Application preferences

Many applications require to save data in the persistent memory and read them in next session in a safe way. Saved data can be sensitive, so in many cases access to the saved preference should be restricted. Preference API allows you to share stored preference data among applications in the same package.

Store and retrieve records

To store a variable, you must create a key-value pair. Use the following function to create a preference for a specific simple type: Preference.Set(string key, value).

Before storing or retrieving a variable, check whether it exists using the Preference.Contains(string key) function. Use the following function to retrieve a stored variable: Preference.Get<T>().

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//set/get integer value Preference.Set("test_integer", 10); if (Preference.Contains("test_integer")) { var testInt = Preference.Get<int>("test_integer"); }

To store and retrieve string variables, use the following functions:

  • Preference.Set("test_string", "TEST VALUE")
  • Preference.Get<string>("test_string")

List records

To list all records, use Keys collection: Preference.Keys()

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Preference.Set("Option_enabled", true); Preference.Set("active_user", "Joe"); Preference.Set("default_volume", 10); Preference.Set("brightness", "0.6"); foreach(string key in Preference.Keys) { Tizen.Log.Info("TEST", string.Format("Key name: {0}", key)); }

Remove records

To safely remove record, use: Preference.Remove(string key);

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if (Preference.Contains("key")) { Preference.Remove("key"); }

To remove all records, use:

  • Preference.RemoveAll()

Managing application preferences

Following code snippet shows how to store counter value, when application is closed using Tizen.Applications.Preference module.

Figure: Preference Application Screenshot

Screenshot

Clicked counter is stored as a pair of key - value data. When the application starts it tries to read this value and inserts it in the label component. To use NUI components and Preference module following namespaces are included:

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using System; using Tizen.NUI; using Tizen.NUI.BaseComponents; using Tizen.NUI.Components; using Tizen.Applications;

The ClickedPreferenceKey key is used to store counter value. Declared as a class member to use it in buttons callbacks. Also the TextLabel have to be a class member to show and update counter value:

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namespace NUIPreference { class Program : NUIApplication { private readonly string LogTag = "NUI_Application"; private readonly string ClickedPreferenceKey = "clicked_counter"; private int ClickedCounter = 0; private TextLabel ResultViewer; //... } }

The OnCreate() handler tries to read value from the Preference module. Try / Catch block is useful when ClickedPreferenceKey is not set previously:

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protected override void OnCreate() { base.OnCreate(); try { ClickedCounter = Preference.Get<int>(ClickedPreferenceKey); } catch (Exception e) { Tizen.Log.Error(LogTag, e.ToString()); } Initialize(); }

In OnTerminate() method you can save key - value pairs:

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protected override void OnTerminate() { Preference.Set(ClickedPreferenceKey, ClickedCounter); base.OnTerminate(); }

The CreateButtons() method is a helper function. It is responsible for:

  • creating buttons layout,
  • creating buttons,
  • setup callbacks.
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private View CreateButtons() { View buttonsContainer = new View() { WidthResizePolicy = ResizePolicyType.FillToParent, HeightResizePolicy = ResizePolicyType.FitToChildren, Layout = new LinearLayout() { LinearAlignment = LinearLayout.Alignment.CenterHorizontal, LinearOrientation = LinearLayout.Orientation.Horizontal } }; var btnSize = new Size2D(220, 80); var addButton = new Button() { Size2D = btnSize, Text = "+" }; var decButton = new Button() { Size2D = btnSize, Text = "-" }; var saveButton = new Button() { Size2D = btnSize, Text = "Save" }; var removeButton = new Button() { Size2D = btnSize, Text = "Remove" }; addButton.Clicked += OnAddClicked; decButton.Clicked += OnDecClicked; saveButton.Clicked += OnSaveClicked; removeButton.Clicked += OnRemoveClicked; buttonsContainer.Add(addButton); buttonsContainer.Add(decButton); buttonsContainer.Add(saveButton); buttonsContainer.Add(removeButton); return buttonsContainer; }

The Initialize() function creates application layout and components:

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void Initialize() { Window.Instance.KeyEvent += OnKeyEvent; View rootView = new View() { BackgroundColor = Color.White, WidthResizePolicy = ResizePolicyType.FillToParent, HeightResizePolicy = ResizePolicyType.FillToParent, Layout = new LinearLayout() { CellPadding = new Size2D(30, 30), Padding = new Extents(30, 30, 30, 30), LinearAlignment = LinearLayout.Alignment.Top, LinearOrientation = LinearLayout.Orientation.Vertical } }; var buttonsContainer = CreateButtons(); rootView.Add(buttonsContainer); ResultViewer = new TextLabel() { Text = string.Format("Current Counter: {0}", ClickedCounter) }; rootView.Add(ResultViewer); Window.Instance.GetDefaultLayer().Add(rootView); }

The OnAddClicked() handler increase the counter and update the result label value:

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public void OnAddClicked(object sender, ClickedEventArgs e) { ClickedCounter++; ResultViewer.Text = string.Format("Current Counter: {0}", ClickedCounter); }

The OnDecClicked() handler decrease the counter and also update the label:

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public void OnDecClicked(object sender, ClickedEventArgs e) { ClickedCounter--; ResultViewer.Text = string.Format("Current Counter: {0}", ClickedCounter); }

The OnSaveClicked() handler saves the ClickedCounter value in the preference module:

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public void OnSaveClicked(object sender, ClickedEventArgs e) { Preference.Set(ClickedPreferenceKey, ClickedCounter); }

The OnRemoveClicked() handler resets ClickedCounter value and removes it from the Preference module:

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public void OnRemoveClicked(object sender, ClickedEventArgs e) { try { Preference.Remove(ClickedPreferenceKey); } catch (Exception error) { Tizen.Log.Error(LogTag, error.ToString()); } ClickedCounter = 0; ResultViewer.Text = string.Format("Current Counter: {0}", ClickedCounter); }

Application entry point:

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static void Main(string[] args) { var app = new Program(); app.Run(args); }
  • Dependencies
    • Tizen 2.4 and Higher
Application Launcher
Next Component Manager
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