Lazarus Tutorial/zh TW

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這是篇 Lazarus 教學的起頭，各位可自由地改進他。

概述

Lazarus 是一個使用 Pascal 編譯器的自由開放原始碼開發工具。Free Pascal 本身也是自由開放軟體。Lazarus IDE (擷圖) 提供一穩定，且專注於強調豐富的程式寫作環境，並用來開發單機的圖形與主控台應用程式。Lazarus 目前可以在 Linux，Mac OS X 與 Win32 下執行。且提供可自訂的原始碼編輯器，並透過套件管理，除錯器與完整的圖形使用介面整合的編譯器做成視覺化的表格創建環境。

我們開始吧

(感謝 User:Kirkpatc)

取得並安裝 (Installing Lazarus) Lazarus，同時安裝所有所需的 Free Pascal 編譯器後執行 Lazarus。

註：在 Linux Ubuntu 下，在主控台啟動 Lazarus 的指令是 "startlazarus"。如果你是從 Debian 的套件來安裝，你應該會在開始選單裡的應用程式/程式寫作 (Application/Programming) 下找到程式捷徑來啟動。 (己知問題: 在 Debian 或 Ubuntu 裡的主要執行檔與套件已經改名成 "lazarus-ide"，因為已經有個 "tct" 的工具套件被取名叫 "lazarus"。)

你的第一個 Lazarus 程式！

從主選單裡，選擇〔專案〕 - 〔新增專案－應用程式〕 (Project - New Project-Application)。 幾個視窗會出現在你的桌面上：上方的主選單，左方的物件檢視器，Lazarus 原始碼編輯器佔桌面的一大半部份，並有一個已經備妥的 Form1 視窗於原始碼編輯器重疊著出現。 在上方的選單視窗，選單列的下方，有一排標籤頁。如果 '標準 (Standard)' 籤頁沒有被選取，請用滑鼠點選他。然後找到〔按鈕〕 (Button) 的圖示 (一個裡面寫著 'OK' 的四方形) 後用滑鼠按一下，游標再移到 Form1 的視窗，大概移到中間偏左的地點再按一下滑鼠鍵。一個立體的四方形，標著 'Button1' 的按鈕物件就會出現。再按一次標準籤頁裡的鈕按圖示，然後移到 Form1 中間偏右的地方再按一次，就會出現一個標著 'Button2' 的按鈕出現。

現在點一下 Button1 來選取它。物件檢視器會顯示出該 Button1 物件的所有內容，靠上的有一項名為 '標題 (Caption)'　的內容，裡面顯示的值是 'Button1'。點一下那個方格，將 'Button1' 改成 '按我'。如果你再按一下 ENTER 或點一下其它的方格，你就會見到原來第一個按鈕裡面標的字就會變成 '按我'。現在點選物作視察器裡的〔事件〕 (Events) 籤頁，裡面會列出所有與這個按鈕有關的事件項目。像是 OnClick，OnEnter，OnExit 等等。再選取 OnClick 右邊的方格，方格會出現三個小點的省略符號。當你再按取該省略符號，會你自動被帶進入原始碼編輯裡，且游標被定在你該撰寫讓事件原始碼的開始處：

 procedure TForm1.Button1Click(Sender: TObject);
 begin
   {現在輸入:}    Button1.caption := '再按一次';
   {程序於此完結}
 end;

按一下 F12 從原始碼編輯器回到 Form1 的視窗。

現在接著編輯 Button2 的〔內容〕：按一下 Button2 使物件檢視器裡顯示出它的內容，變更他的〔標題〕成 '離開'。然後接著再選 OnClick 事件，再點省略符號，這時你又回到原始碼編輯器，從另一段程序開始寫作：

 procedure TForm1.Button2Click(Sender: TObject);
 begin
   {現在輸入:}   Close;
   {程序於此完結}
 end;

