前言

因为源码剖析的代码量比拟大，大部分博客网站的内容显示页面都比拟窄，显示进去的成果都异样俊俏，所以您也能够间接查看《Thinking in Android》来浏览这边文章，心愿这篇文章能帮你梳理分明 “指纹注册流程”。

外围源码

相干类

本篇文章，咱们从源码角度探讨指纹录入的过程（测试样机：Pixel），咱们先看下 UI 图，这个你应该不生疏了。

一、FingerprintEnrollIntroduction

接下来咱们就从指纹疏导界面开始源码剖析，图 1 的逻辑就在 FingerprintEnrollIntroduction 类，点击 Next 执行下一步，会执行 onNextButtonClick() 办法。

1.1 FingerprintEnrollIntroduction.onNextButtonClick()

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollIntroduction.java

public class FingerprintEnrollIntroduction extends BiometricEnrollIntroduction {

    @Override
    protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        mFingerprintManager = Utils.getFingerprintManagerOrNull(this);

        mFooterBarMixin = getLayout().getMixin(FooterBarMixin.class);
        
        // Cancel Button
        mFooterBarMixin.setSecondaryButton(new FooterButton.Builder(this)
                        .setText(R.string.security_settings_face_enroll_introduction_cancel)
                        .setListener(this::onCancelButtonClick)
                        .setButtonType(FooterButton.ButtonType.SKIP)
                        .setTheme(R.style.SudGlifButton_Secondary)
                        .build());

        // Next Button
        mFooterBarMixin.setPrimaryButton(new FooterButton.Builder(this)
                        .setText(R.string.wizard_next)
                        .setListener(this::onNextButtonClick)    // 点击 "下一步" 的解决流程
                        .setButtonType(FooterButton.ButtonType.NEXT)
                        .setTheme(R.style.SudGlifButton_Primary)
                        .build());
    }

}

咱们能够发现：FingerprintEnrollIntroduction 继承自 BiometricEnrollIntroduction，onNextButtonClick() 办法在其父类 BiometricEnrollIntroduction 中解决。

二、BiometricEnrollIntroduction

2.1 BiometricEnrollIntroduction.onNextButtonClick()

// packages/apps/Settings/src/com/android/settings/biometrics/BiometricEnrollIntroduction.java

public abstract class BiometricEnrollIntroduction extends BiometricEnrollBase
        implements LinkSpan.OnClickListener {

    @Override
    protected void onNextButtonClick(View view) {
        mNextClicked = true;
        if (checkMaxEnrolled() == 0) {
            // Lock thingy is already set up, launch directly to the next page
            launchNextEnrollingActivity(mToken);    // 接下来就要拉起指纹录入界面
        } else {setResult(RESULT_FINISHED);
            finish();}
    }
        
}

2.2 BiometricEnrollIntroduction.launchNextEnrollingActivity()

// packages/apps/Settings/src/com/android/settings/biometrics/BiometricEnrollIntroduction.java

public abstract class BiometricEnrollIntroduction extends BiometricEnrollBase
        implements LinkSpan.OnClickListener {private void launchNextEnrollingActivity(byte[] token) {Intent intent = getEnrollingIntent();    // 获取 FingerprintEnrollFindSensor
        if (token != null) {intent.putExtra(ChooseLockSettingsHelper.EXTRA_KEY_CHALLENGE_TOKEN, token);
        }
        if (mUserId != UserHandle.USER_NULL) {intent.putExtra(Intent.EXTRA_USER_ID, mUserId);
        }
        intent.putExtra(EXTRA_FROM_SETTINGS_SUMMARY, mFromSettingsSummary);
        startActivityForResult(intent, BIOMETRIC_FIND_SENSOR_REQUEST);    // 跳转 FingerprintEnrollFindSensor
    }
        
}

咱们看下 getEnrollingIntent() 办法：

// packages/apps/Settings/src/com/android/settings/biometrics/BiometricEnrollIntroduction.java

public abstract class BiometricEnrollIntroduction extends BiometricEnrollBase
        implements LinkSpan.OnClickListener {protected abstract Intent getEnrollingIntent();    // 形象办法，由子类 FingerprintEnrollIntroduction 实现
    
