Android简明开发教程十三：Option Menu 画笔示例

来源：互联网发布：linux里面涉及到单词编辑：程序博客网时间：2024/05/01 11:43

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); 
}

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; 
}

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; 
}

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); 
 } 
}