現在再按 F12 來看看你的 Form1 視窗。現在該是儲存你的工作的時候了 (而且應該時常)！點選專案 > 另存專案 > 你取的檔名.pas (Project > Save Project As > your_selected_file_name.pas)。然後程式會再要求你儲存你的專案資訊，副案名為 .lpi。選一個不同的檔名，如果兩個取了同樣的檔名，你在編譯的時候會遇上 "重覆的識別子" 的錯誤 (請見此教學最後一章節 "Lazarus 檔案")。 你現在已經準備好可以開始編譯了。最簡單的方法就是在上方的主選單裡選 '執行 (Run)' 子選單，然後再按 '執行'。或是最直接地按 F9。程式會進行第一次的編譯並直接執行你的程式。

有幾個文字視窗會在你編譯的時候出現，顯示著你編譯時的所出現的訊息。但直到最後你的 Form1 視窗會重新出現，而且不帶有格子和標點。這就是你的應用程式的主畫面，並正等待你去按按鈕來與它互動。

試著去點標著 '按我' 的按鈕。你會注意到它變成了 '再按一次'，但如果你再按一次，他還是一樣顯示 '再按一次'！

現在在按標著 '離開' 的按鈕，視窗會關閉，程式也隨之結束。然後又回到那個有格子與標點的 Form1 視窗，等待你再進一步的修改它。

改進你的程式

再一次開啟你剛儲存的專案。 在 Form1 視窗下點選 '按我' 按鈕 (Button1)。 再選物件檢視器裡的〔事件〕籤頁，點選方格右邊的省略符號，回到原始碼編輯器的相對地方。

如下編輯你的程式碼:

 procedure TForm1.Button1Click(Sender: TObject);
{使用一個標記物，設定它是１或是零}
 begin
   if Button1.tag = 0 then
   begin
     Button1.caption := '再按一次';
     Button1.tag := 1
   end else
   begin
     Button1.caption := '按我';
     Button1.tag := 0
   end
 end;

儲存你的工作，再重新編譯一次並執行。現在你左邊的按鈕就會交替地顯示訊息了。

接下來就完全看你自己了！

如果你偏好撰寫主控台下的 Pascal 程式 (比如說你正在上一堂 Pascal 的課要交作業用，或是為一個系統撰寫巨集指令)，你也仍然可以使用 Lazarus 來撰寫、編譯並執行。有關於這個部份的開發，請見 主控台模式的 Pascal 的章節。

視窗編輯器

當你第一次執行起 Lazarus，會出現一系列不連續的，或說浮動著的視窗。

首先，桌面最上方會的標題會是 Lazarus 編輯 vXXXXXX - 專案1 (會隨著你目前的專案名稱變化)。這是控制你專案的主視窗，包含了主選單與元件面板。

標題列下面的橫幅就是主選單 (Main Menu)，有著一般常見的檔案，編輯，搜尋與檢視分類項目，下面還有幾個區塊來執行 Lazarus 的特定工作。 再下來的橫幅左邊是一些符號 (可以迅速執行你要的指令)；而右邊就是元件面板。

在 Lazarus 編輯器視窗下左邊顯示的是物件檢視器視窗，而Lazarus 原始碼編輯器在右邊。那裡還有很多其他的小視窗，標著 Form1，並與 Lazarus 原始碼編輯器的視窗重疊著。如果無法立即找到他，可以按下 F12 在原始碼編輯器與表單之間切換顯示。表單視窗就是指你用來為你的應用程式建立圖形介面的地方，並直接與你撰寫中的 Pascal 原始碼關聯上。而物件檢視器的操作會在解說元件面板的時候一起做更多說明。最後，我們還有一個訊息視窗在螢幕的最下方，這裡 Lazarus 會顯示要告訴程式設計師訊息，例如你在編譯過程出了問題。

當你要新開一個新的專案 (或是當你第一次開啟 Lazarus)，一份預設的的表單視窗會先建立好，上面會帶有許多格點用來幫助你定位在上面各似各樣的元件。而最上面一條細長的橫幅就是常見的縮到最小，放到最大與關閉視窗按鈕。點擊表單框框裡隨便一個物作，桌面左側的物件檢視器就會顯示出此物件的所有內容。

