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POSpace Invaders health/array issues
 

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  1. POSpace Invaders health/array issues
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    <p>I've been doing some exercises to learn C#. I've been doing XNA and making a space invaders clone. </p> <p>So far, everything is dandy, but I have come across some walls when coding. </p> <p>The issues and the supporting code are as follows:</p> <p>My top of row of invaders have 2 health points, take 2 hits to destroy and yield more points. However, when one is hit, and destroyed, the rest of the top of row are reduced to 1 HP, and take 1 hit to destroy - which is not my desired result. </p> <p>The offending code I suspect is: </p> <pre><code> if (playerBullet != null &amp;&amp; Type1Invaders != null) { Rectangle rectMissile = new Rectangle((int)playerBullet.getX(), playerBullet.getY(), playerBulletIMG.Width, playerBulletIMG.Height); for (int count = 0; count &lt; 11; count++) { Rectangle rectInvader = new Rectangle(Type1Invaders[count].getX(), Type1Invaders[count].getY(), invader1.Width, invader1.Height); if (Type1Invaders[count].getVis() &amp;&amp; rectMissile.Intersects(rectInvader)) { Type1Invaders[count].setHP(Type1Invaders[count].getHP() - 1); shootTimer = 0; if (Type1Invaders[count].getHP() == 0) { explosionInstance.Play(); playerBullet = null; Type1Invaders[count].setVis(false); score = score + Type1Invaders[count].getPointValue(); } } } } </code></pre> <hr> <p>My second error resides in how I'm detecting the leftmost and rightmost invaders in a row. When an entire row has been destroyed, I get a nullreferenceerror. (Those are a nightmare..)</p> <p>Anyway, this is the offending code</p> <p>The method of finding the left and right most invaders</p> <pre><code>var LeftMost5 = Type5Invaders.Where(i =&gt; i.getVis()).FirstOrDefault(); var RightMost5 = Type5Invaders.Where(i =&gt; i.getVis()).LastOrDefault(); </code></pre> <p>And the if statement is throwing the null error</p> <pre><code> if (RightMost5.getX() &gt;= RightGameEdge) { Type5.setDir(-1); for (int count = 0; count &lt; 11; count++) { invaderMoveInstance5.Play(); Type5Invaders[count].MoveY(8); } } </code></pre> <p>It only happens with the rightmost, but I can assume it will happen to the left too - I'm assuming I can apply the same logic to fix this error to the left side too. </p> <p>I can supply more information and snippets if this is not sufficient. </p> <p>Thanks in advance for the assistance!</p>
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    1. COCheck your Intersects code - it's possible it's returning "true" for every invader.
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      1. USDave Bish
    2. COfor second issue - where is the case of RightMost5/LeftMost5 are null checked? And what is the default value for your collection?
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    3. COfor the first issue - what is invader1?
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