java - 无法让android创建通知

Question

我试图让 android 在按下按钮时显示通知。我遵循了在线教程，但按下按钮时没有任何反应。在线查看我找不到任何可以表明问题所在的信息，而且我是 android 的新手。

我有一节课

import android.app.Notification;
import android.os.Bundle;
import android.app.NotificationManager;
import android.view.View;
import android.content.Context;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.NotificationCompat;

public class MainActivity extends AppCompatActivity {

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

    public void sendNotification(View view) {

        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, "M_CH_ID");

        notificationBuilder.setAutoCancel(true)
                .setDefaults(Notification.DEFAULT_ALL)
                .setWhen(System.currentTimeMillis())
                .setSmallIcon(R.drawable.ic_launcher)
                .setTicker("Hearty365")
                .setContentTitle("Default notification")
                .setContentText("Random words")
                .setContentInfo("Info");

        NotificationManager notificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify(1, notificationBuilder.build());
    }
} 

和一种布局

<LinearLayout 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"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="sendNotification"
        android:text="@string/do_it" />

</LinearLayout>

如果有人可以向我解释问题是什么，或者可以将我链接到截至 API 29 的准确教程，我将不胜感激。

Answer 1

https://developer.android.com/training/notify-user/channels

  public void sendNotification(View view)  
    { 
            NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                NotificationChannel notificationChannel =
                        new NotificationChannel("M_CH_ID", "M_CH_ID", NotificationManager.IMPORTANCE_DEFAULT);
                notificationChannel.setDescription("Test");
                nm.createNotificationChannel(notificationChannel);
            }
            NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, "M_CH_ID");

            notificationBuilder.setAutoCancel(true)
                    .setDefaults(Notification.DEFAULT_ALL)
                    .setWhen(System.currentTimeMillis())
                    .setSmallIcon(R.drawable.ic_add)
                    .setTicker("Hearty365")
                    .setContentTitle("Default notification")
                    .setContentText("Random words")
                    .setContentInfo("Info");

            nm.notify(1, notificationBuilder.build()); 
    }