Versioning is a critical component of your application upgrade/maintenance strategy.
The Android system itself does not ever check the application version information for an application, such as to enforce restrictions on upgrades, compatibility, and so on. Instead, only users or applications themselves are responsible for enforcing any version restrictions for applications themselves.
The Android system does check any system version compatibility expressed
by an application in its manifest, in the minSdkVersion attribute. This
allows an application to specify the minimum system API with which is compatible.
For more information see Specifying Minimum System API Version.
To define the version information for your application, you set attributes in the application's manifest file. Two attributes are available, and you should always define values for both of them:
android:versionCode — An integer value that represents
the version of the application code, relative to other versions.
The value is an integer so that other applications can programatically evaluate it, for example to check an upgrade or downgrade relationship. You can set the value to any integer you want, however you should make sure that each successive release of your application uses a greater value. The system does not enforce this behavior, but increasing the value with successive releases is normative.
Typically, you would release the first version of your application with
versionCode set to 1, then monotonically increase the value with each release,
regardless whether the release constitutes a major or minor release. This means
that the android:versionCode value does not necessarily have a
strong resemblence to the application release version that is visible to the
user (see android:versionName, below). Applications and publishing
services should not display this version value to users.
android:versionName — A string value that represents the
release version of the application code, as it should be shown to users.
The value is a string so that you can describe the application version as a <major>.<minor>.<point> string, or as any other type of absolute or relative version identifier.
As with android:versionCode, the system does not use this value
for any internal purpose, other than to enable applications to display it to
users. Publishing services may also extract the android:versionName
value for display to users.
You define both of these version attributes in the
<manifest> element of the manifest file.
Here's an example manifest that shows the android:versionCode
and android:versionName attributes in the
<manifest> element.
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.package.name"
android:versionCode="2"
android:versionName="1.1">
<application android:icon="@drawable/icon" android:label="@string/app_name">
...
</application>
</manifest>
In this example, note that android:versionCode value indicates
that the current .apk contains the second release of the application code, which
corresponds to a minor follow-on release, as shown by the
android:codeName string.
The Android framework provides an API to let applications query the system
for version information about your application. To obtain version information,
applications use the
getPackageInfo(java.lang.String, int)
method of PackageManager.
If your application requires a specific minimum version of the Android platform, or is designed only to support a certain range of Android platform versions, you can specify those version requirements as API Level identifiers in the application's manifest file. Doing so ensures that your application can only be installed on devices that are running a compatible version of the Android system.
To specify API Level requirements, add a <uses-sdk>
element in the application's manifest, with one or more of these attributes:
android:minSdkVersion — The minimum version
of the Android platform on which the application will run, specified
by the platform's API Level identifier. android:targetSdkVersion — Specifies the API Level
on which the application is designed to run. In some cases, this allows the
application to use manifest elements or behaviors defined in the target
API Level, rather than being restricted to using only those defined
for the minimum API Level.android:maxSdkVersion — The maximum version
of the Android platform on which the application is designed to run,
specified by the platform's API Level identifier. Important: Please read the <uses-sdk>
documentation before using this attribute. When preparing to install your application, the system checks the value of this
attribute and compares it to the system version. If the
android:minSdkVersion value is greater than the system version, the
system aborts the installation of the application. Similarly, the system
installs your application only if its android:maxSdkVersion
is compatible with the platform version.
If you do not specify these attributes in your manifest, the system assumes that your application is compatible with all platform versions, with no maximum API Level.
To specify a minimum platform version for your application, add a
<uses-sdk> element as a child of
<manifest>, then define the
android:minSdkVersion as an attribute.
For more information, see the <uses-sdk>
manifest element documentation and the API Levels document.