How to move a NodeBundle In bevy

Question

I have a node bundle like this:

 commands.spawn((
        NodeBundle {
            style: Style {
                position_type: PositionType::Absolute,
                height: Val::Px(100.0),
                width: Val::Px(100.0),
                ..Default::default()
            },
            transform: Transform::from_translation(Vec3::ZERO),
            visibility: Visibility::Visible,
            background_color: BackgroundColor(Color::BLACK),
            ..Default::default()
        },
        Node {
            x: 0,
            y: 0,
            kind: NodeKind::Player,
        },
    ));

and I want to move this node:

fn move_node(
    mut node: Query<(&mut Transform, &mut Node)>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
) {
    let (mut transform, mut node) = node.single_mut();
    if keyboard_input.pressed(KeyCode::KeyD) {
        transform.translation.x += 100.0;
    } else if keyboard_input.pressed(KeyCode::KeyS) {
        transform.translation.y += 100.0;
    } else if keyboard_input.pressed(KeyCode::KeyA) {
        transform.translation.x -= 100.0;
    } else if keyboard_input.pressed(KeyCode::KeyW) {
        transform.translation.y -= 100.0;
    }
}

but I find that I just can not move it ? I am new to bevy, could anyone help me, thanks a lot !!

Answer 1

I believe the layout for UI nodes are continually re-calculated. The Transform is kept in-sync after the fact so it effectively read-only. Your changes are just being overridden when the UI is rendered.

So if you want to move it, you should do so by modifying the Style - probably with the left and top fields though it uses CSS-based layouts that can be much more complicated.

style: Style {
    position_type: PositionType::Absolute,
    left: Val::Px(100.0),
    top: Val::Px(100.0),
    height: Val::Px(100.0),
    width: Val::Px(100.0),
    ..Default::default()
}

fn move_node(
    mut node: Query<(&mut Style, &mut Node)>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
) {
    let (mut style, mut node) = node.single_mut();
    if keyboard_input.pressed(KeyCode::KeyD) {
        if let Val::Px(left) = &mut style.left {
            *left += 10.0;
        }
    } else if keyboard_input.pressed(KeyCode::KeyS) {
        if let Val::Px(top) = &mut style.top {
            *top += 10.0;
        }
    } else if keyboard_input.pressed(KeyCode::KeyA) {
        if let Val::Px(left) = &mut style.left {
            *left -= 10.0;
        }
    } else if keyboard_input.pressed(KeyCode::KeyW) {
        if let Val::Px(top) = &mut style.top {
            *top -= 10.0;
        }
    }
}

Note: I see this is for you own Node with NodeKind::Player; its probably a bad idea to use UI components for the core of your game. There are plenty of examples for doing 2d games.