The document discusses ways to improve the performance of hybrid mobile applications that use WebView. It describes how WebView has less powerful capabilities and worse web standard compatibility compared to mobile browsers. This can cause issues like fragmentation across device versions. The document proposes techniques for creating a high-performance WebView, including adding new capabilities like WebSockets, and replacing slower native elements like Canvas 2D with optimized custom implementations. It provides code examples for calling JavaScript from native and vice versa on Android and iOS. Lessons learned emphasize minimizing native/JavaScript communication and dealing with threading issues.

1. WebView 뛰어 넘기
부제: 고성능 WebView 만들기
박창현

2. About Us
http://www.skplanet.com
http://readme.skplanet.com

3. About Me
•
•
•
•
•
단말 플랫폼 개발 Specialist
웹 플랫폼 개발 Specialist
Android 보안 시스템 개발 Specialist
Android/HTML5/Hybrid App Framework/...
현) SK planet / Mobile SW 개발 1팀 / 팀장

4. Contents
• Why High-performance WebView?
• Basic Tech. Idea for High-performance
WebView
• Demo
• Lessons Learned

5. Why High-performance WebView?

6. Hybrid Apps. Become More Popular

7. What is Hybrid Application?
Native
Web
WebView

8. • A Part of Android
Fr
ag
m
en
Framework
• Different from Web
Browser (Chrome)
• Less Powerful Than Web
Browser (Chrome...)
• Web Standard
Compatibility
- Depend On Android OS
Version
ta
tio
n
WebView Is ...
• A Part of iOS
• Different from Web
Browser (Safari)
• Less Powerful Than Web
Browser (Safari)
• Web Standard
Compatibility
- Depend On iOS Version

9. Web Standard Compatibility for
WebView
Web
Audio/Vi
Web
Canvas
Worker
deo
Sockets
s
Web
Audio
Web
Notificat WebGL
ion
GB
O
△
X
X
X
X
X
ICS
O
△
X
X
X
X
X
JB
O
△
△
X
X
X
X

10. Web Standard Compatibility for
WebView
Web
Audio/Vi
Web
Canvas
Worker
deo
Sockets
s
Web
Audio
Web
Notificat WebGL
ion
5.0
O
△
O
△
X
X
X
6.0
O
△
O
O
O
X
X
7.0
O
△
O
O
O
X
X

11. Hybrid App’s Problems Are ...
“We have to make several versions of in-app
web contents for each android/iOS version.”
Fragmentation
“We need Web Worker feature for our
Performance can support
contents. But because only iOS
Web Worker spec at this time, we can’s
support android devices.”

12. We Need To Have Special
WebView
Provide The Same Web Standards
Independent of OS version and Manufacturers
Should Be Faster Than Native

13. Basic Technical Ingredient

14. We Need To Know ...
• How To Call JavaScript Function
From Native
• How To Call Native Function From
JavaScript

15. Android
• onPageFinished + bookmarklet
webview.setWebViewClient(new WebViewClient() {
@Override
public void onPageFinished(WebView view, String url) {
// evaluate your javascript code here!
view.loadUrl(“javascript:.... “);
}
});

16. Android
• addJavascriptInterface
//Define Bridge Class
class MyBridgeClass {
public void foo(final String args) {
// do something
}
}
webview.addJavascriptInterface(new MyBridgeClass(), “MyBridge”);
// In javascript code
window.MyBride.foo(“hello world”);

17. iOS
• webViewDidFinishLoad +
stringByEvaluatingJavaScriptFromString
//Insert my own javascript codes like this:
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
outputString = [webView
stringByEvaluatingJavaScriptFromString:@"whatever js code I want
to evaluate"];
}

18. iOS
• shouldStartLoadWithRequest
//Insert my own javascript codes like this:
- (BOOL)webView:(UIWebView *)theWebView
shouldStartLoadWithRequest:(NSURLRequest *)request
navigationType: UIWebViewNavigationType)navigationType {
if ([[[request URL] absoluteString] hasPrefix:@"skp:"]) {
// do my job
return NO;
}
return YES;
}
//Javascript code
var iframe = document.createElement("IFRAME");
iframe.setAttribute("src", "skp:myBridgeFunction";
document.documentElement.appendChild(iframe);
iframe.parentNode.removeChild(iframe);
iframe = null;

19. Add & Replace

20. Web Sockets and Canvas 2D
• Web Sockets
- Android WebView Does Not Support
- Add Web Sockets Features Into WebView
• Canvas 2D
- Android WebView’s Canvas 2D Is Extremely Slow
- Replace Canvas 2D Features With My Own
Implementation (with SurfaceView)

21. Add Web Socket (Android)
WebSocket_shim.js
WebSocket WebSocket
...
NativeWebSocket
WebView
NativeWebSocketImpl
NativeWebSocketImpl
...
NativeWebSocket

