb.append(readOrderDetails(AnotheFileStream)); return sb; } No short term temporary object for String
- 8. Memory overhead Object 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
- 9. Memory overhead class 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
- 10. Primitive Type vs Object Integer (16 bytes) vs int(4 bytes) Boolean(16 bytes) vs boolean(4 bytes) or bit-field(1 bit) //even better!
- 11. Enums vs Ints Very simple - don’t use Enums public final static enum Things { THING_1, THING_2, }; == + 1,112 bytes
- 12. Enums vs Ints Use final static variable: public static int THING_1 = 1; public static int THING_2 = 2; ------------------------ 128 bytes
- 13. Discover by yourself import 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())); } }
- 14. Anonymous and Inner Classes ~500 bytes of code button.setOnClickListener(new Runnable() { public void run(){ //do some stuff } }); unregister as soon as possible
- 15. Service - Very usefull, but overused. - Bind to Lifecycle - Stop it when no need. - Use IntentService instead (will stop when job is done)
- 16. - 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
- 17. Proguard Tool to shrink, optimize and obfuscate the code. Very usefull, hard to configure.