Question

我在Android中编写一个游戏，其中一艘敌舰需要以自己的星形模式射击。基本上，对于任何X次射击我都会将敌舰射击，我希望它能够通过射击次数在自身周围360度分割并以正好等边角度射击。因此，第一次射击360度，第二次射击120度，第三次射击240度，射击3次。 4次射击将是360,90,180,270等等。然后每个镜头将以对角线向外移动，直到它到达屏幕边缘（或路上的其他东西）。到现在为止还挺好。这是我的代码 - 我显然做错了，因为虽然四次射击将在四个相同的方向（北，南，东和西）射击，但是3次射击或6次射击或8次射击（等）将朝错误的方向射击。角度不正确。我很感激任何有关这方面的帮助，因为我已经挣扎了很长一段时间了。在下面的示例中，iShotNumber是齐射中发射的镜头数。距离是镜头在一个'刻度'中行进的距离（以像素为单位）。这些镜头以一个阵列的形式添加在船的周围，然后通过每个“滴答”将镜头向前推进一步。

围绕船只周围拍摄的逻辑：

public void addShot(Context ctx, int iShotNumber, float distance) {



for (int iShot=1; iShot<=iShotNumber; iShot++) {

double 
        dAngle =0, //angle of the shot
        dCosFactor=0, //factor on the x-axis
        dSinFactor=0; //factor on the y-axis

        float 
        fNewX = 0, //new position on the x-axis
        fNewY =0; //new position on the y-axis

        dAngle = 360/iShotNumber;
        dAngle = dAngle*iShot;

        if (iShotNumber == 1) {dAngle=180;} //if there's only one shot then fire straight down

        if (dAngle!=360 && dAngle!=180) //if its 360 or 180 then fire straight up or straight down - no need for X
        {
            fNewX = (float) (getShipRadius()*Math.cos(Math.toRadians(dAngle)));

            if (dAngle<=180) {fNewX=fNewX+distance;} else {fNewX=fNewX-distance;}

            fNewX=fNewX+getXLocation();

        }
        else {fNewX=getXLocation();}        

        if (dAngle!=90 && dAngle !=270) //if its 90 or 270 then fire straight right or straight left - no need for Y
        {
            fNewY = (float) (getShipRadius()*Math.sin(Math.toRadians(dAngle)));

            if (dAngle<=90||dAngle>=270) {fNewY=fNewY+distance;} else {fNewY=fNewY-distance;}

            fNewY=fNewY+getYLocation();
        }
        else {fNewY=getYLocation();}


        if (dAngle>=90&&dAngle<=180) {dSinFactor = Math.sin(Math.toRadians(dAngle)-90); dCosFactor = Math.cos(Math.toRadians(dAngle)-90);}
        else if (dAngle>=181&&dAngle<=270) {dSinFactor = Math.sin(Math.toRadians(dAngle)-180); dCosFactor = Math.cos(Math.toRadians(dAngle)-180);}
        else if (dAngle>=271&&dAngle<360) {dSinFactor = Math.sin(Math.toRadians(dAngle)-270); dCosFactor = Math.cos(Math.toRadians(dAngle)-270);}
        else if (dAngle==360) {dSinFactor = Math.sin(Math.toRadians(dAngle)-271); dCosFactor = Math.cos(Math.toRadians(dAngle)-271);}
        else {dSinFactor = Math.sin(Math.toRadians(dAngle)); dCosFactor = Math.cos(Math.toRadians(dAngle));}

        //dSinFactor = Math.sin(Math.toRadians(dAngle)); dCosFactor = Math.cos(Math.toRadians(dAngle));

        //if (dSinFactor<=0){dSinFactor = dSinFactor*-1;} //neutralize negative angles on upshots
        //if (dCosFactor<=0){dCosFactor = dCosFactor*-1;} //neutralize negative angles on rightshots

        if ( MainActivity.iDebugLevel >= 1) {Log.d("EnemyShip-addShot","add shot number " +String.valueOf(iShot) 
                + " with dAngle " +String.valueOf(dAngle) +" cosan was " +String.valueOf(dCosFactor) +" sinan was " +String.valueOf(dSinFactor));}
        if ( MainActivity.iDebugLevel >= 2) {Log.d("EnemyShip-addShot","add shot number " +String.valueOf(iShot) + " with fNewX " +String.valueOf(fNewX));}
        if ( MainActivity.iDebugLevel >= 2) {Log.d("EnemyShip-addShot","add shot number " +String.valueOf(iShot) + " with fNewY " +String.valueOf(fNewY));}

        if (dAngle==90||dAngle==270) {newShot = new ShotClass(ctx, fNewX, fNewY, dCosFactor /*x-angle*/, 0 /*y-angle*/);} //fire straight to the right or left
        else if (dAngle==360||dAngle==180) {newShot = new ShotClass(ctx, fNewX, fNewY, 0 /*x-angle*/, dSinFactor /*y-angle*/);} //fire straight up or down
        else {newShot = new ShotClass(ctx, fNewX, fNewY, dCosFactor /*x-angle*/, dSinFactor /*y-angle*/);} //fire at an angle

        if ( dAngle <= 90 || dAngle >= 270) {
            newShot.setShotGoingUp(true);
        }
        else
        {
            newShot.setShotGoingUp(false);
        }

        if ( dAngle <= 180 ) {
            newShot.setShotGoingRight(true);
        }
        else
        {
            newShot.setShotGoingRight(false);
        }

        if ( MainActivity.iDebugLevel >= 1) {Log.d("EnemyShip-addShot","add shot number " +String.valueOf(iShot) + " with goingup " +String.valueOf(newShot.getShotGoingUp()) +" with goingright " +String.valueOf(newShot.getShotGoingRight()));}

        arShots.add(newShot);
        if ( MainActivity.iDebugLevel >= 2) {Log.d("EnemyShip-addShot","add shot number " +String.valueOf(iShot) + " with position " +String.valueOf(getXLocation()) +" " +String.valueOf(getYLocation()) +" firing params: " +String.valueOf(dCosFactor) +" " +String.valueOf(dSinFactor) +" angle was " +String.valueOf(dAngle));}
    }

以对角线发射镜头的逻辑：

        inpDistance = inpDistance * .2f; //slow down the shot to one fifth speed

        for (int iShotInTheSequence=1;iShotInTheSequence<=inpNumberShots;iShotInTheSequence++) {

            fFactor = (float) (inpDistance * getYFiringAngle());
            if ( getShotGoingUp() ) { //shot is going up

                fYLocation = fYLocation - fFactor;
            } //shot is going up
            else {//shot is going down

                fYLocation = fYLocation + fFactor; 
            } //shot is going down

            fFactor = (float) (inpDistance * getXFiringAngle());
            if ( getShotGoingRight() ) { //shot is going right
                fXLocation = fXLocation + fFactor;
            } //shot is going right
            else {//shot is going left
                fXLocation = fXLocation - fFactor;
            } //shot is going left


        }

Answer 1

大多数编程语言中的三角函数（包括Java）以弧度而非度数来度量参数。有一个辅助函数可以进行转换，因此无论您拨打sin还是cos，都可以添加对toRadians的调用：

Math.cos(Math.toRadians(dAngle))

Answer 2

第一个错误：

dAngle = 360/iShotNumber;

你想要一个双重作为除法的结果，那么你不能简单地进行整数除法。你应该这样做：

dAngle = 360.0/(double)iShotNumber;

我正在检查其他错误。

计算android中圆圈周围的点数

2 个答案: