Download pdf - Xamarin - Under the bridge

@ITCAMPRO #ITCAMP17Community Conference for IT Professionals @ITCAMPRO #ITCAMP17Community Conference for IT Professionals

Xamarin - Under the Bridge

Microsoft&Xamarin MVP, Xamarin Certified Mobile Developer

CTO Mahiz S.r.l.

[email protected] Twitter: @danardelean

Dan Ardelean

mailto:[email protected]


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POWERED BY


XAMARIN


XAMARIN

C#/F#

Visual Studio

Xamarin Studio

Black Magic

Native


iOS Native Applications


iOS Native Application


DEMO XCODE

SINGLE VIEW APPLICATION


C# to Objective-C world


Xamarin iOS Compilation


• Expose Objectve-C to C# using Selectors• objc_msgSend functions

Selectors

-[NSString sizeWithFont:forWidth:lineBreakMode:]

sizeWithFont Selector:

- (CGSize)sizeWithFont:(UIFont *)font forWidth:(CGFloat)width lineBreakMode:(UILineBreakMode)lineBreakMode

Objective-C declaration:

CGSize objc_msgSend(IntPtr target, IntPtr selector, IntPtr font, nfloat width, UILineBreakMode mode);

objc_msgSend

[DllImport (Constants.ObjectiveCLibrary,EntryPoint="objc_msgSend")]

static extern CGSize cgsize_objc_msgSend_IntPtr_float_int ( IntPtr target, IntPtr selector, IntPtr font,

nfloat width, UILineBreakMode mode);

http://developer.apple.com/iphone/library/documentation/UIKit/Reference/NSString_UIKit_Additions/Reference/Reference.html#//apple_ref/occ/instm/NSString/sizeWithFont:forWidth:lineBreakMode:


• Expose Objectve-C to C# using Selectors• objc_msgSend functions

Selectors

NSString target = ...

Selector selector = new Selector ("sizeWithFont:forWidth:lineBreakMode:");

UIFont font = ...

nfloat width = ...

UILineBreakMode mode = ...

CGSize size = cgsize_objc_msgSend_IntPtr_float_int( target.Handle, selector.Handle, font == null ?

IntPtr.Zero : font.Handle, width, mode);


• Expose Managed Code to Objective-C

Registrars

[Register]

class MyViewController : UIViewController{

[Export ("myFunc")]

public void MyFunc () { }

}

C# (Managed Code)

Objective-C

@interface MyViewController : UIViewController { } -(void)myFunc;

@end @implementation

MyViewController {} -(void) myFunc{ /* code to call the managed MyViewController.MyFunc method */}

@end


DEMO XAMARIN IOS

Single View Application


Xamarin.iOS creates a managed wrapper, called a peer

object, for every native object accessed by the

Xamarin.iOS runtime

Peer wrapper objects

UIKit.UIButton

(peer object)

[UIButton]

(native object)IntPtrHandle

Allocated by

Xamarin.iOS

and collected by the

GC

Allocated by the iOS

runtime

and reference counted


• Peer object increment the retain count; it is released

when the managed peer is disposed or finalized

Memory allocation Xamarin.iOS

1

GC

Collect[brelease] 0

b =null;

b.Dispose(); [brelease] 0

var b = new UIButton(...) [[UIButton alloc] init]

…

or


Monitoring memory allocations

Memory

Analysis

(Heap shot)

Instrument

s

Androi

d

Device

Monitor

Xamarin

Profiler

VS

Profiler


DEMO MEMORY ALLOCATION

Single View Application


Prefer full delegate methods over lambdas – it makes it

easier to see and understand strong references

Call Dispose() to release native resources immediately (vs.

waiting ona GC) when you are finished with a peer

wrapper

Always unsubscribe from events you manually wire up;

alternatively, use the Storyboard to connect events which

can then be cleaned up automatically

Xamarin.iOS Tips


Android native application


Android Native Compilation

.dexfilesJava

compile

r

Android

dex

compiler

Java

bytecodes

Dalvik

bytecodes


Android Native Compilation

.dex files

Resources

(e.g.

images)

.apkfileAndroid

apkbuilde

rThe .apkfile contains

all the app's assets

and is ready to run


Android Native Execution

Bytecodes are compiled to

native code at installation

(called Ahead-of-Time or

AOT)

MyApp.apkAndroid

Runtime

(ART)

Apps run in their own

process with their own

copy of the ART Virtual

Machine


DEMO ANDROID STUDIO


Xamarin.Android Architecture


Xamarin.Android Compilation

assemblyC#

compiler

IL and

metadata

Linke

r

Monoassemblies

yourassemblies

Monoassemblies

(filtered)

Determines which class members are used in

your app and includes only those members in

the output

yourassemblies

(filtered)


Xamarin.Android Compilation

Mono

Runtime

The Xamarin build tools

add the Mono VM to

your application

package

.apkfileAndroid

apkbuilde

r


DEMO XAMARIN.ANDROID


Xamarin.Android GC Process

GC

Collect

Can

collect

object?

Is

Peer

Object

?

Ye

sReplace JNI

handle with

Weak Handle

Ye

s

Force Android GCJNI

handle

collected

?

Collect objectNo

Ye

s

Replace JNI

weak handle

with strong

handle reference

NoPeer

object

kept alive


• Integration between Xamarin GC and JVM GC is

performed through a native extension called the GC

Bridge

GC Bridge

Xamarin

Manage

d

Memory

Android

Manage

d

Memory

GC

Bridge

Process

Memor

y


• GC_ messages provide details about bridge and

collection times

Monitoring GC Performance

GC_MAJOR: (Minor allowance) pause 29.11ms, total 29.35ms, bridge 0.15msmajor

4048K/0K los 2766K/0K

Lower pause, bridge and total times are

preferred


• C# objects must be boxed to create a JVM

representation of the object; intrinsic types (strings,

numeric values and dates) are all special cased

Xamarin and the JAVA VM

C#

ObjectJava

Object

ArrayAdapter<Tweet>ArrayAdapter

ArrayLi

stTweet Tweet Tweet Tweet

Tweet Tweet Tweet Tweet

ListView


• Instead, do as much as possible in either C# or Java,

interop is expensive

Stay in your yard

C# Object

Java

Object

TweetAdapter

List<Tweet>

Tweet Tweet Tweet Tweet

ListView


Should call Dispose() to release the native resources

immediately (vs waiting on a GC) when you are finished

with a peer wrapper

Avoid placing a large numbers of references in peer

objects, remember GC is more expensive for these special

types

Avoid passing pure C# custom types into Java APIs if

possible

Xamarin.Android Tips


Xamarin

Process

Memory

UIView

UIImage

MKMapVie

w

...

Activity

Intent

TextView

...

Managed

Memory

C# and .NET

objects are

allocated here

- this is all GC

knows about


Q & A