我有一个按钮，当按下5次将创建一个用户通知。我能够让应用程序运行，但当按下按钮时，我可以看到“计数器”正在递增，但当>=5时没有任何通知显示。我在AndroidManifest.xml中输入了以下行：

<uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.VIBRATE" />
    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />

下面是我的MainActivity.java文件：

package com.enetapplications.localnotifications;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.app.NotificationCompat;
import androidx.core.app.NotificationManagerCompat;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.Manifest;
public class MainActivity extends AppCompatActivity {
    Button button;
    public final String CHANNEL_ID = "1_" + System.currentTimeMillis();
    int counter = 0;
    private static final int PERMISSION_REQUEST_CODE = 123;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                requestPermission();
                counter++;
                button.setText("" + counter);
                if (counter >= 5) {
                    startNotification();
                }
            }
        });
    }
    public void startNotification() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID, "Channel Name", NotificationManager.IMPORTANCE_DEFAULT);
            NotificationManager manager = getSystemService(NotificationManager.class);
            manager.createNotificationChannel(channel);
        }
        NotificationCompat.Builder builder = new NotificationCompat.Builder(MainActivity.this, CHANNEL_ID)
                .setSmallIcon(R.drawable.ic_add_alert_24)
                .setContentTitle("Title")
                .setContentText("Notification Text")
                .setPriority(NotificationCompat.PRIORITY_DEFAULT);
        NotificationManagerCompat compat = NotificationManagerCompat.from(MainActivity.this);
        if (compat.areNotificationsEnabled()) {
            if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.POST_NOTIFICATIONS) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.POST_NOTIFICATIONS}, PERMISSION_REQUEST_CODE);
            } else {
                compat.notify(1, builder.build());
            }
        }
    }
    private void requestPermission() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(Manifest.permission.VIBRATE) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{Manifest.permission.VIBRATE}, PERMISSION_REQUEST_CODE);
            } else {
                startNotification();
            }
        } else {
            startNotification();
        }
    }
    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == PERMISSION_REQUEST_CODE) {
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                startNotification();
            } else {
                // Handle permission denied
            }
        }
    }
}