Add sample for hastext on clip & check IsNullOrEmpty (#1502)

Author: jamesmontemagno

Samples/Samples/View/ClipboardPage.xaml

@@ -17,6 +17,7 @@
                 <Entry Placeholder="Enter text..." Text="{Binding FieldValue}" />
                 <Button Text="Copy to clipboard" Command="{Binding CopyCommand}" />
                 <Button Text="Paste from clipboard" Command="{Binding PasteCommand}" />
+                <Button Text="Check Status" Command="{Binding CheckCommand}" />
                 <Label Text="{Binding LastCopied}" />
             </StackLayout>
         </ScrollView>

Samples/Samples/ViewModel/ClipboardViewModel.cs

@@ -14,12 +14,15 @@ public ClipboardViewModel()
         {
             CopyCommand = new Command(OnCopy);
             PasteCommand = new Command(OnPaste);
+            CheckCommand = new Command(OnCheck);
         }
 
         public ICommand CopyCommand { get; }
 
         public ICommand PasteCommand { get; }
 
+        public ICommand CheckCommand { get; }
+
         public string FieldValue
         {
             get => fieldValue;
@@ -72,5 +75,10 @@ async void OnPaste()
                 FieldValue = text;
             }
         }
+
+        async void OnCheck()
+        {
+            await DisplayAlertAsync($"Has text: {Clipboard.HasText}");
+        }
     }
 }

Xamarin.Essentials/Clipboard/Clipboard.android.cs

@@ -17,7 +17,7 @@ static Task PlatformSetTextAsync(string text)
         }
 
         static bool PlatformHasText
-            => Platform.ClipboardManager.HasPrimaryClip;
+            => Platform.ClipboardManager.HasPrimaryClip && !string.IsNullOrEmpty(Platform.ClipboardManager.PrimaryClip?.GetItemAt(0)?.Text);
 
         static Task<string> PlatformGetTextAsync()
             => Task.FromResult(Platform.ClipboardManager.PrimaryClip?.GetItemAt(0)?.Text);

Xamarin.Essentials/Clipboard/Clipboard.ios.cs

@@ -16,7 +16,7 @@ static Task PlatformSetTextAsync(string text)
         static NSObject observer;
 
         static bool PlatformHasText
-            => UIPasteboard.General.HasStrings;
+            => UIPasteboard.General.HasStrings && !string.IsNullOrEmpty(UIPasteboard.General.String);
 
         static Task<string> PlatformGetTextAsync()
             => Task.FromResult(UIPasteboard.General.String);

Xamarin.Essentials/Clipboard/Clipboard.macos.cs

@@ -22,7 +22,7 @@ static Task PlatformSetTextAsync(string text)
         }
 
         static bool PlatformHasText =>
-            GetPasteboardText() != null;
+            !string.IsNullOrEmpty(GetPasteboardText());
 
         static Task<string> PlatformGetTextAsync()
             => Task.FromResult(GetPasteboardText());