Anvil is a unique and lightweight Java library designed to simplify the creation of reactive user interfaces (UIs) in Android. Drawing inspiration from popular frameworks like React, Anvil pairs seamlessly with architecture patterns such as MVVM and Redux. In this blog, we’ll guide you through the basics of using Anvil to create dynamic and responsive UIs.

Features of Anvil

• Compact size with only a few classes
• User-friendly with minimal functions to learn (only 5 top-level API functions)
• Fast performance, as it avoids reflection and updates views lazily
• Declarative syntax that enhances readability
• Compatibility with Java 6, 7, and 8; supports Kotlin
• Allows usage of XML layouts

Installation

To incorporate Anvil into your project, add the following lines to your build.gradle file:

repositories {
    jcenter()
}
dependencies {
    compile 'co.trikita:anvil-sdk15:0.5.0'
}

Anvil comes in various builds tailored to different Android SDK versions:

• anvil-sdk15: Supports ICS (99.7% of devices)
• anvil-sdk19: Supports KitKat (94.3% of devices)
• anvil-sdk21: Supports Lollipop (82.3% of devices)

How to Create a Basic Reactive View

Imagine you’re building a simple clock with a start button that updates every second. Anvil simplifies this process by letting you declare your UI in a more understandable way. Here’s how you can create a basic UI:

public int ticktock = 0;

public void onCreate(Bundle b) {
    super.onCreate(b);
    setContentView(new RenderableView(this) {
        @Override
        public void view() {
            linearLayout(() -> {
                size(MATCH, MATCH);
                padding(dip(8));
                orientation(LinearLayout.VERTICAL);

                textView(() -> {
                    size(MATCH, WRAP);
                    text("Tick-tock: " + ticktock);
                });

                button(() -> {
                    size(MATCH, WRAP);
                    text("Close");
                    onClick(v -> finish());
                });
            });
        }
    });
}

In the above code, we create a LinearLayout with a TextView to show the tick count and a Button to close the activity.

Understanding the Code – An Analogy

Think of anvil as a real estate agent managing a property (your UI). When a potential buyer (the user) visits the property, the agent quickly organizes everything to make it presentable. Here’s what happens in the code:

• Setting Up the Property (Layout): The agent organizes the rooms (views) into a spacious linear layout (a hallway).
• Displaying Features (TextView): The agent shares the details (tick count) about the property to the visitors.
• Closing Deal (Button): The agent provides a way for visitors to leave (finish the activity) when they are done exploring.

When the tick count changes (like a buyer showing interest), the agent refreshes the information without rearranging the furniture (updating the view efficiently).

Troubleshooting Common Issues

If you encounter problems while using Anvil, here are some troubleshooting ideas:

• The UI doesn’t update: Ensure that you are calling Anvil.render() when updating mutable data. Though it automatically triggers after event listeners, other cases might need manual rendering.
• Existing XML layouts not working: When using XML, check if your IDs are correctly set. Make sure to use the withId() method to bind properties accurately.
• Library compatibility issues: Verify that you’re using the correct version compatible with your project’s minimum SDK requirements.

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Conclusion

At fxis.ai, we believe that such advancements are crucial for the future of AI, as they enable more comprehensive and effective solutions. Our team is continually exploring new methodologies to push the envelope in artificial intelligence, ensuring that our clients benefit from the latest technological innovations.