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content/ta/fall2017/cpsc220/nov20.md

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+# Lecture for November 20
+
+## Adding a drawing panel to the GUI
+
+You can't put swing and graphics together, therefore you need to make a seperate JPanels for swing and graphics.
+
+Add necessary libraries
+
+```java
+import java.awt.*;
+import java.awt.Graphics;
+import java.awt.event.*;
+import javax.swing.*;
+```
+
+
+
+```java
+public class drawingWindow extends JPanel {
+  JTextField field;
+  JButton draw;
+  DrawingPanel drawingPanel;
+  
+  public drawingWindow() {
+    // Each new component would be vertically stacked upon each other
+    setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
+    
+    JPanel swingSTuff = new JPanel();
+    
+    // Add things to the screen    
+    draw = new JButton("Draw");
+    field = new JTextField();
+    swingStuff.add(field);
+    swingStuff.add(draw)
+    
+    // Add the drawing panel onto the screen
+    drawingPanel = new DrawingPanel(200, 400);
+    add(drawingPanel);
+    
+    // Activate the listener if the button was pressed
+    draw.addActionListener(new Listener());
+  }
+  
+  // Add the listener to respond to events
+  private class listener implements ActionListener {
+    public void actionPerformed(ActionEvent event) {
+      if (event.getSource() == draw) {
+        drawingPanel.setFlag(1);
+        // Repaints the screen so the oval can appear
+        drawingPanel.repaint();
+      }
+    }
+  }
+  
+  // Create the draw panel so we can add it to the screen
+  private class DrawingPanel extends JPanel {
+    private int width, height;
+    DrawingPanel(int width, int height) {
+      this.width = width;
+      this.height = height;
+      setPreferredSize(new Dimension(width, height));
+    }
+    public void setFlag(int flag) {
+      this.flag = flag;
+    }
+  	public void paintComponent(Graphics g) {
+    	super.paintComponent(g);
+    
+    	// Every time the flag is set, draw an oval at a random location and color
+    	if (flag == 1) {
+      	Random rand = new Random();
+      	int x = rand.nextInt(width);
+      	int y = rand.nextInt(height);
+      	g.setColor(Color.RED);
+      	g.fillOval(x, y, 20, 30);
+    	}
+  	}
+  }
+}
+```
+
+There are a myriad of different methods you can use. 
+
+```java
+// Assume width, height, y, x, etc are defined above 
+public void paintComponent(Graphics g) {
+  //....
+  g.dispose(); // Flushes the graphics buffer
+}
+```
+
+You have the traditional fill and draw methods. Fill creates the shape shaded in with a color. Draw creates an outline of the shape.
+
+```java
+  
+// ...
+g.fillRect(x ,y, width, height);
+  g.drawRect(x, y, width, height);
+  g.fillOval(x, y, width, height);
+  g.drawOval(x, y, width, height);
+  //g.drawPoly(parematers...);
+  //g.fillPoly(parameters...);
+  g.drawArc(x, y, width, height, startingAngle, sweepingAngle);
+  g.fillArc(x, y, width, height, startingAngle, sweepingAngle);
+```
+
+You can also create complex shapes like a polygon. When adding points, you need to make sure you add them Clockwise or Counterclockwise (but NOT both)
+
+```java
+  Polygon tri = new Polygon();
+  tri.addPoint(150, 10);
+  tri.addPoint(175, 100);
+  tri.addPoint(125, 100);
+  // Add points clockwise or counterclockwise (NOT BOTH)
+```
+