import java.awt.Graphics;


/**
 * <p>Title: UFO_Play</p>
 *
 * <p>Description: 基于applet的攻擊UFO的小游戲中的UFO爆炸類</p>
 *
 * <p>Copyright: Copyright (c) 2007</p>
 *
 * <p>Company: 鹿児島大學</p>
 *
 * @author 柴 智
 * @version 1.0
 */
public class Explosion extends Piece {
    //Explosion類的構造函數
    public Explosion(UFO_Canvas ufo_canvas, int x, int y) {
        //爆炸對象屬性值的初始化
        super(ufo_canvas);
        w = 30;
        h = 30;
        px = opx = x;
        py = opy = y;
        active = true;
        img = ufo_canvas.getMissile_explosion();
    }

    int seq = 0;
    int seq2 = 0;
    //爆炸對象的繪制函數
    public void draw() {
        //設置繪制的區域
        set_draw_rectangles(ufo_canvas.getPaint_area(), ufo_canvas.getNew_area());

        // 清除舊的圖像
        Graphics bkd_g = ufo_canvas.getBackdrop().getGraphics();
        bkd_g.clipRect(ufo_canvas.getPaint_area().x, ufo_canvas.getPaint_area().y, w, h);
        bkd_g.drawImage(ufo_canvas.getBgimg(), 0, 0, ufo_canvas.getWindow_size().width,
                        ufo_canvas.getWindow_size().height, ufo_canvas.getBaseApplet());

        // 由于爆炸用的圖片是一個序列圖，要進行剪切再使用
        //根據seq2的值選擇相應的部分
        if ((++seq2 % 4) == 0) {
            seq = ++seq % 5;
        }

        // 爆炸圖最后的部分顯示后，將active屬性值設為false，并將其清除
        if (seq == 4) {
            active = false;
        }

        // 將新的區域繪制到緩沖中
        bkd_g.clipRect(ufo_canvas.getNew_area().x, ufo_canvas.getNew_area().y, w, h);
        bkd_g.drawImage(img, ufo_canvas.getNew_area().x - w * seq, ufo_canvas.getNew_area().y, ufo_canvas.getBaseApplet());
        bkd_g.dispose();

        // 將變化繪制到緩沖中
        Graphics bg = ufo_canvas.getBuffer().getGraphics();
        bg.clipRect(ufo_canvas.getNew_area().x, ufo_canvas.getNew_area().y, w, h);
        bg.drawImage(ufo_canvas.getBackdrop(), 0, 0, ufo_canvas.getBaseApplet());
        bg.dispose();

        // 將緩沖繪制到屏幕上
        Graphics g = ufo_canvas.getBaseApplet().getGraphics();
        g.clipRect(ufo_canvas.getPaint_area().x, ufo_canvas.getPaint_area().y, ufo_canvas.getPaint_area().width,
                   ufo_canvas.getPaint_area().height);
        g.drawImage(ufo_canvas.getBuffer(), 0, 0, ufo_canvas.getBaseApplet());
        g.dispose();
    }

    //爆炸對象的清除
    public void erase() {
        //設置繪制的區域
        set_draw_rectangles(ufo_canvas.getPaint_area(), ufo_canvas.getNew_area());

        // 清除舊的圖像
        Graphics bkd_g = ufo_canvas.getBackdrop().getGraphics();
        bkd_g.clipRect(ufo_canvas.getPaint_area().x, ufo_canvas.getPaint_area().y, w, h);
        bkd_g.drawImage(ufo_canvas.getBgimg(), 0, 0, ufo_canvas.getWindow_size().width,
                        ufo_canvas.getWindow_size().height, ufo_canvas.getBaseApplet());
        bkd_g.dispose();

        // 對緩沖和屏幕執行同樣的操作
        super.erase();
    }
}