"_glFlush", referenced from:-[GLLevelMeter _drawView] in GLLevelMeter.o

whenever I am running My code it is showin开发者_开发问答g an error

It looks like you're not linking to the right libraries. You probably want to link to the OpenGLES.framework. That's what it looks like to me.

In Xcode with your project open, select "Add to Project . . . " from the "Project" menu. Use the resulting dialog sheet to find the OpenGL project at /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS4.0.0.sdk/System/Library/Frameworks/OpenGLES.framework