android 获得系统时间

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <!-- 显示网络状态的标签控件 -->
    <TextView
        android:id="@+id/myyl"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp" />

</RelativeLayout>

package com.example.yanlei.yl;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.format.DateFormat;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Calendar;


public class MainActivity extends AppCompatActivity {

    private TextView pTextView;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        pTextView = (TextView) findViewById(R.id.myyl);
        SimpleDateFormat sDateFormat;

        String date;

        if (DateFormat.is24HourFormat(getApplicationContext())) {
            sDateFormat = new SimpleDateFormat("yyyy-MM-dd  HH:mm:ss");
            date = sDateFormat.format(new java.util.Date());

        } else {
            sDateFormat = new SimpleDateFormat("yyyy-MM-dd  hh:mm:ss");
            date = sDateFormat.format(new java.util.Date()) + getPeroidText();

        }
        pTextView.setText("时间:" + date);
    }


    private CharSequence getPeroidText() {

        String am_pm = Calendar.getInstance().getTime().getHours() >= 12 ? "PM" : "AM";

        return am_pm;

    }


}