Android: Annotate and generate JNI code for Metrics.java

Bug: webrtc:8278
Change-Id: I54caee1acb483d7554afd6c0958f1929a78d6a56
Reviewed-on: https://webrtc-review.googlesource.com/22720
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20753}

sdk/android/BUILD.gn

@@ -353,6 +353,14 @@ rtc_static_library("libjingle_peerconnection_jni") {
   ]
 }
 
+generate_jni("generated_metrics_jni") {
+  sources = [
+    "api/org/webrtc/Metrics.java",
+  ]
+  jni_package = ""
+  jni_generator_include = "//sdk/android/src/jni/jni_generator_helper.h"
+}
+
 rtc_static_library("libjingle_peerconnection_metrics_default_jni") {
   sources = [
     "src/jni/androidmetrics_jni.cc",
@@ -362,6 +370,7 @@ rtc_static_library("libjingle_peerconnection_metrics_default_jni") {
 
   deps = [
     ":base_jni",
+    ":generated_metrics_jni",
     ":peerconnection_jni",
     "../../pc:peerconnection",
     "../../system_wrappers",
@@ -550,6 +559,7 @@ rtc_android_library("libjingle_peerconnection_metrics_default_java") {
   java_files = [ "api/org/webrtc/Metrics.java" ]
 
   deps = [
+    ":libjingle_peerconnection_java",
     "../../rtc_base:base_java",
   ]
 }

sdk/android/api/org/webrtc/Metrics.java

@@ -54,11 +54,13 @@ public class Metrics {
       this.bucketCount = bucketCount;
     }
 
+    @CalledByNative("HistogramInfo")
     public void addSample(int value, int numEvents) {
       samples.put(value, numEvents);
     }
   }
 
+  @CalledByNative
   private void add(String name, HistogramInfo info) {
     map.put(name, info);
   }
@@ -66,14 +68,26 @@ public class Metrics {
   // Enables gathering of metrics (which can be fetched with getAndReset()).
   // Must be called before PeerConnectionFactory is created.
   public static void enable() {
-    nativeEnable();
+    enableNative();
   }
 
   // Gets and clears native histograms.
   public static Metrics getAndReset() {
-    return nativeGetAndReset();
+    return getAndResetNative();
   }
 
-  private static native void nativeEnable();
-  private static native Metrics nativeGetAndReset();
+  // TODO(bugs.webrtc.org/8551) Remove.
+  @CalledByNative
+  static Metrics createMetrics() {
+    return new Metrics();
+  }
+
+  // TODO(bugs.webrtc.org/8551) Remove.
+  @CalledByNative
+  static HistogramInfo createHistogramInfo(int min, int max, int bucketCount) {
+    return new HistogramInfo(min, max, bucketCount);
+  }
+
+  private static native void enableNative();
+  private static native Metrics getAndResetNative();
 }

sdk/android/src/jni/androidmetrics_jni.cc

@@ -11,6 +11,7 @@
 #include <map>
 #include <memory>
 
+#include "sdk/android/generated_metrics_jni/jni/Metrics_jni.h"
 #include "sdk/android/src/jni/classreferenceholder.h"
 #include "sdk/android/src/jni/jni_helpers.h"
 #include "system_wrappers/include/metrics.h"
@@ -20,40 +21,30 @@
 namespace webrtc {
 namespace jni {
 
-JNI_FUNCTION_DECLARATION(void, Metrics_nativeEnable, JNIEnv* jni, jclass) {
+JNI_FUNCTION_DECLARATION(void, Metrics_enableNative, JNIEnv* jni, jclass) {
   metrics::Enable();
 }
 
 // Gets and clears native histograms.
 JNI_FUNCTION_DECLARATION(jobject,
-                         Metrics_nativeGetAndReset,
+                         Metrics_getAndResetNative,
                          JNIEnv* jni,
                          jclass) {
-  jclass j_metrics_class = jni->FindClass("org/webrtc/Metrics");
-  jmethodID j_add =
-      GetMethodID(jni, j_metrics_class, "add",
-                  "(Ljava/lang/String;Lorg/webrtc/Metrics$HistogramInfo;)V");
-  jclass j_info_class = jni->FindClass("org/webrtc/Metrics$HistogramInfo");
-  jmethodID j_add_sample = GetMethodID(jni, j_info_class, "addSample", "(II)V");
-
-  // Create |Metrics|.
-  jobject j_metrics = jni->NewObject(
-      j_metrics_class, GetMethodID(jni, j_metrics_class, "<init>", "()V"));
+  jobject j_metrics = Java_Metrics_createMetrics(jni);
 
   std::map<std::string, std::unique_ptr<metrics::SampleInfo>> histograms;
   metrics::GetAndReset(&histograms);
   for (const auto& kv : histograms) {
     // Create and add samples to |HistogramInfo|.
-    jobject j_info = jni->NewObject(
-        j_info_class, GetMethodID(jni, j_info_class, "<init>", "(III)V"),
-        kv.second->min, kv.second->max,
+    jobject j_info = Java_Metrics_createHistogramInfo(
+        jni, kv.second->min, kv.second->max,
         static_cast<int>(kv.second->bucket_count));
     for (const auto& sample : kv.second->samples) {
-      jni->CallVoidMethod(j_info, j_add_sample, sample.first, sample.second);
+      Java_HistogramInfo_addSample(jni, j_info, sample.first, sample.second);
     }
     // Add |HistogramInfo| to |Metrics|.
     jstring j_name = jni->NewStringUTF(kv.first.c_str());
-    jni->CallVoidMethod(j_metrics, j_add, j_name, j_info);
+    Java_Metrics_add(jni, j_metrics, j_name, j_info);
     jni->DeleteLocalRef(j_name);
     jni->DeleteLocalRef(j_info);
   }