The purpose of this signature mechanism is to ensure the authenticity of the source of Apk and that Apk has not been tampered with by a third party. By signing the Apk, the developer wrote a "fingerprint" in the Apk. After the fingerprint is written, any modification in Apk will invalidate the fingerprint, and the Android system will invalidate it when installing Apk for signature verification, thus ensuring security.
Extended data:
Format definition of 1 and APK
In the Android platform, the execution file of dalvikvm is encapsulated in apk format, and eventually the runtime loader will decompress it, and then obtain the security access related to the permission branch in the compiled androidmanifest.xml file, but there are still many security restrictions. If you transfer the apk file to the /system/app folder, you will find that the execution is unrestricted. The installed file may not be in this folder, but in androidrom, the apk file of the system will be placed in this folder by default, and it has root permission.
2. The development environment of 2.APK
Android is a Java-based development environment, and Google has done an excellent job in writing API documents and providing samples.
Step 3 get the SDK
Download and install the SDK [Software Development Kit] of android, which mainly includes core library files, a simulator, development tools and some demo sample files. Eclipse and androideclipse extensions are recommended. If you only use android, Eclipse IDE is enough, but if you are developing a Java application for the first time, it is recommended to download the complete Java SE Development Tool (JDK) because it contains the tools needed to sign and publish the application.
4.APK application architecture
Android application architecture is very important. If you don't learn, the designed game will be a product that is difficult to fix bugs. You need to understand applications, activities, intentions and how they interact. Google provides a good information architecture here. What is really important is to understand why designing a game requires more than one activity process and how to design a game with good user experience. These should be integrated into the application life cycle.
5. Life cycle of 5.APK application
The life cycle of the application is managed by the Android OS operating system, and all active processes will be created as system commands. It is extremely important for applications to handle these events correctly, because end users don't know what is right. You'd better know this before you start designing the game, because it will save debugging time and avoid expensive redesign.
For most applications, the default settings can start to work, but for games, you may need to adjust the signal of the singleton instance to on. Android will create a new active instance process by default, because it thinks it is more appropriate, while the game may only want to have an active instance process, which has little impact and needs to know some system state management.
Baidu encyclopedia -apk
Baidu Encyclopedia-Android Software Development