Скачать или смотреть How to Call a Method from Another Activity in Android

Discover how to effectively communicate between Android activities and call methods in another activity with ease.
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How to Call a Method from Another Activity in Android: A Practical Guide

In Android development, it’s common to have multiple activities that need to communicate with each other. One of the most frequent questions new developers ask is how to call a method in one activity (let’s call it Activity A) from another activity (Activity B). If you've ever faced a situation where you needed to execute some functionality in Activity A based on an action in Activity B, then this post is for you!

The Problem

Imagine you have a main Activity (A) and a dialog Activity (B). When you click "OK" in the dialog (Activity B), you want to close it and then invoke a method in Activity A. This raises a series of questions about how you can effectively and efficiently establish communication between the two activities.

To clarify, directly interacting with one activity from another is not the recommended way due to the Android Activity lifecycle and design best practices. However, there are several established methods to achieve the required functionality safely and efficiently.

Solutions

Here are two primary techniques to call a method in Activity A from Activity B.

1. Using Start Activity For Result

This is the most straightforward approach and aligns with the designed lifecycle of activities.

Step-by-Step Guide:

Start Activity B from Activity A with a request code:
In your Activity A, you can start Activity B like this:

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Override onActivityResult in Activity A:
After Activity B closes, you can capture the result in the onActivityResult callback:

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

Set Result in Activity B:
In Activity B, when the user clicks "OK", make sure to set the result before closing it:

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

2. Passing a Boolean via Intent

This method is somewhat of a hack but can work in certain situations where you want to pass a simple state.

Step-by-Step Guide:

Pass a boolean in the intent:
In Activity B, when the "OK" button is clicked, you can create an intent to start Activity A with a boolean value:

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

Check the boolean in Activity A:
In the onCreate method of Activity A, retrieve the boolean value and call the method if true:

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

Conclusion

Communication between activities can be handled in a couple of ways, and while it may not be advisable to invoke methods directly across activities, using startActivityForResult or passing data via intents are effective methods to achieve your goals.

Be sure also to explore other options for inter-class communication like Interfaces, which can provide more structured communication pathways.

With the information provided in this post, you should now have a clear understanding of how to call a method in one activity from another. Happy coding!