}

所以咱们跳转到 FingerprintEnrollIntroduction：

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollIntroduction.java

public class FingerprintEnrollIntroduction extends BiometricEnrollIntroduction {

    @Override
    protected Intent getEnrollingIntent() {return new Intent(this, FingerprintEnrollFindSensor.class);    // 获取 FingerprintEnrollFindSensor
    }
    
}

三、FingerprintEnrollFindSensor

咱们把下面的图再拿过去，此时就进入了图 2 界面的逻辑，咱们接着往下看。

3.1 FingerprintEnrollFindSensor.onCreate()

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollFindSensor.java

public class FingerprintEnrollFindSensor extends BiometricEnrollBase {

    @Override
    protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);
        setContentView(getContentView());
        mFooterBarMixin = getLayout().getMixin(FooterBarMixin.class);
        // Skip button
        mFooterBarMixin.setSecondaryButton(new FooterButton.Builder(this)
                        .setText(R.string.skip_label)
                        .setListener(this::onSkipButtonClick)
                        .setButtonType(FooterButton.ButtonType.SKIP)
                        .setTheme(R.style.SudGlifButton_Secondary)
                        .build());

        // Touch the sensor
        setHeaderText(R.string.security_settings_fingerprint_enroll_find_sensor_title);

        // 执行 startLookingForFingerprint() 办法
        startLookingForFingerprint(); // already confirmed, so start looking for fingerprint

        // 演示动画
        View animationView = findViewById(R.id.fingerprint_sensor_location_animation);
        if (animationView instanceof FingerprintFindSensorAnimation) {mAnimation = (FingerprintFindSensorAnimation) animationView;
        } else {mAnimation = null;}
    }

}

到这里都只是波及到 UI 界面的相干逻辑，接下来的代码逻辑就略微简单一点了，咱们认真深挖钻研。

3.2 FingerprintEnrollFindSensor.startLookingForFingerprint()

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollFindSensor.java

public class FingerprintEnrollFindSensor extends BiometricEnrollBase {

    private FingerprintEnrollSidecar mSidecar;
    private boolean mNextClicked;

    private void startLookingForFingerprint() {
        // FingerprintEnrollSidecar 这个 fragment 的生命周期正式开启
        mSidecar = (FingerprintEnrollSidecar) getSupportFragmentManager().findFragmentByTag(FingerprintEnrollEnrolling.TAG_SIDECAR);
        if (mSidecar == null) {mSidecar = new FingerprintEnrollSidecar();
            // 增加 FingerprintEnrollEnrolling
            getSupportFragmentManager().beginTransaction()
                    .add(mSidecar, FingerprintEnrollEnrolling.TAG_SIDECAR)
                    .commitAllowingStateLoss();}

        // FingerprintEnrollEnrolling 实现了 BiometricEnrollSidecar.Listener 接口
        mSidecar.setListener(new Listener() {    // 匿名外部类的形式实现接口办法
            @Override
            public void onEnrollmentProgressChange(int steps, int remaining) {
                mNextClicked = true;
                proceedToEnrolling(true /* cancelEnrollment */);
            }

            @Override
            public void onEnrollmentHelp(int helpMsgId, CharSequence helpString) { }

            @Override
            public void onEnrollmentError(int errMsgId, CharSequence errString) {if (mNextClicked && errMsgId == FingerprintManager.FINGERPRINT_ERROR_CANCELED) {
                    mNextClicked = false;
                    proceedToEnrolling(false /* cancelEnrollment */);
                }
            }
        });
    }

}

这外面有个重点办法：onEnrollmentProgressChange()，如果咱们此时用手指贴在指纹传感器上，会产生反馈信息的回调，此时 onEnrollmentProgressChange() 办法被执行，进入执行 proceedToEnrolling() 办法，咱们看下这个办法：

