android系统修改系统时间和日期源码

tvMain = (TextView) findViewById(R.id.tv_main);  
tvMain.setText(TimeUtils.getDateFormat(System.currentTimeMillis()));  
  
datePicker = (DatePicker) findViewById(R.id.datePicker1);  
findViewById(R.id.button1).setOnClickListener(new OnClickListener() {  
  
    @Override  
    public void onClick(View arg0) {  
        Calendar canlendar = Calendar.getInstance();  
        int year = datePicker.getYear();  
        int month = datePicker.getMonth();  
        int day = datePicker.getDayOfMonth();  
        canlendar.set(Calendar.YEAR, year);  
        canlendar.set(Calendar.MONTH, month);  
        canlendar.set(Calendar.DAY_OF_MONTH, day);  
        long when = canlendar.getTimeInMillis();  
        if (when / 1000 < Integer.MAX_VALUE) {  
            SystemClock.setCurrentTimeMillis(when); // 需要系统权限才能执行  
            tvMain.setText(canlendar.get(Calendar.YEAR) + "/" + ((canlendar.get(Calendar.MONTH) + 1)) + "/"  
                    + canlendar.get(Calendar.DAY_OF_MONTH));  
        }  
    }  
});  
  
findViewById(R.id.button2).setOnClickListener(new OnClickListener() {  
  
    @Override  
    public void onClick(View arg0) {  
        tvMain.setText(TimeUtils.getDateFormat(System.currentTimeMillis()));  
    }