{"id":3995,"date":"2021-12-26T05:18:30","date_gmt":"2021-12-26T05:18:30","guid":{"rendered":"http:\/\/truelogic.org\/wordpress\/?p=3995"},"modified":"2021-12-26T05:18:32","modified_gmt":"2021-12-26T05:18:32","slug":"6g-wxwidgets-using-bind-and-unbind","status":"publish","type":"post","link":"https:\/\/truelogic.org\/wordpress\/2021\/12\/26\/6g-wxwidgets-using-bind-and-unbind\/","title":{"rendered":"6g. wxWidgets – Using Bind and Unbind"},"content":{"rendered":"\n

OVERVIEW<\/strong><\/p>\n\n\n\n

As mentioned before in a previous section, Bind<\/em> is the preferred way to do event handling. The main advantage of Bind<\/em> is that you can bind events at runtime. We look at an example of this in the code below. We use Bind and Unbind to attach 3 different event handlers to a single button , one at a time.<\/p>\n\n\n\n

We use an inbuilt function called CallAfter, which we will explore in later sections. The basic purpose of CallAfter is to execute a method when wxWidgets is idle. The reason why we dont call the RemoveHandler directly is because it is not a good idea to remove an event handler from a widget while it is still executing the event handler. Using CallAfter makes sure the event is unbound after it has finished executing.<\/p>\n\n\n\n

SAMPLE CODE<\/strong><\/p>\n\n\n\n

bind-unbind.h\n<\/pre>\n\n\n
\n#include <wx\/wxprec.h>\n#ifndef WX_PRECOMP\n    #include <wx\/wx.h>\n#endif\n\nclass BindUnbind: public wxFrame {\n\n    public:\n      BindUnbind(const wxString &title);\n      void OnClick1(wxCommandEvent &event);\n      void OnClick2(wxCommandEvent &event);\n      void OnClick3(wxCommandEvent &event);\n      void RemoveHandler(int remove, int add);\n    private:\n      wxButton *btn1;\n \n};\n<\/pre><\/div>\n\n\n
bind-unbind.cpp<\/pre>\n\n\n
\n#include "bind-unbind.h"\n\n\nBindUnbind::BindUnbind(const wxString &title):\n\n    wxFrame(NULL, -1, title, wxDefaultPosition, wxSize(500,200)) {\n \n    wxPanel *panel = new wxPanel(this, -1);    \n    wxBoxSizer *hbox = new wxBoxSizer(wxHORIZONTAL);\n    panel->SetSizer(hbox);\n\n    btn1 = new wxButton(panel, -1, wxT("click here"));\n   \n    hbox->Add(btn1, 1, wxEXPAND | wxALL, 35);\n\n    btn1->Bind(wxEVT_BUTTON, &BindUnbind::OnClick1, this);\n    Center();\n\n}\n\nvoid BindUnbind::OnClick1(wxCommandEvent &event) {\n\tbtn1->SetLabel(wxT("in OnClick1"));\n\tCallAfter(&BindUnbind::RemoveHandler, 1, 2);\n\n}\n\nvoid BindUnbind::OnClick2(wxCommandEvent &event) {\n\tbtn1->SetLabel(wxT("in OnClick2"));\n\tCallAfter(&BindUnbind::RemoveHandler, 2, 3);\n\n\n}\nvoid BindUnbind::OnClick3(wxCommandEvent &event) {\n\tbtn1->SetLabel(wxT("in OnClick3"));\n\tCallAfter(&BindUnbind::RemoveHandler, 3, 1);\n\n}\n\nvoid BindUnbind::RemoveHandler(int remove, int add) {\n   if (remove == 1)\n\t     btn1->Unbind(wxEVT_BUTTON, &BindUnbind::OnClick1, this);\n   else if (remove == 2)\n\t     btn1->Unbind(wxEVT_BUTTON, &BindUnbind::OnClick2, this);\n   else if (remove == 3)\n\t     btn1->Unbind(wxEVT_BUTTON, &BindUnbind::OnClick3, this);\n\n   if (add == 1)\n\t     btn1->Bind(wxEVT_BUTTON, &BindUnbind::OnClick1, this);\n   else if (add == 2)\n\t     btn1->Bind(wxEVT_BUTTON, &BindUnbind::OnClick2, this);\n   else if (add == 3)\n\t     btn1->Bind(wxEVT_BUTTON, &BindUnbind::OnClick3, this);\n\n\n\n\n}\n\n\n\n\n\n<\/pre><\/div>\n\n\n
main.h<\/pre>\n\n\n
\n#include &lt;wx\/wxprec.h>\n#ifndef WX_PRECOMP\n    #include &lt;wx\/wx.h>\n#endif\n\nclass Main: public wxApp {\n\n\tpublic:\n\t        virtual bool OnInit();\n};\n<\/pre><\/div>\n\n\n
main.cpp<\/pre>\n\n\n
\n#include "main.h"\n#include "bind-unbind.h"\n \nIMPLEMENT_APP(Main)\n\nbool Main::OnInit() {\n\n    BindUnbind *app = new BindUnbind(wxT("Bind Unbind"));\n    app->Show(true);\n}\n<\/pre><\/div>\n\n\n
The output is shown below<\/p>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n\n\n\n
\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"
OVERVIEW As mentioned before in a previous section, Bind is the preferred way to do event handling. The main advantage of Bind is that you […]<\/a><\/p>\n<\/div>","protected":false},"author":1,"featured_media":3595,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[302,365],"tags":[],"class_list":["post-3995","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cc","category-wxwidgets"],"_links":{"self":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/3995","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/comments?post=3995"}],"version-history":[{"count":5,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/3995\/revisions"}],"predecessor-version":[{"id":4003,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/posts\/3995\/revisions\/4003"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/media\/3595"}],"wp:attachment":[{"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/media?parent=3995"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/categories?post=3995"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/truelogic.org\/wordpress\/wp-json\/wp\/v2\/tags?post=3995"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}