1) APK tool 2) DEX2JAR 3) JD-GUI 4) Basic technical requirements of signature tools 1) Have certain JAVA code reading ability 2) Have a little Android foundation. The more, the better. 3) I will use some tools related to Android debugging in eclipse. 4) I will know the grammar specification and custom fields of smali. 5) I have the ability to change my mind. 6) Although modifying the code is to modify its smali file (using smali grammar), although its language is very complicated and we can adapt it, I need to know the grammar specification and custom fields of smali. Understanding the above methods can easily crack AndroidAPK. After cracking, the page layout, code logic and structure algorithm in the application are clear at a glance. Therefore, in order to avoid being learned by others, especially competitors, it is particularly important to prevent cracking and decompilation. I tried code obfuscation, but code obfuscation only changed the class name, making it harder for the cracker to understand, and it didn't really stop decompiling the project. The following is the APK code structure with chaotic code. As you can see, only the class name is converted into a, b, c and other names. But you can still decompile. Later, I tried to reinforce APK with 360 reinforcement protection, and found that the original code program was hidden and could not be decompiled. Therefore, as a mobile application developer, it is beneficial to protect your application security to properly understand some cracking and decompiling work. If you don't nip in the bud, once there is piracy, then your APP is likely to be abandoned by the market.