Limit number of fingerprint templates that can be enrolled per device user

This change places an upper limit on the number of fingerprint templates that
can be enrolled per account.  This is done primarily for performance reasons, but
may also be imposed by hardware and Trusted Execution Environment (TEE) reasons.

Fixes bug 20731847

Change-Id: I3975290fa8eb2106467493aab6102015697e012c

 On branch max_fingerprint

res/values/strings.xml

@@ -695,11 +695,11 @@
     <!-- Fingerprint managment category title - configuration options for managing enrolled fingerprints [CHAR LIMIT=22] -->
     <string name="fingerprint_manage_category_title">Manage fingerprints</string>
     <!-- Fingerprint category title - configuration options for managing fingerprint enrollment [CHAR LIMIT=22] -->
-	<string name="fingerprint_usage_category_title">Use fingerprint for</string>
+    <string name="fingerprint_usage_category_title">Use fingerprint for</string>
-	<!-- Preference to add another fingerprint -->
+    <!-- Preference to add another fingerprint -->
-	<string name="fingerprint_add_title">Add fingerprint</string>
+    <string name="fingerprint_add_title">Add fingerprint</string>
-	<!-- switch for allowing fingerprint to be used for keyguard -->
+    <!-- switch for allowing fingerprint to be used for keyguard -->
-	<string name="fingerprint_enable_keyguard_toggle_title">screen lock</string>
+    <string name="fingerprint_enable_keyguard_toggle_title">screen lock</string>
     <!-- message shown for menu item that launches fingerprint settings or enrollment -->
     <plurals name="security_settings_fingerprint_preference_summary">
         <item quantity="one"><xliff:g id="count">%1$d</xliff:g> fingerprint set up</item>
@@ -772,6 +772,9 @@
     <!-- Text shown in fingerprint enroll when we didn't observe progress for a few seconds. [CHAR LIMIT=100] -->
     <string name="security_settings_fingerprint_enroll_lift_touch_again">Lift finger, then touch sensor again</string>
 
+    <!-- Text shown when "Add fingerprint" button is disabled -->
+    <string name="fingerprint_add_max">You can add up to <xliff:g id="count" example="5">%d</xliff:g> fingerprints</string>
+
     <!-- Title of the preferences category for preference items to control encryption -->
     <string name="crypt_keeper_settings_title">Encryption</string>
 

src/com/android/settings/fingerprint/FingerprintEnrollFinish.java

@@ -16,10 +16,18 @@
 
 package com.android.settings.fingerprint;
 
+import android.content.Context;
+import android.hardware.fingerprint.Fingerprint;
+import android.hardware.fingerprint.FingerprintManager;
 import android.os.Bundle;
+import android.preference.Preference;
 import android.view.View;
+import android.widget.Button;
 
 import com.android.settings.R;
+import com.android.settings.fingerprint.FingerprintSettings.FingerprintPreference;
+
+import java.util.List;
 
 /**
  * Activity which concludes fingerprint enrollment.
@@ -31,7 +39,18 @@ public class FingerprintEnrollFinish extends FingerprintEnrollBase {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.fingerprint_enroll_finish);
         setHeaderText(R.string.security_settings_fingerprint_enroll_finish_title);
-        findViewById(R.id.add_another_button).setOnClickListener(this);
+        Button addButton = (Button) findViewById(R.id.add_another_button);
+
+        FingerprintManager fpm = (FingerprintManager) getSystemService(Context.FINGERPRINT_SERVICE);
+        int enrolled = fpm.getEnrolledFingerprints().size();
+        int max = getResources().getInteger(
+                com.android.internal.R.integer.config_fingerprintMaxTemplatesPerUser);
+        if (enrolled >= max) {
+            /* Don't show "Add" button if too many fingerprints already added */
+            addButton.setVisibility(View.INVISIBLE);
+        } else {
+            addButton.setOnClickListener(this);
+        }
     }
 
     @Override

src/com/android/settings/fingerprint/FingerprintSettings.java

@@ -179,6 +179,7 @@ public class FingerprintSettings extends SubSettings {
                 switch (msg.what) {
                     case MSG_REFRESH_FINGERPRINT_TEMPLATES:
                         removeFingerprintPreference(msg.arg1);
+                        updateAddPreference();
                     break;
                     case MSG_FINGER_AUTH_SUCCESS:
                         mFingerprintCancel = null;
@@ -330,6 +331,19 @@ public class FingerprintSettings extends SubSettings {
             addPreference.setIcon(R.drawable.ic_add_24dp);
             root.addPreference(addPreference);
             addPreference.setOnPreferenceChangeListener(this);
+            updateAddPreference();
+        }
+
+        private void updateAddPreference() {
+            /* Disable preference if too many fingerprints added */
+            final int max = getContext().getResources().getInteger(
+                    com.android.internal.R.integer.config_fingerprintMaxTemplatesPerUser);
+            boolean tooMany = mFingerprintManager.getEnrolledFingerprints().size() >= max;
+            CharSequence maxSummary = tooMany ?
+                    getContext().getString(R.string.fingerprint_add_max, max) : "";
+            Preference addPreference = findPreference(KEY_FINGERPRINT_ADD);
+            addPreference.setSummary(maxSummary);
+            addPreference.setEnabled(!tooMany);
         }
 
         private static String genKey(int id) {