//测试图片能否显示
-(void)showMyimgview
{
    UIImageView   *backgroundImg=[[UIImageView alloc]init];
    backgroundImg.frame =CGRectMake(50, 200, 200, 100);
    backgroundImg.image=[UIImage imageNamed:@"navbar"];
    [self.view addSubview:backgroundImg];
    [backgroundImg release];
}