坦克大战(一期)-解决闪烁问题（通过双缓冲解决）

src/com/msb/Bullet.java

@@ -12,8 +12,8 @@ public class Bullet extends Frame {
 
     private int x, y;
     private DirEnum dir;
-    public static final int WIDTH = 8;
+    public static final int WIDTH = 20;
-    public static final int HEIGHT = 8;
+    public static final int HEIGHT = 20;
     public static final int SPEED = 5;
 
     public Bullet(int x, int y, DirEnum dir) {

src/com/msb/Tank.java

@@ -22,7 +22,10 @@ public class Tank {
     }
 
     public void paint(Graphics g) {
+        Color color = g.getColor();
+        g.setColor(Color.YELLOW);
         g.fillRect(x, y, 50, 50);
+        g.setColor(color);
         moving();
     }
 

src/com/msb/TankFrame.java

@@ -5,6 +5,7 @@ import java.awt.event.KeyAdapter;
 import java.awt.event.KeyEvent;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;
+import java.util.Objects;
 
 /**
  * @Author bingor
@@ -16,11 +17,13 @@ public class TankFrame extends Frame {
 
     Tank tank = new Tank(200, 200, DirEnum.RIGHT);
     Bullet bullet = new Bullet(200, 200, DirEnum.DOWN);
+    public static final int GAME_WIDTH = 800;
+    public static final int GAME_HEIGHT = 600;
 
     public TankFrame() {
 
         setTitle("Tank war");
-        setSize(800, 600);
+        setSize(GAME_WIDTH, GAME_HEIGHT);
         setResizable(true);
         setVisible(true);
 
@@ -38,11 +41,28 @@ public class TankFrame extends Frame {
 
     @Override
     public void paint(Graphics g) {
-        super.paint(g);
+//        super.paint(g);
         tank.paint(g);
         bullet.paint(g);
     }
 
+    //双缓冲，解决闪烁现象
+    Image offScreenImage = null;
+    @Override   //在paint方法之前会被调用，但是我做实验了，闪烁现象似乎还是存在
+    public void update(Graphics g) {
+//        super.update(g);
+        if(Objects.isNull(offScreenImage)) {
+            offScreenImage = this.createImage(GAME_WIDTH, GAME_HEIGHT);
+        }
+        Graphics gOffScreen = offScreenImage.getGraphics();
+        Color color = gOffScreen.getColor();
+        gOffScreen.setColor(Color.WHITE);
+        gOffScreen.fillRect(0, 0, GAME_WIDTH, GAME_HEIGHT);
+        gOffScreen.setColor(color);
+        paint(gOffScreen);
+        g.drawImage(offScreenImage, 0, 0, null);
+    }
+
     //这里使用内部内的原因是，只有TankFrame用到
     class MyKeyListener extends KeyAdapter {