从如何获得完整的日期与正确的格式?：

请使用

android.text.format.DateFormat.getDateFormat(Context context)
android.text.format.DateFormat.getTimeFormat(Context context)

获得当前用户设置意义上的有效时间和日期格式(例如12/24时间格式)。

import android.text.format.DateFormat;

private void some() {
    final Calendar t = Calendar.getInstance();
    textView.setText(DateFormat.getTimeFormat(this/*Context*/).format(t.getTime()));
}

为显示当前日期和时间的Textview

    /// For Show Date
    String currentDateString = DateFormat.getDateInstance().format(new Date());
    // textView is the TextView view that should display it
    textViewdate.setText(currentDateString);
    /// For Show Time
    String currentTimeString = DateFormat.getTimeInstance().format(new Date());
    // textView is the TextView view that should display it
    textViewtime.setText(currentTimeString);

检查完整的代码Android -显示当前日期和时间在一个Android Studio示例的源代码

public class XYZ extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.main);

        Calendar c = Calendar.getInstance();
        System.out.println("Current time => "+c.getTime());

        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String formattedDate = df.format(c.getTime());
        // formattedDate have current date/time
        Toast.makeText(this, formattedDate, Toast.LENGTH_SHORT).show();


      // Now we display formattedDate value in TextView
        TextView txtView = new TextView(this);
        txtView.setText("Current Date and Time : "+formattedDate);
        txtView.setGravity(Gravity.CENTER);
        txtView.setTextSize(20);
        setContentView(txtView);
    }

}

试试下面的代码:

SimpleDateFormat dateFormat = new SimpleDateFormat(
                                    "yyyy/MM/dd HH:mm:ss");

Calendar cal = Calendar.getInstance();
System.out.println("time => " + dateFormat.format(cal.getTime()));

String time_str = dateFormat.format(cal.getTime());

String[] s = time_str.split(" ");

for (int i = 0; i < s.length; i++) {
     System.out.println("date  => " + s[i]);
}

int year_sys = Integer.parseInt(s[0].split("/")[0]);
int month_sys = Integer.parseInt(s[0].split("/")[1]);
int day_sys = Integer.parseInt(s[0].split("/")[2]);

int hour_sys = Integer.parseInt(s[1].split(":")[0]);
int min_sys = Integer.parseInt(s[1].split(":")[1]);

System.out.println("year_sys  => " + year_sys);
System.out.println("month_sys  => " + month_sys);
System.out.println("day_sys  => " + day_sys);

System.out.println("hour_sys  => " + hour_sys);
System.out.println("min_sys  => " + min_sys);

SimpleDateFormat format = new SimpleDateFormat("dd/MM/yyyy");
Calendar c = Calendar.getInstance();
Date date = Calendar.getInstance().getTime();
String sDate = format.format(date);//31-12-9999
int mYear = c.get(Calendar.YEAR);//9999
int mMonth = c.get(Calendar.MONTH);
mMonth = mMonth + 1;//12
int hrs = c.get(Calendar.HOUR_OF_DAY);//24
int min = c.get(Calendar.MINUTE);//59
String AMPM;
if (c.get(Calendar.AM_PM) == 0) {
    AMPM = "AM";
} else {
    AMPM = "PM";
}

显示时间的明显选择是类比时钟视图(AnalogClock View)和数字时钟视图(DigitalClock View)。

例如，如下布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" 
    android:orientation="vertical">

    <AnalogClock
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content"/>

    <DigitalClock 
        android:layout_width="fill_parent" 
        android:layout_height="wrap_content" 
        android:gravity="center" 
        android:textSize="20sp"/>
</LinearLayout>

看起来是这样的: