Delphi中的Javascript TWebBrowser,关闭线程

发布时间：2020-12-15 10:07:37 所属栏目：大数据来源：网络整理

导读：我试图在delphi中构建一个允许用户使用谷歌地图的系统.一切正常,但我注意到每次创建一个新的TWebBrowser对象并加载处理谷歌地图的javascript时,会生成许多新的线程. 我的问题是,即使一旦web浏览器被破坏(并且它被明确地销毁),创建的线程仍然存在.我正在设计

我试图在delphi中构建一个允许用户使用谷歌地图的系统.一切正常,但我注意到每次创建一个新的TWebBrowser对象并加载处理谷歌地图的javascript时,会生成许多新的线程.

我的问题是,即使一旦web浏览器被破坏(并且它被明确地销毁),创建的线程仍然存在.我正在设计这个程序有很长的运行时间和谷歌地图的打开和关闭发生多次,因此,一段时间后,生成了很多线程,并没有终止该程序显着减慢.

有没有办法自己销毁这些线程,或者我做错了导致线程持续存在？

我的程序基于以下代码：

const
HTMLStr: AnsiString =
'<html> '+    
'<head> '+
'<meta name="viewport" content="initial-scale=1.0,user-scalable=yes" /> '+
'<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=true">        </script> '+
'<script type="text/javascript"> '+
''+
''+
'  var geocoder; '+
'  var map;  '+
'  var trafficLayer;'+
'  var bikeLayer;'+
'  var markersArray = [];'+
''+
''+
'  function initialize() { '+
'    geocoder = new google.maps.Geocoder();'+
'    var latlng = new google.maps.LatLng(40.714776,-74.019213); '+
'    var myOptions = { '+
'      zoom: 13,'+
'      center: latlng,'+
'      mapTypeId: google.maps.MapTypeId.ROADMAP '+
'    }; '+
'    map = new google.maps.Map(document.getElementById("map_canvas"),myOptions); '+
'    trafficLayer = new google.maps.TrafficLayer();'+
'    bikeLayer = new google.maps.BicyclingLayer();'+
'    map.set("streetViewControl",false);'+
'  } '+
''+
''+
'  function codeAddress(address) { '+
'    if (geocoder) {'+
'      geocoder.geocode( { address: address},function(results,status) { '+
'        if (status == google.maps.GeocoderStatus.OK) {'+
'          map.setCenter(results[0].geometry.location);'+
'          PutMarker(results[0].geometry.location.lat(),results[0].geometry.location.lng(),results[0].geometry.location.lat()+","+results[0].geometry.location.lng());'+
'        } else {'+
'          alert("Geocode was not successful for the following reason: " + status);'+
'        }'+
'      });'+
'    }'+
'  }'+
''+
''+
'  function GotoLatLng(Lat,Lang) { '+
'   var latlng = new google.maps.LatLng(Lat,Lang);'+
'   map.setCenter(latlng);'+
'   PutMarker(Lat,Lang,Lat+","+Lang);'+
'  }'+
''+
''+
'function ClearMarkers() {  '+
'  if (markersArray) {        '+
'    for (i in markersArray) {  '+
'      markersArray[i].setMap(null); '+
'    } '+
'  } '+
'}  '+
''+
'  function PutMarker(Lat,Msg) { '+
'   var latlng = new google.maps.LatLng(Lat,Lang);'+
'   var marker = new google.maps.Marker({'+
'      position: latlng,'+
'      map: map,'+
'      title: Msg+" ("+Lat+","+Lang+")"'+
'  });'+
' markersArray.push(marker); '+
'  }'+
''+
''+
'  function TrafficOn()   { trafficLayer.setMap(map); }'+
''+
'  function TrafficOff()  { trafficLayer.setMap(null); }'+
''+''+
'  function BicyclingOn() { bikeLayer.setMap(map); }'+
''+
'  function BicyclingOff(){ bikeLayer.setMap(null);}'+
''+
'  function StreetViewOn() { map.set("streetViewControl",true); }'+
''+
'  function StreetViewOff() { map.set("streetViewControl",false); }'+
''+
''+'</script> '+
'</head> '+
'<body onload="initialize()"> '+
'  <div id="map_canvas" style="width:100%; height:100%"></div> '+
'</body> '+
'</html> ';


procedure TfrmMain.FormCreate(Sender: TObject);
var
  aStream     : TMemoryStream;
begin
   WebBrowser1.Navigate('about:blank');
    if Assigned(WebBrowser1.Document) then
    begin
      aStream := TMemoryStream.Create;
      try
     aStream.WriteBuffer(Pointer(HTMLStr)^,Length(HTMLStr));
     //aStream.Write(HTMLStr[1],Length(HTMLStr));
     aStream.Seek(0,soFromBeginning);
     (WebBrowser1.Document as IPersistStreamInit).Load(TStreamAdapter.Create(aStream));
  finally
     aStream.Free;
  end;
  HTMLWindow2 := (WebBrowser1.Document as IHTMLDocument2).parentWindow;

end;
end;


procedure TfrmMain.ButtonGotoLocationClick(Sender: TObject);
begin
   HTMLWindow2.execScript(Format('GotoLatLng(%s,%s)',[Latitude.Text,Longitude.Text]),'JavaScript');
end;

