android实现一个简单的具有闹钟功能且能提醒的代码和布局文件

以下是一个简单的Android闹钟应用程序的代码和布局文件：

布局文件 activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="设置闹钟时间："
        android:textSize="24sp" />

    <TimePicker
        android:id="@+id/timePicker"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="16dp" />

    <Button
        android:id="@+id/startAlarm"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/timePicker"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="16dp"
        android:text="启动闹钟" />

</RelativeLayout>

Java 代码 MainActivity.java：

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TimePicker;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

    TimePicker timePicker;
    Button startAlarm;

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

        timePicker = findViewById(R.id.timePicker);
        startAlarm = findViewById(R.id.startAlarm);

        startAlarm.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Calendar calendar = Calendar.getInstance();
                calendar.set(Calendar.HOUR_OF_DAY, timePicker.getHour());
                calendar.set(Calendar.MINUTE, timePicker.getMinute());
                calendar.set(Calendar.SECOND, 0);
                calendar.set(Calendar.MILLISECOND, 0);

                Intent intent = new Intent(MainActivity.this, AlarmReceiver.class);
                PendingIntent pendingIntent = PendingIntent.getBroadcast(MainActivity.this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

                AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
                alarmManager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);

                Toast.makeText(getApplicationContext(), "闹钟已设置", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

广播接收器 AlarmReceiver.java：

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.media.Ringtone;
import android.media.RingtoneManager;
import android.net.Uri;

public class AlarmReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        Uri alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM);
        if (alarmUri == null) {
            alarmUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        }
        Ringtone ringtone = RingtoneManager.getRingtone(context, alarmUri);
        ringtone.play();
    }
}

上述代码实现了一个简单的闹钟应用程序，用户可以通过时间选择器设置闹钟时间，点击“启动闹钟”按钮后，闹钟会在设定的时间响起。当闹钟响起时，Android系统将启动AlarmReceiver广播接收器，播放默认的闹钟声音。