当我尝试运行程序并按下某个键时，我不断收到相同的错误。
该错误表明问题出在 keyTyped 函数中，但对我来说看起来不错。
你觉得怎么样？
代码:
//Key Listener.
private class GameKeyListener implements KeyListener {
public void keyTyped (KeyEvent event) {
char inputKey = 'd';
if(isStart == true){
try{
inputKey = event.getKeyChar();
} catch(Exception e){
System.out.println("Bad input.");
}
if(inputKey == 's'){
isStart = false;
timer.start(); // Add timer. Start game here.
}
}
}
public void keyPressed (KeyEvent event) {};
public void keyReleased (KeyEvent event){};
}
错误:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at RoofRunnerGame$GameKeyListener.keyTyped(RoofRunnerGame.java:106)
at java.awt.Component.processKeyEvent(Component.java:6303)
at java.awt.Component.processEvent(Component.java:6125)
at java.awt.Container.processEvent(Container.java:2085)
at java.awt.Window.processEvent(Window.java:1836)
at java.awt.Component.dispatchEventImpl(Component.java:4714)
at java.awt.Container.dispatchEventImpl(Container.java:2143)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4544)
at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1850)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:712)
at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:990)
at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:855)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:676)
at java.awt.Component.dispatchEventImpl(Component.java:4586)
at java.awt.Container.dispatchEventImpl(Container.java:2143)
at java.awt.Window.dispatchEventImpl(Window.java:2478)
at java.awt.Component.dispatchEvent(Component.java:4544)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:635)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:296)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:196)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:188)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
最佳答案
我认为第 106 行的变量未正确初始化。也许是 timer？
关于Java - keyTyped 问题，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/3786393/