管理多个屏幕
我们的菜单屏有2个按钮，一个play一个option。option里就是一些开关的设置，比如音乐音效等。这些设置将会保存到Preferences中。
多屏幕切换是游戏的基本机制，Libgdx提供了一个叫Game的类已经具有了这样的功能。
为了适应多屏幕的功能，我们的类图需要做一些修改：
改动在：CanyonBunnyMain不再实现ApplicationListener接口，而是继承自Game类。这个类提供了setScreen()方法来进行切换。
我们定义抽象的AbstractGameScreen来统一共同的行为。同时，它实现了Libgdx的Screen接口（show,hide）。
GameScreen将取代CanyonBunnyMain的位置。
开始编写类AbstractGameScreen：
package com.packtpub.libgdx.canyonbunny.screens; import com.badlogic.gdx.Game; import com.badlogic.gdx.Screen; import com.badlogic.gdx.assets.AssetManager; import com.packtpub.libgdx.canyonbunny.game.Assets; public abstract class AbstractGameScreen implements Screen { protected Game game; public AbstractGameScreen(Game game) { this.game = game; } public abstract void render(float deltaTime); public abstract void resize(int width, int height); public abstract void show(); public abstract void hide(); public abstract void pause(); public void resume() { Assets.instance.init(new AssetManager()); } public void dispose() { Assets.instance.dispose(); } }
GameScreen把职责拿过来：
package com.packtpub.libgdx.canyonbunny.screens; import com.badlogic.gdx.Game; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.graphics.GL10; import com.packtpub.libgdx.canyonbunny.game.WorldController; import com.packtpub.libgdx.canyonbunny.game.WorldRenderer; public class GameScreen extends AbstractGameScreen { private static final String TAG = GameScreen.class.getName(); private WorldController worldController; private WorldRenderer worldRenderer; private boolean paused; public GameScreen(Game game) { super(game); } @Override public void render(float deltaTime) { // Do not update game world when paused. if (!paused) { // Update game world by the time that has passed // since last rendered frame. worldController.update(deltaTime); } // Sets the clear screen color to: Cornflower Blue Gdx.gl.glClearColor(0x64 / 255.0f, 0x95 / 255.0f, 0xed / 255.0f, 0xff / 255.0f); // Clears the screen Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); // Render game world to screen worldRenderer.render(); } @Override public void resize(int width, int height) { worldRenderer.resize(width, height); } @Override public void show() { worldController = new WorldController(game); worldRenderer = new WorldRenderer(worldController); Gdx.input.setCatchBackKey(true); } @Override public void hide() { worldRenderer.dispose(); Gdx.input.setCatchBackKey(false); } @Override public void pause() { paused = true; } @Override public void resume() { super.resume(); // Only called on Android! paused = false; } }
那么CanyonBunnyMain就瘦身了：
package com.packtpub.libgdx.canyonbunny; import com.badlogic.gdx.Application; import com.badlogic.gdx.Game; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.assets.AssetManager; import com.packtpub.libgdx.canyonbunny.game.Assets; import com.packtpub.libgdx.canyonbunny.screens.MenuScreen; public class CanyonBunnyMain extends Game { @Override public void create() { // Set Libgdx log level Gdx.app.setLogLevel(Application.LOG_DEBUG); // Load assets Assets.instance.init(new AssetManager()); // Start game at menu screen setScreen(new MenuScreen(this)); } }
WorldController开始持有game的引用,以便于跳转;
package com.packtpub.libgdx.canyonbunny.game; import com.badlogic.gdx.Application.ApplicationType; import com.badlogic.gdx.Game; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.Input.Keys; import com.badlogic.gdx.InputAdapter; import com.badlogic.gdx.graphics.Pixmap; import com.badlogic.gdx.graphics.Pixmap.Format; import com.badlogic.gdx.math.Rectangle; import com.packtpub.libgdx.canyonbunny.game.objects.BunnyHead; import com.packtpub.libgdx.canyonbunny.game.objects.BunnyHead.JUMP_STATE; import com.packtpub.libgdx.canyonbunny.game.objects.Feather; import com.packtpub.libgdx.canyonbunny.game.objects.GoldCoin; import com.packtpub.libgdx.canyonbunny.game.objects.Rock; import