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：
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final
Runnable updateCanvas =
new
Runnable() {
public
void
run() {
invalidate();
}
};
public
void
refreshCanvas(){
post(updateCanvas);
}
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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：
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@Override
public
boolean
onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu_option_line, menu);
return
true
;
}
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最后是响应菜单事件：
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@Override
public
boolean
onOptionsItemSelected(MenuItem item) {
menuOption = item.getItemId();
drawImage();
return
true
;
}
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item.getItemId(); 返回菜单的ID（在菜单资源中定义）。
完整代码如下：
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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
);
}
}
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