Xcode Previews

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Create an app UI and configure almost everything your users see using Xcode Previews.

Posts under Xcode Previews tag

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ASWebAuthenticationSession not working in Preview
class ViewModel : NSObject, ObservableObject, ASWebAuthenticationPresentationContextProviding { private var authSession: ASWebAuthenticationSession? func signInWithOpenID(provider: OAuthProvider) { let url = getOIDCAuthenticationURL(provider: provider) authSession?.cancel() authSession = nil authSession = ASWebAuthenticationSession(url: url, callbackURLScheme: "com.ninjanutri") { callbackURL, error in if let error = error { print("Error: \(error.localizedDescription)") return } guard let callbackURL = callbackURL else { return } guard let idToken = callbackURL.valueOf("id_token") else { return } self.signInWithIdToken(provider: provider, idToken: idToken) } authSession?.prefersEphemeralWebBrowserSession = false authSession?.presentationContextProvider = self authSession?.start() } public func presentationAnchor(for session: ASWebAuthenticationSession) -> ASPresentationAnchor { return ASPresentationAnchor() } } struct ContentView: View { @StateObject private var viewModel = ViewModel() var body: some View { Button { viewModel.signInWithOpenID(provider: .github) } label: { Text("Test") } } } when the prefersEphemeralWebBrowserSession is false, the alert and webview is totally working fine in Simulator and Real device, but not XCode Preview. Is this behaviour expected or it's a bug?
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461
Dec ’24
Xcode Preview says:Cannot preview in this file: Failed to launch (App Name)
When I attempt to preview my code, I encounter an error message stating, “Cannot preview in this file: Failed to launch (App Name).” This issue is specific to this particular app. I attempted creating a new project, and that works fine. This is what it says in the diagnostics: | [Remote] JITError | | ================================== | | | [Remote] LLVMError | | | | LLVMError: LLVMError(description: "The file was not recognized as a valid object file")
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2.7k
Dec ’24
SwiftUI Previews not working Xcode 15 iOS 17 simulator
SwiftUI preview hangs on "Preparing iPhone Simulator for Previews". Also simulator hangs when trying to build and run. This occurred after I installed iOS 17 simulator. I tried reverting back to an iOS 16 version of the simulator, but haven't figured out how to do that. Build and run to an iPhone device works fine. Any ideas would be appreciated. Thanks.
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4.3k
Dec ’24
Xcode 15 Beta Stuck on preparing iphone simulator for previews
Hiya, I am having issues trying to use previews in the xcode 15 beta, i am using an M2 macbook air with 8gb of ram. I am using MacOS Sonoma and iOS 17.0 Beta 1 and am struggling using previews, the base simulator works but no previews. I am not receiving any error so am very confused. Any help would be majorly appreciated. Thanks, Gus
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4.6k
Dec ’24
[SwiftUI Preview] App crashes when previewing on physical device but runs normally
Hello everyone, I've encountered an issue with SwiftUI Preview and would appreciate your help. Problem Description In a mixed Objective-C and Swift project, I'm experiencing the following situation with SwiftUI Preview: Crashes when previewing on a physical device The same code runs normally when launched directly through Xcode Project uses CocoaPods for dependency management with static frameworks Project Environment: Project Type: Mixed (Objective-C + Swift) Dependency Management: CocoaPods Dependency Type: Static frameworks Device: Physical device preview Steps to Reproduce: Write Preview code in SwiftUI file Select physical device as Preview device Click Preview button Application crashes
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569
Dec ’24
Preview Crashes with glitched visuals
When working on my Xcode project and using Previews from time to time I find preview crashes and ens up with the image below. The UI is completely unresponsive and only way to bring it back I find is close and relaunch Xcode. Anyone else experience this - is there a known fix or a better way to "kick" preview to restart that doesn't involve full relaunch of XCode
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339
Dec ’24
XCPreviewAgent Crashed / Preview Not Working
