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Learn how to bypass hardcoded parameters in Android ViewModels by using a wrapping class and setter methods for dynamic argument passing.
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How to Dynamically Pass Arguments to ViewModel in Android with ViewModelFactory

Introduction

When working with ViewModels in Android, you might find yourself needing to pass dynamic arguments based on user input. For instance, imagine that your app allows users to select a date, and you want to send this date to your ViewModel for processing. Many developers initially attempt to pass these parameters directly during the ViewModel's instantiation, but this often leads to hardcoding values in the Fragment or Activity. In this guide, we will explore a dynamic solution to handle this situation using a ViewModelFactory along with setter methods.

The Challenge: Hardcoded Parameters in ViewModel

Typically, the conventional way of creating a ViewModel looks something like this:

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

In this approach, the argument "some string value" is hardcoded, meaning that it cannot be changed dynamically based on user input. For our scenario, where a user selects a date, this method is quite unsuitable. To adapt to changing values, we need a different approach.

A Better Solution: Using Setter Methods and a Wrapper Class

Instead of passing parameters directly to the ViewModel constructor, we will leverage a setter method, along with a custom wrapper class. This allows the ViewModel to maintain and update values dynamically.

Step 1: Create a Custom Wrapper Class

First, we will create a wrapper class to encapsulate our parameter (in this case, a String value). This class serves to hold our dynamic data:

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

Step 2: Update the ViewModel Class

Next, we'll modify the ViewModel to use this wrapper class. Here’s how your ViewModel class may look:

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

Step 3: Call the Setter Method from Your Fragment or Activity

Now, while in your Fragment or Activity, you can update the ViewModel by simply calling the setter method. This is how it looks:

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

Putting It All Together

With this new setup, you can now easily update your ViewModel with dynamically selected values without the limitations imposed by hardcoded parameters. Here’s a brief recap of the implemented solution:

Wrapper Class: Used to hold dynamic values.

Setter Method: Allows you to update the state of the ViewModel as needed.

Separation of Concerns: Keeps your ViewModel cleaner and focused on its role without being tightly coupled with UI components.

Conclusion

By following the above approach, you can enable your ViewModel to accept dynamic parameters easily. This is particularly useful in scenarios where user input can change frequently, like selecting dates or other values. Adopting this method not only improves the functionality of your app but also enhances code organization and maintainability.

With these improvements, your application can handle user input more dynamically, resulting in a better user experience. Happy coding!