android 通知使用方法(适配android8.0前后)

import android.annotation.TargetApi;
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    static final int NOTIFICATION_ID = 0x123;
    NotificationManager nm;
    private Button button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = findViewById(R.id.btn_1);


        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {                   //判断版本号

            String channelId = "chat";
            String channelName = "聊天消息";
            int importance = NotificationManager.IMPORTANCE_HIGH;
            createNotificationChannel(channelId, channelName, importance);
            channelId = "subscribe";
            channelName = "订阅消息";
            importance = NotificationManager.IMPORTANCE_DEFAULT;
            createNotificationChannel(channelId, channelName, importance);

            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                    Notification notification = new NotificationCompat.Builder(MainActivity.this, "chat")
                            .setContentTitle("收到一条聊天消息")
                            .setContentText("今天中午吃什么？")
                            .setWhen(System.currentTimeMillis())
                            .setSmallIcon(R.drawable.ic_launcher_background)
                            .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher_background))
                            .setAutoCancel(true)
                            .build();
                    manager.notify(1, notification);
                }
            });

        }else {
            nm = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
            button.setOnClickListener(new View.OnClickListener() {
                @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN)
                @Override
                public void onClick(View v) {
                    Notification_Four();
                }
            });
        }
    }

    @TargetApi(Build.VERSION_CODES.O)
    private void createNotificationChannel(String channelId, String channelName, int importance) {
        NotificationChannel channel = new NotificationChannel(channelId, channelName, importance);
        NotificationManager notificationManager = (NotificationManager) getSystemService(
                NOTIFICATION_SERVICE);
        notificationManager.createNotificationChannel(channel);
    }       //设置渠道

    @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN)
    private void Notification_Four(){
        Intent intent = new Intent(MainActivity.this,Main2Activity.class);
        PendingIntent pi = PendingIntent.getActivity(MainActivity.this,0,intent,0);
        Notification notifi = new Notification.Builder(MainActivity.this)
                .setAutoCancel(true)
                .setSmallIcon(R.drawable.ic_launcher_background)
                .setTicker("有新消息")
                .setContentTitle("一条新通知")
                .setContentText("hello word")
                .setWhen(System.currentTimeMillis())
                .setContentIntent(pi)
                .build();
        nm.notify(NOTIFICATION_ID,notifi);
    }                                                       //安卓8.0以下系统适用

    public void sendSubscribeMsg(View view) {
        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        Notification notification = new NotificationCompat.Builder(this, "subscribe")
                .setContentTitle("收到一条订阅消息")
                .setContentText("地铁沿线30万商铺抢购中！")
                .setWhen(System.currentTimeMillis())
                .setSmallIcon(R.drawable.ic_launcher_background)
                .setLargeIcon(BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher_background))
                .setAutoCancel(true)
                .build();
        manager.notify(2, notification);
    }
}