TcxCustomTreeList.RestoreFromStream(TStream,Boolean,Boolean,string,TcxTreeListStorageOptions) Method

Restores a previously saved Tree List state from a stream.

Declaration

procedure RestoreFromStream(AStream: TStream; AChildrenCreating: Boolean = False; AChildrenDeleting: Boolean = False; const ARestoreTreeListName: string = ''; AOptions: TcxTreeListStorageOptions = []);

Parameters

Name	Type	Description
AStream	TStream	The source stream that contains previously saved Tree List state information at the current position.
AChildrenCreating	Boolean	Optional. Specifies if the procedure creates missing Tree List structure elements (bands and columns): False Default. The procedure does not create any elements if the current structure contains fewer elements compared to the loaded structure state. True The procedure creates additional elements to match the loaded structure state. Tip You can handle the OnInitStoredObject event to initialize created columns. If the current Tree List element structure matches the loaded state, the AChildrenCreating parameter is ignored.
AChildrenDeleting	Boolean	Optional. Specifies if the procedure deletes redundant Tree List structure elements (bands and columns): False Default. The procedure does not delete any elements if the current structure contains more elements than the loaded structure state. True The procedure deletes all elements that do not correspond to the loaded structure state. If the current Tree List element structure matches the loaded state, the AChildrenDeleting parameter is ignored.
ARestoreTreeListName	string	Optional. Specifies the restored Tree List name. This parameter allows you to apply a saved Tree List state to a different Tree List control. If the number of columns in the target control does not match the loaded structure, the RestoreFromStream procedure creates missing or deletes redundant elements if AChildrenCreating and AChildrenDeleting parameter values are True.
AOptions	TcxTreeListStorageOptions	Optional. Specifies a set of individual user interaction states restored from the source stream (AStream). If this parameter is omitted, the procedure loads only Tree List structure information, even if the source stream contains user interaction state information.

Remarks

Call the StoreToStream procedure to save the current data layout and specified user interaction states to a stream. A subsequent RestoreFromStream call restores the saved Tree List state from the stream.

Stored Information

Tree List Structure | Data Layout

Tree List structure information includes the following:

• Tree List name
• All Tree List element settings available to end users for customization: position, dimensions, visibility, sort order, captions, etc. You can use optional AChildrenCreating and AChildrenDeleting parameters to update the current Tree List element structure according to the loaded state.

Important

After each StoreToStream procedure call, make sure that the Tree List control maps to the same underlying dataset fields before the corresponding RestoreFromStream call. Otherwise, errors may occur.

Tree List User Interaction States (Optional)

In addition to the base Tree List Structure/Data Layout, the AOptions parameter available for StoreToStream and RestoreFromStream procedures allows you to store a number of user interaction states (selection, focus, scroll position, node expanded status, etc.)

Pass a set of all required flags as the AOptions parameter to store/restore corresponding Tree List user interaction states:

tsoUseDataViewState

The main flag required for all other user interaction flags listed below. These flags have no effect without tsoUseDataViewState.

Tip

Alternatively, you can use only the cxTreeListStoreAllDataViewStates constant if you need to store all user interaction states for the Tree List as demonstrated in the code example below.

tsoFocusedItem | tsoFocusedRecord

Store/restore the focus position.

tsoSelected

Stores/restores selection.

tsoTopRecord

Stores/restores the Tree List scroll position (the record at the top control border).

tsoExpanded

Stores/restores the expanded status for all nodes.

Code Example: Store Tree List State Between Sessions

The code example in this section demonstrates form OnDestroy and OnCreate event handlers. These handlers call StoreToStream and RestoreFromStream procedures to save and restore user interaction states (selection, focus, scroll position, etc.) in addition to the Tree List structure/data layout.

Delphi

uses
  System.SysUtils,  // Declares the FileExists function
  cxTL,  // Declares TcxTreeList, TcxCustomTreeList, and related types
// ...

procedure TMyForm.FormCreate(Sender: TObject);
var
  AFileStream: TFileStream;
begin
  if FileExists('TreeListConfig.dat') then
  begin
    AFileStream := TFileStream.Create('TreeListConfig.dat', fmOpenReadWrite);
    try
      cxTreeList1.RestoreFromStream(AFileStream, True, False, '', cxTreeListStoreAllDataViewStates);
    finally
      AFileStream.Free;
    end;
  end;
end;

procedure TMyForm.FormDestroy(Sender: TObject);
var
  AFileStream: TFileStream;
begin
  AFileStream := TFileStream.Create('TreeListConfig.dat', fmCreate or fmOpenReadWrite);
  try
    cxTreeList1.StoreToStream(AFileStream, '', cxTreeListStoreAllDataViewStates);
  finally
    AFileStream.Free;
  end;
end;

C++

#include "System.SysUtils.hpp"  // Declares the FileExists function
#include "cxTL.hpp"  // Declares TcxTreeList, TcxCustomTreeList, and related types

// Add the following linker directive to the corresponding CPP source file:
#pragma link "cxTL"  // Required to use cxTL.hpp declarations

void __fastcall TMyForm::FormCreate(TObject *Sender)
{
  TFileStream *AFileStream;
  if(FileExists("TreeListConfig.dat"))
  {
    AFileStream = new TFileStream("TreeListConfig.dat", fmOpenReadWrite);
    try
    {
      cxTreeList1->RestoreFromStream(AFileStream, true, false, "", cxTreeListStoreAllDataViewStates);
    }
    __finally
    {
      delete AFileStream;
    }
  }
}

void __fastcall TMyForm::FormDestroy(TObject *Sender)
{
  TFileStream *AFileStream = new TFileStream("TreeListConfig.dat", fmCreate | fmOpenReadWrite);
  try
  {
    cxTreeList1->StoreToStream(AFileStream, "", cxTreeListStoreAllDataViewStates);
  }
  __finally
  {
    delete AFileStream;
  }
}

Other Tree List Store/Restore Methods

Alternatively, you can store Tree List data layout and user interaction states in an INI file or the system registry. The TcxCustomTreeList class implements the following Store~/Restore~ method pairs in addition to StoreToStream and RestoreFromStream:

StoreToIniFile | RestoreFromIniFile

Allow you to store the Tree List state (both data layout and user interaction states) in an INI file.

StoreToRegistry | RestoreFromRegistry

Allow you to store the Tree List state (both data layout and user interaction states) in the system registry.

StoreDataViewState | RestoreDataViewState

Allow you to store user interaction states in memory during the same session.

StoreDataViewStateToStream | RestoreDataViewStateFromStream

Allow you to store only user interaction states in a separate stream.