com.packtpub.libgdx.canyonbunny.screens.MenuScreen; import com.packtpub.libgdx.canyonbunny.util.CameraHelper; import com.packtpub.libgdx.canyonbunny.util.Constants; public class WorldController extends InputAdapter { private static final String TAG = WorldController.class.getName(); public CameraHelper cameraHelper; public Level level; public int lives; public int score; private float timeLeftGameOverDelay; private Game game; private void backToMenu() { // switch to menu screen game.setScreen(new MenuScreen(game)); } public boolean isGameOver() { return lives < 0; } public boolean isPlayerInWater() { return level.bunnyHead.position.y < -5; } private void initLevel() { score = 0; level = new Level(Constants.LEVEL_01); cameraHelper.setTarget(level.bunnyHead); } // Rectangles for collision detection private Rectangle r1 = new Rectangle(); private Rectangle r2 = new Rectangle(); private void onCollisionBunnyHeadWithRock(Rock rock) { BunnyHead bunnyHead = level.bunnyHead; float heightDifference = Math.abs(bunnyHead.position.y - (rock.position.y + rock.bounds.height)); if (heightDifference > 0.25f) { boolean hitLeftEdge = bunnyHead.position.x > (rock.position.x + rock.bounds.width / 2.0f); if (hitLeftEdge) { bunnyHead.position.x = rock.position.x + rock.bounds.width; } else { bunnyHead.position.x = rock.position.x - bunnyHead.bounds.width; } return; } switch (bunnyHead.jumpState) { case GROUNDED: break; case FALLING: case JUMP_FALLING: bunnyHead.position.y = rock.position.y + bunnyHead.bounds.height + bunnyHead.origin.y; bunnyHead.jumpState = JUMP_STATE.GROUNDED; break; case JUMP_RISING: bunnyHead.position.y = rock.position.y + bunnyHead.bounds.height + bunnyHead.origin.y; break; } } private void onCollisionBunnyWithGoldCoin(GoldCoin goldcoin) { goldcoin.collected = true; score += goldcoin.getScore(); Gdx.app.log(TAG, "Gold coin collected"); } private void onCollisionBunnyWithFeather(Feather feather) { feather.collected = true; score += feather.getScore(); level.bunnyHead.setFeatherPowerup(true); Gdx.app.log(TAG, "Feather collected"); } private void testCollisions() { r1.set(level.bunnyHead.position.x, level.bunnyHead.position.y, level.bunnyHead.bounds.width, level.bunnyHead.bounds.height); // Test collision: Bunny Head <-> Rocks for (Rock rock : level.rocks) { r2.set(rock.position.x, rock.position.y, rock.bounds.width, rock.bounds.height); if (!r1.overlaps(r2)) continue; onCollisionBunnyHeadWithRock(rock); // IMPORTANT: must do all collisions for valid // edge testing on rocks. } // Test collision: Bunny Head <-> Gold Coins for (GoldCoin goldcoin : level.goldcoins) { if (goldcoin.collected) continue; r2.set(goldcoin.position.x, goldcoin.position.y, goldcoin.bounds.width, goldcoin.bounds.height); if (!r1.overlaps(r2)) continue; onCollisionBunnyWithGoldCoin(goldcoin); break; } // Test collision: Bunny Head <-> Feathers for (Feather feather : level.feathers) { if (feather.collected) continue; r2.set(feather.position.x, feather.position.y, feather.bounds.width, feather.bounds.height); if (!r1.overlaps(r2)) continue; onCollisionBunnyWithFeather(feather); break; } } public WorldController(Game game) { this.game = game; Gdx.input.setInputProcessor(this); init(); } private void handleDebugInput(float deltaTime) { if (Gdx.app.getType() != ApplicationType.Desktop) return; if (!cameraHelper.hasTarget(level.bunnyHead)) { // Camera Controls (move) float camMoveSpeed = 5 * deltaTime; float camMoveSpeedAccelerationFactor = 5; if (Gdx.input.isKeyPressed(Keys.SHIFT_LEFT)) camMoveSpeed *= camMoveSpeedAccelerationFactor; if (Gdx.input.isKeyPressed(Keys.LEFT)) moveCamera(-camMoveSpeed, 0); if (Gdx.input.isKeyPressed(Keys.RIGHT)) moveCamera(camMoveSpeed, 0); if (Gdx.input.isKeyPressed(Keys.UP)) moveCamera(0, camMoveSpeed); if (Gdx.input.isKeyPressed(Keys.DOWN)) moveCamera(0, -camMoveSpeed); if (Gdx.input.isKeyPressed(Keys.BACKSPACE)) cameraHelper.setPosition(0, 0); } // Camera Controls (zoom) float camZoomSpeed = 1 * deltaTime; float camZoomSpeedAccelerationFactor = 5; if (Gdx.input.isKeyPressed(Keys.SHIFT_LEFT)) camZoomSpeed *= camZoomSpeedAccelerationFactor; if (Gdx.input.isKeyPressed(Keys.COMMA)) cameraHelper.addZoom(camZoomSpeed); if (Gdx.input.isKeyPressed(Keys.PERIOD)) cameraHelper.addZoom(-camZoomSpeed); if (Gdx.input.isKeyPressed(Keys.SLASH)) cameraHelper.setZoom(1); } private void moveCamera(float x, float y) { x += cameraHelper.getPosition().x; y += cameraHelper.getPosition().y; cameraHelper.setPosition(x, y); } @Override public boolean keyUp(int keycode) { if (keycode == Keys.R) { init(); Gdx.app.debug(TAG, "Game World Resetted!"); }// Toggle camera follow else if (keycode == Keys.ENTER) { cameraHelper.setTarget(cameraHelper.hasTarget() ? null : level.bunnyHead); Gdx.app.debug(TAG, "Camera follow enabled: " + cameraHelper.hasTarget()); } // Back to Menu else if (keycode == Keys.ESCAPE || keycode == Keys.BACK) { backToMenu(); } return false; } private void handleInputGame(float deltaTime) { if (cameraHelper.hasTarget(level.bunnyHead)) { // Player Movement if (Gdx.input.isKeyPressed(Keys.LEFT)) { level.bunnyHead.velocity.x = -level.bunnyHead.terminalVelocity.x; } else if (Gdx.input.isKeyPressed(Keys.RIGHT)) { level.bunnyHead.velocity.x = level.bunnyHead.terminalVelocity.x; } else { // Execute auto-forward movement on non-desktop platform if (Gdx.app.getType() != ApplicationType.Desktop) { level.bunnyHead.velocity.x = level.bunnyHead.terminalVelocity.x; } } // Bunny Jump if (Gdx.input.isTouched() || Gdx.input.isKeyPressed(Keys.SPACE)) level.bunnyHead.setJumping(true); } else { level.bunnyHead.setJumping(false); } } private void init() { Gdx.input.setInputProcessor(this); cameraHelper = new CameraHelper(); lives = Constants.LIVES_START; timeLeftGameOverDelay = 0; initLevel(); } public void update(float deltaTime) { handleDebugInput(deltaTime); if (isGameOver()) { timeLeftGameOverDelay -= deltaTime; if (timeLeftGameOverDelay < 0) backToMenu(); } else { handleInputGame(deltaTime); } level.update(deltaTime); testCollisions(); cameraHelper.update(deltaTime); if (!isGameOver() && isPlayerInWater()) { lives--; if (isGameOver()) timeLeftGameOverDelay = Constants.TIME_DELAY_GAME_OVER; else initLevel(); } } private Pixmap createProceduralPixmap(int width, int height) { Pixmap pixmap = new Pixmap(width, height, Format.RGBA8888); // Fill square with red color at 50% opacity pixmap.setColor(1, 0, 0, 0.5f); pixmap.fill(); // Draw a yellow-colored X shape on square pixmap.setColor(1, 1, 0, 1); pixmap.drawLine(0, 0, width, height); pixmap.drawLine(width, 0, 0, height); // Draw a cyan-colored border around square pixmap.setColor(0, 1, 1, 1); pixmap.drawRectangle(0, 0, width, height); return pixmap; } }
现在，构思下menu screen的样子，准备创建了。
接下来就是这个富有特色的MenuScreen的创建了。首先要准备图片和加载，和前文一样打包。然后使用一个JSON文件来定义Menu的皮肤。
比如我们起名叫：canyonbunnyui.json
{ com.badlogic.gdx.scenes.scene2d.ui.Button$ButtonStyle: { play: { down: play-dn, up: play-up }, options: { down: options-dn, up: options-up } }, com.badlogic.gdx.scenes.scene2d.ui.Image: { background: { drawable: background }, logo: { drawable: logo }, info: { drawable: info }, coins: { drawable: coins }, bunny: { drawable: bunny }, }, }
增加常量到Constants：
public static final String TEXTURE_ATLAS_UI = "images/canyonbunny-ui.pack"; public static final String TEXTURE_ATLAS_LIBGDX_UI = "images/uiskin.atlas"; // Location of description file for skins public static final String SKIN_LIBGDX_UI = "images/uiskin.json"; public static final String SKIN_CANYONBUNNY_UI = "images/canyonbunny-ui.json";
Libgdx构建Scene2D (UI),使用的特性就是TableLayout和skins。
Libgdx附带了一个很牛叉的工具组来让开发者很容易创建场景. 场景的层次组织结构很像硬盘上文件夹文件的结构.在Libgdx里,这些对象被称为演员Actor.
