Try out hacky support for enabling the front light on some devices

git-svn-id: https://zxing.googlecode.com/svn/trunk@1223 59b500cc-1b3d-0410-9834-0bbf25fbcc57

android/src/com/google/zxing/client/android/CameraManager.java

@@ -154,6 +154,7 @@ final class CameraManager {
       }
 
       setCameraParameters();
+      FlashlightManager.enableFlashlight();
     }
   }
 
@@ -162,6 +163,7 @@ final class CameraManager {
    */
   public void closeDriver() {
     if (camera != null) {
+      FlashlightManager.disableFlashlight();
       camera.release();
       camera = null;
     }

android/src/com/google/zxing/client/android/FlashlightManager.java

@@ -0,0 +1,145 @@
+/*
+ * Copyright (C) 2010 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.client.android;
+
+import android.os.IBinder;
+import android.util.Log;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
+/**
+ * This class is used to activate the weak light on some camera phones (not flash)
+ * in order to illuminate surfaces for scanning. There is no official way to do this,
+ * but, classes which allow access to this function still exist on some devices.
+ * This therefore proceeds through a great deal of reflection.
+ *
+ * See <a href="http://almondmendoza.com/2009/01/05/changing-the-screen-brightness-programatically/">
+ * http://almondmendoza.com/2009/01/05/changing-the-screen-brightness-programatically/</a> and
+ * <a href="http://code.google.com/p/droidled/source/browse/trunk/src/com/droidled/demo/DroidLED.java">
+ * http://code.google.com/p/droidled/source/browse/trunk/src/com/droidled/demo/DroidLED.java</a>.
+ */
+final class FlashlightManager {
+
+  private static final String TAG = FlashlightManager.class.getName();
+
+  private static Object iHardwareService;
+  private static Method setFlashEnabledMethod;
+  static {
+    iHardwareService = getHardwareService();
+    setFlashEnabledMethod = getSetFlashEnabledMethod(iHardwareService);
+    if (iHardwareService == null) {
+      Log.i(TAG, "This device does supports control of a flashlight");
+    } else {
+      Log.i(TAG, "This device does not support control of a flashlight");
+    }
+  }
+
+  private FlashlightManager() {
+  }
+
+  private static Object getHardwareService() {
+    Class<?> serviceManagerClass = maybeForName("android.os.ServiceManager");
+    if (serviceManagerClass == null) {
+      return null;
+    }
+
+    Method getServiceMethod = maybeGetMethod(serviceManagerClass, "getService", String.class);
+    if (getServiceMethod == null) {
+      return null;
+    }
+
+    Object hardwareService = invoke(getServiceMethod, null, "hardware");
+    if (hardwareService == null) {
+      return null;
+    }
+
+    Class<?> iHardwareServiceStubClass = maybeForName("android.os.IHardwareService$Stub");
+    if (iHardwareServiceStubClass == null) {
+      return null;
+    }
+
+    Method asInterfaceMethod = maybeGetMethod(iHardwareServiceStubClass, "asInterface", IBinder.class);
+    if (asInterfaceMethod == null) {
+      return null;
+    }
+
+    return invoke(asInterfaceMethod, null, hardwareService);
+  }
+
+  private static Method getSetFlashEnabledMethod(Object iHardwareService) {
+    if (iHardwareService == null) {
+      return null;
+    }
+    Class<?> proxyClass = iHardwareService.getClass();
+    return maybeGetMethod(proxyClass, "setFlashlightEnabled", boolean.class);
+  }
+
+  private static Class<?> maybeForName(String name) {
+    try {
+      return Class.forName(name);
+    } catch (ClassNotFoundException cnfe) {
+      // OK
+      return null;
+    } catch (RuntimeException re) {
+      Log.w(TAG, "Unexpected error while finding class " + name, re);
+      return null;
+    }
+  }
+
+  private static Method maybeGetMethod(Class<?> clazz, String name, Class<?>... argClasses) {
+    try {
+      return clazz.getMethod(name, argClasses);
+    } catch (NoSuchMethodException nsme) {
+      // OK
+      return null;
+    } catch (RuntimeException re) {
+      Log.w(TAG, "Unexpected error while finding method " + name, re);
+      return null;
+    }
+  }
+
+  private static Object invoke(Method method, Object instance, Object... args) {
+    try {
+      return method.invoke(instance, args);
+    } catch (IllegalAccessException e) {
+      Log.w(TAG, "Unexpected error while invoking " + method, e);
+      return null;
+    } catch (InvocationTargetException e) {
+      Log.w(TAG, "Unexpected error while invoking " + method, e.getCause());
+      return null;
+    } catch (RuntimeException re) {
+      Log.w(TAG, "Unexpected error while invoking " + method, re);
+      return null;
+    }
+  }
+
+  static void enableFlashlight() {
+    setFlashlight(true);
+  }
+
+  static void disableFlashlight() {
+    setFlashlight(false);
+  }
+
+  private static void setFlashlight(boolean active) {
+    if (iHardwareService != null) {
+      invoke(setFlashEnabledMethod, iHardwareService, active);
+    }
+  }
+
+}