android游戏开发框架libgdx的使用（五）舞台和常用UI类

本文使用的libgdx是0.92版本，和现在的最新版可能有一些不一样的地方。全文内容仅供参考。

常用的UI类包括标签，按钮，勾选框，下拉框，图片，输入框，列表，滑动面板，滑条，分割面板。它们都在com.badlogic.gdx.scenes.scene2d.ui包中，都属于Actor，可以方便的纳入舞台的管理中。

其实仔细看看UI类的实现代码不难发现其实它们都是大部分继承自Widget或者Table，如果需要自定义UI可以继承以上两个类（它们继承自Actor），这里要说明一下libgdx的布局部分使用了TWL，有兴趣的朋友可以去看看。

在介绍每个控件之前我们先来看一下NinePatch，这是最近的一个比较重大的更新。

何为NinePatch？其实android原生即有NinePatch类，常在按钮中使用。

如图，将图片分成九份。中间部分可以根据需要扩大，使按钮的大小内容变动不受图片的限制。

而在libgdx的NinePatch其实就是九个TextureRegion对象。

常用的实例化方法有两个：

public NinePatch (Texture texture, int left, int right, int top, int bottom)

public NinePatch (TextureRegion region, int left, int right, int top, int bottom)

关于其中的四个int型参数如何取值我们可以参考一下源码：

public NinePatch (TextureRegion region, int left, int right, int top, int bottom) { 
        int middleWidth = region.getRegionWidth() - left - right; 
        int middleHeight = region.getRegionHeight() - top - bottom; 
        this.patches = new TextureRegion[] {new TextureRegion(region, 0, 0, left, top), 
            new TextureRegion(region, left, 0, middleWidth, top), new TextureRegion(region, left + middleWidth, 0, right, top), 
            new TextureRegion(region, 0, top, left, middleHeight), new TextureRegion(region, left, top, middleWidth, middleHeight), 
            new TextureRegion(region, left + middleWidth, top, right, middleHeight), 
            new TextureRegion(region, 0, top + middleHeight, left, bottom), 
            new TextureRegion(region, left, top + middleHeight, middleWidth, bottom), 
            new TextureRegion(region, left + middleWidth, top + middleHeight, right, bottom)}; 
    }

先计算中间部分的宽度和高度。然后开始切图，首先取顶部的最左边的那个，即图中编号1的那块，然后去它右边的，然后再右边的。

取完最上边的那行，然后取中间的那行，然后取最后一行的。

由上自下，由左自右。

而在绘制时又是如何处理的呢？看源码：

public void draw (SpriteBatch batch, float x, float y, float width, float height) { 
        float centerColumnX = x; 
        if (patches[BOTTOM_LEFT] != null) 
            centerColumnX += patches[BOTTOM_LEFT].getRegionWidth(); 
        else if (patches[MIDDLE_LEFT] != null) 
            centerColumnX += patches[MIDDLE_LEFT].getRegionWidth(); 
        else if (patches[TOP_LEFT] != null) // 
            centerColumnX += patches[TOP_LEFT].getRegionWidth();

        float rightColumnX = x + width; 
        if (patches[BOTTOM_RIGHT] != null) 
            rightColumnX -= patches[BOTTOM_RIGHT].getRegionWidth(); 
        else if (patches[MIDDLE_RIGHT] != null) 
            rightColumnX += patches[MIDDLE_RIGHT].getRegionWidth(); 
        else if (patches[TOP_RIGHT] != null) // 
            rightColumnX += patches[TOP_RIGHT].getRegionWidth();

        float middleRowY = y; 
        if (patches[TOP_LEFT] != null) 
            middleRowY += patches[TOP_LEFT].getRegionHeight(); 
        else if (patches[TOP_CENTER] != null) 
            middleRowY += patches[TOP_CENTER].getRegionHeight(); 
        else if (patches[TOP_RIGHT] != null) // 
            middleRowY += patches[TOP_RIGHT].getRegionHeight();

        float topRowY = y + height; 
        if (patches[TOP_LEFT] != null) 
            topRowY -= patches[TOP_LEFT].getRegionHeight(); 
        else if (patches[TOP_CENTER] != null) 
            topRowY -= patches[TOP_CENTER].getRegionHeight(); 
        else if (patches[TOP_RIGHT] != null) // 
            topRowY -= patches[TOP_RIGHT].getRegionHeight();