你在工作的過程中還有可能會看到一些其他的視窗：像專案檢視器，含有你的專案裡所擁有的檔案的詳細資料，讓你可對專案新加入或是刪除檔案。訊息視窗，用來顯示你的專案在編譯過程中出現的錯誤或任何訊息。如果你是在遠端執行 Lazarus，則你原來的這一端還是可以看到在編譯時出現的訊息。

主選單

主選單内容仔細的説明在這裡：Main menu/zh TW

The Button bar

A small toolbar area on the left of the main editor window, just below the Main Menu and to the left of the Component Palette, contains a set of buttons which replicate frequently-used Main Menu selections:

在主編輯視窗左方一個小的工具欄區域，就在主選單下方以及套件板的左邊，包含了一組按鈕用來呼叫一些常用的主選單功能：

New unit, Open (with a down-arrow to display a drop-down list of recently used files), Save, Save all, New Form, Toggle Form/Unit (ie show either form or source code of Unit), View Units, View Forms, Run (ie compile and Run), Pause, Step Into, Step over (the last two are Debugger functions).

The Component Palette

A Tabbed toolbar which displays a large number of icons representing commonly used components for building Forms.

Each tab causes the display of a different set of icons, representing a functional group of components. The left-most icon in each tabbed group is an obliquely leftward-facing arrow, called the Selection Tool.

If you allow the mouse cursor to hover over any of the icons on the Component Palette, without clicking on the icon, the title of that component will pop-up. Note that each title begins with a 'T' - this signifies 'Type' or more accurately 'Class' of the component. When you select a component for inclusion in a form, the Class is added to the type section of the interface part of the Unit (usually as part of the overall TForm1), and an instance of that class is added to the var section (usually as the variable Form1). Any Methods that you design to be used by the Form or its Components (ie Procedures or Functions) will be placed in the implementation part of the Unit.

How To Use the Palette

To use the Palette, there must be an open form on view in the editor (if there isn't one, select File -> New Form). Click on the icon in the appropriate tab of the Palette for the component you want to use, then click on the Form, near where you want the component to appear. When the desired component appears, you can select it by clicking with the mouse. Once selected on the form, the object is also selected in the 物件檢視器 window, where you can edit its properties and events.

Adjustments to the visual appearance of an object can be made either by altering the picture itself on the Form using the mouse, or by changing the relevant Property in the Object Editor for that component.

If you install additional components, either those you have written yourself, or some coming as a package from some other source, then extra tabs with the relevant icons will appear in your Component Palette. These new components can be selected and used on your forms in the same way as those supplied by default.

In the following list of the Components, you will find links to files that contain descriptions of the Units in which they are found. If you want to find out about the properties of a particular component, it is often worth looking at the Inheritance of that component and then inspecting the properties of the base type from which it is derived. For example, to understand TMaskEdit it is also useful to examine TCustomMaskEdit.

Standard

(See Standard tab for components description)

Frequently used components: TMainMenu, TPopupMenu, TButton, TLabel, TEdit, TMemo, TToggleBox, TCheckBox, TRadioButton, TListBox, TComboBox, TScrollBar, TGroupBox, TRadioGroup, TCheckGroup, TPanel, TActionList

Additional

(See Additional tab for components description)

More, often-used components: TBitBtn, TSpeedButton, TStaticText, TImage, TShape, TBevel, TPaintBox, TNotebook, TLabeledEdit, TSplitter, TTrayIcon, TMaskEdit, TCheckListBox, TScrollBox, TApplicationProperties, TStringGrid, TDrawGrid, TPairSplitter, TColorBox, TColorListBox, TChart

Common Controls

(See Common Controls tab for components description)

TTrackBar, TProgressBar, TTreeView, TListView, TStatusBar, TToolBar, TUpDown, TPageControl, TTabControl, THeaderControl, TImageList, TPopupNotifier

Dialogs

(See Dialogs tab for components description)

TOpenDialog, TSaveDialog, TSelectDirectoryDialog, TColorDialog, TFontDialog, TFindDialog, TReplaceDialog, TOpenPictureDialog, TSavePictureDialog, TCalendarDialog, TCalculatorDialog, TPrinterSetupDialog, TPrintDialog, TPageSetupDialog

Several useful Dialog procedures or functions don't appear on the Palette, but are easily used as direct calls from your source program.

For several good examples of the use of Components see the $LazarusPath/lazarus/examples subdirectory of your source installation. Many of the programs show how to use dialogs and other components directly without using the IDE and component palette or having a separate form definition file: all the components are fully and explicitly defined in the main Pascal program. Other example programs make full use of the IDE.

Remember to open these examples as projects, with the .lpi file. Opening the .pas source code file and hitting RUN will just append this source file to whatever project you opened last.

Some examples don't work straight away: you may need to play about with paths and permissions of files or directories. If you want to compile any of the examples, make sure that you have read/write/execute permissions for the files and directories, or copy the files to a directory where you do have the appropriate permissions.

Try running the 'testall' program to see a menu of the available components together with small example test forms for most of them; then inspect the code to find out how they work!

Misc

TColorButton, TSpinEdit, TFloatSpinEdit, TArrow, TCalendar, TEditButton, TFileNameEdit, TDirectoryEdit, TDateEdit, TCalcEdit, TFileListBox, TXMLPropStorage, TIniPropStorage, TBarChart, TButtonPanel, TIDEDialogLayoutStorage

Data Controls

Data-aware components, which largely replicate the Standard and Additional groups but are applicable to Databases: TDBNavigator, TDBText, TDBEdit, TDBMemo, TDBImage, TDBListBox, TDBComboBox, TDBCheckBox, TDBRadioGroup, TDBCalendar, TDBGroupBox, TDBGrid

Data Access

TDatasource, TMemDataset, TSdfDataSet, TFixedFormatDataSet, TDbf

System

TTimer, TIdleTimer, TLazComponentQueue, THtmlHelpDatabase, THtmlBrowserHelpViewer, TProcessUTF8, TAsyncProcess, TProcess, TSimpleIPCClient, TSimpleIPCServer, TXMLConfig, TEventLog

SynEdit

SynEdit is an advanced multi-line edit control, which is integrated into the Lazarus.

SynEdit 是一個整合至 Lazarus 的進階的多行編輯控制。

It is the code editor of the Lazarus IDE and is available in the directory "lazarus/components/synedit".

它是 Lazarus IDE 的源碼編輯器，可以在 "lazarus/components/synedit" 目錄中取得。

It supports Syntax Highlighting, code completion, code folding and includes exporters for html, tex and rtf.

它支援語法高亮，自動完成，源碼摺疊並包含 html, tex, rtf 的輸出者。

It is a fully custom drawn component, meaning that it doesn't wrap native controls of each platform and that no external library is required; this make SynEdit a crossplatform component.

它是完全使用者繪製的套件，意即它包裝了每個平台的原生控制項並且不需要任何外部的 library; 這讓 SynEdit 成為一個跨平台的套件。

Note that the SynEdit available with Lazarus is a fork of the original SynEdit for Borland Delphi, Kylix and C++Builder which can be found in synedit at sourceforge. : TSynEdit, TSynAutoComplete, TSynExporterHTML, TSynMacroRecorder, TSynMemo, TSynPasSyn, TSynFreePascalSyn, TSynCppSyn, TSynJavaSyn, TSynPerlSyn, TSynHTMLSyn, TSynXMLSyn, TSynLFMSyn, TSynUNIXShellScriptSyn, TSynCssSyn, TSynPHPSyn, TSynTeXSyn, TSynSQLSyn, TSynPythonSyn, TSynVBSyn, TSynAnySyn, TSynMultiSyn

How to use Common Controls

The Units StdCtrls, ComCtrls and ExtCtrls contain definitions and descriptions of many of the most commonly used controls for constructing Forms and other Objects in Lazarus Applications.

Many of the final target controls that the application developer wants to use, such as TButton, TMemo, TScrollBar etc, have a corresponding ancestor class such as TCustomButton, TCustomMemo or TCustomScrollBar. Several of the properties and methods relevant to the final target control are defined (and explained) more fully in the TCustomXXX class, and are inherited by the final target control.

