Thinkphp template usage problems

Thinkphp template usage problems in thinkphp combined with the smarty template, all have been configured, in IndexAction. class. $ this-& gt; display (& quot; login & quot;) is used in the PHP file, but DefaultAction is another file. class. if the php file is also used, the thinkphp template usage problem occurs.
The smarty template has been configured in thinkphp. class. $ this-> display ("login") is used in the PHP file, but the DefaultAction is another file. class. if PHP files are used in the same way, the following problems may occur:
Fatal error: Call to a member function display () on a non-object in E: \ php \ AppServ \ www \ DLP \ ThinkPHP \ Lib \ Think \ Core \ Action. class. php on line 103

The code for Action. class. php is:

Protected function display ($ templateFile = '', $ charset ='', $ contentType = 'text/html ')
{Echo $ templateFile;
If (false ===$ templateFile ){
$ This-> showTrace ();
} Else {
$ This-> view-> display ($ templateFile, $ charset, $ contentType );
}
}

Have you ever had the same problem? give me some help...

------ Solution --------------------
I have also seen it, because Action uses the constructor.
Function _ construct ()
{
// Content
}

Use in TP

Function _ construct ()
{
Parent: :__ construct;
}