[WorkingWithFiles] fix #33057

Author: Rustam Zaitov

WorkingWithFiles/PCL/Android/SaveAndLoad_Android.cs

@@ -15,29 +15,29 @@ public class SaveAndLoad_Android : ISaveAndLoad
 
 		public async Task SaveTextAsync (string filename, string text)
 		{
-			var docsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
-			var path = Path.Combine(docsPath, filename);
-
-			using (StreamWriter sw = File.CreateText(path))
-			{
+			var path = CreatePathToFile (filename);
+			using (StreamWriter sw = File.CreateText (path))
 				await sw.WriteAsync(text);
-			}
 		}
 
 		public async Task<string> LoadTextAsync (string filename)
 		{
-			string text;
-			var docsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
-			var path = Path.Combine(docsPath, filename);
-
+			var path = CreatePathToFile (filename);
 			using (StreamReader sr = File.OpenText(path))
-			{
-				text = await sr.ReadToEndAsync();
-			}
-			return text;
+				return await sr.ReadToEndAsync();
+		}
+
+		public bool FileExists (string filename)
+		{
+			return File.Exists (CreatePathToFile (filename));
 		}
 
 		#endregion
-	}
-}
 
+		string CreatePathToFile (string filename)
+		{
+			var docsPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
+			return Path.Combine(docsPath, filename);
+		}
+	}
+}

WorkingWithFiles/PCL/WorkingWithFiles/ISaveAndLoad.cs

@@ -14,6 +14,7 @@ public interface ISaveAndLoad
 	{
 		Task SaveTextAsync (string filename, string text);
 		Task<string> LoadTextAsync (string filename);
+		bool FileExists (string filename);
 	}
 }
 

WorkingWithFiles/PCL/WorkingWithFiles/SaveAndLoadText.cs

@@ -11,10 +11,13 @@ namespace WorkingWithFiles
 	/// </summary>
 	public class SaveAndLoadText : ContentPage
 	{
+		const string fileName = "temp.txt";
 		Button loadButton, saveButton;
 
 		public SaveAndLoadText ()
 		{
+			var fileService = DependencyService.Get<ISaveAndLoad> ();
+
 			var input = new Entry { Text = "" };
 			var output = new Label { Text = "" };
 			saveButton = new Button {Text = "Save"};
@@ -23,8 +26,8 @@ public SaveAndLoadText ()
 				loadButton.IsEnabled = saveButton.IsEnabled = false;
 				// uses the Interface defined in this project, and the implementations that must
 				// be written in the iOS, Android and WinPhone app projects to do the actual file manipulation
-				await DependencyService.Get<ISaveAndLoad>().SaveTextAsync("temp.txt", input.Text);
 
+				await fileService.SaveTextAsync (fileName, input.Text);
 				loadButton.IsEnabled = saveButton.IsEnabled = true;
 			};
 
@@ -34,9 +37,10 @@ public SaveAndLoadText ()
 
 				// uses the Interface defined in this project, and the implementations that must
 				// be written in the iOS, Android and WinPhone app projects to do the actual file manipulation
-				output.Text = await DependencyService.Get<ISaveAndLoad>().LoadTextAsync("temp.txt");
+				output.Text = await fileService.LoadTextAsync(fileName);
 				loadButton.IsEnabled = saveButton.IsEnabled = true;
 			};
+			loadButton.IsEnabled = fileService.FileExists (fileName);
 
 			var buttonLayout = new StackLayout {
 				Orientation = StackOrientation.Horizontal,

WorkingWithFiles/PCL/iOS/SaveAndLoad_iOS.cs

@@ -24,28 +24,28 @@ public static string DocumentsPath {
 
 		public async Task SaveTextAsync (string filename, string text)
 		{
-			string path = BuildPathForDocumentsDir (filename);
+			string path = CreatePathToFile (filename);
 			using (StreamWriter sw = File.CreateText(path))
-			{
 				await sw.WriteAsync(text);
-			}
 		}
 
 		public async Task<string> LoadTextAsync (string filename)
 		{
-			string path = BuildPathForDocumentsDir (filename);
+			string path = CreatePathToFile (filename);
 			using (StreamReader sr = File.OpenText(path))
-			{
 				return await sr.ReadToEndAsync();
-			}
+		}
+
+		public bool FileExists (string filename)
+		{
+			return File.Exists (CreatePathToFile (filename));
 		}
 
 		#endregion
 
-		static string BuildPathForDocumentsDir(string fileName)
+		static string CreatePathToFile(string fileName)
 		{
 			return Path.Combine (DocumentsPath, fileName);
 		}
 	}
-}
-
+}