Fix #369 - Highlight wrong GNSS times on Status (#376)

* Current threshold is more than 5 days different than system clock

FAQ.md

@@ -159,6 +159,10 @@ Then tap on "Send feedback", and GPSTest it will capture success/failure for all
 
 No.  See our [Privacy Policy](https://github.com/barbeau/gpstest/wiki/Privacy-Policy) for more details.
 
+## Why is my GPS time wrong?
+
+As of April 6, 2019, some older devices have been impacted by the [GPS Week Number Rollover](https://www.cisa.gov/gps-week-number-roll-over), which can result in unpredictable behavior. Typically, the time computed by GPS will be wrong. You will need to contact your device manufacturer or cellular carrier to determine if you device can be updated to fix this issue. For example, here is [Verizon's GPS Week Rollover help page](https://www.verizonwireless.com/legal/notices/global-positioning-system/).
+
 ## I'm getting a weird value for Time-to-First-Fix.  What's up?
 
 On Android 4.1 and below, your system clock must be accurate to calculate an accurate Time-To-First-Fix (TTFF) value

GPSTest/src/main/java/com/android/gpstest/GpsStatusFragment.java

@@ -46,6 +46,7 @@
 import androidx.annotation.RequiresApi;
 import androidx.appcompat.app.AlertDialog;
 import androidx.cardview.widget.CardView;
+import androidx.core.graphics.drawable.DrawableCompat;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.Observer;
 import androidx.lifecycle.ViewModelProviders;
@@ -58,6 +59,7 @@
 import com.android.gpstest.model.SatelliteMetadata;
 import com.android.gpstest.model.SatelliteStatus;
 import com.android.gpstest.util.CarrierFreqUtils;
+import com.android.gpstest.util.DateTimeUtils;
 import com.android.gpstest.util.IOUtils;
 import com.android.gpstest.util.MathUtils;
 import com.android.gpstest.util.NmeaUtils;
@@ -95,7 +97,7 @@ public class GpsStatusFragment extends Fragment implements GpsTestListener {
             mAltitudeMslView, mHorVertAccuracyLabelView, mHorVertAccuracyView,
             mSpeedView, mSpeedAccuracyView, mBearingView, mBearingAccuracyView, mNumSats,
             mPdopLabelView, mPdopView, mHvdopLabelView, mHvdopView, mGnssNotAvailableView,
-            mSbasNotAvailableView;
+            mSbasNotAvailableView, mFixTimeErrorView;
 
     private CardView mLocationCard;
 
@@ -160,6 +162,8 @@ public View onCreateView(LayoutInflater inflater, ViewGroup container,
         mLatitudeView = v.findViewById(R.id.latitude);
         mLongitudeView = v.findViewById(R.id.longitude);
         mFixTimeView = v.findViewById(R.id.fix_time);
+        mFixTimeErrorView = v.findViewById(R.id.fix_time_error);
+        mFixTimeErrorView.setOnClickListener(view -> showTimeErrorDialog(mFixTime));
         mTTFFView = v.findViewById(R.id.ttff);
         mAltitudeView = v.findViewById(R.id.altitude);
         mAltitudeMslView = v.findViewById(R.id.altitude_msl);
@@ -271,8 +275,18 @@ private void setStarted(boolean navigating) {
     private void updateFixTime() {
         if (mFixTime == 0 || (GpsTestActivity.getInstance() != null && !GpsTestActivity.getInstance().mStarted)) {
             mFixTimeView.setText("");
+            mFixTimeErrorView.setText("");
         } else {
-            mFixTimeView.setText(mDateFormat.format(mFixTime));
+            if (DateTimeUtils.Companion.isTimeValid(mFixTime)) {
+                mFixTimeErrorView.setVisibility(View.GONE);
+                mFixTimeView.setVisibility(View.VISIBLE);
+                mFixTimeView.setText(mDateFormat.format(mFixTime));
+            } else {
+                // Error in fix time
+                mFixTimeErrorView.setVisibility(View.VISIBLE);
+                mFixTimeView.setVisibility(View.GONE);
+                mFixTimeErrorView.setText(mDateFormat.format(mFixTime));
+            }
         }
     }
 
@@ -739,6 +753,26 @@ private void showSortByDialog() {
         dialog.show();
     }
 
+    private void showTimeErrorDialog(long time) {
+        java.text.DateFormat format = SimpleDateFormat.getDateTimeInstance(java.text.DateFormat.LONG, java.text.DateFormat.LONG);
+
+        TextView textView = (TextView) getLayoutInflater().inflate(R.layout.error_text_dialog, null);
+        textView.setText(getString(R.string.error_time_message, format.format(time), DateTimeUtils.Companion.getNUM_DAYS_TIME_VALID()));
+
+        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+        builder.setTitle(R.string.error_time_title);
+        builder.setView(textView);
+        Drawable drawable = getResources().getDrawable(android.R.drawable.ic_dialog_alert);
+        DrawableCompat.setTint(drawable, getResources().getColor(R.color.colorPrimary));
+        builder.setIcon(drawable);
+        builder.setNeutralButton(R.string.main_help_close,
+                (dialog, which) -> dialog.dismiss()
+        );
+        AlertDialog dialog = builder.create();
+        dialog.setOwnerActivity(getActivity());
+        dialog.show();
+    }
+
     /**
      * Saves the "sort by" order to preferences
      *

GPSTest/src/main/java/com/android/gpstest/util/DateTimeUtils.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2020 Sean J. Barbeau
+ *
+ * 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.android.gpstest.util
+
+import android.os.Build
+import androidx.annotation.VisibleForTesting
+import java.time.Duration
+import java.time.Instant
+import java.util.concurrent.TimeUnit
+
+/**
+ * Utilities for comparing two locations to measure error
+ */
+class DateTimeUtils {
+
+    companion object {
+        val NUM_DAYS_TIME_VALID = 5
+        /**
+         * Returns true if the provided UTC time of the fix, in milliseconds since January 1, 1970,
+         * is valid, and false if it is not
+         */
+        fun isTimeValid(time: Long): Boolean {
+            return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                // If the GPS time is less than five days different than system clock time, consider it valid
+                Duration.between(Instant.ofEpochMilli(time), Instant.now()).toDays() < NUM_DAYS_TIME_VALID
+            } else {
+                isTimeValidLegacy(time)
+            }
+        }
+
+        @VisibleForTesting
+        internal fun isTimeValidLegacy(time: Long): Boolean {
+            return TimeUnit.MILLISECONDS.toDays(Math.abs(System.currentTimeMillis() - time)) < NUM_DAYS_TIME_VALID
+        }
+    }
+}

GPSTest/src/main/res/drawable/error_text_background.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- Outside border -->
+    <item android:id="@+id/error_background_border">
+        <shape>
+            <corners android:radius="9dp" />
+            <padding
+                android:top="3dp"
+                android:left="3dp"
+                android:bottom="3dp"
+                android:right="3dp" />
+            <solid android:color="@color/red" />
+        </shape>
+    </item>
+    <!-- Inside fill -->
+    <item android:id="@+id/error_background_fill">
+        <shape>
+            <corners android:radius="6dp" />
+            <solid android:color="@color/red" />
+        </shape>
+    </item>
+</layer-list>

GPSTest/src/main/res/layout/error_text_dialog.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    style="?android:attr/textAppearance"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:paddingTop="14dp"
+    android:paddingBottom="6dp"
+    android:paddingLeft="24dp"
+    android:paddingRight="10dp"
+    android:textSize="16sp"
+    android:autoLink="all"
+    android:linksClickable="true"></TextView>

GPSTest/src/main/res/layout/gps_status.xml

@@ -72,6 +72,11 @@
                         <TextView
                             android:id="@+id/fix_time"
                             style="@style/info_value" />
+
+                        <TextView
+                            android:id="@+id/fix_time_error"
+                            style="@style/info_value_error"
+                            android:visibility="gone" />
                     </TableRow>
 
                     <TableRow>

GPSTest/src/main/res/values/strings.xml

@@ -113,6 +113,8 @@
     <string name="gnss_not_available">Global Navigation Satellite System (GNSS) satellites not available</string>
     <string name="sbas_not_available">Satellite-based Augmentation System (SBAS) satellites not available</string>
     <string name="menu_option_sort_by">Sort by</string>
+    <string name="error_time_title">Your GNSS time is wrong</string>
+    <string name="error_time_message">The device GNSS time of:\n\n%1$s\n\n…is more than %2$d days different from your system clock. This can be caused by the GPS week rollover issue - ask your device manufacturer for details. See http://bit.ly/gps-week-rollover for more info.</string>
 
     <!-- Map view -->
     <string name="ground_truth_latitude">Your latitude</string>

GPSTest/src/main/res/values/styles.xml

@@ -71,6 +71,19 @@
         <item name="android:textStyle">normal</item>
     </style>
 
+    <style name="info_value_error">
+        <item name="android:layout_height">wrap_content</item>
+        <item name="android:layout_width">wrap_content</item>
+        <item name="android:textSize">@dimen/status_text_size</item>
+        <item name="android:textStyle">normal</item>
+        <item name="android:textColor">@android:color/white</item>
+        <item name="android:paddingTop">3dp</item>
+        <item name="android:paddingBottom">3dp</item>
+        <item name="android:paddingLeft">6dp</item>
+        <item name="android:paddingRight">6dp</item>
+        <item name="android:background">@drawable/error_text_background</item>
+    </style>
+
     <!-- GNSS Sky view -->
     <style name="sky_legend_label">
         <item name="android:layout_height">wrap_content</item>

GPSTest/src/test/java/com/android/gpstest/util/DateTimeUtilsTest.kt

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2020 Sean J. Barbeau
+ *
+ * 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.android.gpstest.util
+
+import junit.framework.Assert.assertFalse
+import junit.framework.Assert.assertTrue
+import org.junit.Test
+import java.time.Instant
+import java.util.concurrent.TimeUnit
+
+class DateTimeUtilsTest {
+
+    @Test
+    fun isTimeValid() {
+        // Valid times within 5 days of now
+        assertTrue(DateTimeUtils.isTimeValid(Instant.now().toEpochMilli()))
+        assertTrue(DateTimeUtils.isTimeValid(Instant.now().toEpochMilli() + TimeUnit.DAYS.toMillis(4)))
+        assertTrue(DateTimeUtils.isTimeValid(Instant.now().toEpochMilli() - TimeUnit.DAYS.toMillis(4)))
+
+        // Invalid times more than 5 days  from now (past or future)
+        assertFalse(DateTimeUtils.isTimeValid(Instant.now().toEpochMilli() + TimeUnit.DAYS.toMillis(6)))
+        assertFalse(DateTimeUtils.isTimeValid(Instant.now().toEpochMilli() - TimeUnit.DAYS.toMillis(6)))
+    }
+
+    @Test
+    fun isTimeValidLegacy() {
+        // Valid times within 5 days of now
+        assertTrue(DateTimeUtils.isTimeValidLegacy(Instant.now().toEpochMilli()))
+        assertTrue(DateTimeUtils.isTimeValidLegacy(Instant.now().toEpochMilli() + TimeUnit.DAYS.toMillis(4)))
+        assertTrue(DateTimeUtils.isTimeValidLegacy(Instant.now().toEpochMilli() - TimeUnit.DAYS.toMillis(4)))
+
+        // Invalid times more than 5 days from now (past or future)
+        assertFalse(DateTimeUtils.isTimeValidLegacy(Instant.now().toEpochMilli() + TimeUnit.DAYS.toMillis(6)))
+        assertFalse(DateTimeUtils.isTimeValidLegacy(Instant.now().toEpochMilli() - TimeUnit.DAYS.toMillis(6)))
+    }
+}

GPSTest/src/test/java/com/android/gpstest/MathUtilTest.java → GPSTest/src/test/java/com/android/gpstest/util/MathUtilTest.java

@@ -13,9 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package com.android.gpstest;
-
-import com.android.gpstest.util.MathUtils;
+package com.android.gpstest.util;
 
 import org.junit.Test;
 

GPSTest/src/test/java/com/android/gpstest/NmeaUtilsTest.java → GPSTest/src/test/java/com/android/gpstest/util/NmeaUtilsTest.java

@@ -13,10 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package com.android.gpstest;
+package com.android.gpstest.util;
 
 import com.android.gpstest.model.DilutionOfPrecision;
-import com.android.gpstest.util.NmeaUtils;
 
 import org.junit.Test;
 

GPSTest/src/test/java/com/android/gpstest/UIUtilsTest.java → GPSTest/src/test/java/com/android/gpstest/util/UIUtilsTest.java

@@ -1,6 +1,4 @@
-package com.android.gpstest;
-
-import com.android.gpstest.util.UIUtils;
+package com.android.gpstest.util;
 
 import org.junit.Test;