Understanding UIWebView’s Selection Persistence Issue

When working with UIWebView and UIPicker or other native views in an iOS application, there are several scenarios where the selection persists across view changes. However, when dealing with UIWebView, this behavior can be problematic if you need to maintain the state of a web-based UI element, such as text selection.

Background: UIWebView’s Behavior

UIWebView is a view that embeds a web view into its content area. While it provides an efficient way to display web content within your application, it does not support some features that WKWebView or other native views do, such as persistent selection state.

This limitation can lead to issues when trying to maintain the state of UI elements across different view controllers or even view changes. In this article, we will explore how to handle these scenarios and provide solutions for maintaining text selection in a UIWebView.

The Problem: Losing Selection After Presenting a Native View Controller

In your scenario, you are presenting a native view controller (colorController) that contains a color palette. When you call [[[self window] rootViewController]presentViewController:colorController animated:YES completion:nil];, the UIWebView loses its selection state.

Saving the Element that is Touched in JavaScript

The solution to this problem lies in saving the element that is touched before presenting the native view controller. In JavaScript, you can use the following code:

document.addEventListener('touchstart', function(event) {
    var touch = event.changedTouches[0];
    var selectedText = document.activeElement.outerHTML;
    // Save the selection state here
});

Saving the Selection State

When you save the selection state, make sure to store it in a way that can be accessed later. In this case, we will use local storage or a simple JavaScript object:

var selectionState = {
    'selectedText': selectedText,
    // Any other relevant data
};

Presenting the Native View Controller

Now that you have saved the selection state, you can present the native view controller. When presenting it, pass the selectionState to the new view controller:

colorController.selectionState = selectionState;

Handling Color Selection in the Native View Controller

When handling color selections in the native view controller, make sure to retrieve the saved selection state and update the UIWebView accordingly.

self.colorSelected = function(color) {
    // Update the selection state here
    self.selectionState['selectedText'] = document.activeElement.outerHTML;
    // Call JavaScript method to change color in UIWebView
    [[[[self window] rootViewController] presentViewController:self.rootViewController animated:YES completion:nil]];
};

JavaScript Method to Change Color in UIWebView

In this method, you will update the UIWebView by using the saved selection state:

[self.window.rootViewController presentViewController:self.rootViewController animated:YES completion:nil];
var uiWebView = [[self window] rootViewController].view;
uiWebView.evaluateJavaScript('document.activeElement.style.color = "' + color + '";');

Conclusion

In conclusion, maintaining text selection in a UIWebView can be challenging when presenting native view controllers. However, by saving the element that is touched before presenting the native view controller and passing the saved selection state to it, you can ensure that the selection persists across different view changes.

Remember to handle color selections in the native view controller accordingly and update the UIWebView using JavaScript methods. By following these steps, you can maintain the state of your web-based UI element while providing a seamless user experience for your iOS application.

Last modified on 2025-02-14