Databases
StackOverflow2013
Postsdbo
POiOS Calling Objective-C from Javascript: Some calls are ignored?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POiOS Calling Objective-C from Javascript: Some calls are ignored?
    primarykey
    data
    text
    <p>I've implemented what seems to be the only way of communicating from javascript to objective-c on iOS using the UIWebView delegate shouldStartLoadWithRequest() method. </p> <p>It seemed to work fine at first, but now I notice that if I make multiple calls from javascript to objective-c within a short period of time, the second call is usually ignored (The application is a piano keyboard, each keypress triggers a call to native code, when dealing with multiple touches the native code doesn't get called for every finger).</p> <p>This is my objective-c code to respond to javascript calls. It's pretty derpy I know but I just wanted something that works for now.</p> <pre><code>- (BOOL)webView:(UIWebView *)webView2 shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType { // Intercept custom location change, URL begins with "js-call:" NSString * requestString = [[request URL] absoluteString]; if ([requestString hasPrefix:@"js-call:"]) { // Extract the selector name from the URL NSArray * components = [requestString componentsSeparatedByString:@":"]; NSString * functionCall = [components objectAtIndex:1]; NSArray * params = [functionCall componentsSeparatedByString:@"%20"]; NSString * functionName = [params objectAtIndex:0]; // Parse playnote event if ([functionName isEqualToString:@"playNote"]) { NSString * param = [params objectAtIndex:1]; NoteInstanceID note_id = [m_audioController playNote:[param intValue]]; NSString * jscall = [NSString stringWithFormat:@"document.PlayNoteCallback(%i);", note_id]; NSLog(@"playNote: %i", (int)note_id); [m_webView stringByEvaluatingJavaScriptFromString:jscall]; } // Parse stopnote event if ([functionName isEqualToString:@"stopNote"]) { NSString * param = [params objectAtIndex:1]; NoteInstanceID note_id = [param intValue]; NSLog(@"stopNote: %i", (int)note_id); [m_audioController stopNote:note_id]; } // Parse log event if ([functionName isEqualToString:@"debugLog"]) { NSString * str = [requestString stringByReplacingOccurrencesOfString:@"%20" withString:@" "]; NSLog(@"%s", [str cStringUsingEncoding:NSStringEncodingConversionAllowLossy]); } // Cancel the location change return NO; } // Accept this location change return YES; } </code></pre> <p>From javascript I call objective-c methods by setting the src attribute of a single hidden iframe. This will trigger the delegate method in objective-c and then the desired native code will get called.</p> <pre><code>$("#app_handle").attr("src", "js-call:playNote " + key.data("pitch")); </code></pre> <p>app_handle is the id of the iframe in question. </p> <p>To sum up, the basics of my method work, but multiple calls within a short period of time do not work. Is this just an artifact of the terrible method in which we are forced to communicate from javascript to objective-c? Or am I doing something wrong? I know PhoneGap does something similar to achieve the same goal. I'd rather not use PhoneGap, so if they don't have this problem then I'd love to figure out what they are doing to make this work.</p> <p>Update:</p> <p>I just found this: <a href="https://stackoverflow.com/questions/5671742/send-a-notification-from-javascript-in-uiwebview-to-objectivec">send a notification from javascript in UIWebView to ObjectiveC</a> Which confirms my suspicions about calls made in quick succession getting lost. Apparently I need to either lump my calls together or manually delay the calls so that the url request has returned by the time I make another call. </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCommunity
    1. USphosphoer
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POiOS Calling Objective-C from Javascript: Some calls are ignored?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POiOS Calling Objective-C from Javascript: Some calls are ignored?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThe issue is that the first window.src set has to have completed before you can send another one, ultimately because the runloop is single-threaded and synchronous. There's no way around that except queuing and/or batching calls until the first one has finished. Getting this perfect is actually pretty tricky, especially when you take into account the delay before sending the first onClick on Mobile Safari, so your best bet is to look over the source to one of the open source bridges—or, better yet, just use one.
      singulars
      1. POiOS Calling Objective-C from Javascript: Some calls are ignored?
      1. USabarnert
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload