Android P 指纹 Framework
从Android的官方API可以查到,向上层提供接口的是FingerprintManager,它的代码在路径frameworks/base/core/java/android/hardware/fingerprint下。
/** * A class that coordinates access to the fingerprint hardware. * @deprecated See {@link BiometricPrompt} which shows a system-provided dialog upon starting * authentication. In a world where devices may have different types of biometric authentication, * it's much more realistic to have a system-provided authentication dialog since the method may * vary by vendor/device. */@Deprecated@SystemService(Context.FINGERPRINT_SERVICE)@RequiresFeature(PackageManager.FEATURE_FINGERPRINT)public class FingerprintManager implements BiometricFingerprintConstants
frameworks/base/core/java/android/hardware/fingerprint目录下内容其实很少,一共只有几个文件。
这里除了FingerprintManager之外,就只有Fingerprint一个类了,其他都是aidl文件。
粗略的看了下Fingerprint类,它里面的内容超级少,主要是包含了几个成员变量,用来记录指纹的信息。
/** * Container for fingerprint metadata. * @hide */public final class Fingerprint extends BiometricAuthenticator.BiometricIdentifier { private CharSequence mName; private int mGroupId; private int mFingerId; private long mDeviceId; // physical device this is associated with public Fingerprint(CharSequence name, int groupId, int fingerId, long deviceId) { mName = name; mGroupId = groupId; mFingerId = fingerId; mDeviceId = deviceId; } //...}
如果仔细看代码的话,可以发现一个很神奇的东西,那个就Fingerprint类的所有成员都是private的,并且没有提供任何public的set方法!
这个就厉害了,因为有做过指纹部分的朋友一定记得指纹提供一个rename的接口。没有public的set方法,那它又是怎么实现rename接口的呢?
带着问题看源码!
rename方法在Manager中的实现如下:
/** * Renames the given fingerprint template * @param fpId the fingerprint id * @param userId the user who this fingerprint belongs to * @param newName the new name * * @hide */@RequiresPermission(MANAGE_FINGERPRINT)public void rename(int fpId, int userId, String newName) { // Renames the given fpId if (mService != null) { try { mService.rename(fpId, userId, newName); } catch (RemoteException e) { throw e.rethrowFromSystemServer(); } } else { Slog.w(TAG, "rename(): Service not connected!"); }}
这里先直接找到Manager的服务类:FingerprintService
指纹服务的相关代码在frameworks\base\services\core\java\com\android\server\fingerprint下。
/** * A service to manage multiple clients that want to access the fingerprint HAL API. * The service is responsible for maintaining a list of clients and dispatching all * fingerprint-related events. * * @hide */public class FingerprintService extends SystemService implements IHwBinder.DeathRecipient
看一下它里面的rename是在内部类FingerprintServiceWrapper中实现的,具体如下:
@Override // Binder callpublic void rename(final int fingerId, final int groupId, final String name) { checkPermission(MANAGE_FINGERPRINT); if (!isCurrentUserOrProfile(groupId)) { return; } mHandler.post(new Runnable() { @Override public void run() { mFingerprintUtils.renameFingerprintForUser(mContext, fingerId, groupId, name); } }}
找到同文件夹下FingerprintUtils类,这个是工具类,里面维护了一组FingerprintsUserState,具体得继续看FingerprintsUserState;
FingerprintsUserState中维护了一组Fingerprint,下面具体看下rename操作:
@GuardedBy("this")private final ArrayList mFingerprints = new ArrayList();//...public void renameFingerprint(int fingerId, CharSequence name) { synchronized (this) { for (int i = 0; i < mFingerprints.size(); i++) { if (mFingerprints.get(i).getFingerId() == fingerId) { Fingerprint old = mFingerprints.get(i); mFingerprints.set(i, new Fingerprint(name, old.getGroupId(), old.getFingerId(), old.getDeviceId())); scheduleWriteStateLocked(); break; } } }}
这里可以看到,在rename的实现时,代码直接霸气的new一个Fingerprint对象,然后覆盖List中对应id的对象。
OK,以上只是一个小小的流程。
下面看下FingerprintManager的主要API:
public void enroll(byte [] token, CancellationSignal cancel, int flags, int userId, EnrollmentCallback callback);public void remove(Fingerprint fp, int userId, RemovalCallback callback);public void rename(int fpId, int userId, String newName);public List getEnrolledFingerprints();//不是hide的方法public void authenticate(@Nullable CryptoObject crypto, @Nullable CancellationSignal cancel,int flags, @NonNull AuthenticationCallback callback, @Nullable Handler handler);public boolean hasEnrolledFingerprints();public boolean isHardwareDetected()
真正对三方开放的API只有最下面的三个,分别用来授权、判断是否录入过指纹、判断设备是否支持指纹器件。
这里面要特别提一下authenicate方法;
/** * Request authentication of a crypto object. This call warms up the fingerprint hardware * and starts scanning for a fingerprint. It terminates when * {@link AuthenticationCallback#onAuthenticationError(int, CharSequence)} or * {@link AuthenticationCallback#onAuthenticationSucceeded(AuthenticationResult)} is called, at * which point the object is no longer valid. The operation can be canceled by using the * provided cancel object. * * @param crypto object associated with the call or null if none required. * @param cancel an object that can be used to cancel authentication * @param flags optional flags; should be 0 * @param callback an object to receive authentication events * @param handler an optional handler to handle callback events * * @throws IllegalArgumentException if the crypto operation is