If you drop a component on the form editor you don't need to add code explicitly to create it. The component is automatically created by the IDE together with the form, and destroyed when the form is destroyed. However, if you create the component yourself by code don't forget to free it when it is no longer needed.

Ways to Set Properties

If you place a component on the Form Designer and look at the 物件檢視器, you can observe the properties change as you move the component around.

For example, if you place a button (TButton) on the form, click on it to select it, then move it around the form with the mouse, you can watch the values of Top and Left change in the 物件檢視器 to reflect the new position. If you use the object's re-sizing bars to adjust its size, you can watch the Height and Width properties change as well.

On the other hand, by using the 物件檢視器, you can select the value associated with a property such as height, and type in a new value; you can watch the size of the object on the form change to reflect the new value.

You can also explicitly change the properties of the object in code by typing (in the appropriate Implementation section of the 原始碼編輯器), for example

Form1.Button1.Height := 48; If you type this new value into the 原始碼編輯器 and then look back at the Form Designer, you will see that the button on the Form has taken the new size. The new value will also be shown in the 物件檢視器.

In summary, there are usually about three different ways to determine each property of an object:

• by using the mouse on the form,
• by setting the values in the 物件檢視器,
• or explicitly by writing code in the editor.

Common Properties

The components defined in these Units have several properties that are common to most of them, and other properties that are specific to the individual components. We shall describe the most common ones here. Unusual or control-specific properties will be described for the individual controls.

Additional Help can always be obtained by selecting a property or keyword, in either the 物件檢視器 or the 原始碼編輯器, and pressing F1. You will be taken by your Help browser to the appropriate page in the documentation.

If the description of a property on that page is insufficient, you can navigate to the corresponding description in the ancestor classes, by selecting the links in the Inheritance listing or by selecting the ancestor Type in the declaration of the object.

Some commonly listed properties

Property	Meaning
Action	The main action or event associated with the object. For example selecting an 'Exit' Button might cause the 'Close' action
Align	Defines the way in which an object is to be lined up with the parent object. Possible values are alTop (placed at the top and using the full available width), alBottom, alLeft (placed at the left and using the full available height), alRight. alNone (place anywhere on parent control) or alClient (takes all available space next to controls aligned to top, bottom, left or right)
Anchor	Used to keep a control a certain distance from the defined edges of a parent control, when the parent is resized. For example [akBottom, akRight] will keep the control a fixed distance from the bottom right corner.
AutoSelect	When True, an editing control will select all its text when it receives focus or when the Enter key is pressed.
AutoSelected	True indicate that the edit or combobox control has just performed an AutoSelect operation so that subsequent mouse-clicks and keystrokes proceed normally without selecting the text.
BorderSpacing	The space around the edge between an Anchored control and its parent.
Caption	The text that is displayed on or near the control; it should preferably give some clue as to the function of the control, or an instruction such as 'Close' or 'Execute'. By default Caption is set to be the same as the 'Name' property, and the application programmer should substitute meaningful text instead of the default values.
CharCase	Indicates how text is displayed in a text editing control: Normal (retaining the case of the letters typed by the user), converted to uppercase, or converted to lowercase
Constraints	Sets the minimum and maximum sizes for a control. If a control is resized the new dimensions are always within the ranges given here. You should take care when setting these options that they do not conflict with the Anchors and Align settings.
Color	The Colour to be used to draw the control or to write the text it contains.
Enabled	A Boolean property to determine whether or not a control is capable of being selected and performing an action. If it is not Enabled, it is often Grayed out on the Form.
Font	The Font to be used for writing the text associated with the control - either the caption or label, or the text-strings contained within the control. The entry on the 物件檢視器 usually has a (+) box on the left, and selecting this box reveals further options such as character set, colour and size.
Hint	A short piece of informative pop-up text that appears if the mouse-cursor hovers over the control.
Items	The list of 'Things' that the object contains, such as a group of images, a series of lines of text, a number of actions in an actionlist, etc
Lines	An array of strings, containing the textual data in controls with more than a single line of data, such as an Edit-Box or a Combo-Box. The array is zero-indexed, ie the lines are numbered [0..numLines-1]
Name	The identifier by which the control is known in the program. The IDE gives it a default name based on the underlying type, for example successive instances of TBitButton would be named Form1.BitBitton1 and Form1.BitButton2; it is up to the application programmer to give them more meaningful names such as ExitButton or OKButton. By default the Name of the control is applied to the Caption for the control, but the text of the Caption may be changed separately.
PopUpMenu	A window containing context-sensitive menu information that pops up when the right mouse button is clicked on the object.
Position (or Top, Left)	Determines where the control is located on the parent form or window
ReadOnly	Boolean property which, if True, signifies that the contents of the control can be read by the user or the calling routine, but cannot be written or changed.
ShowHint	Allows a small window containing a context-sensitive Help or other description to be displayed when the mouse cursor 'hovers' over the control.
Size (or Height and Width)	The dimensions of the control
Style	The options available for Style depend upon the sort of Control being considered: for instance the Style may be defined by TFormStyle, TBorderStyle, TButtonStyle etc.
TabOrder	Integer defining where in the sequence of tabs on the Form this control is to lie
TabStop	Boolean property which if True places this control in the sequence of objects that the user can reach by successively pressing the Tab key
Text	The String of Text that represents the actual data that this control contains. Applies particularly to Text, Memo and StringList types of object. Most of the editing operations (such as Select, Clear, Cut, Copy) are performed in this part of the object, which holds the actual string being edited. If the control contains more than a single line of text, for example TMemo or TComboBox, then the textual elements are arranged as an array of strings (zero-indexed, ie numbered from [0..numLines-1]) in Lines.
Visible	If true, the object can be seen on the Form; if False, object is hidden
WordWrap	Logical flag to show whether or not word-wrap is enabled, ie if a word comes close to the end of a line and is going to be too long for the line, it is wrapped down to the next line.

