我已經創建了一個帶有畫布的JFrame,就像您可以在下面的代碼中看到的一樣。我想要做的是在屏幕大小更新時調整openGL上下文的大小。這應該像調用glViewport()一樣簡單,我在調用resize()的事件處理函數中執行此操作。然而,結果如下:JFrame + Canvas:爲什麼在調用glViewport時遇到NUllPointerException?
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at org.lwjgl.opengl.GL11.glViewport(GL11.java:3199)
at gltest.GameMain.resize(GameMain.java:149)
at gltest.GameMain$1.componentResized(GameMain.java:59)
(...)
我完全無能爲力。從畫布大小返回的邊界似乎是好的,但是一旦我在視口上使用它們,它們就會拋出錯誤。當我改爲像「glViewport(1,1,100,100)」這樣的視口調用時,會發生同樣的情況。所有這些值都在窗口的邊界內,但是當我調整窗口大小時,它仍會拋出非常相同的nullPointerExceptions。
我沒有想法和精力來弄清楚爲什麼(我一直在用谷歌搜索3個小時,沒有結果)。我究竟做錯了什麼?
import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JFrame;
import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import static org.lwjgl.util.glu.GLU.*;
import static org.lwjgl.opengl.GL11.*;
public class GameMain {
public JFrame frame;
public Canvas canvas;
public boolean initialize(int width, int height) {
try {
Canvas canvas = new Canvas();
JFrame frame = new JFrame("Open Rock Raiders - Delta");
this.canvas = canvas;
this.frame = frame;
ComponentAdapter adapter = new ComponentAdapter() {
public void componentResized(ComponentEvent e) {
resize();
}
};
canvas.addComponentListener(adapter);
canvas.setIgnoreRepaint(true);
frame.setSize(640, 480);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(canvas);
frame.setVisible(true);
Dimension dim = this.canvas.getSize();
Display.setLocation(100, 100);
Display.setTitle("GL Window");
Display.setDisplayMode(new DisplayMode(dim.width, dim.height));
Display.setParent(canvas);
Display.create();
//openGL setup
glViewport(0, 0, dim.width, dim.height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0f, (float)(dim.width/dim.height), 0.1f, 10000.0f);
glMatrixMode(GL_MODELVIEW);
glClearColor(94.0f/255.0f, 161.0f/255.0f, 255.0f/255.0f, 0.5f);
glClearDepth(1.0);
glShadeModel(GL_FLAT);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
glEnable(GL11.GL_CULL_FACE);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
} catch (LWJGLException le) {
le.printStackTrace();
}
return false;
}
public void resize()
{
Dimension dim = this.canvas.getSize();
GL11.glViewport(0, 0, dim.width, dim.height);
}
}