2018【Delphi7】《零基础入门学习Delphi》(from b站)（2）

B站： https://www.bilibili.com/video/BV12s411c7ct/

相关论坛：https://fishc.com.cn/forum-120-1.html

P9:结构化程序设计

  • system里timer定时器组件，inteval属性单位为毫秒，1000毫秒为一秒
  • 隐藏窗体边框： borderStyle 设置为 bsNone
  • autosize 属性设置为true，控件自动调整大小
  • 不等于： <>
unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls;

type
  TForm1 = class(TForm)
    Timer1: TTimer;
    Label1: TLabel;
    procedure Timer1Timer(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Timer1Timer(Sender: TObject);
begin
Label1.Font.Size :=random(40);
Form1.Left:=random(500);
Form1.Top:=random(600);
end;

end.

P10:结构化程序设计 if else

如果是单语句，if结构如下，复合语句用 begin … end;

if () then
    s1 //无分号
else
    s2; //有分号

猜数字示例，有调用windows API：

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Edit1: TEdit;
    Button1: TButton;
    Label2: TLabel;
    Label3: TLabel;
    Button2: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  randomNum: Integer;
  guessNum: Integer;

procedure TForm1.Button1Click(Sender: TObject);
begin
  guessNum := strtoint(Edit1.Text);

  if guessNum = randomNum then
    // Delphi封装的消息窗口
    ShowMessage('bingo!')
  else if guessNum > randomNum then
    ShowMessage('你猜大了!')
  else
  begin
    // ShowMessage('你猜小了!')
    // windows 风格消息框
    // 可以在delphi帮助中搜索 MessageBox
    MessageBox(handle, '消息内容：你猜小了', '标题：提醒', MB_OK);
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  // 生成随机数
  randomNum := random(101); // 0<=x<x
  Label3.Caption := inttostr(randomNum);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  // 调用windows API 设置光标
  // ES_CENTER ,中间
  SetWindowLong(Edit1.handle, GWL_STYLE, GetWindowLong(Edit1.handle, GWL_STYLE)
    or ES_CENTER);
  Edit1.Invalidate; // 该函数的作用是使整个窗口客户区无效,需要重新绘制

  // 生成随机数
  randomNum := random(101); // 0<=x<x
  Label3.Caption := inttostr(randomNum);
end;

end.

P11:结构化程序设计 多分支case语句

case (表达式) of
v1:s1;
v2:s2;
v3,v4:s4;
v5:
    begin
    
    end;
...
Vn:sn;
ELSE  // 无匹配时执行，可省略
s;
end;

示例：

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Timer1: TTimer;
    procedure Timer1Timer(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Form1.AutoSize := True;
  Label1.AutoSize := True;
  Form1.BorderStyle := bsNone;
  Label1.Transparent := False; // 必须改为false，否则背景为父容器颜色
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Label1.Font.Size := random(50);
  Form1.Left := random(500);
  Form1.Top := random(500);

  // 0-7 共8种情况
  case (random(8)) of
    0:
      Label1.Color := clBlack;
    1:
      Label1.Color := clYellow;
    2:
      Label1.Color := clRed;
    3:
      Label1.Color := clBlue;
    4:
      Label1.Color := clGreen;
    5:
      Label1.Color := clFuchsia;
    6:
      Label1.Color := clLtGray;
    7:
      Label1.Color := clOlive;
  end;

  // 0-7 共8种情况
  case (random(8)) of
    0:
      Label1.Font.Color := clBlack;
    1:
      Label1.Font.Color := clYellow;
    2:
      Label1.Font.Color := clRed;
    3:
      Label1.Font.Color := clBlue;
    4:
      Label1.Font.Color := clGreen;
    5:
      Label1.Font.Color := clFuchsia;
    6:
      Label1.Font.Color := clLtGray;
    7:
      Label1.Font.Color := clOlive;
  end;
end;

end.

P12 小结

对话框示例：

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Label1: TLabel;
    Button1: TButton;
    CheckBox1: TCheckBox;
    procedure FormActivate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure CheckBox1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  numCanTry: Integer = 3;

const
  password: string = 'password';

procedure TForm1.Button1Click(Sender: TObject);
begin
  // 密码正确
  if Edit1.Text = password then
    messagebox(handle, 'correct!', '恭喜', MB_OK)
  else
  begin
    numCanTry := numCanTry - 1;

    if numCanTry <> 0 then
    begin
      messagebox(handle, 'wrong!', '提醒', MB_OK);
      Label1.Caption := '请输入密码，你还有' + inttostr(numCanTry) + '次机会';
      edit1.Text :='';
    end // 注意这里没有分号才能和下面的else连起来
    else
    begin
      messagebox(handle, 'wrong! you have no change!', '提醒', MB_OK);
      close;
      // 密码错误
    end;
  end;

end;

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  if CheckBox1.checked = true then
    Edit1.PasswordChar := #0
  else
    Edit1.PasswordChar := '*';

end;

procedure TForm1.FormActivate(Sender: TObject);
begin
  // 对话框窗口
  Form1.BorderStyle := bsDialog;
  Label1.Caption := '请输入密码，你还有' + inttostr(numCanTry) + '次机会';
  // edit 内容居中 , windows api 方法如下。也可以直接设置属性
  // SetWindowLong(Edit1.Handle, GWL_STYLE, GetWindowLong(Edit1.Handle, GWL_STYLE) or  ES_CENTER);
  // Edit1.Invalidate; // 该函数的作用是使整个窗口客户区无效,需要重新绘制
  Edit1.Alignment := taCenter;
  Edit1.Text := '';
  Edit1.PasswordChar := '*';
end;

end.

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