procedure TfrmMain.ButtonClearMarkersClick(Sender: TObject);
begin
  HTMLWindow2.execScript('ClearMarkers()','JavaScript')
end;

procedure TfrmMain.ButtonGotoAddressClick(Sender: TObject);
var
   address    : string;
begin
   address := MemoAddress.Lines.Text;
   address := StringReplace(StringReplace(Trim(address),#13,' ',[rfReplaceAll]),#10,[rfReplaceAll]);
   HTMLWindow2.execScript(Format('codeAddress(%s)',[QuotedStr(address)]),'JavaScript');
end;

procedure TfrmMain.CheckBoxStreeViewClick(Sender: TObject);
begin
    if CheckBoxStreeView.Checked then
     HTMLWindow2.execScript('StreetViewOn()','JavaScript')
    else
     HTMLWindow2.execScript('StreetViewOff()','JavaScript');

end;

procedure TfrmMain.CheckBoxBicyclingClick(Sender: TObject);
begin
    if CheckBoxBicycling.Checked then
     HTMLWindow2.execScript('BicyclingOn()','JavaScript')
    else
     HTMLWindow2.execScript('BicyclingOff()','JavaScript');
 end;


procedure TfrmMain.CheckBoxTrafficClick(Sender: TObject);
begin
    if CheckBoxTraffic.Checked then
     HTMLWindow2.execScript('TrafficOn()','JavaScript')
    else
     HTMLWindow2.execScript('TrafficOff()','JavaScript');
 end;


end.

程序使用一个基本的析构函数来设置HTMLWindow导航到about：blank.
提前致谢

解决方法

这不回答这个问题,它只是简化了要模拟的问题.

查看每次单击按钮后运行的线程数.它使用Simple Google Maps example,所以问题甚至不在你的javascript部分.

Unit1 – 包含主窗体,其中只是一个带有OnClick事件处理程序的按钮

unit Unit1;

interface

uses
  Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,Dialogs,StdCtrls,PsAPI,TlHelp32,Unit2;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function GetThreadCount(const APID: Cardinal): Integer;
var
  NextProc: Boolean;
  ProcHandle: THandle;
  ThreadEntry: TThreadEntry32;
begin
  Result := 0;
  ProcHandle := CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD,0);
  if (ProcHandle <> INVALID_HANDLE_VALUE) then
  try
    ThreadEntry.dwSize := SizeOf(ThreadEntry);
    NextProc := Thread32First(ProcHandle,ThreadEntry);
    while NextProc do
    begin
      if ThreadEntry.th32OwnerProcessID = APID then
      Inc(Result);
      NextProc := Thread32Next(ProcHandle,ThreadEntry);
    end;
  finally
    CloseHandle(ProcHandle);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  ModalForm: TForm2;
begin
  ModalForm := TForm2.Create(nil);
  try
    ModalForm.ShowModal;
  finally
    ModalForm.Free;
  end;
  ShowMessage('Thread count: ' + 
    IntToStr(GetThreadCount(GetCurrentProcessId)));
end;

end.

Unit2 – 包含带有TWebBrowser的表单和表单的OnCreate事件处理程序

unit Unit2;

interface

uses
  Windows,OleCtrls,SHDocVw,ActiveX;

type
  TForm2 = class(TForm)
    WebBrowser1: TWebBrowser;
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form2: TForm2;

implementation

{$R *.dfm}

const
  HTMLString: AnsiString =
    '<!DOCTYPE html>' +
    '<html>' +
    '  <head>' +
    '    <title>Google Maps JavaScript API v3 Example: Map Simple</title>' +
    '    <meta name="viewport"' +
    '        content="width=device-width,initial-scale=1.0,user-scalable=no">' +
    '    <meta charset="UTF-8">' +
    '    <style type="text/css">' +
    '      html,body,#map_canvas {' +
    '        margin: 0;' +
    '        padding: 0;' +
    '        height: 100%;' +
    '      }' +
    '    </style>' +
    '    <script type="text/javascript"' +
    '        src="http://maps.googleapis.com/maps/api/js?sensor=false"></script>' +
    '    <script type="text/javascript">' +
    '      var map;' +
    '      function initialize() {' +
    '        var myOptions = {' +
    '          zoom: 8,' +
    '          center: new google.maps.LatLng(-34.397,150.644),' +
    '          mapTypeId: google.maps.MapTypeId.ROADMAP' +
    '        };' +
    '        map = new google.maps.Map(document.getElementById(''map_canvas''),' +
    '            myOptions);' +
    '      }' +
    '      google.maps.event.addDomListener(window,''load'',initialize);' +
    '    </script>' +
    '  </head>' +
    '  <body>' +
    '    <div id="map_canvas"></div>' +
    '  </body>' +
    '</html>';

procedure TForm2.FormCreate(Sender: TObject);
var
  HTMLStream: TMemoryStream;
begin
  WebBrowser1.Navigate('about:blank');
  if Assigned(WebBrowser1.Document) then
  begin
    HTMLStream := TMemoryStream.Create;
    try
      HTMLStream.WriteBuffer(Pointer(HTMLString)^,Length(HTMLString));
      HTMLStream.Seek(0,soFromBeginning);
      (WebBrowser1.Document as IPersistStreamInit).Load(TStreamAdapter.Create(HTMLStream));
    finally
      HTMLStream.Free;
    end;
  end;
end;

end.

（编辑：李大同）

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