windows phone 8.1开发:文件选择器FileSavePicker

上一篇文章小梦分享了文件选择器FileOpenPicker的用法,这篇文章我们继续分享FileSavePicker的用法,FileSavePicker的用法几乎和FileOpenPicker用法一模一样.唯一的区别就是在FileOpenPicker中是通过FileTypeFilter属性添家字符串元素的,但是在FileSavePicker中是向FileTypeChoices属性表示的集合中添加元素的.FileTypeChoices是字典类型,因此它的每一个元素都必须具有唯一的键名,对应的值是IList<string>类型.

下面我们通过将textbox的内容存入一个txt文件来说明FileSavePicker的用法,过程和FileOpenPicker用法是一样的.

就把代码依次贴出来了:

   private void saveButton_Click(object sender, RoutedEventArgs e)
        {
            FileSavePicker savePicker = new FileSavePicker();

            savePicker.FileTypeChoices.Add("TXT", new List<string>() { ".txt" });

            savePicker.SuggestedFileName = "小梦";
            savePicker.ContinuationData["Operation"] = "Save";
            savePicker.PickSaveFileAndContinue();
        }

protected override void OnActivated(IActivatedEventArgs args)
        {
                if (args is FileSavePickerContinuationEventArgs)
            {
                Frame rootFrame = Window.Current.Content as Frame;
                if (!rootFrame.Navigate(typeof(MainPage)))
                {
                    throw new Exception("Failed to create target page");
                }

                var s = rootFrame.Content as MainPage;
                s.SavePickerArgs = (FileSavePickerContinuationEventArgs)args;

            }
            Window.Current.Activate();
        }

private FileSavePickerContinuationEventArgs savePickerArgs;
        public FileSavePickerContinuationEventArgs SavePickerArgs
        {
            get { return savePickerArgs; }
            set
            {
                savePickerArgs = value;
                ContinuFileSavePicker(savePickerArgs);
            }
        }

        private async void ContinuFileSavePicker(FileSavePickerContinuationEventArgs args)
        {
            if (args.ContinuationData["Operation"] as string == "Save" && args.File != null)
            {
                StorageFile txtFile = args.File;

              await   FileIO.WriteTextAsync(txtFile, this.text.Text.ToString(), Windows.Storage.Streams.UnicodeEncoding.Utf8);

            }

        }