How Android sets the system date and time by applying

How Android sets the system date and time by applying

Android 2.3

Android 4.0

Testing is possible, but requires root access.

Import Java.io.dataoutputstream;import java.io.file;import Java.io.ioexception;import Java.util.Calendar;import Android.os.systemclock;public class Systemdatetime {static final String TAG = "systemdatetime"; public static void SetDate    Time (int year, int month, Int. day, int hour, int minute) throws IOException, interruptedexception {requestpermission ();        Calendar C = calendar.getinstance ();        C.set (Calendar.year, year);        C.set (Calendar.month, month-1);        C.set (Calendar.day_of_month, day);        C.set (Calendar.hour_of_day, HOUR);                        C.set (Calendar.minute, MINUTE);        Long when = C.gettimeinmillis ();        if (when/1000 < Integer.max_value) {Systemclock.setcurrenttimemillis (when);        } Long now = Calendar.getinstance (). Gettimeinmillis ();        LOG.D (TAG, "set tm=" +when + ", now tm=" +now);         if (Now-when >) throw new IOException ("failed to set Date."); }public static void setDate (int year, int month, int day) throws IOException, interruptedexception {requestpermission ();        Calendar C = calendar.getinstance ();        C.set (Calendar.year, year);        C.set (Calendar.month, MONTH);        C.set (Calendar.day_of_month, day);        Long when = C.gettimeinmillis ();        if (when/1000 < Integer.max_value) {Systemclock.setcurrenttimemillis (when);        } Long now = Calendar.getinstance (). Gettimeinmillis ();        LOG.D (TAG, "set tm=" +when + ", now tm=" +now); if (Now-when >) throw new IOException ("failed to set Date.");        public static void SetTime (int hour, int minute) throws IOException, interruptedexception {requestpermission ();        Calendar C = calendar.getinstance ();        C.set (Calendar.hour_of_day, HOUR);        C.set (Calendar.minute, MINUTE); Long when = C.gettimeinmillis (), if (when/1000 < Integer.max_value) {Systemclock.setcurrenttimemillis (when);}   Long now = Calendar.getinstance (). Gettimeinmillis ();     LOG.D (TAG, "set tm=" +when + ", now tm=" +now); if (Now-when >) throw new IOException ("Failed to set time."); static void Requestpermission () throws Interruptedexception, IOException {createsuprocess ("chmod 666/dev/alarm"). WaitFor ();} Static Process createsuprocess () throws IOException {file Rootuser = new File ("/system/xbin/ru"); if (Rootuser.exists ()) { Return Runtime.getruntime (). EXEC (Rootuser.getabsolutepath ());} else {return runtime.getruntime (). EXEC ("su");}} Static Process createsuprocess (String cmd) throws IOException {DataOutputStream os = null; Process process = createsuprocess (); try {os = new DataOutputStream (Process.getoutputstream ()); Os.writebytes (cmd + "\ n") ; Os.writebytes ("Exit $?\n");} finally {if (OS! = null) {try {os.close ()} catch (IOException e) {}}}return process;}}