Xamarin 表单在启动应用程序时读取文件并在关闭时保存

Question

I want to save config file. My save and load function works correctly when I call it from the button. But I want to improve it and save my file and load when app is closing /opening. These methods are on MainPage.xaml.cs.

 protected override void OnStart()
    {
        MainPage mainPage = new MainPage();
        mainPage.Load_File();

    }

    protected override void OnSleep()
    {
        MainPage mainPage = new MainPage();
        mainPage.Save_File();
    }

When I created it like this save and load not working.

Answer 1

when you create your MainPage , save a reference to it so you can reuse it later

MainPage main;

public App ()
{
    InitializeComponent ();
    MainPage = main = new MainPage();
}

protected override void OnStart()
{
    main.Load_File();
}

protected override void OnSleep()
{
    main.Save_File();
}