4 files changed, 80 insertions, 0 deletions
diff --git a/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/ZygoteHooks.java b/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/ZygoteHooks.java
index 166389f0d..9be61a98a 100644
--- a/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/ZygoteHooks.java
+++ b/android_icu4j/libcore_bridge/src/java/com/android/i18n/system/ZygoteHooks.java
@@ -27,6 +27,8 @@ import android.icu.text.DecimalFormatSymbols;
 import android.icu.util.TimeZone;
 import android.icu.util.ULocale;
 
+import com.android.icu.util.UResourceBundleNative;
+
 import dalvik.annotation.compat.VersionCodes;
 
 /**
@@ -85,6 +87,10 @@ public final class ZygoteHooks {
         // It's in the end of preload because preload and ICU4J initialization should succeed
         // without this property. Otherwise, it indicates that the Android patch is not working.
         System.setProperty(PROP_ICUBINARY_DATA_PATH, AndroidDataFiles.generateIcuDataPath());
+
+        // Cache the timezone bundles, e.g. metaZones.res, in Zygote due to app compat.
+        // http://b/339899412
+        UResourceBundleNative.cacheTimeZoneBundles();
     }
 
     /**
diff --git a/android_icu4j/libcore_bridge/src/java/com/android/icu/util/UResourceBundleNative.java b/android_icu4j/libcore_bridge/src/java/com/android/icu/util/UResourceBundleNative.java
new file mode 100644
index 000000000..eae5cf60a
--- /dev/null
+++ b/android_icu4j/libcore_bridge/src/java/com/android/icu/util/UResourceBundleNative.java
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * 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.icu.util;
+
+/**
+ * @hide
+ */
+public class UResourceBundleNative {
+    public static native void cacheTimeZoneBundles();
+}
diff --git a/android_icu4j/libcore_bridge/src/native/Register.cpp b/android_icu4j/libcore_bridge/src/native/Register.cpp
index ad7c9c197..25d53f3e5 100644
--- a/android_icu4j/libcore_bridge/src/native/Register.cpp
+++ b/android_icu4j/libcore_bridge/src/native/Register.cpp
@@ -53,6 +53,7 @@ jint JNI_OnLoad(JavaVM* vm, void*) {
     REGISTER(register_com_android_icu_util_CaseMapperNative);
     REGISTER(register_com_android_icu_util_Icu4cMetadata);
     REGISTER(register_com_android_icu_util_LocaleNative);
+    REGISTER(register_com_android_icu_util_UResourceBundleNative);
     REGISTER(register_com_android_icu_util_regex_PatternNative);
     REGISTER(register_com_android_icu_util_regex_MatcherNative);
     REGISTER(register_com_android_icu_util_charset_NativeConverter);
diff --git a/android_icu4j/libcore_bridge/src/native/com_android_icu_util_UResourceBundleNative.cpp b/android_icu4j/libcore_bridge/src/native/com_android_icu_util_UResourceBundleNative.cpp
new file mode 100644
index 000000000..c1615aa61
--- /dev/null
+++ b/android_icu4j/libcore_bridge/src/native/com_android_icu_util_UResourceBundleNative.cpp
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#define LOG_TAG "UResourceBundleNative"
+
+#include <nativehelper/JNIHelp.h>
+#include <nativehelper/jni_macros.h>
+
+#include <log/log.h>
+#include "unicode/ures.h"
+#include "unicode/utypes.h"
+
+static inline void openDirectAndCloseRes(const char* res_name) {
+    UErrorCode status = U_ZERO_ERROR;
+    UResourceBundle *res = ures_openDirect(nullptr, res_name, &status);
+    if (U_FAILURE(status)) {
+        ALOGE("Failed to load ICU resource '%s': %s", res_name, u_errorName(status));
+        return;
+    }
+
+    ures_close(res);
+}
+
+static void UResourceBundleNative_cacheTimeZoneBundles(JNIEnv* env, jclass) {
+    openDirectAndCloseRes("zoneinfo64");
+    openDirectAndCloseRes("timezoneTypes");
+    openDirectAndCloseRes("metaZones");
+    openDirectAndCloseRes("windowsZones");
+}
+
+static JNINativeMethod gMethods[] = {
+    NATIVE_METHOD(UResourceBundleNative, cacheTimeZoneBundles, "()V"),
+};
+
+void register_com_android_icu_util_UResourceBundleNative(JNIEnv* env) {
+    jniRegisterNativeMethods(env, "com/android/icu/util/UResourceBundleNative", gMethods, NELEM(gMethods));
+}