Add camera characteristics checker

Those classes consist of 1 abstract class, which provide a factory for
2 classes each of which implements different behaviors according to
the Android API version.

app/src/main/java/org/fdroid/fdroid/views/swap/device/camera/CameraCharacteristicsChecker.java

@@ -0,0 +1,20 @@
+package org.fdroid.fdroid.views.swap.device.camera;
+
+import android.content.Context;
+
+public abstract class CameraCharacteristicsChecker {
+    public static CameraCharacteristicsChecker getInstance(final Context context) {
+        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
+            return new CameraCharacteristicsMinApiLevel21(context);
+        } else
+            return new CameraCharacteristicsMaxApiLevel20();
+    }
+
+    public abstract boolean hasAutofocus();
+
+    class FDroidDeviceException extends Exception {
+        FDroidDeviceException(final String message, final Throwable cause) {
+            super(message, cause);
+        }
+    }
+}

app/src/main/java/org/fdroid/fdroid/views/swap/device/camera/CameraCharacteristicsMaxApiLevel20.java

@@ -0,0 +1,50 @@
+package org.fdroid.fdroid.views.swap.device.camera;
+
+import android.hardware.Camera;
+import android.util.Log;
+
+import java.util.List;
+
+public class CameraCharacteristicsMaxApiLevel20 extends CameraCharacteristicsChecker {
+
+    private static final String TAG = "CameraCharMaxApiLevel20";
+
+    protected CameraCharacteristicsMaxApiLevel20() {
+    }
+
+    @Override
+    public boolean hasAutofocus() {
+        boolean hasAutofocus = false;
+        try {
+            hasAutofocus = hasDeviceAutofocusCapability();
+        } catch (FDroidDeviceException e) {
+            Log.e(TAG, e.getMessage(), e);
+        }
+        return hasAutofocus;
+    }
+
+    private boolean hasDeviceAutofocusCapability() throws FDroidDeviceException {
+        try {
+            final int numberOfCameras = Camera.getNumberOfCameras();
+            if (numberOfCameras == 0) {
+                Log.i(TAG, "No camera on device");
+                return false;
+            }
+
+            boolean hasAutofocus = false;
+            for (int cameraId = 0; cameraId < numberOfCameras; cameraId++) {
+                Camera camera = Camera.open(cameraId);
+                Camera.Parameters parameters = camera.getParameters();
+                List<String> availableAFModes = parameters.getSupportedFocusModes();
+                hasAutofocus = availableAFModes.contains(Camera.Parameters.FOCUS_MODE_AUTO);
+            }
+
+            return hasAutofocus;
+        } catch (Exception e) {
+            String msg = "Exception accessing device camera";
+            Log.e(TAG, msg, e);
+            throw new FDroidDeviceException(msg, e);
+        }
+    }
+
+}

app/src/main/java/org/fdroid/fdroid/views/swap/device/camera/CameraCharacteristicsMinApiLevel21.java

@@ -0,0 +1,112 @@
+package org.fdroid.fdroid.views.swap.device.camera;
+
+import android.annotation.TargetApi;
+import android.content.Context;
+import android.hardware.camera2.CameraAccessException;
+import android.hardware.camera2.CameraCharacteristics;
+import android.hardware.camera2.CameraManager;
+import android.os.Build;
+import android.support.annotation.NonNull;
+import android.util.Log;
+
+@TargetApi(Build.VERSION_CODES.LOLLIPOP)
+public class CameraCharacteristicsMinApiLevel21 extends CameraCharacteristicsChecker {
+
+    private static final String TAG = "CameraCharMinApiLevel21";
+    final private CameraManager cameraManager;
+
+
+    protected CameraCharacteristicsMinApiLevel21(final Context context) {
+        this.cameraManager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
+    }
+
+    @Override
+    public boolean hasAutofocus() {
+        boolean hasAutofocus = false;
+        try {
+            hasAutofocus = hasDeviceAutofocus();
+        } catch (FDroidDeviceException e) {
+            Log.e(TAG, e.getMessage(), e);
+        }
+        return hasAutofocus;
+    }
+
+    private boolean hasDeviceAutofocus() throws FDroidDeviceException {
+        try {
+            boolean deviceHasAutofocus = false;
+            final String[] cameraIdList = getCameraIdList();
+
+            for (final String cameraId : cameraIdList) {
+                if (isLensFacingBack(cameraId)) {
+                    deviceHasAutofocus = testAutofocusModeForCamera(cameraId);
+                    break;
+                }
+            }
+            return deviceHasAutofocus;
+        } catch (Exception e) {
+            Log.e(TAG, e.getMessage(), e);
+            throw new FDroidDeviceException("Exception accessing the camera list", e);
+        }
+
+    }
+
+    @NonNull
+    private String[] getCameraIdList() throws FDroidDeviceException {
+        try {
+            return cameraManager.getCameraIdList();
+        } catch (CameraAccessException e) {
+            Log.e(TAG, e.getMessage(), e);
+            throw new FDroidDeviceException("Exception accessing the camera list", e);
+        }
+    }
+
+    private boolean isLensFacingBack(final String cameraId) throws FDroidDeviceException {
+        final Integer lensFacing = getCameraCharacteristics(cameraId).get(CameraCharacteristics.LENS_FACING);
+
+        return lensFacing != null && lensFacing == CameraCharacteristics.LENS_FACING_BACK;
+    }
+
+    @NonNull
+    private CameraCharacteristics getCameraCharacteristics(final String cameraId) throws FDroidDeviceException {
+        try {
+            return cameraManager.getCameraCharacteristics(cameraId);
+        } catch (CameraAccessException e) {
+            Log.e(TAG, e.getMessage(), e);
+            throw new FDroidDeviceException("Exception accessing the camera id = " + cameraId, e);
+        }
+
+    }
+
+    private boolean testAutofocusModeForCamera(final String cameraId) throws FDroidDeviceException {
+        try {
+            boolean hasAutofocusMode = false;
+            final int[] autoFocusModes = getAvailableAFModes(cameraId);
+            if (autoFocusModes != null) {
+                hasAutofocusMode = testAvailableMode(autoFocusModes);
+            }
+
+            return hasAutofocusMode;
+        } catch (FDroidDeviceException e) {
+            Log.e(TAG, e.getMessage(), e);
+            throw new FDroidDeviceException("Exception accessing the camera id = " + cameraId, e);
+        }
+    }
+
+    private int[] getAvailableAFModes(final String cameraId) throws FDroidDeviceException {
+        return getCameraCharacteristics(cameraId).get(CameraCharacteristics.CONTROL_AF_AVAILABLE_MODES);
+    }
+
+    private boolean testAvailableMode(final int[] autoFocusModes) {
+        boolean hasAutofocusMode = false;
+        for (final int mode : autoFocusModes) {
+            boolean afMode = isAutofocus(mode);
+            hasAutofocusMode |= afMode;
+        }
+        return hasAutofocusMode;
+    }
+
+    private boolean isAutofocus(final int mode) {
+        return mode != android.hardware.camera2.CameraMetadata.CONTROL_AF_MODE_OFF;
+    }
+
+}