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Set userdata on the body instead of on fixture

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This commit is contained in:
Lukas Klingsbo
2020-05-03 12:59:50 +02:00
parent ac6abfcd24
commit 94cd8b6f2b
3 changed files with 12 additions and 4 deletions
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8
doc/box2d.md
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@ -18,6 +18,14 @@ A simple `Box2DGame` implementation example can be seen in the [examples folder]
If you are using `Box2DGame` you can take advantage of its way of handling contacts between two `BodyComponent`s. If you are using `Box2DGame` you can take advantage of its way of handling contacts between two `BodyComponent`s.
When creating the body definition for your `BodyComponent` make sure that you set the userdata to the current object, otherwise it will not be possible to detect collisions.
Like this:
```dart
final bodyDef = BodyDef()
// To be able to determine object in collision
..setUserData(this);
```
To do this you have to make an implementation of `ContactCallback` where you set which two types that it should react when they come in contact. To do this you have to make an implementation of `ContactCallback` where you set which two types that it should react when they come in contact.
If you have two `BodyComponent`s named Ball and Wall and you want to do something when they come in contact you would do like this: If you have two `BodyComponent`s named Ball and Wall and you want to do something when they come in contact you would do like this:

4
doc/examples/box2d/contact_callbacks/lib/main.dart
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@ -38,14 +38,14 @@ class Ball extends BodyComponent {
shape.radius = radius; shape.radius = radius;
final fixtureDef = FixtureDef() final fixtureDef = FixtureDef()
// To be able to determine object in collision
..setUserData(this)
..shape = shape ..shape = shape
..restitution = 1.0 ..restitution = 1.0
..density = 1.0 ..density = 1.0
..friction = 0.1; ..friction = 0.1;
final bodyDef = BodyDef() final bodyDef = BodyDef()
// To be able to determine object in collision
..setUserData(this)
..position = position ..position = position
..type = BodyType.DYNAMIC; ..type = BodyType.DYNAMIC;

4
lib/box2d/contact_callbacks.dart
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@ -40,8 +40,8 @@ class ContactCallbacks extends ContactListener {
} }
void _maybeCallback(Contact contact, ContactCallback callback, Function f) { void _maybeCallback(Contact contact, ContactCallback callback, Function f) {
final Object a = contact.fixtureA.userData; final Object a = contact.fixtureA.getBody().userData;
final Object b = contact.fixtureB.userData; final Object b = contact.fixtureB.getBody().userData;
final ContactTypes wanted = callback.types; final ContactTypes wanted = callback.types;
if (wanted.match(a, b) || (wanted.has(BodyComponent) && wanted.hasOne(a, b))) { if (wanted.match(a, b) || (wanted.has(BodyComponent) && wanted.hasOne(a, b))) {