通知不显示

Question

我正在尝试显示android通知，很多努力来显示android通知。请帮助我，不确定这是怎么回事。

public class MainActivity extends AppCompatActivity {

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

        int notifyID = 1;
        String CHANNEL_ID = "my_channel_01";// The id of the channel.
        CharSequence name = "Testing";// The user-visible name of the channel.
        int importance = NotificationManager.IMPORTANCE_HIGH;
        NotificationChannel mChannel = new NotificationChannel(CHANNEL_ID, name, importance);
        Notification notification = new Notification.Builder(MainActivity.this)
            .setContentTitle("New Message")
            .setContentText("You've received new messages.")
            .setSmallIcon(R.drawable.ic_launcher_foreground)
            .setChannelId(CHANNEL_ID)
            .build();
    }}