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollFindSensor.java

public class FingerprintEnrollFindSensor extends BiometricEnrollBase {private void proceedToEnrolling(boolean cancelEnrollment) {if (mSidecar != null) {if (cancelEnrollment) {if (mSidecar.cancelEnrollment()) {
                    // Enrollment cancel requested. When the cancellation is successful,
                    // onEnrollmentError will be called with FINGERPRINT_ERROR_CANCELED, calling
                    // this again.
                    return;
                }
            }
            getSupportFragmentManager().beginTransaction().remove(mSidecar).
                    commitAllowingStateLoss();
            mSidecar = null;
            // getFingerprintEnrollingIntent() 办法会返回一个蕴含 FingerprintEnrollEnrolling 的 Intent
            startActivityForResult(getFingerprintEnrollingIntent(), ENROLL_REQUEST);
        }
    }

}

失常流程会走到 startActivityForResult() 办法，跳转到 FingerprintEnrollEnrolling 界面。

四、FingerprintEnrollEnrolling

咱们把下面的图再拿过去，此时就进入了图 3 界面的逻辑，咱们接着往下看。

4.1 FingerprintEnrollEnrolling.onStart()

咱们重点关注 onStart() 办法：

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollEnrolling.java

/**
 * Activity which handles the actual enrolling for fingerprint.
 */
public class FingerprintEnrollEnrolling extends BiometricsEnrollEnrolling {

    @Override
    protected void onStart() {super.onStart();    // 调用父类 BiometricEnrollSidecar 的 onStart() 办法
        updateProgress(false /* animate */);    // 更新录入进度
        updateDescription();
        if (mRestoring) {startIconAnimation();
        }
    }

}

FingerprintEnrollEnrolling 类继承自 BiometricsEnrollEnrolling 类，而 BiometricsEnrollEnrolling 类实现了 BiometricEnrollSidecar.Listener 接口，所以 FingerprintEnrollEnrolling 也实现了 BiometricEnrollSidecar.Listener 接口。

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollEnrolling.java

/**
 * Activity which handles the actual enrolling for fingerprint.
 */
public class FingerprintEnrollEnrolling extends BiometricsEnrollEnrolling {

    // 指纹录制时提醒（比方太快，挪动手指之类）@Override
    public void onEnrollmentHelp(int helpMsgId, CharSequence helpString) {if (!TextUtils.isEmpty(helpString)) {mErrorText.removeCallbacks(mTouchAgainRunnable);
            showError(helpString);
        }
    }

    // 提醒指纹录制过程中超时，或者未注册
    @Override
    public void onEnrollmentError(int errMsgId, CharSequence errString) {
        int msgId;
        switch (errMsgId) {
            case FingerprintManager.FINGERPRINT_ERROR_TIMEOUT:
                msgId = R.string.security_settings_fingerprint_enroll_error_timeout_dialog_message;
                break;
            default:
                msgId = R.string.security_settings_fingerprint_enroll_error_generic_dialog_message;
                break;
        }
        showErrorDialog(getText(msgId), errMsgId);
        stopIconAnimation();
        mErrorText.removeCallbacks(mTouchAgainRunnable);
    }

    // 录制过程中进度的变动（手指按压指纹传感区，onEnrollmentProgressChange() 会被触发，执行一系列解决工作）@Override
    public void onEnrollmentProgressChange(int steps, int remaining) {updateProgress(true /* animate */);    // 更新进度
        updateDescription();    // 更新形容
        clearError();
        animateFlash();    // 更新动画
        mErrorText.removeCallbacks(mTouchAgainRunnable);
        mErrorText.postDelayed(mTouchAgainRunnable, HINT_TIMEOUT_DURATION);
    }

}

五、BiometricsEnrollEnrolling

5.1 BiometricsEnrollEnrolling.onStart()

// packages/apps/Settings/src/com/android/settings/biometrics/BiometricsEnrollEnrolling.java

public abstract class BiometricsEnrollEnrolling extends BiometricEnrollBase
        implements BiometricEnrollSidecar.Listener {

    @Override
    protected void onStart() {super.onStart();
        if (shouldStartAutomatically()) {    // 恒定为 true
            startEnrollment();    // 调用 startEnrollment() 办法
        }
    }
        
