Android 12小时制和24小时制的切换

在开发中会涉及到对12小时和24小时的切换，查阅资料终于找到解决方案，代码如下：
1.获取当前小时制：

private String getTimeformat(){
    
    
      return  Settings.System.getString(mContext.getContentResolver(),
                Settings.System.TIME_12_24);
    }

2.切换时区

Settings.System.putString(mContext.getContentResolver(),
                    Settings.System.TIME_12_24,
                    isChecked ? "24" : "12");
            Intent timeChanged = new Intent(Intent.ACTION_TIME_CHANGED);
            int timeFormatPreference =
                    isChecked ? Intent.EXTRA_TIME_PREF_VALUE_USE_24_HOUR
                            : Intent.EXTRA_TIME_PREF_VALUE_USE_12_HOUR;
            timeChanged.putExtra(Intent.EXTRA_TIME_PREF_24_HOUR_FORMAT, timeFormatPreference);
            mContext.sendBroadcast(timeChanged);

private BroadcastReceiver mIntentReceiver = new BroadcastReceiver() {
    
    
        @Override
        public void onReceive(Context context, Intent intent) {
    
    
            updateTimeAndDateDisplay(mContext);
        }
    };

 IntentFilter filter = new IntentFilter();
        filter.addAction(Intent.ACTION_TIME_TICK);
        filter.addAction(Intent.ACTION_TIME_CHANGED);
        filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);
        mContext.registerReceiver(mIntentReceiver, filter);

private void updateTimeAndDateDisplay(Context context) {
    
    
        String format = getTimeformat();
        final Calendar now = Calendar.getInstance();
        String dateform="";
        if(!TextUtils.isEmpty(format)) {
    
    
            if (format.equals("12")) {
    
    
                dateform = "hh:mmaa";
            } else {
    
    
                dateform = "HH:mm";
            }
        }else{
    
    
            dateform = "HH:mm"; 
        }
        SimpleDateFormat sdf = new SimpleDateFormat(dateform);
        String currenttime = sdf.format(now.getTime());
		Log.e("MainActivity","currenttime:"+currenttime+"---format:"+format);
        if(!TextUtils.isEmpty(format)) {
    
    
            if (format.equals("12")) {
    
    
                if (currenttime.contains("上午")) {
    
    
                    currenttime = "上午" + currenttime.substring(0, currenttime.indexOf("上午"));
                } else {
    
    
                    currenttime = "下午" + currenttime.substring(0, currenttime.indexOf("下午"));
                }
            }
        }
        time_textview.setText(currenttime);
//        mTimeZone.setSummary(ZoneGetter.getTimeZoneOffsetAndName(getActivity(),
//                now.getTimeZone(), now.getTime()));
    }

就这样就可以切换小时制了