android下如何设置系统时间

最近做项目涉及到了怎么设置系统时间，起初觉得这个问题是很简单的，但是事实并非如此，在这个问题上卡壳了好几天。

试了好几种方法，总算有了一定的成果。

1：

第一反应是查看android setting的源码（packages\apps\Settings），因为系统-日期和时间里面有能够设置时间的选项。

在其DateTimeSettings里面发现了它是利用Calendar和系统类SystemClock来进行设置时间，我依样画葫芦，却提示Unable to open alarm driver。

百度了下，对于这个问题众说缤纷，有说是缺少权限配置文件，有说是通过把应用改为系统应用，来达到使用这个api的目的。把应用改为系统应用肯定不能满足我的需求，于是我又去试了下前面的方法，我在配置文件里面增加了这个权限。

  <uses-permission android:name="android.permission.WRITE_SETTINGS" />

结果依然提示我Unable to open alarm driver。

2：

因为我的应用允许Root，所以我第二反应是想到利用linux命令来进行设置系统时间。但是我试了好几种方法,

系统时间虽然可以设置，但是却出现了时间不准确，甚至系统崩溃重启的情况。

Runtime.getRuntime().exec("su");RootTools.sendShell("date -s 20130409 \n",10);RootTools.sendShell("date -s 1311420409637 \n",10);

3：

搜遍了所有的中文android论坛，对于这个问题的解决方法都是千篇一律，后来总算在stackoverflow上面找到了答案。

给出的解决方法有二种，一种是修改系统的/dev/alarm文件，一种是直接利用date -s 命令。

方法一：

 public void setTime(long time) {    if (ShellInterface.isSuAvailable()) {      ShellInterface.runCommand("chmod 666 /dev/alarm");      SystemClock.setCurrentTimeMillis(time);      ShellInterface.runCommand("chmod 664 /dev/alarm");    }  }

/** * Interface to the Superuser shell on Android devices with some helper functions.<p/><p/> * Common usage for su shell:<p/> * <code>if(ShellInterface.isSuAvailable()) { ShellInterface.runCommand("reboot"); }</code> * <p/><p/> * To get process output as a String:<p/> * <code>if(ShellInterface.isSuAvailable()) { String date = ShellInterface.getProcessOutput("date"); }</code> * <p/><p/> * To run command with standard shell (no root permissions): * <code>ShellInterface.setShell("sh");</code><p/> * <code>ShellInterface.runCommand("date");</code> * <p/><p/> * Date: Mar 24, 2010 * Time: 4:14:07 PM * * @author serge */public class ShellInterface {  private static final String TAG = "ShellInterface";  private static String shell;  // uid=0(root) gid=0(root)  private static final Pattern UID_PATTERN = Pattern.compile("^uid=(\\d+).*?");  enum OUTPUT {    STDOUT,    STDERR,    BOTH  }  private static final String EXIT = "exit\n";  private static final String[] SU_COMMANDS = new String[]{    "su",    "/system/xbin/su",    "/system/bin/su"  };  private static final String[] TEST_COMMANDS = new String[]{    "id",    "/system/xbin/id",    "/system/bin/id"  };  public static synchronized boolean isSuAvailable() {    if (shell == null) {      checkSu();    }    return shell != null;  }  public static synchronized void setShell(String shell) {    ShellInterface.shell = shell;  }  private static boolean checkSu() {    for (String command : SU_COMMANDS) {      shell = command;      if (isRootUid()) return true;    }    shell = null;    return false;  }  private static boolean isRootUid() {    String out = null;    for (String command : TEST_COMMANDS) {      out = getProcessOutput(command);      if (out != null && out.length() > 0) break;    }    if (out == null || out.length() == 0) return false;    Matcher matcher = UID_PATTERN.matcher(out);    if (matcher.matches()) {      if ("0".equals(matcher.group(1))) {        return true;      }    }    return false;  }  public static String getProcessOutput(String command) {    try {      return _runCommand(command, OUTPUT.STDERR);    } catch (IOException ignored) {      return null;    }  }  public static boolean runCommand(String command) {    try {      _runCommand(command, OUTPUT.BOTH);      return true;    } catch (IOException ignored) {      return false;    }  }  private static String _runCommand(String command, OUTPUT o) throws IOException {    DataOutputStream os = null;    Process process = null;    try {      process = Runtime.getRuntime().exec(shell);      os = new DataOutputStream(process.getOutputStream());      InputStreamHandler sh = sinkProcessOutput(process, o);      os.writeBytes(command + '\n');      os.flush();      os.writeBytes(EXIT);      os.flush();      process.waitFor();      if (sh != null) {        String output = sh.getOutput();        Log.d(TAG, command + " output: " + output);        return output;      } else {        return null;      }    } catch (Exception e) {      final String msg = e.getMessage();      Log.e(TAG, "runCommand error: " + msg);      throw new IOException(msg);    } finally {      try {        if (os != null) {          os.close();        }        if (process != null) {          process.destroy();        }      } catch (Exception ignored) {}    }  }  public static InputStreamHandler sinkProcessOutput(Process p, OUTPUT o) {    InputStreamHandler output = null;    switch (o) {      case STDOUT:        output = new InputStreamHandler(p.getErrorStream(), false);        new InputStreamHandler(p.getInputStream(), true);        break;      case STDERR:        output = new InputStreamHandler(p.getInputStream(), false);        new InputStreamHandler(p.getErrorStream(), true);        break;      case BOTH:        new InputStreamHandler(p.getInputStream(), true);        new InputStreamHandler(p.getErrorStream(), true);        break;    }    return output;  }  private static class InputStreamHandler extends Thread {    private final InputStream stream;    private final boolean     sink;    StringBuffer output;    public String getOutput() {      return output.toString();    }    InputStreamHandler(InputStream stream, boolean sink) {      this.sink = sink;      this.stream = stream;      start();    }    @Override    public void run() {      try {        if (sink) {          while (stream.read() != -1) {}        } else {          output = new StringBuffer();          BufferedReader b = new BufferedReader(new InputStreamReader(stream));          String s;          while ((s = b.readLine()) != null) {            output.append(s);          }        }      } catch (IOException ignored) {}    }  }}

方法二：

public void setDate()    {        try {            Process process = Runtime.getRuntime().exec("su");        DataOutputStream os = new DataOutputStream(process.getOutputStream());            os.writeBytes("date -s 20120419.024012; \n");        } catch (Exception e) {            Log.d(TAG,"error=="+e.toString());            e.printStackTrace();        }    }

总结：出现了这种问题，归根究底在于我自己的知识积累不够，对于linux命令熟悉度不高，应当多加强多接触这方面的知识，弥补不足。

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