19.10 The Importance of Opposing Constraints and Bias

As discussed in the previous chapter, opposing constraints, margins and bias form the cornerstone of responsive layout design in Android when using the ConstraintLayout. When a widget is constrained without opposing constraint connections, those constraints are essentially margin constraints. This is indicated visually within the Layout Editor tool by solid straight lines accompanied by margin measurements as shown in Figure 19-21.

Figure 19-21

The above constraints essentially fix the widget at that position. The result of this is that if the device is rotated to landscape orientation, the widget will no longer be visible since the vertical constraint pushes it beyond the top edge of the device screen (as is the case in Figure 19-22). A similar problem will arise if the app is run on a device with a smaller screen than that used during the design process.

Figure 19-22

When opposing constraints are implemented...