RE: app-release-unsigned.apk – Can’t install?
Yes, you are correct. An Android application package (APK) must be signed before it can be installed on an Android device. The signing process adds a cryptographic signature to the APK file, which verifies that the file has not been tampered with and comes from a legitimate source. This is a necessary security measure enforced by the Android operating system. The `app-release-unsigned.apk` file you have is an unsigned version of an application and cannot be directly installed. Here are the steps you typically need to follow to sign an APK: **Manual Signing with jarsigner:** 1. Generate a keystore (if you don't already have one) using the `keytool` that comes with the JDK: ```sh keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000 ``` This command asks for some information, like organizational details and a password. Remember to keep the keystore file and the passwords secure, as you will need them for future app updates. 2. Sign the APK with the `jarsigner` tool: ```sh jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.keystore app-release-unsigned.apk alias_name ``` Replace `my-release-key.keystore` with the path to your actual keystore file, `app-release-unsigned.apk` with the path to your APK, and `alias_name` with your keystore alias. 3. If you're targeting Android 7.0 (API level 24) or higher, you should also use the `apksigner` tool (which provides stronger protection against unauthorized alterations to the APK) to sign the APK instead of `jarsigner` or after using `jarsigner`. Here's how: ```sh apksigner sign --ks my-release-key.keystore --ks-key-alias alias_name app-release-unsigned.apk ``` You'll be prompted for the keystore and key passwords. 4. Once signed, you should align the APK with the `zipalign` tool to ensure that all uncompressed data starts with a particular byte alignment, which reduces the amount of RAM consumed by an app: ```sh zipalign -v 4 app-release-unsigned.apk app-release-signed.apk ``` This creates a new APK file, `app-release-signed.apk`, which is now ready for installation. **Automated Signing with Android Studio:** If you are using Android Studio, it automates the signing process for you when you generate a signed APK. To do this: 1. Click on Build > Generate Signed Bundle / APK. 2. Follow the prompts to create a new keystore (if necessary), select your keystore and enter its password, and fill in key details. 3. Choose the build type and APK destination. **Installing the Signed APK:** After you have your signed `app-release-signed.apk`, you can install it on your device. You can either: - Transfer it to your device and install it through a file manager app. - Install it via ADB with the following command: ```sh adb install path_to_your_app-release-signed.apk ``` Remember that for an APK to be installed on a non-development device (i.e., user devices), the APK should be signed with the release key, not the debug key, and the release key keystore should be kept in a safe place since you will need it for future updates of your app.