WhatTime : アクティブになった時のみ時刻表示

MainActivity

package app.lightbox.winofsql.jp.whattime;
 
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
 
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
 
 
public class MainActivity extends Activity {
 
        // *************************************
        // 自動作成( onCreate )
        // *************************************
        @Override
        protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);
 
                Log.i("lightbox", "開始");
 
        }
 
        // *************************************
        // CTRL + O から追加( onStart, onStop, onPause )
        // *************************************
        @Override
        protected void onStart() {
                super.onStart();
 
                TimeZone tz = TimeZone.getTimeZone("Asia/Tokyo");
                Date date = new Date();
                SimpleDateFormat sdf = new SimpleDateFormat("HH'時'mm'分'ss'秒'");
                sdf.setTimeZone(tz);
                String time = sdf.format(date);
                Log.i("lightbox", time);
 
                TextView tv = (TextView) this.findViewById(R.id.text);
                tv.setText(time);
 
        }
 
        @Override
        protected void onStop() {
                super.onStop();
 
                Log.i("lightbox", "画面が切り替わりました");
 
        }
 
        @Override
        protected void onPause() {
                super.onPause();
 
                Log.i("lightbox", "画面が切り替わろうとしています");
 
        }
 
        // *************************************
        // 自動作成( onCreateOptionsMenu )
        // *************************************
        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
                getMenuInflater().inflate(R.menu.menu_main, menu);
                return true;
        }
 
        // *************************************
        // 自動作成( onOptionsItemSelected )
        // *************************************
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
                int id = item.getItemId();
 
                if (id == R.id.action_settings) {
 
                        Log.i("lightbox", "メニュー");
 
                        Intent intent = new Intent(MainActivity.this, NextPage.class);
                        startActivity(intent);
 
                        return true;
                }
 
                return super.onOptionsItemSelected(item);
        }
}

クラス java.util.TimeZone
クラス java.util.Date
クラス java.text.SimpleDateFormat


画面 ( activity_main.xml )

<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:paddingLeft="@dimen/activity_horizontal_margin"
                android:paddingRight="@dimen/activity_horizontal_margin"
                android:paddingTop="@dimen/activity_vertical_margin"
                android:paddingBottom="@dimen/activity_vertical_margin"
                tools:context=".MainActivity">
 
    <TextView
        android:text="@string/hello_world"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:textSize="40dp"
        android:textColor="#ff000000"
        android:id="@+id/text"/>
 
</RelativeLayout>

次画面 ( NextPage )

次画面には、Hello World が表示されます

package app.lightbox.winofsql.jp.whattime;
 
import android.app.Activity;
import android.os.Bundle;
 
/**
 * Created by lightbox on 2015/05/22.
 */
public class NextPage extends Activity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
 
                setContentView(R.layout.activity_main);
 
        }
 
}

AndroidManifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="app.lightbox.winofsql.jp.whattime" >
 
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
 
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <activity android:name=".NextPage">
        </activity>
    </application>
 
</manifest>

タイマーを使って時刻を変化させる

private Timer timer = null;
private Handler handler = null;
 
// *************************************
// CTRL + O から追加( onStart, onStop, onPause )
// *************************************
@Override
protected void onStart() {
        super.onStart();
 
        timer = new Timer();
        handler = new Handler();
        timer.schedule(new TimerTask() {
                @Override
                public void run() {
                        handler.post(new Runnable() {
                                @Override
                                public void run() {
                                        Log.i("lightbox", "タイマー実行中です");
 
                                        TimeZone tz = TimeZone.getTimeZone("Asia/Tokyo");
                                        Date date = new Date();
                                        SimpleDateFormat sdf = new SimpleDateFormat("HH'時'mm'分'ss'秒'");
                                        sdf.setTimeZone(tz);
                                        TextView tv = (TextView) MainActivity.this.findViewById(R.id.text);
                                        tv.setText(sdf.format(date));
 
                                }
                        });
                }
        }, 0, 1000);
 
}
 
@Override
protected void onStop() {
        super.onStop();
 
        timer.cancel();
        timer.purge();
 
        Log.i("lightbox", "画面が切り替わりました");
 
}

クラス java.util.Timer
クラス java.util.TimerTask

クラス android.os.Handler
インタフェース java.lang.Runnable