bevy ui 案例1

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, button_interaction)
        .run();
}

#[derive(Component)]
struct ClickText; // 标记需要更新的文本

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    println!("{}","程序成功载入");
    // 2D 相机
    commands.spawn(Camera2dBundle::default());

    // 根节点（全屏居中）
    commands
        .spawn(NodeBundle {
            style: Style {
                width: Val::Percent(100.0),
                height: Val::Percent(100.0),
                justify_content: JustifyContent::Center,
                align_items: AlignItems::Center,
                ..default()
            },
            ..default()
        })
        .with_children(|parent| {
            // 按钮
            parent.spawn(ButtonBundle {
                style: Style {
                    width: Val::Px(150.0),
                    height: Val::Px(65.0),
                    justify_content: JustifyContent::Center,
                    align_items: AlignItems::Center,
                    ..default()
                },
                background_color: Color::rgb(0.25, 0.25, 0.25).into(),
                ..default()
            })
            .with_children(|btn| {
                // 按钮文本
                btn.spawn(TextBundle::from_section(
                    "点击我!",
                    TextStyle {
                        font: asset_server.load("fonts/FiraSans-Bold.ttf"),
                        font_size: 30.0,
                        color: Color::WHITE,
                    },
                ));
            });

            // 显示点击次数的文本
            parent.spawn((
                TextBundle::from_section(
                    "Clicks: 0",
                    TextStyle {
                        font: asset_server.load("fonts/FiraSans-Bold.ttf"),
                        font_size: 40.0,
                        color: Color::WHITE,
                    },
                )
                .with_style(Style {
                    margin: UiRect::top(Val::Px(50.0)),
                    ..default()
                }),
                ClickText, // 标记组件
            ));
        });
}

// 按钮交互系统
fn button_interaction(
    mut interaction_query: Query<&Interaction, (Changed<Interaction>, With<Button>)>,
    mut text_query: Query<&mut Text, With<ClickText>>,
    mut clicks: Local<u32>,
) {
    for interaction in &mut interaction_query {
        if *interaction == Interaction::Pressed {
            *clicks += 1;
            for mut text in &mut text_query {
                text.sections[0].value = format!("Clicks: {}", *clicks);
            }
        }
    }
}