Constraint Layout: Flow

Overview

• Flow is a new feature in Constraint Layout.
• Acts as a replacement for Linear Layout.
• Maintains flat hierarchy (single view group).
• Requires Constraint Layout version 2.0.
• Offers benefits of linear layouts without nested views.
• Integrated with Motion Layout for animations.

Setting Up Flow

• Update Constraint Layout to version 2.0 in Gradle.
• Motion Layout: Add custom animations.

Using Flow in XML

• Six buttons example.
  • Align horizontally using Flow (a virtual layout needing width and height).
  • Width options: match parent, match constraint, percentage.
  • Aligned using reference IDs.

Handling Visibility and Space

• Constraints: Assign top and start of parent constraints to Flow; applies to all referenced views.
• Orientation: Default is horizontal.
• Wrap Mode Options:
  • None: Default, views may get cut off.
  • Align: New row, views fill from the row's start.
  • Chain: Equal spacing within rows; use biases and styles.

Chain Features

1. Biases: Start (0%), Center (50%), Custom (e.g., 20% = 0.2).
2. Styles: Horizontal (packed, spread, spread inside).

• Apply to individual rows or globally.
• Max Element Wrap: Limit views per row (e.g., 2 views per row).

Visibility Handling

• Gone Visibility: Adjusts other views automatically.
  • E.g., Removing view 4 aligns views automatically with equal spacing.

Adjusting Gaps

• Spacing: flow_gap for consistent spacing (e.g., flow_gap = 3).
• Padding and Margin: Set padding/margin for overall view in the flow.
• Background: Set color or drawable.

Conclusion

• Flow simplifies layouts by avoiding nested view groups.
• Offers flexibility in design and consistency.
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