        // Bottom row 
        if (patches[BOTTOM_LEFT] != null) batch.draw(patches[BOTTOM_LEFT], x, y, centerColumnX - x, middleRowY - y); 
        if (patches[BOTTOM_CENTER] != null) 
            batch.draw(patches[BOTTOM_CENTER], centerColumnX, y, rightColumnX - centerColumnX, middleRowY - y); 
        if (patches[BOTTOM_RIGHT] != null) 
            batch.draw(patches[BOTTOM_RIGHT], rightColumnX, y, x + width - rightColumnX, middleRowY - y);

        // Middle row 
        if (patches[MIDDLE_LEFT] != null) batch.draw(patches[MIDDLE_LEFT], x, middleRowY, centerColumnX - x, topRowY - middleRowY); 
        if (patches[MIDDLE_CENTER] != null) 
            batch.draw(patches[MIDDLE_CENTER], centerColumnX, middleRowY, rightColumnX - centerColumnX, topRowY - middleRowY); 
        if (patches[MIDDLE_RIGHT] != null) 
            batch.draw(patches[MIDDLE_RIGHT], rightColumnX, middleRowY, x + width - rightColumnX, topRowY - middleRowY);

        // Top row 
        if (patches[TOP_LEFT] != null) batch.draw(patches[TOP_LEFT], x, topRowY, centerColumnX - x, y + height - topRowY); 
        if (patches[TOP_CENTER] != null) 
            batch.draw(patches[TOP_CENTER], centerColumnX, topRowY, rightColumnX - centerColumnX, y + height - topRowY); 
        if (patches[TOP_RIGHT] != null) 
            batch.draw(patches[TOP_RIGHT], rightColumnX, topRowY, x + width - rightColumnX, y + height - topRowY); 
    }

先计算左右栏的宽度，在计算中间和顶部的高度。然后从下自上的绘制。说实话我觉得这段代码看着很好玩的。

现在来说说几个常用的控件的使用吧。先构建一个舞台。

先来试试Label吧，label是有缓存的，所以替换显示内容不是用setText方法，而是使用setWrappedText方法。

代码如下：

package com.cnblogs.htynkn.listener;

import com.badlogic.gdx.ApplicationListener; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.graphics.GL10; 
import com.badlogic.gdx.graphics.g2d.BitmapFont; 
import com.badlogic.gdx.graphics.g2d.BitmapFont.HAlignment; 
import com.badlogic.gdx.scenes.scene2d.Stage; 
import com.badlogic.gdx.scenes.scene2d.actors.Label;

public class FirstGame implements ApplicationListener {

    private Stage stage; 
    Label label;

    @Override 
    public void create() { 
        stage = new Stage(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), 
                true); 
        label = new Label("fpsLabel", new BitmapFont(Gdx.files.internal("cf.fnt"),Gdx.files.internal("cf.png"),false), "label1"); 
        label.x=5; 
        label.y=Gdx.graphics.getHeight()-label.height-5; 
        stage.addActor(label); 
        Gdx.input.setInputProcessor(stage); 
    }

    @Override 
    public void dispose() { 
        stage.dispose(); 
    }

    @Override 
    public void pause() { 
        // TODO Auto-generated method stub

    }

    @Override 
    public void render() { 
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); 
        label.setWrappedText("FPS： "+Gdx.graphics.getFramesPerSecond(), 
                HAlignment.CENTER); 
        stage.act(Gdx.graphics.getDeltaTime()); 
        stage.draw(); 
    }

    @Override 
    public void resize(int width, int height) { 
        // TODO Auto-generated method stub

    }

    @Override 
    public void resume() { 
        // TODO Auto-generated method stub

