diff options
Diffstat (limited to 'Xamarin.Forms.Pages/DataSourceBinding.cs')
| -rw-r--r-- | Xamarin.Forms.Pages/DataSourceBinding.cs | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/Xamarin.Forms.Pages/DataSourceBinding.cs b/Xamarin.Forms.Pages/DataSourceBinding.cs new file mode 100644 index 00000000..44af47b4 --- /dev/null +++ b/Xamarin.Forms.Pages/DataSourceBinding.cs @@ -0,0 +1,157 @@ +using System; +using System.Globalization; +using System.Threading.Tasks; + +namespace Xamarin.Forms.Pages +{ + public class DataSourceBinding : BindingBase + { + internal const string SelfPath = "."; + IValueConverter _converter; + object _converterParameter; + WeakReference _dataSourceRef; + + BindingExpression _expression; + string _path; + + public DataSourceBinding() + { + } + + public DataSourceBinding(string path, BindingMode mode = BindingMode.Default, IValueConverter converter = null, object converterParameter = null, string stringFormat = null) + { + if (path == null) + throw new ArgumentNullException(nameof(path)); + if (string.IsNullOrWhiteSpace(path)) + throw new ArgumentException("path can not be an empty string", nameof(path)); + + AllowChaining = true; + Path = path; + Converter = converter; + ConverterParameter = converterParameter; + Mode = mode; + StringFormat = stringFormat; + } + + public IValueConverter Converter + { + get { return _converter; } + set + { + ThrowIfApplied(); + + _converter = value; + } + } + + public object ConverterParameter + { + get { return _converterParameter; } + set + { + ThrowIfApplied(); + + _converterParameter = value; + } + } + + public string Path + { + get { return _path; } + set + { + ThrowIfApplied(); + + _path = value; + _expression = GetBindingExpression($"DataSource[{value}]"); + } + } + + internal override void Apply(bool fromTarget) + { + base.Apply(fromTarget); + + if (_expression == null) + _expression = new BindingExpression(this, SelfPath); + + _expression.Apply(fromTarget); + } + + internal override async void Apply(object newContext, BindableObject bindObj, BindableProperty targetProperty) + { + var view = bindObj as VisualElement; + if (view == null) + throw new InvalidOperationException(); + + base.Apply(newContext, bindObj, targetProperty); + + Element dataSourceParent = await FindDataSourceParentAsync(view); + + var dataSourceProviderer = (IDataSourceProvider)dataSourceParent; + if (dataSourceProviderer != null) + _dataSourceRef = new WeakReference(dataSourceProviderer); + + dataSourceProviderer?.MaskKey(_path); + ApplyInner(dataSourceParent, bindObj, targetProperty); + } + + internal override BindingBase Clone() + { + return new DataSourceBinding(Path, Mode) { Converter = Converter, ConverterParameter = ConverterParameter, StringFormat = StringFormat }; + } + + internal override object GetSourceValue(object value, Type targetPropertyType) + { + if (Converter != null) + value = Converter.Convert(value, targetPropertyType, ConverterParameter, CultureInfo.CurrentUICulture); + + return base.GetSourceValue(value, targetPropertyType); + } + + internal override object GetTargetValue(object value, Type sourcePropertyType) + { + if (Converter != null) + value = Converter.ConvertBack(value, sourcePropertyType, ConverterParameter, CultureInfo.CurrentUICulture); + + return base.GetTargetValue(value, sourcePropertyType); + } + + internal override void Unapply() + { + base.Unapply(); + + if (_dataSourceRef != null && _dataSourceRef.IsAlive) + { + var dataSourceProviderer = (IDataSourceProvider)_dataSourceRef.Target; + dataSourceProviderer?.UnmaskKey(_path); + } + + _expression?.Unapply(); + } + + void ApplyInner(Element templatedParent, BindableObject bindableObject, BindableProperty targetProperty) + { + if (_expression == null && templatedParent != null) + _expression = new BindingExpression(this, SelfPath); + + _expression?.Apply(templatedParent, bindableObject, targetProperty); + } + + static async Task<Element> FindDataSourceParentAsync(Element element) + { + while (!Application.IsApplicationOrNull(element)) + { + if (element is IDataSourceProvider) + return element; + element = await TemplateUtilities.GetRealParentAsync(element); + } + + return null; + } + + BindingExpression GetBindingExpression(string path) + { + return new BindingExpression(this, !string.IsNullOrWhiteSpace(path) ? path : SelfPath); + } + } +}
\ No newline at end of file |