Hey there, let's figure out how to fix that "Unable to detect adb version" error that's blocking you from testing your app. I've dealt with this exact issue a handful of times, so here are the most tried-and-true solutions to get you back up and running:

First things first—let's make sure ADB actually exists on your system:

• Open Android Studio and go to File > Settings > Appearance & Behavior > System Settings > Android SDK (on macOS, it's Android Studio > Settings instead). Note down the SDK Location path.
• Navigate to that folder on your computer, then check the platform-tools subdirectory. You should see an adb.exe file (Windows) or just adb (macOS/Linux) there.
• If ADB is missing, head back to the SDK Settings, switch to the SDK Tools tab, check the box for Android SDK Platform-Tools, click Apply, and let Studio install it.

Glitches happen, and a quick restart often clears them up:

• Open the Terminal in Android Studio (it's at the bottom right, next to Logcat).
• Run these two commands one after the other:

  adb kill-server
  adb start-server
  

• If that doesn't do it, close Android Studio entirely. Then, kill any leftover adb processes using Task Manager (Windows) or Activity Monitor (macOS/Linux). Relaunch Studio and try connecting your device/emulator again.

Windows might not know where to find ADB if it's not added to your system PATH:

• Right-click This PC > Properties > Advanced system settings.
• Click Environment Variables. Under System variables, find Path and hit Edit.
• Add the full path to your platform-tools folder (something like C:\Users\YourUsername\AppData\Local\Android\Sdk\platform-tools).
• Save all changes, restart your computer, and give it another go.

Sometimes the issue isn't ADB itself—it's the connection:

• Physical phones: Make sure USB Debugging is turned on. Go to Settings > About Phone, tap the Build Number 7 times to unlock Developer Options, then flip the switch for USB Debugging. Also, try a different USB cable or port—cheap cables often cause detection issues.
• Emulators: Try wiping your emulator's data (open the AVD Manager, select your emulator, click the down arrow > Wipe Data). If that doesn't work, create a brand new emulator instance—corrupted system images can mess with adb detection.

Outdated software is a common culprit for compatibility bugs:

• Update Android Studio: Go to Help > Check for Updates (Windows/Linux) or Android Studio > Check for Updates (macOS) and install any available updates.
• Update SDK Tools: Head back to the SDK Settings' SDK Tools tab, check the box for Show Package Details, and make sure all tools (platform-tools, emulator, etc.) are on their latest versions. Click Apply to update.

If nothing else works, try replacing ADB entirely:

• Download the latest platform-tools package directly (search for "Android SDK Platform-Tools" to get it).
• Unzip the downloaded file, then replace the existing platform-tools folder in your Android SDK directory with this new one.
• Restart Android Studio, then run adb version in the Terminal to confirm it's working properly.

内容的提问来源于stack exchange，提问作者Ajiva