uitextfield 不显示leftview解决思路

uitextfield 不显示leftviewUITextField *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;