uitextfield 不显示leftview

uitextfield 不显示leftview
UITextField *fromField= [[UITextField alloc] initWithFrame:CGRectMake(43,8,215,30)];
                    fromField.delegate = self;
                    fromField.backgroundColor= [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:@"input_field.png"]];
                    fromField.textAlignment = UITextAlignmentLeft;
                    fromField.clearButtonMode = UITextFieldViewModeWhileEditing;
                    fromField.returnKeyType = UIReturnKeyGo;
                    fromField.placeholder=@"输入起点";
                    fromField.tag=indexPath.row;
                    fromField.font=[UIFont fontWithName:@"Arial" size:12.0];
                    fromField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
                    
                    
                    UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 45, 21)];    
                    lbl.backgroundColor = [UIColor clearColor];
                    lbl.textColor = [UIColor lightGrayColor];
                    lbl.text = @"Start:";
                    
                    UIButton *btnLeftImg = [UIButton buttonWithType:UIButtonTypeCustom];
                    [btnLeftImg setBackgroundImage:[UIImage imageNamed:@"hint_start_point.png"] forState:UIControlStateNormal];
                    btnLeftImg.frame = CGRectMake(0, 0, 9,9);
                    fromField.leftView=lbl;