Event Actions

Many actions are commonly listed in the 'Events' tab of the 物件檢視器. If you select an entry in the list, a ComboBox appears with a DropDown list showing any actions that have aleady been defined, and allowing you to choose one to be associated with this event. Alternatively you can select the ellipsis (three dots ...) and you will be taken to an area of the 原始碼編輯器 where you can begin typing your own action instructions for the selected event.

While a large number of events is available for any given control, in practice it is only necessary to populate a few of them. For most controls, it is sufficient to provide coding for 'OnClick'; for more complex controls it may be necessary also to provide for 'OnEntry' (when the mouse cursor enters the Control and gives it focus) and 'OnExit' (when the mouse cursor leaves the Control; or you may need to write an event handler for 'OnChange' or 'OnScroll', depending on the nature of the particular control with which you are dealing.

The pop-up menu that appears when you right-click an object in the Form Designer has, as its first item: 'Create default event' and selecting this option will have the same effect as selecting the ellipsis in the 物件檢視器 for the default event, usually OnClick: you are taken to the Implementation area of the 原始碼編輯器 where you can type the code for the event handler.

A common strategy in Object-Oriented programming is to provide an ActionList with the facility for entering, removing or editing a number of pre-defined actions from which the most appropriate can be selected to use in any particular instance.

