Here we need to use the mobile phone signature tool ZipSigner, which can not only sign APK, but also support zip and jar formats. You can also use it to sign the ROM package after you modify it yourself. Let's put it on our mobile phones first.
Delete APK original signature file
We open the modified APK on the computer with decompression software, open it to the META-INF folder, and delete several signature files in it. This step is to improve the success rate of signature, and it is usually not necessary to do it.
APK signature
ZipSigner opens the interface after installation, as shown in the figure below. The default signature file on SD card is unsigned.zip. You can change the APK that needs to be signed to this name, put it in the root directory of SD card, and sign it. After signing, just change the suffix of signed.zip to APK. You can also put the APK file to be signed in the root directory of SD card without renaming it, and then click "Select Input/Output File" to find the APK to be signed, and the input/output file name of ZipSigner in the program will automatically change accordingly. After the file is selected, click "Select File by Signature" and the signature will be completed soon.
Install after signing
Let's verify whether the signed APK program can be installed normally, and use the file manager to find the newly signed APK on the SD card and install it. Sure enough, it can be installed normally. All right, let's call it a day.
Signing a contract is actually a very simple process, but we can simplify it with procedures. Of course, we should remember a principle that no matter what elements of APK are modified, as long as the structure of APK changes, it must be re-signed before it can be used normally.