not supported or is not backed * by Android Keystore * facility. * @throws IllegalStateException if the crypto primitive is not initialized. * @deprecated See {@link BiometricPrompt#authenticate(CancellationSignal, Executor, * BiometricPrompt.AuthenticationCallback)} and {@link BiometricPrompt#authenticate( * BiometricPrompt.CryptoObject, CancellationSignal, Executor, * BiometricPrompt.AuthenticationCallback)} */ @Deprecated @RequiresPermission(anyOf = {USE_BIOMETRIC, USE_FINGERPRINT}) public void authenticate(@Nullable CryptoObject crypto, @Nullable CancellationSignal cancel, int flags, @NonNull AuthenticationCallback callback, @Nullable Handler handler) { authenticate(crypto, cancel, flags, callback, handler, mContext.getUserId()); }
其中flags暂时没用起来,直接设置为0。
这里稍微讲下crypto objiect。它是的一个内部类。暂时支持三种类型对象。如下:
/** * A wrapper class for the crypto objects supported by FingerprintManager. Currently the * framework supports {@link Signature}, {@link Cipher} and {@link Mac} objects. * @deprecated See {@link android.hardware.biometrics.BiometricPrompt.CryptoObject} */
这个参数用于加密,保护指纹在使用过程中不被恶意软件截获和篡改。
Google的示例中用的是Cipher的加密对象。
需要结束监听的话,使用CancellationSignal对象的cancel方法即可。
上面提到过Manager里面的API具体实现都是Service中。
Manager中保存有Service的对象private IFingerprintService mService;
这对象看命名方式就可以大概猜到是个AIDL了;
/** * Communication channel from client to the fingerprint service. * @hide */interface IFingerprintService
它是在Manager的构造函数作为参数传入的,找到创建Manager的地方:
frameworks/base/core/java/android/app/SystemServiceRegistry.java
registerService(Context.FINGERPRINT_SERVICE, FingerprintManager.class, new CachedServiceFetcher() { @Override public FingerprintManager createService(ContextImpl ctx) throws ServiceNotFoundException { final IBinder binder; if (ctx.getApplicationInfo().targetSdkVersion >= Build.VERSION_CODES.O) { binder = ServiceManager.getServiceOrThrow(Context.FINGERPRINT_SERVICE); } else { binder = ServiceManager.getService(Context.FINGERPRINT_SERVICE); } IFingerprintService service = IFingerprintService.Stub.asInterface(binder); return new FingerprintManager(ctx.getOuterContext(), service);}});
从这里看,关键字是Context.FINGERPRINT_SERVICE这个服务!
这时候,灵机一动看一眼FingerprintService(通过搜索可以搜到FingerprintService),它的onStart方法中有发布这个服务,发布的是它的内部类FingerprintServiceWrapper,这里就解释了为什么之前Manager里面的rename方法最后会在FingerprintServiceWrapper被搜索到。
@Overridepublic void onStart() { publishBinderService(Context.FINGERPRINT_SERVICE, new FingerprintServiceWrapper()); SystemServerInitThreadPool.get().submit(this::getFingerprintDaemon, TAG + ".onStart"); listenForUserSwitches();}
而FingerprintService本身是在frameworks/base/services/java/com/android/server/SystemServer.java中启动的;
if (mPackageManager.hasSystemFeature(PackageManager.FEATURE_FINGERPRINT)) { traceBeginAndSlog("StartFingerprintSensor"); mSystemServiceManager.startService(FingerprintService.class); traceEnd();}
下面来看一下一个消息反馈的AIDL:IFingerprintServiceReceiver;
/** * Communication channel from the FingerprintService back to FingerprintManager. * @hide */oneway interface IFingerprintServiceReceiver { void onEnrollResult(long deviceId, int fingerId, int groupId, int remaining); void onAcquired(long deviceId, int acquiredInfo, int vendorCode); void onAuthenticationSucceeded(long deviceId, in Fingerprint fp, int userId); void onAuthenticationFailed(long deviceId); void onError(long deviceId, int error, int vendorCode); void onRemoved(long deviceId, int fingerId, int groupId, int remaining); void onEnumerated(long deviceId, int fingerId, int groupId, int remaining);}
它的实例在Manager中;
private IFingerprintServiceReceiver mServiceReceiver = new IFingerprintServiceReceiver.Stub
作为参数被传递给Service,实现消息反馈机制。
如果仔细看下FingerprintService所在的文件夹,除了之前提到过的FingerprintService、FingerprintUtils和FingerprintsUserState以外就只剩下大量和ClientMonitor 相关的类了;
/** * Abstract base class for keeping track and dispatching events from fingerprint HAL to the * the current client. Subclasses are responsible for coordinating the interaction with * fingerprint HAL for the specific action (e.g. authenticate, enroll, enumerate, etc.). */public abstract class ClientMonitor implements IBinder.DeathRecipient
它的子类包括AuthenticationClient、EnrollClient、EnumerateClient、InternalEnumerateClient、InternalRemovalClient和RemovalClient。
它们是真正负责和更下层的HAL层交互的类。
HAL层有关的内容这里暂不讨论。
这样的话,大概的一组流程被整理出来,FingerprintManager内部持有FingerprintService内部类FingerprintServiceWrapper的AIDL,FingerprintManager的API都是调用FingerprintServiceWrapper提供的接口实现的,同时通过参数实现IFingerprintServiceReceiver消息回传。
这里还有一点可以提一下,那就是指纹授权时的震动;
- frameworks/base/services/core/java/com/android/server/fingerprint/AuthenticationClient.java中会在授权成功或失败后调用vibrateSuccess()和vibrateError()方法实现不同的震动效果
- frameworks/base/services/core/java/com/android/server/fingerprint/ClientMonitor.java有vibrateSuccess()和vibrateError()两个方法的具体实现
- 在ClientMonitor中可以看到frameworks\base\core\java\android\os\VibrationEffect.java是真正实现震动的类
- 可以通过用VibrationEffect的createOneShot或createWaveform方法创建想要的震动效果
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