我建议不仅存储布尔标志，还存储完整的版本代码。这样，您也可以在开始时查询它是否是新版本中的第一个开始。例如，您可以使用此信息显示“新功能”对话框。
以下代码应可在任何“属于上下文”的Android类（活动，服务等）中使用。如果您希望将其放在单独的（POJO）类中，则可以考虑使用“静态上下文”，例如此处所述。
/**
* Distinguishes different kinds of app starts: <li>
* <ul>
* First start ever ({@link #FIRST_TIME})
* </ul>
* <ul>
* First start in this version ({@link #FIRST_TIME_VERSION})
* </ul>
* <ul>
* Normal app start ({@link #NORMAL})
* </ul>
*
* @author schnatterer
*
*/
public enum AppStart {
FIRST_TIME, FIRST_TIME_VERSION, NORMAL;
}
/**
* The app version code (not the version name!) that was used on the last
* start of the app.
*/
private static final String LAST_APP_VERSION = "last_app_version";
/**
* Finds out started for the first time (ever or in the current version).<br/>
* <br/>
* Note: This method is <b>not idempotent</b> only the first call will
* determine the proper result. Any subsequent calls will only return
* {@link AppStart#NORMAL} until the app is started again. So you might want
* to consider caching the result!
*
* @return the type of app start
*/
public AppStart checkAppStart() {
PackageInfo pInfo;
SharedPreferences sharedPreferences = PreferenceManager
.getDefaultSharedPreferences(this);
AppStart appStart = AppStart.NORMAL;
try {
pInfo = getPackageManager().getPackageInfo(getPackageName(), 0);
int lastVersionCode = sharedPreferences
.getInt(LAST_APP_VERSION, -1);
int currentVersionCode = pInfo.versionCode;
appStart = checkAppStart(currentVersionCode, lastVersionCode);
// Update version in preferences
sharedPreferences.edit()
.putInt(LAST_APP_VERSION, currentVersionCode).commit();
} catch (NameNotFoundException e) {
Log.w(Constants.LOG,
"Unable to determine current app version from pacakge manager. Defenisvely assuming normal app start.");
}
return appStart;
}
public AppStart checkAppStart(int currentVersionCode, int lastVersionCode) {
if (lastVersionCode == -1) {
return AppStart.FIRST_TIME;
} else if (lastVersionCode < currentVersionCode) {
return AppStart.FIRST_TIME_VERSION;
} else if (lastVersionCode > currentVersionCode) {
Log.w(Constants.LOG, "Current version code (" + currentVersionCode
+ ") is less then the one recognized on last startup ("
+ lastVersionCode
+ "). Defenisvely assuming normal app start.");
return AppStart.NORMAL;
} else {
return AppStart.NORMAL;
}
}
可以从这样的活动中使用它：
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
switch (checkAppStart()) {
case NORMAL:
// We don't want to get on the user's nerves
break;
case FIRST_TIME_VERSION:
// TODO show what's new
break;
case FIRST_TIME:
// TODO show a tutorial
break;
default:
break;
}
// ...
}
// ...
}
可以使用此JUnit测试来验证基本逻辑：
public void testCheckAppStart() {
// First start
int oldVersion = -1;
int newVersion = 1;
assertEquals("Unexpected result", AppStart.FIRST_TIME,
service.checkAppStart(newVersion, oldVersion));
// First start this version
oldVersion = 1;
newVersion = 2;
assertEquals("Unexpected result", AppStart.FIRST_TIME_VERSION,
service.checkAppStart(newVersion, oldVersion));
// Normal start
oldVersion = 2;
newVersion = 2;
assertEquals("Unexpected result", AppStart.NORMAL,
service.checkAppStart(newVersion, oldVersion));
}
稍加努力，您就可以测试与android相关的东西（PackageManager和SharedPreferences）。对编写测试感兴趣吗？:)
请注意，以上代码仅在您不搞乱android:versionCodeAndroidManifest.xml中的情况下才能正常工作！