22. Add Web Socket (Android)
• Define Web Socket (JavaScript)
// websocket_shim.js
(function() {
var store = {};
// Websocket constructor
var WebSocket = window.WebSocket = function(url) {
// Initialize web socket
this.socketId = nativewebsocket.getInstance(url);
WebSocket.store[this.socketId] = this;
}
// declare prototype method
WebSocket.prototype.send = function(data) {
// bind to native
nativewebsocket.send(data, this.socketId);
}
...
// event dispatcher
WebSocket.onopen = function(evt) {
// dispatch event to proper instance
WebSocket.store[evt.id].onopen(evt);
}
...
})();

23. Add Web Socket (Android)
• Define Web Socket / Register /
Callback(Java)
// Define Bridge Interface
class NativeWebSocket {
class NativeWebSocketImpl {
public String id;
public void send(String data) { }
public void onOpen(...) {
webview.post(new Runnable() {
@override
public void run() {
webview.loadUrl(“javascript:WebSocket.onopen({targetId:“ + id + “,
data:” + “data + “});”);
}
});
}
};
...
public void send(String data, String id) { }
public String getInstance(String url) { hash.put(getId(), new
NativeWebSocketImpl(url, id)); }
}
...
// Register NativeWebSocket
webview.addJavascriptInterface(new NativeWebSocket(), “nativewebsocket”);

24. Add Web Socket (Android)
• Install WebSocket_shim.js!
webview.setWebViewClient(new WebViewClient() {
@Override
public void onPageFinished(WebView view, String url) {
// evaluate your javascript code here!
view.loadUrl(“javascript:“ + <WebSocket_shim.js 파일 내용>);
}
});

25. Replace Canvas 2D (Android)
Original Canvas
(JavaScript)
Image
Image
canvas_shim.js
(JavaScript)
...
CanvasRenderingContext2D
CanvasRenderingContext2D
...
Canvas
Canvas
...
Image
Image
...
CanvasRenderingContext2D
CanvasRenderingContext2D
...
Canvas
Canvas
...
NativeCanvas2DContext
WebView
WebView
Bitmap
Bitmap
...
SurfaceView
SurfaceView
...
NativeCanvas2DContext
WebKit
WebKit

26. Replace Canvas 2D (Android)
HTML
Canvas
WebView
SurfaceView

27. Replace Canvas 2D (Android)
• Override Canvas.getContext(“2d”)
// canvas2d_shim.js
// Replace built-in function prototype with your own
HTMLCanvasElement.prototype.getContext = function(getCtxOld) {
return function (val) {
var ctx;
ctx = getCtxOld.apply(this, arguments);
if (val == ‘2d’) {
// make Native Canvas
NativeCanvas2DContext.createNativeCanvas(...);
// Object Instance Mixin
}
return ctx;
};
}(HTMLCanvasElement.prototype.getContext);

28. Replace Canvas 2D (Android)
• Override CanvasRendering2DContext
// Replace built-in CanvasRenderingContext2D prototype with your
own
CanvasRenderingContext2D.prototype.fillText = function(..) {
NativeCanvas2DContext.fillText(...);
};
CanvasRenderingContext2D.prototype.drawImage = function(..) {
if (arguments.length == 9) {
NativeCanvas2DContext.drawImage(...);
} else if (arguments.length == 3) {
...
} else {
}
};

29. Replace Canvas 2D (Android)
• Override Image
// Replace built-in constructor of Image object with my own
Image = function() {
var image = {};
var imageId = NativeCanvas2DContext.getImageId();
image.__defineSetter__("src", function(val) {
NativeCanvas2DContext.setImageSrc(imageId, val);
this._src = val;
});
image.__defineGetter__("width", function() {
return NativeCanvas2DContext.getImageWidth(imageId);
});
image.__defineGetter__("height", function() {
return NativeCanvas2DContext.getImageHeight(imageId);
});
...
return image;
};

30. Replace Canvas 2D (Android)
• Define Native Canvas / Register
// Define Bridge Interface
class NativeCanvas2DContext {
public SurfaceView nativeView;
public Bitmap image;
public void createCanvas(int width, int height) { ... }
public void fillText(..) { ... }
public void drawImage(..) { ... }
public void drawArc(..) { ...}
...
public String getImageId() { ... }
public void setImageSrc(..) { ... }
...
}
...
// Register NativeCanvas2DContext
webview.addJavascriptInterface(new NativeCanvas2DContext(),
“NativeCanvas2DContext”);

31. Replace Canvas 2D (Android)
• Install canvas2d_shim.js!
webview.setWebViewClient(new WebViewClient() {
@Override
public void onPageFinished(WebView view, String url) {
// evaluate your javascript code here!
view.loadUrl(“javascript:“ + <canvas2d_shim.js 파일 내용>);
}
});

32. Demo

34. Lessons Learned

35. General Lessons
• Do as many implementations as possible in
javascript world
• Minimize Javascript ⬌ Native
communications
• Watch out threads (PostMessage)

36. Android Specific Lessons
• We Can’t Override Native Properties In
WebView
- Object.defineProperty Doesn’t Work for Native
Properties
• Object Instance Mixin
- Add Getter/Setter into CanvasRendering2DContext’s
Instance
• Object.defineProperty bugs
- Use __defineGetter__, __defineSetter__ instead

37. Q&A