Android活动生命周期

Question

活动1通过单击按钮启动活动2。 设置好活动2的静态内容并将其显示给用户后，我想启动AsyncTask。 在执行AsyncTask时，应该向用户显示一个ProgressBar。 我的问题是，而不是在重点关注活动2之后出现ProgressBar，而是在AsyncTask执行时活动1仍然可见，然后在执行完成后切换到活动2。 我尝试将我的AsyncTask放在：

• OnCreate
• OnPostCreate
• OnStart
• 简历

...活动2的内容，但活动2仅在任务执行完成后才可见。 为了实现我想要的目标，我需要在Activity 2的生命周期中的什么时候放置AsyncTask？ 代码，以防您需要：

活动1启动AsyncTask，以在继续前进之前验证用户的输入。 在该任务的OnPostExecute中，如果信息有效：

Intent intent = new Intent(_context, typeof(Activity2));
intent.PutExtra("Call", _call);
intent.PutExtra("Site", _site);
intent.PutExtra("ServiceType", _serviceType);
intent.PutExtra("Priority", _priority);
_context.StartActivity(intent);

Activity2.cs

public class Activity2 : Activity
{
    private string Call { get; set; }
    private string Site { get; set; }
    private string Priority { get; set; }
    private string ServiceType { get; set; }
    private ViewAnimator Animator { get; set; }
    private Spinner PrioritySpin { get; set; }
    private Spinner ProblemSpin { get; set; }
    private Spinner CauseSpin { get; set; }
    private Spinner RepairSpin { get; set; }
    private Spinner LaborHrsSpin { get; set; }
    private Spinner LaborDecSpin { get; set; }
    private Spinner TravelHrsSpin { get; set; }
    private Spinner TravelDecSpin { get; set; }
    private Spinner SerlModelSpin { get; set; }

    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        Intent intent = Intent;
        Call = intent.GetStringExtra("Call");
        Site = intent.GetStringExtra("Site");
        Priority = intent.GetStringExtra("Priority");
        ServiceType = intent.GetStringExtra("ServiceType");

        Title = "Service Report for Call #" + Call + " at Site " + Site;

        SetContentView(Resource.Layout.Activity2);

        Animator = (ViewAnimator) FindViewById(Resource.Id.contentContainer);

        Button basic = (Button) FindViewById(Resource.Id.basicBtn);
            basic.Click += WizardClick;
        Button equipment = (Button) FindViewById(Resource.Id.equipmentBtn);
            equipment.Click += WizardClick;
        Button parts = (Button) FindViewById(Resource.Id.partsBtn);
            parts.Click += WizardClick;
        Button comments = (Button) FindViewById(Resource.Id.commentsBtn);
            comments.Click += WizardClick;
        Button review = (Button) FindViewById(Resource.Id.reviewSubmit);
            review.Click += WizardClick;

        PrioritySpin = (Spinner) FindViewById(Resource.Id.prioritySpinner);
        ProblemSpin = (Spinner) FindViewById(Resource.Id.problemSpinner);
        CauseSpin = (Spinner) FindViewById(Resource.Id.causeSpinner);
        RepairSpin = (Spinner) FindViewById(Resource.Id.repairSpinner);
        LaborHrsSpin = (Spinner) FindViewById(Resource.Id.laborHrsSpinner);
        LaborDecSpin = (Spinner) FindViewById(Resource.Id.laborDecSpinner);
        TravelHrsSpin = (Spinner) FindViewById(Resource.Id.travelHrsSpinner);
        TravelDecSpin = (Spinner) FindViewById(Resource.Id.travelDecSpinner);

        ArrayAdapter<string> priorityAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, Priorities());
        ArrayAdapter<string> problemAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, Problems());
        ArrayAdapter<string> causeAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, Cause());
        ArrayAdapter<string> repairAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, Repair());
        ArrayAdapter<string> hoursAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, Hours());
        ArrayAdapter<string> decAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, QuarterHours());

        PrioritySpin.Adapter = priorityAdapter;
        ProblemSpin.Adapter = problemAdapter;
        CauseSpin.Adapter = causeAdapter;
        RepairSpin.Adapter = repairAdapter;
        LaborHrsSpin.Adapter = hoursAdapter;
        LaborDecSpin.Adapter = decAdapter;
        TravelHrsSpin.Adapter = hoursAdapter;
        TravelDecSpin.Adapter = decAdapter;

        PrioritySpin.SetSelection(Convert.ToInt32(Priority));

        if (ServiceType == "PM")
        {
            ProblemSpin.SetSelection(Array.IndexOf(Problems(), "Scheduled"));
            CauseSpin.SetSelection(Array.IndexOf(Cause(), "Scheduled"));
        }

        Window.SetSoftInputMode(SoftInput.StateAlwaysHidden);
    }

    protected override void OnResume()
    {
        base.OnResume();

        SerlModelSpin = (Spinner)FindViewById(Resource.Id.equipSpinner);

        IEquipment equipInterface = new EquipmentHelper(this, Animator, 5, 0);
        string[] equipList = equipInterface.GetEquipmentList(Site);
        ArrayAdapter<string> equipAdapter = new ArrayAdapter<string>(this, Android.Resource.Layout.SimpleSpinnerDropDownItem, equipList);

        SerlModelSpin.Adapter = equipAdapter;
    }
}

Answer 1

为什么在此AsyncTask在后台运行时活动2在后台很重要？ 无论如何，都将向用户显示一个对话框...为什么不将标志放在AsyncTask中，然后等待设置标志并显示对话框，直到onResume()方法执行完毕。 或者您可以尝试在活动时从活动1调用静态启动方法。 也许通过调用finish（）然后覆盖onDestroy（）方法。 很难把握时机。