Android系统要求所有的程序经过数字签名才能安装，如果没有可用的数字签名，系统将不许安装运行此程序。不管是模拟器还是真实设备，只要是android系统，这都适用。鉴于此原因，在设备或者是模拟器上运行调试程序之前，你必须为你的应用程序设置数字签名。

理解android程序签名的重要几点：:

• 　　所有的程序都必须签名，没有被签名的程序，系统将不能安装。

• 　　你可使用自签署证书签署你的应用程序，必须是无凭证授权是的。

• 　　系统仅仅会在安装的时候测试签名证书的有效期，如果应用程序的签名是在安装之后才到期，那么应用程序仍然可以正常启用。

• 　　你可以使用标准工具-Keytool and Jarsigner-生成密钥，来签名应用程序的.apk文件。

-Android system requirements for all programs through digital signatures to install, if there is no available digital signatures, the system will not run the installation program. Whether simulator or real equipment, as long as it is android system, this all applicable. For this reason, in the equipment or simulator operation commissioning before program, you must for your application Settings digital signature.

Understand the important time signature android program: :

· all programs are must sign, not be the signature program, the system will not be installed.

· you can use since the signing certificate signed your application, must be no vouchers authorized yes.

· system will only in the installation test signature the period of validity of the certificate, if the application s signature is in after installation expires, so the application can still normal enabled.

· you can use a standard tools-Keytool and Jarsigner-generate the keys, to sign the application s. Apk files.