自定義通用查詢組件

1、  設計通用查詢窗口，嚴格的說這是一個目前只適合數據庫表中字符串類型或相似類型的查詢窗口，數字類型不支持，不過稍加修改（增加一個類型選擇，判斷處理即可）就可支持。窗體的界面如下：

相關代碼如下：

unit GenQueryBox; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, ComCtrls, Buttons, StdCtrls, DB, ADODB; type TGenQueryBoxFrm = class(TForm) Panel1: TPanel; Panel2: TPanel; Label1: TLabel; Label2: TLabel; Label3: TLabel; cbFieldName: TComboBox; cbSymbol: TComboBox; cbValue: TComboBox; Label4: TLabel; btnInit: TSpeedButton; btnAnd: TSpeedButton; btnOr: TSpeedButton; btnClear: TSpeedButton; btnResult: TSpeedButton; btnGiveup: TSpeedButton; ADOQuery1: TADOQuery; Panel3: TPanel; Panel4: TPanel; mCon: TMemo; ADOConnection1: TADOConnection; procedure FormCreate(Sender: TObject); procedure FormClose(Sender: TObject; var Action: TCloseAction); procedure FormActivate(Sender: TObject); procedure btnInitClick(Sender: TObject); procedure btnAndClick(Sender: TObject); procedure btnOrClick(Sender: TObject); procedure btnClearClick(Sender: TObject); procedure btnResultClick(Sender: TObject); procedure btnGiveupClick(Sender: TObject); procedure cbFieldNameChange(Sender: TObject); private { Private declarations } procedure BtnValid; //按鈕互斥 procedure getParams(var qStr1, qStr2, qStr3: String); //獲取串聯的字符串子串 procedure getAllValues; //根據字段名獲取全部的字段值 public pTableName: String; //表名 pFields: TStrings; //字段列表 isConf: Boolean; //判斷是否按下缺人按鈕，沒按下代表放棄 filterValue: String;//過濾的條件值 end; var GenQueryBoxFrm: TGenQueryBoxFrm; implementation {$R *.dfm} { TForm1 } procedure TGenQueryBoxFrm.BtnValid; begin btnInit.Enabled := not btnInit.Enabled; btnAnd.Enabled := not btnAnd.Enabled; btnOr.Enabled := not btnOr.Enabled; btnClear.Enabled := not btnClear.Enabled; btnResult.Enabled := not btnResult.Enabled; btnGiveup.Enabled := not btnGiveup.Enabled; end; procedure TGenQueryBoxFrm.FormCreate(Sender: TObject); begin pFields := TStringList.Create; isConf := False; self.cbSymbol.Items.Clear; self.cbSymbol.Items.Add('='); self.cbSymbol.Items.Add('>'); self.cbSymbol.Items.Add('>='); self.cbSymbol.Items.Add('<'); self.cbSymbol.Items.Add('<='); self.cbSymbol.Items.Add('<>'); self.cbSymbol.Items.Add('like'); self.cbSymbol.ItemIndex := -1; end; procedure TGenQueryBoxFrm.FormClose(Sender: TObject; var Action: TCloseAction); begin pFields.Free; end; procedure TGenQueryBoxFrm.FormActivate(Sender: TObject); begin self.cbFieldName.Items.AddStrings(pFields); self.cbFieldName.SetFocus; end; procedure TGenQueryBoxFrm.btnInitClick(Sender: TObject); var qStr1, qStr2, qStr3: String; begin if Trim(self.cbFieldName.Text) = '' then begin MessageBox(Handle, '字段名不能爲空！', '信息提示', MB_ICONWARNING + MB_OK); Exit; end; if Trim(self.cbSymbol.Text) = '' then begin MessageBox(Handle, '操作符不能爲空！', '信息提示', MB_ICONWARNING + MB_OK); Exit; end; qStr1 := self.cbFieldName.Items.Strings[self.cbFieldName.ItemIndex]; qStr2 := self.cbSymbol.Items.Strings[self.cbSymbol.ItemIndex]; if qStr2 <> 'like' then qStr3 := self.cbValue.Text else qStr3 := '%' + self.cbValue.Text + '%'; filterValue := qStr1 + ' ' + qStr2 + ' ''' + qStr3 + ''' '; self.mCon.Lines.Add(qStr1 + ' ' + qStr2 + ' ' + self.cbValue.Text); btnValid; self.cbFieldName.ItemIndex := -1; self.cbSymbol.ItemIndex := -1; self.cbValue.Text := ''; end; procedure TGenQueryBoxFrm.getParams(var qStr1, qStr2, qStr3: String); begin qStr1 := ''; qStr2 := ''; qStr3 := ''; if Trim(self.cbFieldName.Text) = '' then begin MessageBox(Handle, '字段名不能爲空！', '信息提示', MB_ICONWARNING + MB_OK); Exit; end; if Trim(self.cbSymbol.Text) = '' then begin MessageBox(Handle, '操作符不能爲空！', '信息提示', MB_ICONWARNING + MB_OK); Exit; end; qStr1 := self.cbFieldName.Items.Strings[self.cbFieldName.ItemIndex]; qStr2 := self.cbSymbol.Items.Strings[self.cbSymbol.ItemIndex]; if qStr2 <> 'like' then qStr3 := self.cbValue.Text else qStr3 := '%' + self.cbValue.Text + '%'; end; procedure TGenQueryBoxFrm.btnAndClick(Sender: TObject); var qStr1, qStr2, qStr3: String; begin getParams(qStr1, qStr2, qStr3); if (qStr1 <> '') and (qStr2 <> '') then begin filterValue := filterValue + ' and ' + qStr1 + ' ' + qStr2 + ' ''' + qStr3 + ''' '; self.mCon.Lines.Add('並且 ' + qStr1 + ' ' + qStr2 + ' ' + self.cbValue.Text); //btnValid; end; end; procedure TGenQueryBoxFrm.btnOrClick(Sender: TObject); var qStr1, qStr2, qStr3: String; begin getParams(qStr1, qStr2, qStr3); if (qStr1 <> '') and (qStr2 <> '') then begin filterValue := filterValue + ' or ' + qStr1 + ' ' + qStr2 + ' ''' + qStr3 + ''' '; self.mCon.Lines.Add('或者 ' + qStr1 + ' ' + qStr2 + ' ' + self.cbValue.Text); //btnValid; end; end; procedure TGenQueryBoxFrm.btnClearClick(Sender: TObject); begin self.mCon.Lines.Clear; self.cbFieldName.SetFocus; btnValid; end; procedure TGenQueryBoxFrm.btnResultClick(Sender: TObject); begin isConf := True; Close; end; procedure TGenQueryBoxFrm.btnGiveupClick(Sender: TObject); begin Close; end; procedure TGenQueryBoxFrm.cbFieldNameChange(Sender: TObject); begin self.cbValue.Items.Clear; getAllValues; self.cbValue.Text := ''; end; procedure TGenQueryBoxFrm.getAllValues; var sField: String; begin self.cbValue.Items.Clear; if self.cbFieldName.ItemIndex < 0 then Exit; sField := pFields[self.cbFieldName.ItemIndex]; self.ADOQuery1.Close; self.ADOQuery1.SQL.Text := 'select distinct ' + sField + ' from ' + pTableName; try self.ADOQuery1.Open; except MessageBox(HANDLE, '列舉出錯！', '錯誤', MB_ICONERROR + MB_OK); exit; end; self.ADOQuery1.First; while not self.ADOQuery1.Eof do begin self.cbValue.Items.Add(self.ADOQuery1.fieldByName(sField).AsString); self.ADOQuery1.Next; end; self.ADOQuery1.Close; end; end.

