小賢的部落格

結論：

[UWP] 在進入背景或進入前景時，觸發OnNavigatedTo, OnNavigatedFrom。

　　每個Page都會有自己的進入頁面跟離開頁面的邏輯，有時會希望App進入背景 or 進入前景時也能夠呼叫到目前頁面的 OnNavigatedTo, OnNavigatedFrom，但預設是不會被呼叫的，

Package.appxmanifest:

<Package xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"

參考資料：

https://www.youtube.com/watch?v=vuGSkrx8fuo

        private const string strKey = "Key";
        private const string strIV = "IV";

        public static string Encrypt(string message) 
        {
            if (string.IsNullOrEmpty(message))
            {
                return string.Empty;
            }

            var keyBuffer = CryptographicBuffer.ConvertStringToBinary(strKey, BinaryStringEncoding.Utf8);
            var ivBuffer = CryptographicBuffer.ConvertStringToBinary(strIV, BinaryStringEncoding.Utf8);
            var messageBuffer = CryptographicBuffer.ConvertStringToBinary(message, BinaryStringEncoding.Utf8);

            var provider = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.DesCbcPkcs7);
            var key = provider.CreateSymmetricKey(keyBuffer);
            var buffEncrypt = CryptographicEngine.Encrypt(key, messageBuffer, ivBuffer);

            return CryptographicBuffer.EncodeToBase64String(buffEncrypt);
        }

        public static string Decrypt(string encryptedBase64String)
        {
            if (string.IsNullOrEmpty(encryptedBase64String))
            {
                return string.Empty;
            }

            var buffer = CryptographicBuffer.ConvertStringToBinary(strKey, BinaryStringEncoding.Utf8);
            var ivBuffer = CryptographicBuffer.ConvertStringToBinary(strIV, BinaryStringEncoding.Utf8);

            var provider = SymmetricKeyAlgorithmProvider.OpenAlgorithm(SymmetricAlgorithmNames.DesCbcPkcs7);
            var keyBuffer = provider.CreateSymmetricKey(buffer);
            
            var decryptedBuffer = CryptographicEngine.Decrypt(keyBuffer, CryptographicBuffer.DecodeFromBase64String(encryptedBase64String), ivBuffer);
            return CryptographicBuffer.ConvertBinaryToString(BinaryStringEncoding.Utf8, decryptedBuffer);
        }

    public partial class TakePhotoPage
    {
        private MediaCapture _mediaCapture;
        private bool _isPreviewing;
        private DisplayRequest _displayRequest;

        private async Task StartPreviewAsync()
        {
            try
            {
                _mediaCapture = new MediaCapture();
                await _mediaCapture.InitializeAsync();

                PreviewControl.Source = _mediaCapture;
                await _mediaCapture.StartPreviewAsync();
                _isPreviewing = true;

                _displayRequest = new DisplayRequest();
                _displayRequest.RequestActive();
                DisplayInformation.AutoRotationPreferences = DisplayOrientations.PortraitFlipped;

                // 解決手機上的旋轉問題
                SimpleOrientationSensor sensor = SimpleOrientationSensor.GetDefault();
                if (sensor == null)
                {
                    return;
                }

                sensor.OrientationChanged += (s, arg) =>
                {
                    switch (arg.Orientation)
                    {
                        case SimpleOrientation.Rotated90DegreesCounterclockwise:
                            _mediaCapture.SetPreviewRotation(VideoRotation.None);
                            break;
                        case SimpleOrientation.Rotated180DegreesCounterclockwise:
                        case SimpleOrientation.Rotated270DegreesCounterclockwise:
                            _mediaCapture.SetPreviewRotation(VideoRotation.Clockwise180Degrees);
                            break;
                        default:
                            _mediaCapture.SetPreviewRotation(VideoRotation.Clockwise90Degrees);
                            break;
                    }
                };

            }
            catch (UnauthorizedAccessException)
            {
                // This will be thrown if the user denied access to the camera in privacy settings
                var messageDialog = new MessageDialog("The app was denied access to the camera");
                await messageDialog.ShowAsync();
            }
            catch (Exception ex)
            {
                var messageDialog = new MessageDialog("MediaCapture initialization failed. {0}", ex.Message);
                await messageDialog.ShowAsync();
            }
        }

        private async Task CleanupCameraAsync()
        {
            if (_mediaCapture == null)
            {
                return;
            }

            if (_isPreviewing)
            {
                await _mediaCapture.StopPreviewAsync();
            }

            await Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                PreviewControl.Source = null;

                if (_displayRequest == null)
                {
                    return;
                }

                _displayRequest.RequestRelease();
            });

            _mediaCapture.Dispose();
            _mediaCapture = null;

        }

    }

1.在OnNavigateTo 裡，設定是否顯示Back Button

SystemNavigationManager.GetForCurrentView().AppViewBackButtonVisibility = frame.CanGoBack ? AppViewBackButtonVisibility.Visible : AppViewBackButtonVisibility.Collapsed;

假如想根據不同螢幕寬度來變更GridViewItem的大小，可用Adaptive Trigger 搭配Multi Style 的方式

客製化StateTriggerBase ，實現類似WinRT 8.1 的Behavior SDK DataTrigger

1.加一個判斷用的bool flag

2.在 PointerPressed 中

目前找到暫時性的解法是使用:FallbackValue

http://blog.spinthemoose.com/2013/03/24/disable-the-xaml-designer-in-visual-studio/

　　Object reference not set to an instance of an object.

　　找了很久，再一層一層過濾後發現是DataTemplate 內的 因為在DataTemplate內找不到ViewModel， 將ViewModel中的ButtonClick寫在Collection Type 的Class 內即可..

　　今天使用x:Bind(Compiled Binding) 的時候遇到 無法將類型 'Microsoft.MetadataReader.MetadataOnlyPropertyInfo' 的物件轉換為類型 'System.Reflection.MethodInfo'，

　　與Richie經過一番討論後，忽然發現問題是除了自己以外，Base也有一個"同名"的Property，所以修改方法是換一個變數名稱即可。

處理方式:

1.[Delete] ListViewItemTextBlockStyle

VS2015RC with Win10Mobile ，按F5後出現，

錯誤 錯誤 : DEP4100 : 無法建立資料夾 "D:\WPSystem\SharedData\PhoneTools\AppxLayouts\xxx"。

App樣式:

1.Pivots

Win10 for developer mode 進不去解法