}

5.2 BiometricsEnrollEnrolling.startEnrollment()

// packages/apps/Settings/src/com/android/settings/biometrics/BiometricsEnrollEnrolling.java

public abstract class BiometricsEnrollEnrolling extends BiometricEnrollBase
        implements BiometricEnrollSidecar.Listener {

    protected BiometricEnrollSidecar mSidecar;

    protected abstract BiometricEnrollSidecar getSidecar();    // 形象办法，由子类实现

    public void startEnrollment() {// 调用 BiometricEnrollSidecar 的 onStart() 办法
        mSidecar = (BiometricEnrollSidecar) getSupportFragmentManager()
                .findFragmentByTag(TAG_SIDECAR);
        if (mSidecar == null) {mSidecar = getSidecar();    // 获取 mSidecar
            getSupportFragmentManager().beginTransaction().add(mSidecar, TAG_SIDECAR)
                    .commitAllowingStateLoss();}
        mSidecar.setListener(this);
    }
        
}

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollEnrolling.java

public class FingerprintEnrollEnrolling extends BiometricsEnrollEnrolling {

    @Override
    protected BiometricEnrollSidecar getSidecar() {
        // 返回了一个继承自 BiometricEnrollSidecar 的 FingerprintEnrollSidecar 对象
        return new FingerprintEnrollSidecar();}

}

六、FingerprintEnrollSidecar

6.1 FingerprintEnrollSidecar.startEnrollment()

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollSidecar.java

/**
 * Sidecar fragment to handle the state around fingerprint enrollment.
 */
public class FingerprintEnrollSidecar extends BiometricEnrollSidecar {

    private FingerprintManager mFingerprintManager;

    @Override
    protected void startEnrollment() {super.startEnrollment();
        if (mUserId != UserHandle.USER_NULL) {mFingerprintManager.setActiveUser(mUserId);
        }
        /*
         * 调用 FingeprintManager 的 enroll() 办法开始录入，并且传入了 EnrollmentCallback 对象
         * EnrollmentCallback 是指纹录入后果的回调，别离调用了 BiometricEnrollSidecar.Listener 接口中的办法，* 这样就能更新指纹录制的进度和录制后果。*/
        mFingerprintManager.enroll(mToken, mEnrollmentCancel, 0 /* flags */, mUserId, mEnrollmentCallback);
    }

咱们看下 EnrollmentCallback 对象是什么：

// packages/apps/Settings/src/com/android/settings/biometrics/fingerprint/FingerprintEnrollSidecar.java

public class FingerprintEnrollSidecar extends BiometricEnrollSidecar {

    private FingerprintManager.EnrollmentCallback mEnrollmentCallback
            = new FingerprintManager.EnrollmentCallback() {

        @Override
        public void onEnrollmentProgress(int remaining) {FingerprintEnrollSidecar.super.onEnrollmentProgress(remaining);
        }

        @Override
        public void onEnrollmentHelp(int helpMsgId, CharSequence helpString) {FingerprintEnrollSidecar.super.onEnrollmentHelp(helpMsgId, helpString);
        }

        @Override
        public void onEnrollmentError(int errMsgId, CharSequence errString) {FingerprintEnrollSidecar.super.onEnrollmentError(errMsgId, errString);
        }
    };

}

七、FingerprintManager

7.1 FingerprintManager.enroll()

// frameworks/base/core/java/android/hardware/fingerprint/FingerprintManager.java

public class FingerprintManager implements BiometricAuthenticator, BiometricFingerprintConstants {

    private IFingerprintService mService;

