Why am I getting an InvocationTargetException? Android 2D game

问题

I am making a 2D game in Android with Cocos2D, written in Java. Here is my code for the main stuff:

public void gameLoop(float dt) {
    //Player Gravity
    if(canExecuteMovement(0, 6)) {
        guy.moveY(6);
    }

    //Player Movement
    if(direction == 1) {
        if(canExecuteMovement(-3, 0))
            guy.moveX(-3);
    } else if(direction == 2) {
        if(canExecuteMovement(3, 0))
            guy.moveX(3);
    }
}

private boolean canExecuteMovement(int xChange, int yChange) {
    int projectedX = guy.getBounds().left + xChange;
    int projectedY = guy.getBounds().top + yChange;
    Log.i("DD", "guy:" + guy.getBounds().toString());
    Rect projectedBounds = new Rect(projectedX, projectedY, projectedX + guy.getWidth(), projectedY + guy.getHeight());
    Log.i("DD", "guy:" + projectedBounds.toString());
    for (int i = 0; i < platformCount; i++) {
        if (Rect.intersects(projectedBounds, platform[i].getBounds())) {
            return false;
        }
    }

    return true;
}

As you see, this function looks just fine, and the rectangles in canExecuteMovement are perfectly fine too, however in this line:

LINE 107: if (Rect.intersects(projectedBounds, platform[i].getBounds())) {

I am getting a InvocationTargetException. Here is the logcat:

01-21 23:10:12.601: W/System.err(13118): java.lang.reflect.InvocationTargetException
01-21 23:10:12.601: W/System.err(13118):    at java.lang.reflect.Method.invokeNative(Native Method)
01-21 23:10:12.605: W/System.err(13118):    at java.lang.reflect.Method.invoke(Method.java:511)
01-21 23:10:12.605: W/System.err(13118):    at org.cocos2d.actions.CCTimer.update(CCTimer.java:82)
01-21 23:10:12.605: W/System.err(13118):    at org.cocos2d.actions.CCScheduler.tick(CCScheduler.java:253)
01-21 23:10:12.605: W/System.err(13118):    at org.cocos2d.nodes.CCDirector.drawCCScene(CCDirector.java:679)
01-21 23:10:12.605: W/System.err(13118):    at org.cocos2d.nodes.CCDirector.onDrawFrame(CCDirector.java:649)
01-21 23:10:12.605: W/System.err(13118):    at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1462)
01-21 23:10:12.605: W/System.err(13118):    at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1216)
01-21 23:10:12.605: W/System.err(13118): Caused by: java.lang.NullPointerException
01-21 23:10:12.608: W/System.err(13118):    at com.qasim.platformer.GameLayer.canExecuteMovement(GameLayer.java:107)
01-21 23:10:12.608: W/System.err(13118):    at com.qasim.platformer.GameLayer.gameLoop(GameLayer.java:86)
01-21 23:10:12.608: W/System.err(13118):    ... 8 more
01-21 23:10:12.620: D/dalvikvm(13118): GC_CONCURRENT freed 460K, 6% free 9279K/9863K, paused 2ms+3ms
01-21 23:10:12.624: I/DD(13118): guy:Rect(252, 63 - 300, 111)

What could be the problem? the getBounds() class in guy is this:

public Rect getBounds() {
    return new Rect(x, y, x+width, y+height);
}

回答1:

InvocationTargetException is just a wrapper for an exception that's thrown within a dynamic invocation. The true problem is the NullPointerException that it's wrapping:

Caused by: java.lang.NullPointerException
  at com.qasim.platformer.GameLayer.canExecuteMovement(GameLayer.java:107)
  at com.qasim.platformer.GameLayer.gameLoop(GameLayer.java:86)

As you've pointed out, this is the offending line:

if (Rect.intersects(projectedBounds, platform[i].getBounds())) {

The only place a null pointer could be happening on this line is at platform[i].getBounds(). Either platform itself is null, or the element at platform[i] is.

来源：https://stackoverflow.com/questions/8958882/why-am-i-getting-an-invocationtargetexception-android-2d-game