 

2、  創建組件

Delphi->Component->New Component 創建一個組件單元，並填選好相關信息，參考如下圖：

保存後，編寫代碼如下：

unit GenQ; interface uses SysUtils, Classes, GenQueryBox, ADODB, Forms; type TGenQ = class(TComponent) private FConString: String; //數據庫連接字符串 FTableName: String; //表名 FFieldsStrings: TStrings; //字段名列表 procedure SetFieldsStrings(Value: TStrings); //設置字段名列表方法 protected { Protected declarations } public FSqlFilterValue: String; constructor Create(AOwner: TComponent); override; destructor Destroy; override; function Execute: Boolean; //調用通用查詢窗體方法 published property ConString: String read FConString write FConString; property TableName: String read FTableName write FTableName; property FieldsStrings: TStrings read FFieldsStrings write SetFieldsStrings; end; procedure Register; implementation procedure Register; begin RegisterComponents('Samples', [TGenQ]); end; { TGenQ } constructor TGenQ.Create(AOwner: TComponent); begin inherited Create(AOwner); FFieldsStrings := TStringList.Create; end; destructor TGenQ.Destroy; begin FFieldsStrings.Free; inherited Destroy; end; function TGenQ.Execute: Boolean; var GenQBoxFrm: TGenQueryBoxFrm; bFlag: Boolean; begin bFlag := False; GenQBoxFrm := TGenQueryBoxFrm.Create(nil); GenQBoxFrm.pTableName := FTableName; GenQBoxFrm.ADOConnection1.ConnectionString := ConString; GenQBoxFrm.ADOConnection1.Connected := True; GenQBoxFrm.pFields.Assign(FFieldsStrings); // := FFieldsStrings; 注意多單元對象傳遞的釋放問題 try GenQBoxFrm.ShowModal; bFlag := GenQBoxFrm.isConf; FSqlFilterValue := GenQBoxFrm.filterValue; finally GenQBoxFrm.Free; end; result := bFlag; end; procedure TGenQ.SetFieldsStrings(Value: TStrings); begin if Assigned(Value) then FFieldsStrings.Assign(Value); end; end.

注意，引用上一步設計好的 GenQueryBox ，這樣就完成了封裝；完成這步在註冊組件之間，最好先建一個工程調用測試一下，沒問題了再進行後續的註冊。

3、  爲組件增加自定義圖標

Delphi->Tools->Image Editor ，新建一個 dcr 文件，名字要與組件單元名相同 GenQ.dcr ，並保存在同一目錄； Contens 右鍵 new 一個 Bitmap(24 * 24) ，這個位圖名字必須與組件的類名相同並大寫，比例爲 TGENQ ，這樣安裝組件後自定義的圖標就顯示出來了。

注意如果不像自己設計 Bitmap ，可拷貝其他的好看的 bmp 文件，但 Image Editor 不能直接打開 256 色的圖片，你可以用 windows 的畫圖工具打開再拷貝過來即可。

4、  註冊組件

Delphi->Component->Install Component ，出現如下組件安裝對話框：

點擊 OK 後完成編譯安裝，另外這塊編譯成功後原以爲會出現 PGenQ.dpk ，但卻找不到，只有 PGenQ.dcu ，此處還有點疑問。

5 、組件使用

好了，去體驗一下成果吧，注意那個小圖標 就是自定義的組件，如下圖：

調用代碼如下：

unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, GenQ, StdCtrls, DB, Grids, DBGrids, ADODB; type TForm1 = class(TForm) GenQ1: TGenQ; ADOConnection1: TADOConnection; ADOQuery1: TADOQuery; DBGrid1: TDBGrid; DataSource1: TDataSource; Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; implementation {$R *.dfm} procedure TForm1.Button1Click(Sender: TObject); begin self.GenQ1.Execute; self.ADOQuery1.Close; self.ADOQuery1.Filter := self.GenQ1.FSqlFilterValue; self.ADOQuery1.Filtered := True; self.ADOQuery1.Open; end; end.