This page provides notes on how to read from and write to forms that are displayed in a web page in a TWebBrowser.
Contents:
- Get the number of forms on a page
- Get a form by number
- Get the name of a form
- Get a form by name
- List the names of all the fields on a form
- Get the value of a named field
- Set the value of a named field
- Submit the form
The examples on this page assume that the page has been loaded into a TWebBrowser called WebBrowser.
Get the number of forms on a page
function NumberOfForms(document: IHTMLDocument2): integer; var forms: IHTMLElementCollection; begin forms := document.Forms as IHTMLElementCollection; result := forms.Length; end;
and to call it:
procedure TMyForm.Button1Click(Sender: TObject);
var
nForms: integer;
begin
nForms := NumberOfForms(WebBrowser.Document as IHTMLDocument2);
ShowMessage('Form count: ' + IntToStr(nForms));
end;
Get a form by number
Pages can have more than one form on them. The following function will return an instance of a form by number – where the first form is numbered 0, the next 1 and so on:
function GetFormByNumber(document: IHTMLDocument2;
formNumber: integer): IHTMLFormElement;
var
forms: IHTMLElementCollection;
begin
forms := document.Forms as IHTMLElementCollection;
if formNumber < forms.Length then
result := forms.Item(formNumber,'') as IHTMLFormElement
else
result := nil;
end;
For an example of this function in use see “Get the name of a form” (below).
Get the name of a form
It should be appreciated that HTML does not require forms to be named.
var
firstForm: IHTMLFormElement;
document: IHTMLDocument2;
begin
document := WebBrowser.Document as IHTMLDocument2;
firstForm := GetFormByNumber(document,0);
if Assigned(firstForm) then
ShowMessage('Name of first form is ' + firstForm.Name)
else
ShowMessage('This page does not contain any forms');
Get a form by name
Since forms can be named, if you know the name of a form it may be preferable to access the form by name rather than by number.
function GetFormByName(document: IHTMLDocument2;
const formName: string): IHTMLFormElement;
var
forms: IHTMLElementCollection;
begin
forms := document.Forms as IHTMLElementCollection;
result := forms.Item(formName,'') as IHTMLFormElement
end;
This function will return nil if there is no form with the required name.
List the names of all the fields on a form
function GetFormFieldNames(fromForm: IHTMLFormElement): TStringList;
var
index: integer;
field: IHTMLElement;
input: IHTMLInputElement;
select: IHTMLSelectElement;
text: IHTMLTextAreaElement;
begin
result := TStringList.Create;
for index := 0 to fromForm.length do
begin
field := fromForm.Item(index,'') as IHTMLElement;
if Assigned(field) then
begin
if field.tagName = 'INPUT' then
begin
// Input field.
input := field as IHTMLInputElement;
result.Add(input.name);
end
else if field.tagName = 'SELECT' then
begin
// Select field.
select := field as IHTMLSelectElement;
result.Add(select.name);
end
else if field.tagName = 'TEXTAREA' then
begin
// TextArea field.
text := field as IHTMLTextAreaElement;
result.Add(text.name);
end;
end;
end;
end;
and to call it:
procedure TMyForm.Button1Click(Sender: TObject);
var
document: IHTMLDocument2;
theForm: IHTMLFormElement;
index: integer;
begin
document := TWebBrowser.Document as IHTMLDocument2;
theForm := GetFormByNumber(WebBrowser.Document as IHTMLDocument2,0);
fields := GetFormFieldNames(theForm);
for index := 0 to fields.count-1 do
ShowMessage('Field ' + IntToStr(index) + ' called ' + fields[index]);
end;
Get the value of a named field
To get the value of a named field from a form:
function GetFieldValue(fromForm: IHTMLFormElement;
const fieldName: string): string;
var
field: IHTMLElement;
inputField: IHTMLInputElement;
selectField: IHTMLSelectElement;
textField: IHTMLTextAreaElement;
begin
field := fromForm.Item(fieldName,'') as IHTMLElement;
if not Assigned(field) then
result := ''
else
begin
if field.tagName = 'INPUT' then
begin
inputField := field as IHTMLInputElement;
result := inputField.value
end
else if field.tagName = 'SELECT' then
begin
selectField := field as IHTMLSelectElement;
result := selectField.value
end
else if field.tagName = 'TEXTAREA' then
begin
textField := field as IHTMLTextAreaElement;
result := textField.value;
end;
end
end;
and to call it:
procedure TMyForm.Button1Click(Sender: TObject);
var
document: IHTMLDocument2;
theForm: IHTMLFormElement;
index: integer;
begin
document := TWebBrowser.Document as IHTMLDocument2;
theForm := GetFormByNumber(WebBrowser.Document as IHTMLDocument2,0);
ShowMessage('Field "name" has value ' + GetFieldValue(theForm,'name'));
Set the value of a named field
To set the value of a field:
procedure SetFieldValue(theForm: IHTMLFormElement;
const fieldName: string; const newValue: string);
var
field: IHTMLElement;
inputField: IHTMLInputElement;
selectField: IHTMLSelectElement;
textField: IHTMLTextAreaElement;
begin
field := theForm.Item(fieldName,'') as IHTMLElement;
if Assigned(field) then
begin
if field.tagName = 'INPUT' then
begin
inputField := field as IHTMLInputElement;
inputField.value := newValue;
end
else if field.tagName = 'SELECT' then
begin
selectField := field as IHTMLSelectElement;
selectField.value := newValue;
end
else if field.tagName = 'TEXTAREA' then
begin
textField := field as IHTMLTextAreaElement;
textField.value := newValue;
end;
end;
end;
and to call it:
procedure TMyForm.Button1Click(Sender: TObject); var document: IHTMLDocument2; theForm: IHTMLFormElement; index: integer; begin document := TWebBrowser.Document as IHTMLDocument2; theForm := GetFormByNumber(WebBrowser.Document as IHTMLDocument2,0); SetFieldValue(theForm,'name','Brian Cryer');
Submit the form
The above functions demonstrate how to read values from a form and how to set values in the form. The only thing remaining is how to submit a form. This si simply:
theForm.submit;
for example:
procedure TMyForm.Button1Click(Sender: TObject); var document: IHTMLDocument2; theForm: IHTMLFormElement; index: integer; begin document := TWebBrowser.Document as IHTMLDocument2; theForm := GetFormByNumber(document,0); SetFieldValue(theForm,'name','Brian Cryer'); theForm.submit;
Note: Be aware that there are cases where this will not achieve the expected effect. This is because some forms are not actually submitted, but the action is either performed in response to JavaScript on a button or by the “onsubmit” handler of the form.