找回Eclipse旧Android应用的application_id，解决版本升级识别问题

Hey Mario, let's tackle this problem step by step—this is a super common issue when migrating from Eclipse to Android Studio, so I’ve got you covered.

Back in the Eclipse era, Android apps didn’t use the applicationId field we have in Gradle today; the app’s unique identifier was just its package name defined in the AndroidManifest.xml. Here are the easiest ways to find it:

• From the old APK file:
  If you still have the original APK of your old app, you can extract its package name using either:

  1. Android Studio’s built-in tool: Go to Build > Analyze APK, select your old APK, then check the AndroidManifest.xml for the package attribute in the root <manifest> tag.
  2. The aapt command-line tool: Run this command in your terminal:

     aapt dump badging path/to/your-old-app.apk
     

     Look for the line starting with package: name='com.your.old.package'—the value inside the quotes is your old app’s identifier (what we now call applicationId).

• From the old Eclipse project:
  If you still have the original Eclipse project files, open the AndroidManifest.xml file. The root <manifest> element has a package attribute—this is exactly the value you need.

• From the app installed on a device:
  If the old app is still installed on a phone, you can use ADB commands to get its package name:

  1. First, list all installed packages to find your app:

     adb shell pm list packages
     

  2. Once you spot your app’s package name, run this to confirm details:

     adb shell dumpsys package com.your.app.package.name
     

  Alternatively, you can use a third-party app like Package Viewer (no root needed) to look up the package name directly on the device.

Once you have the old package name, you need to make two critical changes to your new Android Studio project:

1. Set the correct applicationId in Gradle:
   Open your app module’s build.gradle file, and in the defaultConfig block, set applicationId to match the old package name exactly:

   android {
       defaultConfig {
           applicationId "com.your.old.package.name" // Must match the old app's package name
           minSdkVersion 21
           // Rest of your config...
       }
   }
   

   Even a tiny difference (like uppercase vs lowercase) can cause the system to treat it as a new app, so double-check for exact matches.

2. Use the same signing certificate as the old app:
   This is non-negotiable—Android uses the app’s signature to verify its identity, even if the package name matches. If you sign the new app with a different keystore, the system will reject it as an update.

   • If you have the original keystore file from Eclipse (usually a .keystore or .jks file), configure it in your build.gradle:

     android {
         signingConfigs {
             release {
                 storeFile file("path/to/your-old-keystore.jks")
                 storePassword "your-store-password"
                 keyAlias "your-key-alias"
                 keyPassword "your-key-password"
             }
         }
         buildTypes {
             release {
                 signingConfig signingConfigs.release
                 // Rest of your build config...
             }
         }
     }
     

   • If you don’t have the old keystore, unfortunately, you can’t update the existing app—users will have to uninstall the old version before installing the new one. There’s no way around this, as Android’s security model prevents unsigned or differently signed apps from overwriting each other.

If you’ve done both steps above and it’s still being treated as a new app:

• Verify that the signed APK you’re installing uses the exact same applicationId and signature as the old app. You can use the aapt dump badging command on both APKs to compare the package name and signature details.
• Make sure you’re installing a release build (not a debug build)—debug builds use a default Android Studio keystore, which won’t match your old app’s signature.

内容的提问来源于stack exchange，提问作者mgiammarco