If you are working with React Native (especially 0.84+) and suddenly your Android app:

• Opens the emulator but does not launch the app
• Fails with configureCMakeDebug error
• Shows std::format not found error
• Or says “No Android device connected”

Then this complete guide will help you fix everything step by step.

This guide is based on a real-world troubleshooting session on Windows with React Native 0.84.

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Problem 1: Gradle Using Wrong Java Version (JDK 25 Instead of JDK 17)

Symptoms

Running:

gradlew.bat -version

Showed:

Launcher JVM: 25.0.2
Daemon JVM: jdk-25

Even though java -version showed JDK 17.

This caused:

Execution failed for task ':app:configureCMakeDebug[arm64-v8a]'
WARNING: A restricted method in java.lang.System has been called

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Why This Happens

Gradle was using JDK 25 internally, but React Native Android builds are stable with JDK 17.

Gradle launcher and daemon must both use Java 17.

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Solution: Force Gradle to Use JDK 17

Step 1: Locate Your JDK 17 Folder

Example:

C:\Program Files\Microsoft\jdk-17.0.18.8-hotspot

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Step 2: Add This to android/gradle.properties

Open:

android/gradle.properties

Add:

org.gradle.java.home=C:\\Program Files\\Microsoft\\jdk-17.0.18.8-hotspot

Use double backslashes.

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Step 3: Stop Gradle and Clean

cd android
gradlew.bat --stop
rmdir /s /q .gradle
rmdir /s /q .cxx
rmdir /s /q app\.cxx
gradlew.bat clean

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Step 4: Verify

gradlew.bat -version

Now both should show:

Launcher JVM: 17.x
Daemon JVM: 17.x

If not, temporarily force in CMD:

set "JAVA_HOME=C:\Program Files\Microsoft\jdk-17.0.18.8-hotspot"
set "PATH=%JAVA_HOME%\bin;%PATH%"

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Problem 2: CMake Error – std::format Not Found (NDK Issue)

After fixing Java, build failed with:

error: no member named 'format' in namespace 'std'
return std::format("{}%", dimension.value);

This came from:

react-native-safe-area-context

And NDK path showed:

ndk\26.1.10909125

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Why This Happens

React Native 0.84 uses C++20 features like std::format.

NDK 26 does not properly support this setup.

You must use NDK 27.1+.

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Solution: Install and Force NDK 27.1

Step 1: Install NDK 27.1

In Android Studio:

• Settings
• Android SDK
• SDK Tools
• Enable “NDK (Side by side)”
• Select 27.1.12297006
• Apply

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Step 2: Force Project to Use NDK 27.1

Open:

android/build.gradle

Inside android {} add:

ndkVersion "27.1.12297006"

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Step 3: Clean Native Build

cd android
gradlew.bat --stop
rmdir /s /q .cxx
rmdir /s /q app\.cxx
rmdir /s /q .gradle
gradlew.bat clean

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Step 4: Run Again

cd ..
npx react-native run-android

Now build succeeds.

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Problem 3: Emulator Opens but CLI Says “No Android Device Connected”

Even though:

adb devices

Showed:

emulator-5554 device

Sometimes it showed blank.

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Why This Happens

• ADB server mismatch
• Multiple adb.exe in PATH
• Emulator not cold booted

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Fix Emulator Detection

Step 1: Restart Emulator

Cold boot from Android Studio Device Manager.

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Step 2: Reset ADB

adb kill-server
taskkill /F /IM adb.exe
adb start-server
adb devices

Now emulator should show:

emulator-5554 device

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Step 3: Run with Correct Flag

New React Native versions use:

npx react-native run-android --device emulator-5554

(Not --deviceId)

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Step 4: Ensure Correct ADB in PATH

where adb

Make sure this path is first:

C:\Users\YourUser\AppData\Local\Android\Sdk\platform-tools\adb.exe

If not:

set "ANDROID_SDK_ROOT=%LOCALAPPDATA%\Android\Sdk"
set "PATH=%ANDROID_SDK_ROOT%\platform-tools;%PATH%"

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Final Working Configuration Summary

For React Native 0.84 (Windows):

• Java: JDK 17
• Gradle JVM: 17
• NDK: 27.1.12297006
• CMake: Installed via SDK Tools
• Use: --device instead of --deviceId

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Final Command That Worked

npx react-native run-android --device emulator-5554

Everything built smoothly.

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Key Lessons Learned

1. Gradle launcher and daemon must both use Java 17.
2. NDK 26 is not compatible with React Native 0.84 C++20 requirements.
3. Always force ndkVersion in build.gradle.
4. Always clean .cxx when changing NDK.
5. If emulator shows but CLI doesn’t detect, reset ADB.

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