Android简明开发教程十三：Option Menu 画笔示例

jerry Android 2015年08月24日收藏

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);
 }
}