When designing user interface components for the Android platform, particularly for system-level UI elements or custom views, I adhere to several key practices:

1. **Understanding Requirements**: I collaborate closely with UX designers to thoroughly grasp the requirements, ensuring that the design aligns with user expectations and follows industry best practices.

2. **Custom Views and Reusable Components**:
   - **Custom Views**: I develop custom views tailored to specific needs, such as unique progress bars, buttons, and other UI elements, which promotes consistency and reusability throughout the application.
   - **RecyclerView**: I utilize RecyclerView to efficiently display large data sets and enable custom drawing for particular UI needs.

3. **Optimizing Layouts**:
   - **Avoiding Multiple Layouts**: I create custom components to minimize redundancy and ensure optimal performance across various screen sizes.
   - **Effective Handling Mechanisms**: I implement view caching and selectively disable hardware acceleration to boost performance.

4. **System UI Customization**:
   - **Overlay and Notification Bar**: I customize system overlays and notification bars to align with the application’s theme and requirements.
   - **Custom Dashboards and Widgets**: I design responsive custom dashboards, launchers, and widgets that operate efficiently.

5. **Performance Focus**:
   - **Animation and Interaction**: I integrate custom animations and extend view objects to enhance user interaction.
   - **Testing Across Devices**: I ensure that the custom UI components function seamlessly across different devices and screen sizes, maintaining both performance and usability.

By concentrating on these elements, I create user interface components that are not only visually appealing but also efficient and user-friendly, delivering a smooth experience across all devices.