Shulou(Shulou.com)06/01 Report--

This article mainly introduces "what is the signature of Android". In the daily operation, I believe that many people have doubts about what the signature of Android is. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful for you to answer the doubt of "what is the signature of Android?" Next, please follow the editor to study!

What is a signature?

If this question is not asked in Android development, if it is put in a general section, I think everyone knows the meaning of signature. But often some of the terms commonly used in life are put in the professional field of computers, and people begin to be confused. Isn't what computers do, or programming languages do, simulating reality as much as possible? Therefore, the signature in the computer is essentially the same as the signature in life, and its role is the same!

Why sign an Android application?

If I could only answer this question in a simple sentence, I would say, "this is what the Android system requires."

The Android system requires that every Android application must be digitally signed before it can be installed into the system, that is, if an Android application is not digitally signed, there is no way to install it into the system! Android uses digital signatures to identify the author of the application and to establish a trust relationship between the application, not to determine which applications the end user can install. This digital signature is done by the author of the application and does not require authentication by an authoritative digital certificate signing authority, it is only used to allow the application package to authenticate itself.

Why does the Android application I develop run on simulators and mobile phones without signing anything?

Just because you didn't sign the Android application doesn't mean the Android application isn't signed. In order to make it easier for us to develop and debug programs, ADT will automatically sign the application using the debug key. Debug key? Where is it? The debug key is a file called debug.keystore whose location is:

System drive letter: / Documents and Settings/liufeng/.android/debug.keystore

Liufeng corresponds to your own windows operating system user name, so, have you found it? This means that if we want to have our own signature instead of having ADT sign it for us, we need to have our own key file (* .KeyStore).

If your previous program is signed by default (i.e. debug signature), once you change the new signature application, you will not be able to overwrite the installation. You must uninstall the original program before you can install it. Because the program covers the installation, there are two main checks:

1) whether the entry Activity of the two programs is the same. If the package names of two programs are different, even if all other code is exactly the same, they will not be regarded as different versions of the same program.

2) whether the signatures used by the two programs are the same. If the two programs use different signatures, even if the package name is the same, it will not be considered different versions of the same program and cannot overwrite the installation.

In addition, some people may think that debug-signed applications can be installed anyway, so there's no need to sign them yourself. Never think of it this way. Debug-signed applications have two limitations, or risks:

1) debug-signed applications cannot be sold on Android Market, it will force you to use your own signature

2) debug.keystore may be generated differently on different machines, which means that if you change the machine to upgrade the apk version, there will be the problem that the above program cannot cover the installation. Do not underestimate this problem, if you develop the program only for your own use, of course, it does not matter, uninstall and then install it. But if your software has a lot of users, this is a big problem, which means that the software does not have the upgrade function!

At this point, the study of "what is the signature of Android" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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