220 lines
4.3 KiB
Markdown
220 lines
4.3 KiB
Markdown
# Extra2D API 教程 - 03. 节点系统
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## 节点基础
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节点(Node)是游戏对象的基本单位，可以包含子节点，形成树形结构。
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### 创建节点
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```cpp
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#include <extra2d/extra2d.h>
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using namespace extra2d;
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class MyNode : public Node {
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public:
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MyNode() {
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// 设置位置
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setPosition(Vec2(100.0f, 200.0f));
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// 设置旋转（度）
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setRotation(45.0f);
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// 设置缩放
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setScale(Vec2(2.0f, 2.0f));
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// 设置锚点（0-1范围，默认0.5是中心）
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setAnchor(0.5f, 0.5f);
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// 设置可见性
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setVisible(true);
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}
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// 每帧更新
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void onUpdate(float dt) override {
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Node::onUpdate(dt);
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// 自定义更新逻辑
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}
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// 渲染
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void onRender(RenderBackend &renderer) override {
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Node::onRender(renderer);
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// 自定义渲染
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}
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};
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```
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## 节点层级
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### 添加子节点
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```cpp
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void onEnter() override {
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Scene::onEnter();
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// 创建子节点
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auto child = makePtr<MyNode>();
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// 添加到场景
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addChild(child);
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// 在指定位置添加
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addChild(child, 0); // z-order = 0
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}
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```
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### 移除子节点
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```cpp
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// 移除指定子节点
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removeChild(child);
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// 移除所有子节点
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removeAllChildren();
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// 通过名称移除
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removeChildByName("myNode");
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```
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### 获取子节点
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```cpp
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// 获取子节点数量
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size_t count = getChildren().size();
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// 通过名称查找
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auto node = getChildByName("myNode");
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// 遍历子节点
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for (auto &child : getChildren()) {
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// 处理子节点
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}
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```
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## 空间索引
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### 启用空间索引
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```cpp
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class PhysicsNode : public Node {
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public:
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PhysicsNode() {
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// 启用空间索引（用于碰撞检测）
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setSpatialIndexed(true);
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}
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// 必须实现 getBoundingBox()
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Rect getBoundingBox() const override {
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Vec2 pos = getPosition();
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return Rect(pos.x - 25.0f, pos.y - 25.0f, 50.0f, 50.0f);
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}
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};
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```
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### 边界框
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```cpp
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// 获取节点边界框
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Rect bounds = node->getBoundingBox();
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// 检查点是否在边界框内
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if (bounds.contains(Vec2(x, y))) {
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// 点在边界框内
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}
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// 检查两个边界框是否相交
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if (bounds.intersects(otherBounds)) {
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// 边界框相交
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}
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```
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## 精灵节点
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### 创建精灵
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```cpp
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// 加载纹理
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auto texture = resources.loadTexture("assets/player.png");
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// 创建精灵
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auto sprite = Sprite::create(texture);
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// 设置位置
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sprite->setPosition(Vec2(640.0f, 360.0f));
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// 设置锚点（中心）
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sprite->setAnchor(0.5f, 0.5f);
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// 添加到场景
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addChild(sprite);
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```
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### 精灵动画
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```cpp
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// 创建动画
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auto animation = Animation::create("walk", 0.1f);
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animation->addFrame(resources.loadTexture("assets/walk1.png"));
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animation->addFrame(resources.loadTexture("assets/walk2.png"));
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animation->addFrame(resources.loadTexture("assets/walk3.png"));
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// 播放动画
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sprite->playAnimation(animation, true); // true = 循环播放
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// 停止动画
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sprite->stopAnimation();
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```
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## 完整示例
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```cpp
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class Player : public Node {
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public:
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Player() {
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setSpatialIndexed(true);
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// 加载精灵
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auto &resources = Application::instance().resources();
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auto texture = resources.loadTexture("assets/player.png");
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sprite_ = Sprite::create(texture);
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sprite_->setAnchor(0.5f, 0.5f);
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addChild(sprite_);
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}
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void onUpdate(float dt) override {
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Node::onUpdate(dt);
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// 移动
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Vec2 pos = getPosition();
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pos = pos + velocity_ * dt;
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setPosition(pos);
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// 边界检查
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auto &app = Application::instance();
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float width = static_cast<float>(app.getConfig().width);
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float height = static_cast<float>(app.getConfig().height);
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if (pos.x < 0 || pos.x > width) {
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velocity_.x = -velocity_.x;
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}
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if (pos.y < 0 || pos.y > height) {
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velocity_.y = -velocity_.y;
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}
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}
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Rect getBoundingBox() const override {
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Vec2 pos = getPosition();
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return Rect(pos.x - 25.0f, pos.y - 25.0f, 50.0f, 50.0f);
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}
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private:
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Ptr<Sprite> sprite_;
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Vec2 velocity_{100.0f, 100.0f};
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};
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```
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## 下一步
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- [04. 资源管理](04_Resource_Management.md)
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- [05. 输入处理](05_Input_Handling.md)
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