Android简明开发教程十三：Option Menu 画笔示例
引路蜂二维图形画笔（Pen）示例含有四个示例，Lines ，Dashes ,LineJoin 和LineCap。打算采用Option Menu（主菜单）的方式来选择不同示例。
首先要对GuidebeeGraphics2DView，和Graphics2DActivity做些改动，从这个示例开始，GuidebeeGraphics2DView需要动态绘制不同图形（可以通过菜单，或是Thread）。在GuidebeeGraphics2DView增加下面两个方法：
final Runnable updateCanvas = new Runnable() {
public void run() {
invalidate();
}
};
public void refreshCanvas(){
post(updateCanvas);
}
post可以用在非UI Thread中Call UI Thread中方法。这里只是触发屏幕重绘事件以刷新屏幕显示。
在Graphics2DActivity增加一个变量protected GuidebeeGraphics2DView graphic2dView; 来获得对应的GuidebeeGraphics2DView实例。
graphic2dView=(GuidebeeGraphics2DView)findViewById(R.id.graphics2dview);
使用Option Menu，尽管也可以完全使用代码来创建菜单，更一般的方法是使用菜单资源。在res 下创建menu 子目录，然后在res\menu下创建menu_option_line.xml 用来显示Pen的四个示例选项：
<?xml version=”1.0″ encoding=”utf-8″?>
<menu
xmlns:android=”http://schemas.android.com/apk/res/android“>
<item
android:id=”@+id/mnuLines”
android:title=”Lines”
android:icon=”@drawable/icon1″>
</item>
<item
android:id=”@+id/mnuDashes”
android:title=”Dashes”
android:icon=”@drawable/icon2″>
</item>
<item
android:id=”@+id/mnuLineCap”
android:title=”LineCap”
android:icon=”@drawable/icon3″>
</item>
<item
android:id=”@+id/mnuLineJoin”
android:title=”LineJoin”
android:icon=”@drawable/icon4″>
</item>
</menu>
<menu></menu> 定义菜单，<item></item>定义菜单项，<item></item>可以嵌套以定义子菜单。菜单可以定义id, Icon,Text等属性。也可以支持单选，多选，此时就需要借助<group></group>,使用group可以把一最菜单项定义为一个组，可以使用setGroupVisible()来显示隐藏整个菜单组，Enable 或是Disable整个菜单组setGroupEnabled()等。最关键的，有了组才能实现菜单的单选和多选功能：
<?xml version=”1.0″ encoding=”utf-8″?>
<menu xmlns:android=”http://schemas.android.com/apk/res/android“>
<item android:id=”@+id/item1″
android:icon=”@drawable/item1″
android:title=”@string/item1″ />
<!– menu group –>
<group android:id=”@+id/group1″>
<item android:id=”@+id/groupItem1″
android:title=”@string/groupItem1″ />
<item android:id=”@+id/groupItem2″
android:title=”@string/groupItem2″ />
</group>
</menu>
定义好菜单资源后，就可以使用MenuInflater.inflate()展开菜单，一般需要在Activity的onCreateOptionsMenu()展开菜单：
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_option_line, menu);
return true;
}
最后是响应菜单事件：
@Override
public boolean onOptionsItemSelected(MenuItem item) {
menuOption = item.getItemId();
drawImage();
return true;
}
item.getItemId(); 返回菜单的ID（在菜单资源中定义）。
完整代码如下：
public class Pen extends Graphics2DActivity {
int menuOption;
@Override
protected void drawImage() {
switch (menuOption) {
case R.id.mnuLines:
drawLines();
break;
case R.id.mnuDashes:
drawDash();
break;
case R.id.mnuLineCap:
drawLineCap();
break;
case R.id.mnuLineJoin:
drawLineJoin();
break;
default:
drawLines();
break;
}
graphic2dView.refreshCanvas();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_option_line, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
menuOption = item.getItemId();
drawImage();
return true;
}
private void drawLineJoin() {
Color blackColor = new Color(0xff000000);
Color whiteColor = new Color(0xffffffff);
com.mapdigit.drawing.geometry.Path path
= new com.mapdigit.drawing.geometry.Path();
path.moveTo(40, 60);
path.lineTo(90, 20);
path.lineTo(140, 60);
// Clear the canvas with white color.