    } 
} 

效果：

然后再看看Button吧，实例化需要一个ButtonStyle，定义了按钮三种状态对应的图片样式，按下和松开时的X,Y偏移还有Button中文字绘制所需的BitmapFont和Color。

按钮的三种状态的图片我就省了，只用一张图片。

修改代码如下：

package com.cnblogs.htynkn.listener;

import com.badlogic.gdx.ApplicationListener; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.graphics.Color; 
import com.badlogic.gdx.graphics.GL10; 
import com.badlogic.gdx.graphics.Texture; 
import com.badlogic.gdx.graphics.g2d.BitmapFont; 
import com.badlogic.gdx.graphics.g2d.NinePatch; 
import com.badlogic.gdx.graphics.g2d.BitmapFont.HAlignment; 
import com.badlogic.gdx.scenes.scene2d.Stage; 
import com.badlogic.gdx.scenes.scene2d.actors.Label; 
import com.badlogic.gdx.scenes.scene2d.ui.Button; 
import com.badlogic.gdx.scenes.scene2d.ui.Button.ButtonStyle;

public class FirstGame implements ApplicationListener {

    private Stage stage; 
    Label label; 
    Texture texture; 
    Button button;

    @Override 
    public void create() { 
        stage = new Stage(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), 
                true); 
        texture = new Texture(Gdx.files.internal("06.png")); 
        NinePatch n1 = new NinePatch(texture, 7, 7, 9, 9); 
        BitmapFont bitmapFont = new BitmapFont(Gdx.files.internal("cf.fnt"), 
                Gdx.files.internal("cf.png"), false); 
        label = new Label("fpsLabel", bitmapFont, "label1"); 
        label.x = 5; 
        label.y = Gdx.graphics.getHeight() - label.height - 5; 
        stage.addActor(label); 
        button = new Button("button", new ButtonStyle(n1, n1, n1, 0f, 0f, 0f, 
                0f, bitmapFont, new Color(1, 1, 0, 0.5f)), "button"); 
        button.x=10; 
        button.y=10; 
        button.width=100f; 
        button.height=32f; 
        stage.addActor(button); 
        Gdx.input.setInputProcessor(stage); 
    }

    @Override 
    public void dispose() { 
        stage.dispose(); 
    }

    @Override 
    public void pause() { 
        // TODO Auto-generated method stub

    }

    @Override 
    public void render() { 
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); 
        label.setWrappedText("FPS： " + Gdx.graphics.getFramesPerSecond(), 
                HAlignment.CENTER); 
        stage.act(Gdx.graphics.getDeltaTime()); 
        stage.draw(); 
    }

    @Override 
    public void resize(int width, int height) { 
        // TODO Auto-generated method stub

    }

    @Override 
    public void resume() { 
        // TODO Auto-generated method stub

    } 
} 

效果：

按钮自然应该有点击事件，通过setClickListener来设置

button.setClickListener(new ClickListener() { 
            @Override 
            public void click(Actor actor) { 
                Gdx.app.log("Info", "点击事件触发了"); 
            } 
        });

然后再看看CheckBox。CheckBox的样式定义在CheckBoxStyle中，需要4个参数，两种状态的各一张图片，一个BitmapFont和Color。

这里我再添加一张图片

原理差不多，直接贴代码了。

package com.cnblogs.htynkn.listener;

import android.graphics.Paint.Align;

import com.badlogic.gdx.ApplicationListener; 
import com.badlogic.gdx.Gdx; 
import com.badlogic.gdx.graphics.Color; 
import com.badlogic.gdx.graphics.GL10; 
import com.badlogic.gdx.graphics.Texture; 
import com.badlogic.gdx.graphics.g2d.BitmapFont; 
import com.badlogic.gdx.graphics.g2d.NinePatch; 
import com.badlogic.gdx.graphics.g2d.TextureRegion; 
import com.badlogic.gdx.graphics.g2d.BitmapFont.HAlignment; 
import com.badlogic.gdx.scenes.scene2d.Actor; 
import com.badlogic.gdx.scenes.scene2d.Stage; 
import com.badlogic.gdx.scenes.scene2d.actors.Label; 
import com.badlogic.gdx.scenes.scene2d.ui.Button; 
import com.badlogic.gdx.scenes.scene2d.ui.CheckBox; 
import com.badlogic.gdx.scenes.scene2d.ui.ClickListener; 
import com.badlogic.gdx.scenes.scene2d.ui.Button.ButtonStyle; 
import com.badlogic.gdx.scenes.scene2d.ui.CheckBox.CheckBoxStyle;

