界面有【寫入數據】和【讀取數據】兩個按鈕

程序代碼如下：

package com.twac.sharedPReferancestests;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Random;import android.app.Activity;import android.content.SharedPreferences;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;public class MainActivity extends Activity {	private Button btn_save;	private Button btn_load;	private SharedPreferences preferences;	private SharedPreferences.Editor editor;	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.activity_main);		btn_save = (Button) findViewById(R.id.btn_save);		btn_load = (Button) findViewById(R.id.btn_load);		// 獲取只能被本應用程序讀寫的sharedpreferances對象		preferences = getSharedPreferences("twac", MODE_PRIVATE);		editor = preferences.edit();		// 寫入數據		btn_save.setOnClickListener(new OnClickListener() {			@Override			public void onClick(View arg0) {				SimpleDateFormat sdf = new SimpleDateFormat("yyyy 年 MM 月 dd 日"						+ "hh:mm:ss");				int randomNumber = (int) (Math.random() * 1000);				editor.putString("date", sdf.format(new Date()));				editor.putInt("randomNumber", randomNumber);				editor.commit();				Toast.makeText(MainActivity.this, "數據寫入成功", Toast.LENGTH_LONG)						.show();			}		});		// 讀出數據		btn_load.setOnClickListener(new OnClickListener() {			@Override			public void onClick(View arg0) {				String date = preferences.getString("date", null);				int randomNumber = preferences.getInt("randomNumber", 0);				String message = date == null ? "數據還未寫入" : "寫入時間為:" + date						+ "/n 寫入的隨機數為：" + randomNumber;				// 使用toast顯示信息				Toast.makeText(MainActivity.this, message, Toast.LENGTH_LONG)						.show();			}		});	}}