如何在Android中获取应用程序安装日期的当前日期和时间

我想在Android中获取Android应用程序安装日期。但是当我运行该应用程序时，出现NullPointerException。有人可以帮帮我吗。

这是我的代码

public void onCreate(Bundle savedInstanceState)
     {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.registration_details);

        try 
        {        long installed = 
                 context.getPackageManager().getPackageInfo("package.com.sqlitedemo",          
                 PackageManager.GET_META_DATA).firstInstallTime;
                 Log.e("installed  = ","  "  + installed);
        }
        catch (NameNotFoundException e) 
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
}

这是我的日志猫错误

08-06 11:40:34.758: E/AndroidRuntime(335): FATAL EXCEPTION: main
08-06 11:40:34.758: E/AndroidRuntime(335): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sqlitedemo/com.sqlitedemo.Registration_Form}: java.lang.NullPointerException
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.os.Looper.loop(Looper.java:123)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.ActivityThread.main(ActivityThread.java:3683)
08-06 11:40:34.758: E/AndroidRuntime(335):  at java.lang.reflect.Method.invokeNative(Native Method)
08-06 11:40:34.758: E/AndroidRuntime(335):  at java.lang.reflect.Method.invoke(Method.java:507)
08-06 11:40:34.758: E/AndroidRuntime(335):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-06 11:40:34.758: E/AndroidRuntime(335):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-06 11:40:34.758: E/AndroidRuntime(335):  at dalvik.system.NativeStart.main(Native Method)
08-06 11:40:34.758: E/AndroidRuntime(335): Caused by: java.lang.NullPointerException
08-06 11:40:34.758: E/AndroidRuntime(335):  at com.sqlitedemo.Registration_Form.onCreate(Registration_Form.java:61)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
08-06 11:40:34.758: E/AndroidRuntime(335):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
08-06 11:40:34.758: E/AndroidRuntime(335):  ... 11 more

谢谢欣赏。