child_guard/app/src/main/java/com/example/childguard/MainActivity.java

package com.example.childguard;

import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.app.NotificationCompat;
import androidx.core.app.NotificationManagerCompat;

import android.annotation.SuppressLint;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothManager;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Vibrator;

import com.google.android.material.bottomnavigation.BottomNavigationView;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;
import java.util.UUID;

public class MainActivity extends AppCompatActivity {

    BluetoothManager bluetoothManager;
    BluetoothAdapter bluetoothAdapter;

    //↓日付を取得するやつ
    public static String getNowDate() {
        @SuppressLint("SimpleDateFormat") final DateFormat df = new SimpleDateFormat("yyy/MM/dd HH:mm:ss");
        final Date date = new Date(System.currentTimeMillis());
        return df.format(date);
    }

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


        //通知のやつ↓
        int importance = NotificationManager.IMPORTANCE_DEFAULT;

        NotificationChannel channel = new NotificationChannel("CHANNEL_ID", "通報通知", importance);
        //説明・説明　ここに通知の説明を書くことができる↓
        channel.setDescription("第3者からの通報を検知しました");

        NotificationManager notificationManager = getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(channel);
        //通知のやつ↑


        BottomNavigationView bottomNavigationView = findViewById(R.id.nav_view);

        bottomNavigationView.setOnNavigationItemSelectedListener(v -> {
            if (v.getItemId() == findViewById(R.id.navigation_home).getId()) {
                getSupportFragmentManager().beginTransaction()
                        .replace(findViewById(R.id.fragmentContainerView).getId(), HomeFragment.newInstance("test", "tset"))
                        .commit();
            } else if (v.getItemId() == findViewById(R.id.navigation_QR).getId()) {
                getSupportFragmentManager().beginTransaction()
                        .replace(findViewById(R.id.fragmentContainerView).getId(), QRFragment.newInstance("test", "tset"))
                        .commit();
            } else if (v.getItemId() == findViewById(R.id.navigation_notification).getId()) {
                getSupportFragmentManager().beginTransaction()
                        .replace(findViewById(R.id.fragmentContainerView).getId(), NotificationFragment.newInstance("test", "test"))
                        .commit();
            }

            return true;

        });
    }

    //↓通知のやつ
    public void notifyMain() {
        //↓通知をする際に起動するバイブレーション
        ((Vibrator) getSystemService(Context.VIBRATOR_SERVICE)).vibrate(1000);
        //↓通知の詳細設定的な奴
        NotificationCompat.Builder builder = new NotificationCompat
                .Builder(this, "CHANNEL_ID")
                .setSmallIcon(android.R.drawable.ic_menu_info_details)
                .setContentTitle("通報検知")
                .setContentText("子供の置き去りを検知しました。")
                .setPriority(NotificationCompat.PRIORITY_DEFAULT);

        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);

        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.POST_NOTIFICATIONS) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        notificationManager.notify(R.string.app_name, builder.build());


    }

    //Bluetooth_setupの戻るボタン
    public void setupBackButton(boolean enableBackButton) {
        ActionBar actionBar = getSupportActionBar();
        actionBar.setDisplayHomeAsUpEnabled(enableBackButton);
    }
}