Slide 1
Slide 1 text
Building stable
and flexible libraries
@KeithYokoma - Drivemode, Inc.
potatotips #12
Slide 2
Slide 2 text
KeithYokoma
Keishin Yokomaku
Drivemode, Inc.
Android Engineer
GitHub: https://github.com/KeithYokoma
e-Book: http://amzn.to/1mZNydv
Slide 3
Slide 3 text
Agenda
• Stability
• Flexibility
Slide 4
Slide 4 text
Make libraries STABLE
Slide 5
Slide 5 text
Make libraries STABLE
• Entity class declaration
• Multi-thread compatibility
• Lifecycle management
Slide 6
Slide 6 text
Make libraries STABLE
• Entity class declaration
• Don’t
• Do
void setToken(String token, String type, String refresh, long by);
void setToken(AccessToken token);
Slide 7
Slide 7 text
Make libraries STABLE
• Entity class declaration
• Hard to remember the type of args
• Not Type-Safe(ref. Effective Java)
void setToken(String token, String type, String refresh, long by);
Slide 8
Slide 8 text
• Entity class declaration
• Easy to remember the type of args
• Type-Safe
void setToken(AccessToken token);
Make libraries STABLE
Slide 9
Slide 9 text
Make libraries STABLE
• Multi-thread compatibility
• Synchronization
• Immutable entity
• Thread pool and callback lifecycle
• Singleton implementation
Slide 10
Slide 10 text
Make libraries STABLE
• Multi-thread compatibility
• Synchronization
• “synchronized” block
• Synchronization utils(CyclicBarrier, …)
• Atomicity(AtomicInteger, …)
• “volatile” field
Slide 11
Slide 11 text
Make libraries STABLE
• Multi-thread compatibility
• Immutable entity
• Immutable entity is thread safe
Slide 12
Slide 12 text
Make libraries STABLE
• Multi-thread compatibility
• Thread pool and callback lifecycle
• Reduce thread initialization cost
• Align callback lifetime with “Context”
• Do NOT callback to dead object
Slide 13
Slide 13 text
Make libraries STABLE
• Multi-thread compatibility
• Singleton implementation
• Be aware of “Lazy Initialization”
Slide 14
Slide 14 text
// NOT thread safe!!
public class Singleton {
private static Singleton sInstance;
public static Singleton getInstance() {
if (sInstance == null) {
sInstance = new Singleton();
}
return sInstance;
}
}
Case Study
Multi-thread compatibility
Slide 15
Slide 15 text
Make libraries STABLE
• Multi-thread compatibility
• Singleton implementation
• “synchronized” block
• Double checked locking
• Initialization on demand holder
Slide 16
Slide 16 text
private static Singleton sInstance;
public static synchronized Singleton getInstance() {
if (sInstance == null) {
sInstance = new Singleton();
}
return sInstance;
}
Case Study
Multi-thread compatibility
Slide 17
Slide 17 text
private static volatile Singleton sInstance;
public static Singleton getInstance() {
if (sInstance == null) {
synchronized (Singleton.class) {
if (sInstance == null) {
sInstance = new Singleton();
}
}
}
return sInstance;
}
Case Study
Multi-thread compatibility
Slide 18
Slide 18 text
static class Holder {
public static final Singleton SINGLETON = new Singleton();
}
public static getInstance() {
return Holder.SINGLETON;
}
Case Study
Multi-thread compatibility
Slide 19
Slide 19 text
Make libraries STABLE
• Lifecycle management
• Object lifetime alignment
Slide 20
Slide 20 text
Make libraries STABLE
• Lifecycle management
• Object lifetime alignment
• Lifecycle methods of various “Context”
• onCreate/onDestroy
• onStart/onStop, onResume/onPause
Slide 21
Slide 21 text
Make libraries STABLE
• Lifecycle management
• Object lifetime alignment
• Naming convention
• add/remove, register/unregister
• start/finish, initialize/destroy
Slide 22
Slide 22 text
Make libraries FLEXIBLE
Slide 23
Slide 23 text
Make libraries FLEXIBLE
• Annotations vs Listeners
• Customizable resources
• Split package by domain
Slide 24
Slide 24 text
Make libraries FLEXIBLE
• Annotations
✓ Fast and easy development for client
✓ Automatic code generation(with apt)
✗ Slow(both runtime and apt takes time)
✗ Hard to dig into library itself
Slide 25
Slide 25 text
Make libraries FLEXIBLE
• Listeners
✓ Faster than annotations(runtime)
✓ Simple architecture
✗ Client should maintain the lifetime
Slide 26
Slide 26 text
Make libraries FLEXIBLE
• Annotations and Listeners
• Do NOT call methods of dead object
Slide 27
Slide 27 text
• Customizable resources
• If the library has UI resources…
• Theme should be customizable
• What about layout resources?
Make libraries FLEXIBLE
Slide 28
Slide 28 text
• Customizable resources
• At least you need to…
• Define ID resources that the library uses
• Otherwise layout may not be customized
Make libraries FLEXIBLE
Slide 29
Slide 29 text
Make libraries FLEXIBLE
• Split package by domain
• Avoid exceeding 65k method limit
• Less effort to strip out codes not used
Slide 30
Slide 30 text
Make libraries FLEXIBLE
• Split package by domain
• e.g. Guava
• guava, guava-gwt, guava-annotations, …
• e.g. Google Play Services 6.5
• play-services, play-services-wearable, …
Slide 31
Slide 31 text
–Joshua Bloch
“Never make the client do anything
the library can do for the client.”
Slide 32
Slide 32 text
Building stable
and flexible libraries
@KeithYokoma - Drivemode, Inc.
potatotips #12