DisplayAlert With changing Text xamarin forms - xamarin

Question

I have a requirement where i have to show the status of the download on a DisplayAlert. But with changing text on it asynchronously.
How to achieve this?
DisplayAlert("Download Info", "Downloading.....", "Ok");
I want to show status like...
Connected to server
Downloading
Download Complete

Answer 1

Here is a simple "Dynamic Alert" for Forms and iOS using UIAlertController and Android using a DialogFragment and a Xamarin.Forms dependency service:
Dependency Interface:
public interface IDynamicAlert
{
void Show(string title, string message);
void Update(string message);
void Dismiss();
}
iOS IDynamicAlert Dependency Implementation:
public class DynamicAlert : IDynamicAlert
{
UIAlertController alert;
public void Show(string title, string message)
{
if (alert != null) throw new Exception("DynamicAlert already showing");
alert = UIAlertController.Create(title, message, UIAlertControllerStyle.Alert);
var rootVC = UIApplication.SharedApplication.Windows[0].RootViewController;
rootVC.PresentViewController(alert, true, () =>
{
});
}
public void Update(string message)
{
if (alert == null) throw new Exception("DynamicAlert is not showing, call Show first");
alert.Message = message;
}
public void Dismiss()
{
if (alert == null) throw new Exception("DynamicAlert is not showing, call Show first");
alert.DismissViewController(true, () =>
{
alert.Dispose();
alert = null;
});
}
}
Example Usage:
var alert = DependencyService.Get<IDynamicAlert>();
if (alert != null)
{
alert.Show("StackOverflow", "Starting your request...");
await Task.Delay(2000); // Do some work...
alert.Update("Your request is processing...");
await Task.Delay(2000); // Do some work...
alert.Update("Your request is complete...");
await Task.Delay(750);
alert.Dismiss();
}
else
{
throw new Exception("IDynamicAlert Dependency not found");
}
Output:
Android Version:
The android version consists of a couple of parts, a DialogFragment subclass and the IDynamicAlert implementation that uses the custom DialogFragment.
Android DialogFragment Subclass:
public class DynamicAlertDialogFragment : DialogFragment
{
AlertDialog alertDialog;
readonly Context context;
public static DynamicAlertDialogFragment Instance(Context context, string title, string message)
{
var fragment = new DynamicAlertDialogFragment(context);
Bundle bundle = new Bundle();
bundle.PutString("title", title);
bundle.PutString("message", message);
fragment.Arguments = bundle;
return fragment;
}
public DynamicAlertDialogFragment(Context context)
{
this.context = context;
}
public override Dialog OnCreateDialog(Bundle savedInstanceState)
{
var title = Arguments.GetString("title");
var message = Arguments.GetString("message");
alertDialog = new AlertDialog.Builder(context)
.SetIcon(Android.Resource.Drawable.IcDialogInfo)
.SetTitle(title)
.SetMessage(message)
.Create();
return alertDialog;
}
public void SetMessage(string message)
{
(context as Activity).RunOnUiThread(() => { alertDialog.SetMessage(message);});
}
}
Android IDynamicAlert Dependency Implementation:
public class DynamicAlert : IDynamicAlert
{
const string FRAGMENT_TAG = "DynamicAlert_Fragment";
DynamicAlertDialogFragment fragment;
static FormsAppCompatActivity currentActivity;
public static FormsAppCompatActivity CurrentActivity { set { currentActivity = value; } }
public void Show(string title, string message)
{
if (currentActivity == null) throw new Exception("DynamicAlert.CurrentActivity needs assigned");
var fragMgr = currentActivity.FragmentManager;
var fragTransaction = fragMgr.BeginTransaction();
var previous = fragMgr.FindFragmentByTag(FRAGMENT_TAG);
if (previous != null)
{
fragTransaction.Remove(previous);
}
fragTransaction.DisallowAddToBackStack();
fragment = DynamicAlertDialogFragment.Instance(currentActivity, title, message);
fragment.Show(fragMgr, FRAGMENT_TAG);
}
public void Update(string message)
{
if (fragment == null) throw new Exception("DynamicAlert is not showing, call Show first");
fragment.SetMessage(message);
}
public void Dismiss()
{
if (fragment == null) throw new Exception("DynamicAlert is not showing, call Show first");
fragment.Dismiss();
fragment.Dispose();
fragment = null;
}
}
Android Init / Usage:
When creating the AlertDialog in the DialogFragment we need access to the current Activity and when using Xamarin.Forms, that is normally the MainActivity that is a FormsAppCompatActivity subclass. Thus you will need to initialize the DynamicAlert.CurrentActivity static property with this Activity in your MainActivity.OnCreate subclass:
Example:
protected override void OnCreate(Bundle bundle)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(bundle);
////////////
DynamicAlert.CurrentActivity = this;
////////////
global::Xamarin.Forms.Forms.Init(this, bundle);
LoadApplication(new App());
}
Android Output: