Speculative fix for issue #3084. NullPointerException is encountered specifically on Android version 8.1.0, this is due to String.format inserted with Double values.

The proposed fix is to use DecimalFormat to format the values before being inserted in String.format

Author: visumickey

firebase-perf/src/main/java/com/google/firebase/perf/transport/TransportManager.java

@@ -52,6 +52,7 @@
 import com.google.firebase.perf.v1.TraceMetric;
 import java.lang.ref.WeakReference;
 import java.util.Collections;
+import java.text.DecimalFormat;
 import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -617,9 +618,9 @@ private static String getLogcatMsg(TraceMetric traceMetric) {
     long durationInUs = traceMetric.getDurationUs();
     return String.format(
         Locale.ENGLISH,
-        "trace metric: %s (duration: %.4fms)",
+        "trace metric: %s (duration: %sms)",
         traceMetric.getName(),
-        durationInUs / 1000.0);
+        new DecimalFormat("#.####").format(durationInUs / 1000.0));
   }
 
   private static String getLogcatMsg(NetworkRequestMetric networkRequestMetric) {
@@ -635,10 +636,10 @@ private static String getLogcatMsg(NetworkRequestMetric networkRequestMetric) {
 
     return String.format(
         Locale.ENGLISH,
-        "network request trace: %s (responseCode: %s, responseTime: %.4fms)",
+        "network request trace: %s (responseCode: %s, responseTime: %sms)",
         networkRequestMetric.getUrl(),
         responseCode,
-        durationInUs / 1000.0);
+        new DecimalFormat("#.####").format(durationInUs / 1000.0));
   }
 
   private static String getLogcatMsg(GaugeMetric gaugeMetric) {