问题：XE8 for Android 方向传感器无法正常运作（在 XE7 是正常的）
测试：官方示例 Samples\Object Pascal\Mobile Snippets\OrientationSensor\
适用：XE8 for Android
修复方法：
请将源码 System.Android.Sensors.pas 复制到自己的工程目录里，再进行修改。
修改下面代码：
TAndroidNativeMagneticSensor = class(TCustomOrientationSensor) strict private FNativeSensor: TNativeSensor; protected function GetUpdateInterval: Double; override; procedure SetUpdateInterval(AInterval: Double); override; function GetOrientationSensorType: TOrientationSensorType; override;{+++>} // 加入下面二行代码 function DoStart: Boolean; override; procedure DoStop; override;{<+++} function GetSensorCategory: TSensorCategory; override; function GetState: TSensorState; override; function GetTimeStamp: TDateTime; override; function GetAvailableProperties: TCustomOrientationSensor.TProperties; override; function GetDoubleProperty(Prop: TCustomOrientationSensor.TProperty): Double; override; public constructor Create(AManager: TSensorManager); override; function Supported: Boolean; end;
找到 TAndroidNativeMagneticSensor.Create 加入下面代码：
... 略 ...constructor TAndroidNativeMagneticSensor.Create(AManager: TSensorManager);begin inherited; FNativeSensor := TNativeSensor.Create(ASENSOR_TYPE_MAGNETIC_FIELD);end;{+++>} // 加入下面代码function TAndroidNativeMagneticSensor.DoStart: Boolean;begin Result := FNativeSensor.DoStart;end;procedure TAndroidNativeMagneticSensor.DoStop;begin inherited; FNativeSensor.DoStop;end;{<+++} // 加入上面代码 ... 略 ...