    // CancellationSignal 类提供删除信号类，提供终止操作的能力
    @RequiresPermission(MANAGE_FINGERPRINT)
    public void enroll(byte [] token, CancellationSignal cancel, int flags,
            int userId, EnrollmentCallback callback) {if (userId == UserHandle.USER_CURRENT) {userId = getCurrentUserId();
        }
        if (callback == null) {throw new IllegalArgumentException("Must supply an enrollment callback");
        }

        if (cancel != null) {if (cancel.isCanceled()) {Slog.w(TAG, "enrollment already canceled");
                return;
            } else {cancel.setOnCancelListener(new OnEnrollCancelListener());
            }
        }

        if (mService != null) try {
            mEnrollmentCallback = callback;
            // 调用 FingerprintServiceWrapper 的 enroll() 办法
            mService.enroll(mToken, token, userId, mServiceReceiver, flags,
                    mContext.getOpPackageName());
        } catch (RemoteException e) {Slog.w(TAG, "Remote exception in enroll:", e);
            if (callback != null) {
                // Though this may not be a hardware issue, it will cause apps to give up or try
                // again later.
                callback.onEnrollmentError(FINGERPRINT_ERROR_HW_UNAVAILABLE,
                        getErrorString(mContext, FINGERPRINT_ERROR_HW_UNAVAILABLE,
                            0 /* vendorCode */));
            }
        }
    }

}

八、FingerprintService

8.1 FingerprintServiceWrapper.enroll()

FingerprintManager 与 FingerprintService 间接通过 aidl 进行通信，在 FingerprintService 中外部类 FingerprintServiceWrapper 实现了 IFingerprintService.Stub，咱们调用的 FingerManger 的 enroll() 办法就是调用 FingerprintServiceWrapper 类中的 enroll() 办法。

// frameworks/base/services/core/java/com/android/server/biometrics/fingerprint/FingerprintService.java

public class FingerprintService extends BiometricServiceBase {

    /**
     * Receives the incoming binder calls from FingerprintManager.
     */
    private final class FingerprintServiceWrapper extends IFingerprintService.Stub {
    
        @Override // Binder call
        public void enroll(final IBinder token, final byte[] cryptoToken, final int userId,
                final IFingerprintServiceReceiver receiver, final int flags,
                final String opPackageName) {checkPermission(MANAGE_FINGERPRINT);

            final boolean restricted = isRestricted();
            final int groupId = userId; // default group for fingerprint enrollment
            final EnrollClientImpl client = new EnrollClientImpl(getContext(), mDaemonWrapper,
                    mHalDeviceId, token, new ServiceListenerImpl(receiver), mCurrentUserId, groupId,
                    cryptoToken, restricted, opPackageName, new int[0] /* disabledFeatures */,
                    ENROLL_TIMEOUT_SEC) {
                @Override
                public boolean shouldVibrate() {return true;}

                @Override
                protected int statsModality() {return FingerprintService.this.statsModality();
                }
            };

            enrollInternal(client, userId);    // 调用 BiometricServiceBase 的 enrollInternal() 办法}

    }

}

九、BiometricServiceBase

9.1 BiometricServiceBase.enrollInternal()

// frameworks/base/services/core/java/com/android/server/biometrics/BiometricServiceBase.java

public abstract class BiometricServiceBase extends SystemService
        implements IHwBinder.DeathRecipient {protected void enrollInternal(EnrollClientImpl client, int userId) {if (hasReachedEnrollmentLimit(userId)) {return;}

        // Group ID is arbitrarily set to parent profile user ID. It just represents
        // the default biometrics for the user.
        if (!isCurrentUserOrProfile(userId)) {return;}

        mHandler.post(() -> {startClient(client, true /* initiatedByClient */);    // 调用 startClient() 办法});
    }        

}

9.2 BiometricServiceBase.startClient()

// frameworks/base/services/core/java/com/android/server/biometrics/BiometricServiceBase.java

public abstract class BiometricServiceBase extends SystemService
        implements IHwBinder.DeathRecipient {private void startClient(ClientMonitor newClient, boolean initiatedByClient) {
        ClientMonitor currentClient = mCurrentClient;
        if (currentClient != null) {if (DEBUG) Slog.v(getTag(), "request stop current client" +
                    currentClient.getOwnerString());
            if (currentClient instanceof InternalEnumerateClient
                    || currentClient instanceof InternalRemovalClient) {if (newClient != null) {Slog.w(getTag(), "Internal cleanup in progress but trying to start client"
                            + newClient.getClass().getSuperclass().getSimpleName()
                            + "(" + newClient.getOwnerString() + ")"
                            + ", initiatedByClient =" + initiatedByClient);
                }
            } else {currentClient.stop(initiatedByClient);