public class FirstGame implements ApplicationListener {

    private Stage stage; 
    Label label; 
    Texture texture1; 
    Texture texture2; 
    CheckBox checkBox;

    @Override 
    public void create() { 
        stage = new Stage(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), 
                true); 
        texture1 = new Texture(Gdx.files.internal("06.png")); 
        texture2 = new Texture(Gdx.files.internal("07.png")); 
        NinePatch n1 = new NinePatch(texture1, 7, 7, 9, 9); 
        BitmapFont bitmapFont = new BitmapFont(Gdx.files.internal("cf.fnt"), 
                Gdx.files.internal("cf.png"), false); 
        label = new Label("fpsLabel", bitmapFont, "label1"); 
        label.x = 5; 
        label.y = Gdx.graphics.getHeight() - label.height - 5; 
        CheckBoxStyle style = new CheckBoxStyle(new TextureRegion(texture1), 
                new TextureRegion(texture2), bitmapFont, new Color(1, 1, 1, 
                        0.5f));

        checkBox = new CheckBox("checkbox", style, "checkbox"); 
        checkBox.x = 100; 
        checkBox.y = 100; 
        checkBox.width = 158f; 
        checkBox.height = 32f; 
        checkBox.setText("Yes"); 
        checkBox.setClickListener(new ClickListener() {

            @Override 
            public void click(Actor actor) { 
                if (checkBox.isChecked) { 
                    checkBox.setText("Yes"); 
                } else { 
                    checkBox.setText("NO"); 
                } 
            } 
        }); 
        stage.addActor(checkBox); 
        stage.addActor(label); 
        Gdx.input.setInputProcessor(stage); 
    }

    @Override 
    public void dispose() { 
        stage.dispose(); 
    }

    @Override 
    public void pause() { 
        // TODO Auto-generated method stub

    }

    @Override 
    public void render() { 
        Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); 
        label.setWrappedText("FPS： " + Gdx.graphics.getFramesPerSecond(), 
                HAlignment.CENTER); 
        stage.act(Gdx.graphics.getDeltaTime()); 
        stage.draw(); 
    }

    @Override 
    public void resize(int width, int height) { 
        // TODO Auto-generated method stub

    }

    @Override 
    public void resume() { 
        // TODO Auto-generated method stub

    } 
} 

效果：

其他的UI大致用法差不多，显示的样式在对应的Style或者Skin中定义。但是要注意有些UI类需要手动设置width和height，不然有些显示会很奇怪的。

最后说一下Slider的用法。

SliderStyle需要一个NinePath和Texture，我最初没有想通为什么不是两个NinePath，仔细看一下源码才了解到，NinePath是作为背景，而Texture那个是中间的那个滑动的方块。

关于用配置文件设置Style的问题，google code的wiki上似乎没有写，但是在libgdx的论坛里面有，比如

somePatch1: [
    { height: 13,  9, x: 761, y: 78 },
    { height: 13,  1, x: 770, y: 78 },
    { height: 13,  9, x: 771, y: 78 },
    { height: 1,  9, x: 761, y: 91 },
    { height: 1,  1, x: 770, y: 91 },
    { height: 1,  9, x: 771, y: 91 },
    { height: 13,  9, x: 761, y: 92 },
    { height: 13,  1, x: 770, y: 92 },
    { height: 13,  9, x: 771, y: 92 }
]

或者

somePatch2: [
    { height: 13,  9, x: 761, y: 78 },
]