android游戏开发框架libgdx的使用（五）--舞台和常用UI类
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) &
补充：移动开发 , Android ,