                mHandler.removeCallbacks(mResetClientState);
                mHandler.postDelayed(mResetClientState, CANCEL_TIMEOUT_LIMIT);
            }
            mPendingClient = newClient;
        } else if (newClient != null) {if (newClient instanceof AuthenticationClient) {AuthenticationClient client = (AuthenticationClient) newClient;
                if (client.isBiometricPrompt()) {if (DEBUG) Slog.v(getTag(), "Returning cookie:" + client.getCookie());
                    mCurrentClient = newClient;
                    if (mBiometricService == null) {
                        mBiometricService = IBiometricService.Stub.asInterface(ServiceManager.getService(Context.BIOMETRIC_SERVICE));
                    }
                    try {mBiometricService.onReadyForAuthentication(client.getCookie(),
                                client.getRequireConfirmation(), client.getTargetUserId());
                    } catch (RemoteException e) {Slog.e(getTag(), "Remote exception", e);
                    }
                    return;
                }
            }

            // We are not a BiometricPrompt client, start the client immediately
            mCurrentClient = newClient;
            startCurrentClient(mCurrentClient.getCookie());    // 调用 startCurrentClient() 办法}
    }
        
}

9.3 BiometricServiceBase.startCurrentClient()

// frameworks/base/services/core/java/com/android/server/biometrics/BiometricServiceBase.java

public abstract class BiometricServiceBase extends SystemService
        implements IHwBinder.DeathRecipient {

    private ClientMonitor mCurrentClient;

    protected void startCurrentClient(int cookie) {if (mCurrentClient == null) {Slog.e(getTag(), "Trying to start null client!");
            return;
        }
        if (DEBUG) Slog.v(getTag(), "starting client"
                + mCurrentClient.getClass().getSuperclass().getSimpleName()
                + "(" + mCurrentClient.getOwnerString() + ")"
                + "targetUserId:" + mCurrentClient.getTargetUserId()
                + "currentUserId:" + mCurrentUserId
                + "cookie:" + cookie + "/" + mCurrentClient.getCookie());
        if (cookie != mCurrentClient.getCookie()) {Slog.e(getTag(), "Mismatched cookie");
            return;
        }
        notifyClientActiveCallbacks(true);
        mCurrentClient.start();    // 调用 EnrollClient 的 start() 办法
    }

}

十、EnrollClient

10.1 EnrollClient.start()

// frameworks/base/services/core/java/com/android/server/biometrics/EnrollClient.java

// EnrollClient 是为给定的客户端跟踪指纹录制状态
public abstract class EnrollClient extends ClientMonitor {

    // start 办法会调用 fingerprintd，调用底层的指纹库，底层库返回后果后会调用 onEnrollResult 来反馈后果给 receiver，再往下层反馈。@Override
    public int start() {mEnrollmentStartTimeMs = System.currentTimeMillis();
        try {final ArrayList<Integer> disabledFeatures = new ArrayList<>();
            for (int i = 0; i < mDisabledFeatures.length; i++) {disabledFeatures.add(mDisabledFeatures[i]);
            }

            final int result = getDaemonWrapper().enroll(mCryptoToken, getGroupId(), mTimeoutSec,
                    disabledFeatures);
            if (result != 0) {Slog.w(getLogTag(), "startEnroll failed, result=" + result);
                mMetricsLogger.histogram(mConstants.tagEnrollStartError(), result);
                onError(getHalDeviceId(), BiometricConstants.BIOMETRIC_ERROR_HW_UNAVAILABLE,
                        0 /* vendorCode */);
                return result;
            }
        } catch (RemoteException e) {Slog.e(getLogTag(), "startEnroll failed", e);
        }
        return 0; // success
    }

}

getDaemonWrapper().enroll() 会调用 fingerprintd，调用底层的指纹库，底层库返回后果后会调用 onEnrollResult 来反馈后果给 receiver，在往下层反馈。这就是指纹的录制流程。

