网络时间同步

1，froyo\packages\apps\Settings\AndroidManifest.xml

注册一个service

2，froyo\packages\apps\Settings\src\com\android\settings\DateTimeSettings.java

导入包文件：import com.android.settings.sntp.SNTP;

把public void onSharedPreferenceChanged(SharedPreferences preferences, String key){

}方法改成如下

public void onSharedPreferenceChanged(SharedPreferences preferences, String key) {
if (key.equals(KEY_DATE_FORMAT)) {
String format = preferences.getString(key,
getResources().getString(R.string.default_date_format));
Settings.System.putString(getContentResolver(),
Settings.System.DATE_FORMAT, format);
updateTimeAndDateDisplay();
} else if (key.equals(KEY_AUTO_TIME)) {
boolean autoEnabled = preferences.getBoolean(key, true);

/* add at 2011.6.21 */
if( autoEnabled ){

// Log.d("---------->"," startService !! " );

Intent intent = new Intent(DateTimeSettings.this,SNTP.class);

intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

startService(intent);

}else{

// Log.d("---------->"," endService !! " );

Intent intent = new Intent(DateTimeSettings.this,SNTP.class);

stopService(intent) ;

}

Settings.System.putInt(getContentResolver(),
Settings.System.AUTO_TIME,
autoEnabled ? 1 : 0);
mTimePref.setEnabled(!autoEnabled);
mDatePref.setEnabled(!autoEnabled);
mTimeZone.setEnabled(!autoEnabled);
}
}

3，froyo\packages\apps\Settings\src\com\android\settings\sntp\SNTP.java

加入此service文件

package com.android.settings.sntp ;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Calendar;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.SystemClock;
import android.text.format.DateFormat;
import android.util.Log;

import android.content.Context;
import android.os.Handler;
import android.app.Service;
import android.os.IBinder;

/**
* {@hide}
*
* Simple SNTP client class for retrieving network time.
*
* Sample usage:
* <pre>
* SntpClient client = new SntpClient();
* if (client.requestTime("203.117.180.36")) {
* long now = client.getNtpTime() + SystemClock.elapsedRealtime() - client.getNtpTimeReference();
* }
* </pre>
*/

public class SNTP extends Service {

private static final String TAG = "SNTP--->";
private static final boolean DBUG = true;
private static Context mContext ;

/*public static void SNTP( Context context ) {
mContext = context ;
}*/

@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}

@Override
public void onDestroy()
{
mSntpHandler.removeCallbacks(mSntpTask);
if(DBUG) Log.d(TAG," SNTP Service end !! " );
}

@Override
public void onStart(Intent intent, int startId){
super.onStart(intent, startId);

if(DBUG) Log.d(TAG," start SNTP Service !! " );
startSyncSNTP();
}

public void startSyncSNTP() {
mSntpHandler.postDelayed(mSntpTask, 10);
}

private Handler mSntpHandler = new Handler();

private Runnable mSntpTask = new Runnable(){
public void run(){
mSntpHandler.removeCallbacks(mSntpTask);
if( ! syncSNTP() ) {
mSntpHandler.postDelayed(mSntpTask, 3000);
}
}
};

public boolean syncSNTP( ) {
SntpClient client = new SntpClient();
if(client.requestTime("203.117.180.36",3000)) {

long now = client.getNtpTime() + SystemClock.elapsedRealtime() - client.getNtpTimeReference();

CharSequence ch=DateFormat.format("hh:mm:ss", now );
if(DBUG) Log.d(TAG,"ch="+ch);
CharSequence date=DateFormat.format("yyyy MM dd", now);
if(DBUG) Log.d(TAG,"date="+date);

if( SystemClock.setCurrentTimeMillis(now) ){
if(DBUG) Log.d(TAG,"set Current Time ="+System.currentTimeMillis());
}else{
if(DBUG) Log.d(TAG," set Current Time false !" );
}

}else{
if(DBUG) Log.d(TAG,"sntp request time false !!" );
return false ;
}

return true ;
}

public class SntpClient
{
private static final int NTP_PACKET_SIZE = 48 ;
private static final int NTP_PORT = 123;
private static final int NTP_MODE_CLIENT = 3;
private static final int NTP_VERSION = 3;
/*
* Number of seconds between Jan 1, 1900 and Jan 1, 1970
* 70 years plus 17 leap days
*/
private static final long OFFSET_1900_TO_1970 = ((365L * 70L) + 17L) * 24L * 60L * 60L;
private static final int TRANSMIT_TIME_OFFSET = 40;

private static final int ORIGINATE_TIME_OFFSET = 24;
private static final int RECEIVE_TIME_OFFSET = 32;

// system time computed from NTP server response
private long mNtpTime;
// value of SystemClock.elapsedRealtime() corresponding to mNtpTime
private long mNtpTimeReference;
// round trip time in milliseconds
private long mRoundTripTime;

public boolean requestTime(String host, int timeout) {

try {
DatagramSocket socket = new DatagramSocket();
socket.setSoTimeout(timeout);

