Android studio 28 通知栏报错Failed to post notification on channel "null"

今天老师上课上到通知，教材是第一行代码，可能教材上的源码太久了，我在用安卓9的时候，模拟器报错Failed to post notification on channel “null”，在网上查了很久才知道，Notification在android 26以上设置时，需要设置渠道信息才可以正常显示通知，这是

官方文档地址[https://developer.android.google.cn/about/versions/pie/android-9.0]

接下来说说我的解决办法，首先建立布局，布局文件非常简单，里面只有一个发送通知按钮，用于发出一条通知

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/send_notice"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="send notifi"
        />

</LinearLayout>

然后修改MainActivity代码，懒得找图片了，直接设置了ic_launcher这张图

package com.example.ch08;

import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.graphics.Color;
import android.os.Build;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;


public class MainActivity extends AppCompatActivity implements View.OnClickListener {

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

        Button sendNotice = findViewById(R.id.send_notice);
        sendNotice.setOnClickListener(this);
    }

    @Override
    public void onClick(View v){
        switch (v.getId()){
            case R.id.send_notice:

                Intent intent = new Intent(this,NotificationActivity.class);
                PendingIntent pi = PendingIntent.getActivity(this,0,intent,0);

                String id = "channel_001";
                String name = "name";
                NotificationManager notificationManager = (NotificationManager)
                        this.getSystemService(NOTIFICATION_SERVICE);

                Notification notification = null;
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {//判断API
                    NotificationChannel mChannel = new NotificationChannel(id, name, NotificationManager.IMPORTANCE_LOW);
                    notificationManager.createNotificationChannel(mChannel);
                    notification = new Notification.Builder(this)
                            .setChannelId(id)
                            .setContentTitle("通知")
                            .setContentText("你有一个新的通知")
                            .setContentIntent(pi)
                            .setLights(Color.GREEN, 1000, 1000)//设置三色灯
                            .setSmallIcon(R.mipmap.ic_launcher_round).build();
                }else{
                    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
                            .setContentTitle("通知")
                            .setContentText("你有新的通知")
                            .setSmallIcon(R.mipmap.ic_launcher_round)
                            .setOngoing(true)
                            .setContentIntent(pi)
                            .setLights(Color.GREEN, 1000, 1000)//设置三色灯
                            .setChannelId(id);//无效

                    notification = notificationBuilder.build();
                }

                notificationManager.notify(1,notification);                                            //5
                break;
            default:
                break;
        }
    }
}

最后运行一下，这是效果图

我这里做了两个页面，下拉通知栏可以看见通知，点击通知后会进入第二个界面

					Intent intent = new Intent(this,NotificationActivity.class);
                    PendingIntent pi = PendingIntent.getActivity(this,0,intent,0);
                    .setContentIntent(pi)

加入这几行代码就可以了
还是要多关心一下技术圈的更新，就不用找的这么辛苦了