作者olys (查无昵称)
看板java
标题[问题] 在JPanel上面绘图的完整准备工作?
时间Fri Nov 12 21:44:16 2010
一直找不到一个完整的教学 =_=........
现在好像只有看到
1.要创一个新的class是继承JPanel, 里面到底要加什麽不知道,
然後宣告Panel时要用那个Class
2.要加一行 Graphics g = gPanel.getGraphics(); , 要放在哪里不知道
然後以上备齐似乎就可以g.drawline等等乱画了
可是完整的过程是怎麽样啊 orz
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※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.117.169.131
1F：→ kanandg1:主要是取得该元件的Graphics，取得後就能画了 11/12 22:42
2F：→ kanandg1:可以写一个class继承JPanel，并Override paint(Graphics) 11/12 22:45
3F：→ kanandg1:或是用getGraphics()来取得某个JPanel的Graphics 11/12 22:47
4F：→ olys:所以我只要2的那一行出来以下就能任意画画了? 要放在哪里呢? 11/12 23:03
5F：→ kanandg1:要放在能存取到gPanel的地方..此method是public的 11/12 23:17
6F：→ kanandg1:我比较建议第一种方法 11/12 23:19
7F：→ olys:第一种方法请问能说详细吗? 刚刚试了方法2都会执行error 11/12 23:21
8F：→ kanandg1:如果此元件是不可视的话，getGraphics会return null 11/13 00:06
9F：→ olys:意思是先用gPanel.setVisible(true)吗? 还是error了orz 11/13 18:49
10F：→ kanandg1:有出现在画面上吗?如果不是这个问题就贴详细的错误出来~ 11/13 18:59
IWAV0052E Invocation Target Exception creating Voronoi.Voronoi
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at
org.eclipse.ve.internal.java.vce.launcher.remotevm.JFCLauncher$1.run(JFCLauncher.java:59)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Caused by: java.lang.NullPointerException
at Voronoi.Voronoi$2.<init>(Voronoi.java:60)
at Voronoi.Voronoi.<init>(Voronoi.java:59)
... 13 more
※ 编辑: olys 来自: 114.47.82.26 (11/13 19:00)