Some commonly listed Actions

Action	Meaning
OnChange	Action to be taken if any change is detected (eg mouse move, mouse click, key press, edit text, alter picture, etc)
OnClick	Action to be taken when the (first, usually left) mouse button is clicked. This is commonly the main or default action of the control; for example clicking on a button or checkbox initiates the action associated with the checkbox. It may alternatively initate a process of selection, for instance in a TextBox or Memo, or signal the beginning of painting with a Pen or Brush.
Click	A method to emulate in code the effect of clicking on a control. This method is most often found in Button-type controls (TButton, TBitBtn, TSpeedButton etc). A procedure can be written that calls the same code as the OnClick action. This facility can be particularly useful if the activation of one control by clicking causes a cascade of other controls to be activated, and the Click method can be used to initiate the action rather than having the user explicitly click on a lot of controls.
OnDragDrop	Action to be taken during Drag-Drop manoeuvres, ie when the mouse is used to 'capture' an item or some text etc and move it around the screen to a new location.
OnEntry	Action to be taken when the mouse cursor enters the area occupied by the object, usually transfering focus to that object. This might include changes in the appearance of the object such as highlighting or raising the border.
OnExit	Action to be taken when the mouse moves out of the area of the object, usually transferring focus out of the object.
OnKeyPress	Action to be taken for any key-press. Subtly different from OnKeyDown, which simply responds to a key being down, whether or not it was already down when focus was given to this control. OnKeyPress requires that a key becomes pressed while focus is in this control.
OnKeyDown	Action to be taken if a key is down while focus is in this control. Subtly different from OnKeyPress - for example the key might already have been down when focus entered this control, whereas OnKeyPress requires the key to become pressed while focus is in the control.
OnKeyUp	Action to be taken if a key is up (ie not pressed) while focus is in this control.
OnMouseMove	Action to be taken if the mouse cursor moves while focus is in this control.
OnMouseDown	Action to be taken if the mouse button is down while focus is in this control.
OnMouseUp	Action to be taken if the mouse button is up while the cursor is over this control. Implies that the mouse button was previously down and has been released. The case where the cursor enters the control but the mouse button has not yet been pressed is covered by OnEntry or OnMouseEnter.
OnResize	Action to be taken when the control is resized. Might include re-alignment of text or selection of a different font size etc.

Contructors & Destructors

These are two special methods associated with each control:

• Constructors: such as Create allocate memory and system resources needed by the object. They also call the constructor of any sub-objects present in the class.

• Destructors: remove the object and de-allocate memory and other resources. If you call Destroy for an object which hasn't being initialized yet it will generate an error. Always use the Free method to deallocate objects, because it checks whether an object's value is nil before invoking Destroy.

Take the following precautions when creating your own Destroy method:

• Declare Destroy with the override directive, because it is a virtual method.
• Always call 'inherited Destroy;' as the last thing on the destructor code.
• Be aware that an exception may be raised on the constructor in case there is not enought memory to create an object, or something else goes wrong. If the exception is not handled inside the constructor, the object will be only partially built. In this case Destroy will be called when you weren't expecting it, so your destructor must check if the resources were really allocated before disposing of them.
• Remember to call Free for all objects created on the constructor.

How to use Menu Controls

Hints for creating Menus for your Forms

TMainMenu is the Main Menu that appears at the top of most forms; form designers can customise by choosing various menu items. TPopupMenu is a menu window that pops up with pertinent, usually context-sensitive, details and choices when the right mouse button is clicked near a control

Main Menu is a non-visible component : that is, if the icon is selected from the Component Palette and placed on the Form, it will not appear at Run-time. Instead, a Menu bar with a structure defined by the Menu Editor will appear. Popup menus, placed on the form by selecting the icon from the Component Palette, do not appear at all unless the right mouse button is clicked on a control that owns such a menu.

To see the Menu Editor, right-click on the Main Menu or Popup Menu icon on your Form. A pop-up box appears, that invites you to enter items into the Menu bar.

An Edit box is displayed, containing a Button labelled New Item1. If you right-click on that box, a pop-up menu is displayed that allows you to add a new item before or after (along the same level) or create a sub-menu with the opportunity to add further items below (or above) the new item in a downward column.

Any or all of the MenuItems that you add can be configured using the 物件檢視器.

At the least you should give each item a Caption which will appear on the Menu Bar (you may also wish to give it a more meaningful Name). The caption should indicate the activity to be selected, such as "File Open" or "Close", "Run" or "Quit"

If you want a particular letter in the Caption to be associated with a shortcut key, that letter should be preceded by an ampersand. The Menu item at run-time will appear with the shortcut letter underlined, and hitting that letter key will have the same effect as selecting the menu item. Alternatively you can choose a shortcut key sequence (such as Ctrl+C for Copy or Ctrl+V for Paste - the standard Keyboard shortcuts) with the ShortCut property of the MenuItem.

It is often helpful to use the Menu controls in conjuction with an ActionList which contains a series of standard or customised Actions. Menu Items can be linked in the 物件檢視器 to Actions on the list, and the same actions can be linked to Buttons, ToolBar Buttons, SpeedButtons etc. It is obviously economic of effort to re-use the same code to respond to the various events, rather than writing separate OnClick event handlers for each individual control.

