回答編集履歴

見直しキャンペーン中

2023/08/13 12:06

投稿

TN8001

スコア9862

test CHANGED Viewed

@@ -1,263 +1,132 @@
 直接的な原因は`getGraphics()`したものは、`Foreground`の色が設定されます。
 そのため`setColor()`したとしても`getGraphics()`するたびに、黒に戻ってしまいます。
 方針としては`Color`をメンバ変数にもち、`g.drawLine()`の前で`setColor()`することです。
 しかし現在の実装ですと再描画される（ウィンドウサイズを変更する等）と、すべて消えてしまうのでよろしくありません。
 通常は`BufferedImage`に描き、消えないように保持しておきます。
-AWTよりSwingのほうがよいと思いますので、「java swing お絵かき」等で検索してみてください。
+AWTよりSwingのほうがよいと思いますので、「[java swing お絵かき](https://www.google.co.jp/search?q=java+swing+%E3%81%8A%E7%B5%B5%E3%81%8B%E3%81%8D)」等で検索してみてください。
 ---
 追記
 上記内容を分かったうえで、とりあえず動かすだけでよいならこんな感じ？
 ```Java
 import java.awt.Button;
 import java.awt.Color;
 import java.awt.Frame;
 import java.awt.Graphics;
 import java.awt.GridLayout;
 import java.awt.Panel;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;
 class Draw extends Frame {
     int x, y, cx, cy;
     Color currentColor = Color.black;
     public Draw() {
         super("ペイント");
         addWindowListener(new SampleWindowListener());
         addMouseListener(new SampleMouseAdapter());
         addMouseMotionListener(new SampleMouseAdapter());
     }
     public void setColor(Color newColor) {
         currentColor = newColor;
     }
+    class SampleWindowListener extends WindowAdapter {
+        public void windowClosing(WindowEvent e) {
+            System.exit(0);
+        }
+    }
-    class SampleWindowListener extends WindowAdapter {
+    class SampleMouseAdapter extends MouseAdapter {
-        public void windowClosing(WindowEvent e) {
+        public void mousePressed(MouseEvent e) {
-            System.exit(0);
+            x = e.getX();
+            y = e.getY();
         }
+        public void mouseDragged(MouseEvent e) {
+            Graphics g = getGraphics();
+            cx = e.getX();
+            cy = e.getY();
+            g.setColor(currentColor);
+            g.drawLine(x, y, cx, cy);
+            x = cx;
+            y = cy;
+        }
     }
-    class SampleMouseAdapter extends MouseAdapter {
-        public void mousePressed(MouseEvent e) {
-            x = e.getX();
-            y = e.getY();
-        }
-        public void mouseDragged(MouseEvent e) {
-            Graphics g = getGraphics();
-            cx = e.getX();
-            cy = e.getY();
-            g.setColor(currentColor);
-            g.drawLine(x, y, cx, cy);
-            x = cx;
-            y = cy;
-        }
-    }
 }
 class Draw2 extends Draw {
     private Button Whitebt, Blackbt, Redbt, Bluebt, Greenbt, Clearbt;
 //    Draw drawarea; // Drawを継承しているのだから自分自身
     public static void main(String[] args) {
         Draw2 ft = new Draw2();
     }
     Draw2() {
         setSize(500, 500);
 //        drawarea = new Draw();
         Whitebt = new Button("White");
 //        add(Whitebt); // pan.add(Whitebt); しているので2重登録
         Whitebt.addActionListener(new SampleActionListener());
         Blackbt = new Button("Black");
         Blackbt.addActionListener(new SampleActionListener());
         Redbt = new Button("Red");
         Redbt.addActionListener(new SampleActionListener());
         Bluebt = new Button("Blue");
         Bluebt.addActionListener(new SampleActionListener());
         Greenbt = new Button("Green");
         Greenbt.addActionListener(new SampleActionListener());
         Clearbt = new Button("Clear");
         Clearbt.addActionListener(new SampleActionListener());
         Panel pan = new Panel();
         pan.setLayout(new GridLayout(1, 6));
         pan.add(Whitebt);
         pan.add(Blackbt);
         pan.add(Redbt);
         pan.add(Bluebt);
         pan.add(Greenbt);
         pan.add(Clearbt);
         add("North", pan);
         setVisible(true);
     }
     class SampleActionListener implements ActionListener {
         public void actionPerformed(ActionEvent e) {
             if (e.getSource() == Whitebt) {
                 setColor(Color.white);
             } else if (e.getSource() == Blackbt) {
                 setColor(Color.black);
             } else if (e.getSource() == Redbt) {
                 setColor(Color.red);
             } else if (e.getSource() == Bluebt) {
                 setColor(Color.blue);
             } else if (e.getSource() == Greenbt) {
                 setColor(Color.green);
             } else if (e.getSource() == Clearbt) {
                 Graphics g = getGraphics();
                 setColor(Color.white);
                 g.fillRect(0, 0, getSize().width, getSize().height);
                 setColor(Color.black);
                 repaint();
             }
         }
     }
 }
 ```