// frameworks/base/core/java/android/hardware/fingerprint/FingerprintManager.java

public class FingerprintManager implements BiometricAuthenticator, BiometricFingerprintConstants {

    private Handler mHandler;

    // mServiceReceiver 对象会通过 handler 发送相干音讯去调用 EnrollmentCallback 或者 AuthenticationCallback 中办法
    private IFingerprintServiceReceiver mServiceReceiver = new IFingerprintServiceReceiver.Stub() {

        @Override // binder call
        public void onEnrollResult(long deviceId, int fingerId, int groupId, int remaining) {
            mHandler.obtainMessage(MSG_ENROLL_RESULT, remaining, 0,
                    new Fingerprint(null, groupId, fingerId, deviceId)).sendToTarget();}

        @Override // binder call
        public void onAcquired(long deviceId, int acquireInfo, int vendorCode) {
            mHandler.obtainMessage(MSG_ACQUIRED, acquireInfo, vendorCode,
                    deviceId).sendToTarget();}

        @Override // binder call
        public void onAuthenticationSucceeded(long deviceId, Fingerprint fp, int userId) {mHandler.obtainMessage(MSG_AUTHENTICATION_SUCCEEDED, userId, 0, fp).sendToTarget();}

        @Override // binder call
        public void onAuthenticationFailed(long deviceId) {mHandler.obtainMessage(MSG_AUTHENTICATION_FAILED).sendToTarget();}

        @Override // binder call
        public void onError(long deviceId, int error, int vendorCode) {mHandler.obtainMessage(MSG_ERROR, error, vendorCode, deviceId).sendToTarget();}

        @Override // binder call
        public void onRemoved(long deviceId, int fingerId, int groupId, int remaining) {
            mHandler.obtainMessage(MSG_REMOVED, remaining, 0,
                    new Fingerprint(null, groupId, fingerId, deviceId)).sendToTarget();}

        @Override // binder call
        public void onEnumerated(long deviceId, int fingerId, int groupId, int remaining) {
            // TODO: propagate remaining
            mHandler.obtainMessage(MSG_ENUMERATED, fingerId, groupId, deviceId).sendToTarget();}
    };
    
    private class MyHandler extends Handler {private MyHandler(Context context) {super(context.getMainLooper());
        }

        private MyHandler(Looper looper) {super(looper);
        }

        @Override
        public void handleMessage(android.os.Message msg) {switch (msg.what) {
                case MSG_ENROLL_RESULT:
                    sendEnrollResult((Fingerprint) msg.obj, msg.arg1 /* remaining */);
                    break;
                case MSG_ACQUIRED:
                    sendAcquiredResult((Long) msg.obj /* deviceId */, msg.arg1 /* acquire info */,
                            msg.arg2 /* vendorCode */);
                    break;
                case MSG_AUTHENTICATION_SUCCEEDED:
                    sendAuthenticatedSucceeded((Fingerprint) msg.obj, msg.arg1 /* userId */);
                    break;
                case MSG_AUTHENTICATION_FAILED:
                    sendAuthenticatedFailed();
                    break;
                case MSG_ERROR:
                    sendErrorResult((Long) msg.obj /* deviceId */, msg.arg1 /* errMsgId */,
                            msg.arg2 /* vendorCode */);
                    break;
                case MSG_REMOVED:
                    sendRemovedResult((Fingerprint) msg.obj, msg.arg1 /* remaining */);
                    break;
                case MSG_ENUMERATED:
                    sendEnumeratedResult((Long) msg.obj /* deviceId */, msg.arg1 /* fingerId */,
                            msg.arg2 /* groupId */);
                    break;
            }
        }
    };
}

看下 MSG_ENROLL_RESULT：

// frameworks/base/core/java/android/hardware/fingerprint/FingerprintManager.java

public class FingerprintManager implements BiometricAuthenticator, BiometricFingerprintConstants {private void sendEnrollResult(Fingerprint fp, int remaining) {if (mEnrollmentCallback != null) {
            // 调用 EnrollmentCallback 的 onEnrollmentProgress 办法
            mEnrollmentCallback.onEnrollmentProgress(remaining);
        }
    }

}