InetAddress address = InetAddress.getByName(host);
byte[] buffer = new byte[NTP_PACKET_SIZE];
DatagramPacket request = new DatagramPacket(buffer, buffer.length, address, NTP_PORT);
/*
* set mode = 3 (client) and version = 3
* mode is in low 3 bits of first byte
* version is in bits 3-5 of first byte
*/
buffer[0] = NTP_MODE_CLIENT | (NTP_VERSION << 3);
//get current time and write it to the request packet
long requestTime = System.currentTimeMillis();
if(DBUG) Log.d(TAG, "System.currentTimeMillis(): " + requestTime + " ms");
long requestTicks = SystemClock.elapsedRealtime();
writeTimeStamp(buffer, TRANSMIT_TIME_OFFSET, requestTime);
socket.send(request);

// read the response
DatagramPacket response = new DatagramPacket(buffer, buffer.length);
socket.receive(response);
long responseTicks = SystemClock.elapsedRealtime();
long responseTime = requestTime + (responseTicks - requestTicks);
socket.close();

// extract the results
long originateTime = readTimeStamp(buffer, ORIGINATE_TIME_OFFSET);
long receiveTime = readTimeStamp(buffer, RECEIVE_TIME_OFFSET);
long transmitTime = readTimeStamp(buffer, TRANSMIT_TIME_OFFSET);
long roundTripTime = responseTicks - requestTicks - (transmitTime - receiveTime);
long clockOffset = (receiveTime - originateTime) + (transmitTime - responseTime);
if(DBUG) Log.d(TAG, "round trip: " + roundTripTime + " ms");
if(DBUG) Log.d(TAG, "clock offset: " + clockOffset + " ms");

// save our results
mNtpTime = receiveTime;//requestTime + clockOffset;
mNtpTimeReference = requestTicks;
mRoundTripTime = roundTripTime;

}catch (Exception e) {
// TODO: handle exception
if(DBUG) Log.d(TAG, "error: " + e);
return false;
}

return true ;
}

/**
* Returns the time computed from the NTP transaction.
*
* @return time value computed from NTP server response.
*/
public long getNtpTime() {
return mNtpTime;
}

/**
* Returns the reference clock value (value of SystemClock.elapsedRealtime())
* corresponding to the NTP time.
*
* @return reference clock corresponding to the NTP time.
*/
public long getNtpTimeReference() {

return mNtpTimeReference;
}

/**
* Returns the round trip time of the NTP transaction
*
* @return round trip time in milliseconds.
*/
public long getRoundTripTime() {
return mRoundTripTime;
}

/**
* Reads an unsigned 32 bit big endian number from the given offset in the buffer.
*/
private long read32(byte[] buffer, int offset) {
byte b0 = buffer[offset];
byte b1 = buffer[offset+1];
byte b2 = buffer[offset+2];
byte b3 = buffer[offset+3];

// convert signed bytes to unsigned values
int i0 = ((b0 & 0x80) == 0x80 ? (b0 & 0x7F) + 0x80 : b0);
int i1 = ((b1 & 0x80) == 0x80 ? (b1 & 0x7F) + 0x80 : b1);
int i2 = ((b2 & 0x80) == 0x80 ? (b2 & 0x7F) + 0x80 : b2);
int i3 = ((b3 & 0x80) == 0x80 ? (b3 & 0x7F) + 0x80 : b3);
return ((long)i0 << 24) + ((long)i1 << 16) + ((long)i2 << 8) + (long)i3;
}

/**
* Reads the NTP time stamp at the given offset in the buffer and returns
* it as a system time (milliseconds since January 1, 1970).
*/
private long readTimeStamp(byte[] buffer, int offset) {
long seconds = read32(buffer, offset);
long fraction = read32(buffer, offset + 4);
return ((seconds - OFFSET_1900_TO_1970) * 1000) + ((fraction * 1000L) / 0x100000000L);
}

/**
* Writes system time (milliseconds since January 1, 1970) as an NTP time stamp
* at the given offset in the buffer.
*/
private void writeTimeStamp(byte[] buffer, int offset, long time) {
long seconds = time / 1000L;
long milliseconds = time - seconds * 1000L;
seconds += OFFSET_1900_TO_1970;

// write seconds in big endian format
buffer[offset++] = (byte)(seconds >> 24);
buffer[offset++] = (byte)(seconds >> 16);
buffer[offset++] = (byte)(seconds >> 8);
buffer[offset++] = (byte)(seconds >> 0);
long fraction = milliseconds * 0x100000000L / 1000L;

// write fraction in big endian format
buffer[offset++] = (byte)(fraction >> 24);
buffer[offset++] = (byte)(fraction >> 16);
buffer[offset++] = (byte)(fraction >> 8);

// low order bits should be random data
buffer[offset++] = (byte)(Math.random() * 255.0);

}
}//class SntpClient

}

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