Android Application Development Cookbook - Second Edition

Creating a custom component

As we have seen in previous recipes, the Android SDK provides a wide range of components. But what happens when you can't find a prebuilt component that fits your unique needs? You can always create your own!

In this recipe, we will walk through creating a custom component that derives from the View class, just like the built-in widgets. Here's a high-level overview:

1. Create a new class that extends View.
2. Create custom constructor(s).
3. Override onMeasure(), and the default implementation returns a size of 100 x 100.
4. Override onDraw(), and the default implementation draws nothing.
5. Define custom methods and listeners (such as on<Event>()).
6. Implement custom functionality.

Tip

While overriding onMeasure() and onDraw() is not strictly ...