By default a number of standard actions is pre-loaded from StdActns or, if DataAware controls are being used, from DBActns, and these can be chosen using the ActionList editor which appears when you right-click on the ActionList icon on the Form Designer.

除錯器

撰寫中.

可參見 IDE 視窗－除錯

The Lazarus files

   (Thanks to Kevin Whitefoot.)
   (Additions by Giuseppe Ridino, User:Kirkpatc and Tom Lisjac)

When you save you will actually be saving two files:

  xxx.pas and yyy.lpr 

(You save more than that but those are the ones you get to name). The project file (lpr) and the unit file (pas) must not have the same name because Lazarus will helpfully rename the unit (inside the source code) to the same as the unit file name and the program to the name of the project file (it needs to do this or the compiler will probably not be able to find the unit later when referred to in the project file). Of course to be consistent it changes all the occurrences of unit1 to xxx.

So if you are saving a project called again, trying to save again.pas and again.lpr fails because unit names and program names are in the same name space resulting in a duplicate name error.

So here is what I ended up with:

e:/lazarus/kj/lazhello:

total 4740  free 76500
-rwxrwxrwx   1 kjwh     root  4618697 Mar 24 11:19 again.exe
-rw-rw-rw-   1 kjwh     root     3002 Mar 24 11:21 again.lpi
-rw-rw-rw-   1 kjwh     root      190 Mar 24 11:18 again.lpr
-rw-rw-rw-   1 kjwh     root      506 Mar 24 11:08 againu.lfm
-rw-rw-rw-   1 kjwh     root      679 Mar 24 11:08 againu.lrs
-rw-rw-rw-   1 kjwh     root      677 Mar 24 11:08 againu.pas
-rw-rw-rw-   1 kjwh     root     2124 Mar 24 11:08 againu.ppu
-rwxrwxrwx   1 kjwh     root      335 Mar 24 11:07 ppas.bat

Note that there are many more files than the two that I thought I was saving.

Here is a brief note about each file:

again.exe: The main program binary executable. Win32 adds an "exe" extension. Linux has none (just the name of the program). This file will be huge in Linux due to the inclusion of debugging symbols. Run the "strip" utility to remove them and substantially shrink the executable size.

again.lpi: (Lazarus Project Information). This is the main information file of a Lazarus project; the equivalent Delphi main file of an application will be the .dpr file. It is stored in an XML format and contains instructions about all the libraries and units required to build the executable file.

again.lpr: The main program source file or master file. Despite its lazarus specific extension it is in fact a perfectly normal Pascal source file. It has a uses clause that lets the compiler find all the units it needs. Note that the program statement does not have to name the program the same as the file name. This file is usually fairly small, with just a few statements to initialise, build the forms, run and close the application. Most of the work is done in the unit source files, with suffix '.pas'

againu.lfm: This is where Lazarus stores the layout of the form unit, in human readable form. It reflects the properties of the various components, as set in the 物件檢視器. Each object description starts with a line:

object xxxx 
  then there follows a list of properties 
  (including embedded or nested objects) then an 
end 

line. Lazarus uses this file to generate a resource file (.lrs) that is included in the initialisation section of the againu.pas unit. Delphi dfm files can be converted to lfm format in the Lazarus IDE using the Tools->Convert DFM file to LFM utility.

againu.lrs: This is the generated resource file which contains the instructions to the program for building the form (if you look in the main Unit file, you will see in the initialization section the line

{$i againu.lrs} 

which instructs the program to load the resource file). Note that it is not a Windows resource file.

againu.pas: The unit that contains the code for the form; this is usually the only file that the application programmer needs to edit or inspect, and contains any code specifically supplied by the programmer (especially event handlers).

againu.ppu: This is the compiled unit which gets linked into the executable file together with any other units named in the Uses section.

ppas.bat: This is a simple script that links the program to produce the executable. If compilation is successfull, it is deleted by the compiler.

See also

• Lazarus IDE Tools