My preview crashed because it could not access my font resources. I am working on a Framework, and it seems that for frameworks, the resources are not copied into the app package of the preview. Investigation: I verified this by examining the contents of the preview: /Users/YOUR_NAME/Library/Developer/Xcode/UserData/Previews/Simulator Devices/DEVICE_UUID/data/Containers/Bundle/Application/APPLICATION_UUID/APPLICATION_NAME.app Make sure to replace "YOUR_NAME," "DEVICE_UUID," "APPLICATION_UUID," and "APPLICATION_NAME" with the actual names or UUIDs relevant to your specific situation. Now right-click on the app and select Show Package Contents. For previews that work correctly, the name of the associated app is used, and you will see all the resources in the package. However, my framework was not using the framework name. Instead, it was named XCPreviewAgent.app and did not contain any resources from my framework. Fix: As of November 2024 (Xcode 16.0 and Xcode 16.1), the fix is to use Legacy Preview Execution. In the menu, select Editor > Canvas > Legacy Preview Execution. Please leave a comment if this is fixed in a newer Xcode version.
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750
Nov ’24
CrashReportError: Fatal Error in PersistentModel.swift
I got a preview crash info as this: xxx crashed due to fatalError in PersistentModel.swift at line 559. This KeyPath does not appear to relate RecordInfo to anything - \RecordInfo.<computed 0x00000001921dfb4e (Array<SomeInfo>)> If I change preview device to iPhoneSE, It is no crash. I think the reason is I have some dirty data in iPhone16 Pro preview device. If I'm right and how to delete it? Model of RecordInfo like this: @Model class RecordInfo { @Relationship(deleteRule: .cascade) var someInfo:[SomeInfo] } @Model class SomeInfo { var date: Date var info: String }
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524
Nov ’24
Hi, I have an issue with app preview
I can't seem to access preview for any of my views in any of my swift projects at all (using Mac to code and using iPhone 16 pro as preview and simulation, simulation can work), even after restarting Mac and Xcode itself. The preview section has a popup saying "Cannot preview in this file, unexpected error occured" (for every file), please tell me what is wrong and help me solve it to see the preview, thank you! details
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547
Nov ’24
VisionOS Simulator Stuck on Black Screen with "Hello World" Code in Xcode
Hello everyone, I’m currently developing my first VisionOS app in Xcode, starting with the default "Hello World" code provided when creating a new VisionOS Mixed Reality App. However, I’m facing some issues with performance and previewing that I can’t seem to resolve. When I load the preview, it takes an extremely long time, and sometimes it doesn’t load at all. Even when I try to run the app in the VisionOS Simulator, the simulator shows an endless black screen and never displays the intended view. I’ve made no changes to the code, so it’s purely the base setup. Here are my system details: Xcode version: 16.1, VisionOs 2.0; macOS version: 15.0.1; Hardware: MacBook Air 2020 M1 I’ve tried restarting Xcode and my machine, but the issue persists. Has anyone else faced similar problems or have any suggestions for fixing this? Or is my hardware simply too weak? Any help would be greatly appreciated! Thank you in advance!
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412
Nov ’24
How to mock CBPeripheral data when develop with Core Bluetooth
I'm developing an app which supports for connect with an BLE device. There are some views for showing data from bluetooth. The code below for an example: @EnvironmentObject var bleManager: BLEManager // a class implemented CBCentralManagerDelegate var body: some View { // bleConnected is a CBPeripheral if let bleConnected = bleManager.bleConnected { if let services = bleConnected.services { ForEach(services, id:\.self) { service in // UI for print uuid, descriptions ... showServiceDescriptionView(services) if let characteristics = service.characteristics { ForEach(characteristics, id:\.self) { characteristic in // UI for print uuid, data for each characteristic showCharacteristicsDetailView(characteristic) } } } } } } } But it seems that Xcode Preview do not support connect to a real bluetooth device. So the preview window in Xcode will always be a empty view. I only can see the data on the real device. But it's important for me to design UI on the preview. So are there any method to mock a fake CBPeripheral in the Previewer? Or are there any other way to achieve this?
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Nov ’24