graphics2D.clear(Color.WHITE);
AffineTransform matrix = new AffineTransform();
graphics2D.setAffineTransform(matrix);
com.mapdigit.drawing.Pen pen
= new com.mapdigit.drawing.Pen(blackColor,
20, com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_MITER);
graphics2D.draw(pen, path);
pen = new com.mapdigit.drawing.Pen(whiteColor, 1);
graphics2D.draw(pen, path);
matrix.translate(0, 50);
graphics2D.setAffineTransform(matrix);
pen = new com.mapdigit.drawing.Pen(blackColor, 20,
com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_ROUND);
graphics2D.draw(pen, path);
pen = new com.mapdigit.drawing.Pen(whiteColor, 1);
graphics2D.draw(pen, path);
matrix = new AffineTransform();
matrix.translate(0, 100);
graphics2D.setAffineTransform(matrix);
pen = new com.mapdigit.drawing.Pen(blackColor, 20,
com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_BEVEL);
graphics2D.draw(pen, path);
pen = new com.mapdigit.drawing.Pen(whiteColor, 1);
graphics2D.draw(pen, path);
}
private void drawLineCap() {
Color blackColor = new Color(0xff000000);
Color whiteColor = new Color(0xffffffff);
// Clear the canvas with white color.
graphics2D.clear(Color.WHITE);
AffineTransform matrix = new AffineTransform();
graphics2D.setAffineTransform(matrix);
com.mapdigit.drawing.Pen pen
= new com.mapdigit.drawing.Pen(blackColor,
20, com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_MITER);
graphics2D.drawLine(pen, 40, 60, 140, 60);
pen = new com.mapdigit.drawing.Pen(whiteColor, 1);
graphics2D.drawLine(pen, 40, 60, 140, 60);
pen = new com.mapdigit.drawing.Pen(blackColor, 20,
com.mapdigit.drawing.Pen.CAP_ROUND,
com.mapdigit.drawing.Pen.JOIN_MITER);
graphics2D.drawLine(pen, 40, 100, 140, 100);
pen = new com.mapdigit.drawing.Pen(whiteColor, 1);
graphics2D.drawLine(pen, 40, 100, 140, 100);
pen = new com.mapdigit.drawing.Pen(blackColor, 20,
com.mapdigit.drawing.Pen.CAP_SQUARE,
com.mapdigit.drawing.Pen.JOIN_MITER);
graphics2D.drawLine(pen, 40, 140, 140, 140);
pen = new com.mapdigit.drawing.Pen(whiteColor, 1);
graphics2D.drawLine(pen, 40, 140, 140, 140);
}
private void drawLines() {
Color greenColor = new Color(0xff00ff00);
// Clear the canvas with white color.
graphics2D.clear(Color.WHITE);
AffineTransform matrix = new AffineTransform();
graphics2D.setAffineTransform(matrix);
com.mapdigit.drawing.Pen pen
= new com.mapdigit.drawing.Pen(greenColor,1);
graphics2D.drawLine(pen, 20, 150, 60, 50);
pen = new com.mapdigit.drawing.Pen(greenColor, 2);
graphics2D.drawLine(pen, 40, 150, 80, 50);
pen = new com.mapdigit.drawing.Pen(greenColor, 3);
graphics2D.drawLine(pen, 60, 150, 100, 50);
pen = new com.mapdigit.drawing.Pen(greenColor, 5);
graphics2D.drawLine(pen, 80, 150, 120, 50);
pen = new com.mapdigit.drawing.Pen(greenColor, 7);
graphics2D.drawLine(pen, 100, 150, 140, 50);
pen = new com.mapdigit.drawing.Pen(greenColor, 10);
graphics2D.drawLine(pen, 120, 150, 160, 50);
}
private void drawDash() {
Color blackColor = new Color(0xff000000);
int dashArray1[] = { 2, 2 };
int dashArray2[] = { 6, 6 };
int dashArray3[] = { 4, 1, 2, 1, 1, 6 };
// Clear the canvas with white color.
graphics2D.clear(Color.WHITE);
AffineTransform matrix = new AffineTransform();
graphics2D.setAffineTransform(matrix);
com.mapdigit.drawing.Pen pen
= new com.mapdigit.drawing.Pen(blackColor,
20, com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_MITER, dashArray1, 0);
graphics2D.drawLine(pen, 40, 60, 140, 60);
pen = new com.mapdigit.drawing.Pen(blackColor, 20,
com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_MITER, dashArray2, 0);
graphics2D.drawLine(pen, 40, 100, 140, 100);
pen = new com.mapdigit.drawing.Pen(blackColor, 20,
com.mapdigit.drawing.Pen.CAP_BUTT,
com.mapdigit.drawing.Pen.JOIN_MITER, dashArray3, 0);
graphics2D.drawLine(pen, 40, 140, 140, 140);
}
}
