Скачать или смотреть How to Create a Reusable Custom Entry in Xamarin Forms with Binding Support

Learn how to create a reusable custom Entry in Xamarin Forms that supports `Binding` for both placeholder text and entry text. Understand the issues and solutions with step-by-step guidance!
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This video is based on the question https://stackoverflow.com/q/62894322/ asked by the user 'acb1980' ( https://stackoverflow.com/u/7133060/ ) and on the answer https://stackoverflow.com/a/62894926/ provided by the user 'Lucas Zhang' ( https://stackoverflow.com/u/10216982/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Create a Reusable Custom Entry in Xamarin Forms

In the world of mobile app development, creating reusable UI components is key to efficient and maintainable code. One common component developers often need is a custom Entry field with specific styling or functionality. In this post, we’ll explore how to create a reusable custom Entry within Xamarin Forms while ensuring it properly binds to data contexts.

The Problem

Imagine you want to create a custom Entry wrapped in a Frame that features only the top and bottom borders. You start constructing your UI but hit a snag when you try to bind the Text property of your custom Entry. The text updates properly when directly using a standard Entry but fails when utilizing your custom component.

Here’s the relevant part of your XAML:

[[See Video to Reveal this Text or Code Snippet]]

Although the placeholder is displayed correctly, the Text property remains empty. This is a frustrating hurdle that many developers encounter. What’s going wrong?

Understanding the Issue

The culprit is within your custom control, specifically how the BindingContext is set. When you assign BindingContext = this; in the constructor of your CbSingleEntry class, you are effectively overriding the context for any bindings made from outside of your custom control. As a result, the parent context doesn’t propagate down to your Entry.

Steps to Solve the Problem

Let’s break down the solution into manageable sections.

Step 1: Modify the XAML for Binding

You need to ensure that the Entry inside your custom Frame binds to properties defined within the CbSingleEntry. To do this, specify the binding source as the custom view itself. Update your XAML like so:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Adjust the Code Behind

Now that you've specified the binding context in the XAML, it is vital to remove the line that sets the BindingContext in the code behind. Here’s how your code should look:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the adjustments made in both your XAML and code behind, you can create a custom Entry component that properly supports data binding from its parent context.

Remove the explicit BindingContext assignment in the constructor.

Use x:Reference in your XAML to bind the Entry’s placeholder and text properties directly.

Now you can enjoy having a cleaner, more effective custom Entry that enhances your Xamarin Forms application. Happy coding!