mvvmcross keep program settings using file plugin and json serialize/deserialize - json

Question

I'm trying to use the fileplugin and json serializer to do this.
I have the following DcsSetup class, in the core project.
For now I'm working with droid. I can't seem to save the file. The json serialize is ok. The WriteFile seems ok, but next time I try to read the file using TryReadTextFile it fails.
I can't find the file on the device, so I think the WriteFile stuff is wrong.
What is the correct way to save and read my Settings class on Android?
public class DcsSetup
{
public class Settings
{
//Server
public string Server;
public int Port;
public int Device;
public string EncodingFromClient;
public string EncodingToClient;
public int FontCorrectionPixelsWidth; //Pixels to add or subtract i Y dimension to get the right font size
public int FontCorrectionPixelsHeight; //Pixels to add or subtract i Y dimension to get the right font size
public float XPct;//Pct to add to vertical placement of textBox and Buttons.
public float YPct;//Pct to add to horisontal placement of textBox and Buttons.
public float SizePct;//Pct to add to horisontal size of textBox and Buttons.
public bool FullScreen;
public bool DontSleep;
//Diverse
public bool AutoSendEnter;
}
public Settings Setting;
public DcsSetup()
{
var setupFound=true;
var fileService = Mvx.Resolve<IMvxFileStore>();
var jsonConvert = Mvx.Resolve<IMvxJsonConverter>();
var path = fileService.PathCombine("Setting", "Settings.txt");
Setting = new Settings();
try {
string settingFile;
if (fileService.TryReadTextFile(path, out settingFile)){
Setting = jsonConvert.DeserializeObject<Settings>(settingFile);
} else{
setupFound = false;
}
}
catch(Exception e) {
AppTrace.Error("Failed to read settings: {0}", e.Message);
setupFound=false;
}
if(setupFound==false){
Setting.Server = "192.168.1.100";
Setting.Port = 1650;
Setting.Device = 1;
Setting.EncodingFromClient = "CP1252";
Setting.EncodingToClient = "CP1252";
Setting.FontCorrectionPixelsWidth = 0;
Setting.FontCorrectionPixelsHeight = 0;
Setting.XPct = 97.0f;
Setting.YPct = 100.0f;
Setting.SizePct = 98.0f;
Setting.FullScreen = false;
Setting.DontSleep = true;
Setting.AutoSendEnter = true;
try {
//json
var json = jsonConvert.SerializeObject(Setting);
fileService.EnsureFolderExists("Setting");
fileService.WriteFile(path, json);
}
catch (Exception e) {
AppTrace.Error("Failed to save settings: {0}", e.Message);
}
}
}
}
}

Answer 1

I just created a project in VS2012 using the 3.1.1-beta2 packages for MvvmCross
I then added the File and Json plugin packages
I changed the core FirstViewModel to:
public class FirstViewModel
: MvxViewModel
{
private readonly IMvxFileStore _fileStore;
private readonly IMvxJsonConverter _jsonConverter;
private readonly string _filePath;
public class ToStore
{
public string Foo { get; set; }
}
public ICommand SaveCommand
{
get
{
return new MvxCommand(() =>
{
var toStore = new ToStore() {Foo = Hello};
var json = _jsonConverter.SerializeObject(toStore);
_fileStore.WriteFile(_filePath, json);
});
}
}
public ICommand LoadCommand
{
get
{
return new MvxCommand(() =>
{
string txt;
if (_fileStore.TryReadTextFile(_filePath, out txt))
{
Mvx.Trace("Loaded {0}", txt);
var stored = _jsonConverter.DeserializeObject<ToStore>(txt);
Hello = stored.Foo;
}
});
}
}
private string _hello = "Hello MvvmCross";
public FirstViewModel(IMvxFileStore fileStore, IMvxJsonConverter jsonConverter)
{
_fileStore = fileStore;
_jsonConverter = jsonConverter;
_filePath = _fileStore.PathCombine("SubDir", "MyFile.txt");
_fileStore.EnsureFolderExists("SubDir");
}
public string Hello
{
get { return _hello; }
set { _hello = value; RaisePropertyChanged(() => Hello); }
}
}
I called this from a test Android UI:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:local="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<EditText
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="40dp"
local:MvxBind="Text Hello"
/>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="40dp"
local:MvxBind="Text Hello"
/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="40dp"
android:text="Load"
local:MvxBind="Click LoadCommand"
/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textSize="40dp"
android:text="Save"
local:MvxBind="Click SaveCommand"
/>
</LinearLayout>
This seemed to work OK - it saved and loaded the JSON fine within and between test runs.
Based on this, my only guess is whether you are redeploying the app between runs - if you do this and you don't have MonoDroid's Preserve application data/cache on device between deploys checked, then you won't see the settings preserved.