如何在bevy中读取鼠标运动？

Question

我想创建一个第一人称相机。我已经研究了其他几个实现的源代码，比如

https://github.com/mcpar-land/bevy_fly_camera

https://github.com/sburris0/bevy_flycam

但当我自己实现它时(主要是复制粘贴tbh)，当在git上使用最新的bevy版本时，它无法编译。

编译输出：

error[E0277]: `*mut (usize, PhantomData<MouseMotion>)` cannot be sent between threads safely
   --> src/player_input.rs:151:13
    |
151 |     mut state: ResMut<State>,
    |                ^^^^^^^^^^^^^ `*mut (usize, PhantomData<MouseMotion>)` cannot be sent between threads safely
    | 
   ::: /home/luca/.cargo/git/checkouts/bevy-f7ffde730c324c74/89a41bc/crates/bevy_ecs/src/resource/resource_query.rs:66:26
    |
66  | pub struct ResMut<'a, T: Resource> {
    |                          -------- required by this bound in `bevy::prelude::ResMut`
    |
    = help: within `player_input::State<'_>`, the trait `Send` is not implemented for `*mut (usize, PhantomData<MouseMotion>)`
    = note: required because it appears within the type `Local<'_, (usize, PhantomData<MouseMotion>)>`
    = note: required because it appears within the type `bevy::prelude::EventReader<'_, MouseMotion>`
    = note: required because it appears within the type `player_input::State<'_>`
    = note: required because of the requirements on the impl of `Resource` for `player_input::State<'_>`

代码如下：

#[derive(Default)]
struct State<'a> {
    mouse_motion_event_reader: EventReader<'a, MouseMotion>,
}

fn mouse_motion_system(
    time: Res<Time>,

    mut state: ResMut<State>, //<-- IMPORTANT LINE (Line 151)

    mouse_motion_events: Res<Events<MouseMotion>>,
    mut query: Query<(&mut FlyCamera, &mut Transform)>,
) {
    //...
}

它仅在最新版本的bevy上抛出此错误，而不在0.4.0版上抛出此错误。

我做错了什么吗?或者我应该在github上打开一个问题，因为这是引擎的错误？

我要怎么做才能让它工作呢？

Answer 1

在这里，您根本不应该在State中使用EventReader。也许您想要跟踪状态中的最后一个光标位置？

由于在Bevy 0.5中简化了event API，因此只需要将EventReader作为系统参数；mouse_motion_events: Res<Events<MouseMotion>>,现在已经过时，可以用mut mouse_motion_events: EventReader<MouseMotion>替代。