雷电小学问

雷电小知识
突然看到以前写过一个总结，做j2me的 小雷电，发个帖子 看看有用没，
如果做android游戏，这些多少也是基础，有用了可以看看

初始化多个子弹(原理是子弹运动的角度不同)

void doFire() {int m = 0;for (int i = 0; i < Balls.length; i++) {if (Balls[i][0] == 0) {m++;Balls[i][0] = 1;Balls[i][1] = shipX + shipImg.getWidth() / 2 - 3;Balls[i][2] = shipY - 20;Balls[i][3] = m;switch (m) {case 1: Balls[i][4] = 9;  break;    case 2:  Balls[i][4] = 8;  break;case 3: Balls[i][4] = 10; break;case 4: Balls[i][4] = 7; break;case 5: Balls[i][4] = 11; break;}if (m >= 5) break;} }

小球撞墙,宝物移动
之前初始化x,y和inx, incy的坐标(位置移动，如果越界根据inx,iny的正负确定移动方向，从而位置纠正)

                          x+= incX;y+= incY;if (x] <= 0|| x + giftImg.getWidth() >= width) {x = incX > 0 ? width- giftImg.getWidth() : 0;incX = -incX;}if (y <= 0|| y + giftImg.getHeight() >= height) {y = incY > 0 ? height- giftImg.getHeight() : 0;incY = -incY;}

宝物飞机碰撞, 飞机处理碰撞的原理等碰撞的原理(利用坐标和长和宽确定两个矩形 是否相交)

boolean checkCollide(int x1, int y1, int w1, int h1, int x2, int y2,int w2, int h2) {if (x1 + w1 >= x2 && x1 <= x2 + w2 && y1 + h1 >= y2 && y1 <= y2 + h2) {return true;}return false;}

组合键的实现

int  keyQueue[]=new int [3];void putKey(int keyCode){keyQueue[2]=keyQueue[1];keyQueue[1]=keyQueue[0];keyQueue[0]=keyCode;}void clearKey(){keyQueue[2]=keyQueue[1]=keyQueue[0]=0;}protected void keyPressed(int keyCode){if(System.currentTimeMillis()-keyReleasedTime>400){ clearKey();}putKey(keyCode);}protected void keyReleased(int keyCode){keyReleasedTime=System.currentTimeMillis();}

抛物线:

int [][] enemyFleets=new int [14][4];//active ,x,y,type//初始化抛物线运动void createEnemyFleets(){int p=0;for(int i=0;i<enemyFleets.length;i++){if(enemyFleets[i][0]==0){p++;enemyFleets[i][0]=1;enemyFleets[i][2]=-enemyFleetImg.getHeight();enemyFleets[i][3]=p;if(p>=2){break;}}}}//画抛物线int [][] enemyFleets=new int [14][4];//active ,x,y,typefor(int i=0;i<enemyFleets.length;i++){if(enemyFleets[i][0]==1){enemyFleets[i][2]+=7;if(enemyFleets[i][3]==1){enemyFleets[i][1]=-enemyFleets[i][2]*enemyFleets[i][2]/200+width/2-enemyFleetImg.getWidth();}else{enemyFleets[i][1]=enemyFleets[i][2]*enemyFleets[i][2]/200+width/2;}if(enemyFleets[i][2]>height){enemyFleets[i][0]=0;}g.drawImage(enemyFleetImg, enemyFleets[i][1], enemyFleets[i][2], 20);}}

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