追記コード

2021/01/24 09:33

投稿

TN8001

スコア9862

test CHANGED Viewed

@@ -13,3 +13,251 @@
 AWTよりSwingのほうがよいと思いますので、「java swing お絵かき」等で検索してみてください。
+---
+追記
+上記内容を分かったうえで、とりあえず動かすだけでよいならこんな感じ？
+```Java
+import java.awt.Button;
+import java.awt.Color;
+import java.awt.Frame;
+import java.awt.Graphics;
+import java.awt.GridLayout;
+import java.awt.Panel;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+import java.awt.event.WindowAdapter;
+import java.awt.event.WindowEvent;
+class Draw extends Frame {
+    int x, y, cx, cy;
+    Color currentColor = Color.black;
+    public Draw() {
+        super("ペイント");
+        addWindowListener(new SampleWindowListener());
+        addMouseListener(new SampleMouseAdapter());
+        addMouseMotionListener(new SampleMouseAdapter());
+    }
+    public void setColor(Color newColor) {
+        currentColor = newColor;
+    }
+    class SampleWindowListener extends WindowAdapter {
+        public void windowClosing(WindowEvent e) {
+            System.exit(0);
+        }
+    }
+    class SampleMouseAdapter extends MouseAdapter {
+        public void mousePressed(MouseEvent e) {
+            x = e.getX();
+            y = e.getY();
+        }
+        public void mouseDragged(MouseEvent e) {
+            Graphics g = getGraphics();
+            cx = e.getX();
+            cy = e.getY();
+            g.setColor(currentColor);
+            g.drawLine(x, y, cx, cy);
+            x = cx;
+            y = cy;
+        }
+    }
+}
+class Draw2 extends Draw {
+    private Button Whitebt, Blackbt, Redbt, Bluebt, Greenbt, Clearbt;
+//    Draw drawarea; // Drawを継承しているのだから自分自身
+    public static void main(String[] args) {
+        Draw2 ft = new Draw2();
+    }
+    Draw2() {
+        setSize(500, 500);
+//        drawarea = new Draw();
+        Whitebt = new Button("White");
+//        add(Whitebt); // pan.add(Whitebt); しているので2重登録
+        Whitebt.addActionListener(new SampleActionListener());
+        Blackbt = new Button("Black");
+        Blackbt.addActionListener(new SampleActionListener());
+        Redbt = new Button("Red");
+        Redbt.addActionListener(new SampleActionListener());
+        Bluebt = new Button("Blue");
+        Bluebt.addActionListener(new SampleActionListener());
+        Greenbt = new Button("Green");
+        Greenbt.addActionListener(new SampleActionListener());
+        Clearbt = new Button("Clear");
+        Clearbt.addActionListener(new SampleActionListener());
+        Panel pan = new Panel();
+        pan.setLayout(new GridLayout(1, 6));
+        pan.add(Whitebt);
+        pan.add(Blackbt);
+        pan.add(Redbt);
+        pan.add(Bluebt);
+        pan.add(Greenbt);
+        pan.add(Clearbt);
+        add("North", pan);
+        setVisible(true);
+    }
+    class SampleActionListener implements ActionListener {
+        public void actionPerformed(ActionEvent e) {
+            if (e.getSource() == Whitebt) {
+                setColor(Color.white);
+            } else if (e.getSource() == Blackbt) {
+                setColor(Color.black);
+            } else if (e.getSource() == Redbt) {
+                setColor(Color.red);
+            } else if (e.getSource() == Bluebt) {
+                setColor(Color.blue);
+            } else if (e.getSource() == Greenbt) {
+                setColor(Color.green);
+            } else if (e.getSource() == Clearbt) {
+                Graphics g = getGraphics();
+                setColor(Color.white);
+                g.fillRect(0, 0, getSize().width, getSize().height);
+                setColor(Color.black);
+                repaint();
+            }
+        }
+    }
+}
+```