演员可以相互嵌套来组成演员组. 演员组是一个非常有用的特性, 因为任何对父Actor的改动，都会应用到他的子Actor. 此外, 每个演员都有自己的坐标系, 这就使得定义演员组里的成员的相对偏移量变得很容易（无论是位置，旋转角度还是缩放）.
Scene2D支持已经旋转或者缩放的Actor的碰撞检测. Libgdx灵活的事件系统允许按需处理和分发输入事件以便父Actor可以在输入事件到达子Actor之前拦截它. 最后, 内置的action系统可以很容易用来操纵actors,
也可以通过执行动作序列来完成复杂的效果，平移, 或者是两者组合. 所有这些描述的功能都封装在Stage类, 它包含层次结构和分发用户的事件. 在任何时候，Actor都能够加入它或者从它移除.
Stage类和Actor类都包含act()方法,这个方法得到一个时间作为参数然后执行基于时间的动作。调用Stage的act()将会引起整个场景的act()调用。
Stage和Actor的act()方法其实基本上和我们所知道的update()方法一样,只是用了一个不同的名字. 更多关于Scene2D, 参考官方文档https://code.google.com/p/libgdx/wiki/scene2d/.
到目前为止, 在我们的游戏中我们没有使用任何的Scene2D的这些特性， 虽然我们都已经用Scene2D的对象实现了游戏的场景。记住,使用场景有一定的开销. Libgdx试图全力保持开销在最低的程度,比如： 如果对象不需要旋转和缩放就跳过复杂的转换矩阵的计算. 所以, 这取决于你的需求.
我们要创建的菜单很复杂，我们直接用libgdx已经支持的 Scene2D UI来做. 如果有特殊需要，我们还可以继承这些UI，实现它们的接口，以增强它们的功能.
在Libgdx中, 这些UI元素都叫做组件widgets.
下面是所有在当前Scene2D UI有效的widget简表:
Button, CheckBox, Dialog, Image, ImageButton, Label, List, ScrollPane,SelectBox, Slider, SplitPane, Stack, Window, TextButton, TextField,Touchpad 和 Tree.
Scene2D UI 也支持简单的创建新的自定义的widgets种类.
我们将只涉及我们的菜单中将要用到的一些widget.
完整描述每一个widget的列表,请参考官方文档https://code.google.com/p/libgdx/wiki/scene2dui/.
除了Scene2D UI, Libgdx还集成了一个单独的项目--TableLayout.
TableLayout使用Tables很容易创建和维护动态的(或者叫与分辨率无关的）布局，也提供了很直观的API. Table提供了访问TableLayout的功能, 同时Table也实现了作为widget的功能, 因此Table可以完全无缝集成到Scene2D的UI中.
强烈推荐去看官方文档https://code.google.com/p/table-layout/.
Scene2D UI另一个重要的特征就是支持皮肤skins.
皮肤是资源的集合,包括样式和UI组件. 资源可以是texture regions(纹理区域), fonts(字体)和 colors(颜色). 通常来讲, 皮肤使用的纹理区域,来自一个纹理集. 每个部件的样式定义使用JSON文件存储在一个单独的文件中.