在 Android 中创建包含图片的可扩展通知

通知是由手机内的任何应用程序生成的一种消息，建议检查应用程序，这可能是从更新（低优先级通知）到应用程序中出现问题的任何内容（高优先级通知） .基本通知由标题、一行文本以及用户可以执行的一个或多个操作作为响应组成。要提供更多信息，还可以通过应用本文所述的多个通知模板之一来创建大型、可扩展的通知。一些日常生活示例可能是 Whatsapp、Gmail、SMS 等在通知抽屉中附加的通知，用户可以在其中展开它并可以找到有关收到的消息的一些详细信息，例如发件人姓名、主题和部分文本Gmail 的情况。在本文中，让我们在包含图片的应用程序中创建一个通知。

方法

步骤 1：创建一个新项目

要在 android studio 中创建新项目，请参阅如何在 Android Studio 中创建/启动新项目。

第二步：修改activity_main.xml文件

在 XML 文件中只需添加一个按钮，单击该按钮将构建一个可展开的通知。通过从通知抽屉展开通知将显示一张图片。

第三步：修改MainActivity文件

现在，看看下面的 Kotlin 代码。首先，构建一个包含所有基本内容的通知，如创建通知中所述。然后，使用样式对象调用setStyle()并提供与每个模板对应的信息，如下所示。

MainActivity.kt

package com.example.expandablenotification
  
import android.app.*
import android.content.Context
import android.content.Intent
import android.graphics.BitmapFactory
import android.graphics.Color
import android.os.Build
import android.os.Bundle
import android.widget.Button
import androidx.appcompat.app.AppCompatActivity
  
class MainActivity : AppCompatActivity() {
  
    // Assigning variables to Notification Manager, Channel and Builder
    lateinit var notifManager: NotificationManager
    lateinit var notifChannel: NotificationChannel
    lateinit var notifBuilder: Notification.Builder
  
    // Evaluating ChannelID and Description for the Custom Notification
    private val description = "Some Description"
    private val channelID = "Some Channel ID"
  
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
  
        // Declaring the button which onclick generates a notification
        val btn = findViewById(R.id.btn)
  
        // Notification Service for the Manager
        notifManager = getSystemService(Context.NOTIFICATION_SERVICE)
                as NotificationManager
  
        // Notifications are in the form of Intents
        val someintent = Intent(this, LauncherActivity::class.java)
        val pendingIntent = PendingIntent.getActivity(
            this, 0, someintent,
            PendingIntent.FLAG_UPDATE_CURRENT
        )
  
        // Idea is to click the button and the notification appears
        btn.setOnClickListener {
            // This is how an Image to be displayed in our Notification
            // is decoded and stored in a variable. I've added a picture
            // named "download.jpeg" in the "Drawables".
            val myBitmap = BitmapFactory.decodeResource(resources, 
                                                        R.drawable.download)
  
            // If Min. API level of the phone is 26, then notification could be
            // made asthetic
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                notifChannel = NotificationChannel(
                    channelID, description,
                    NotificationManager.IMPORTANCE_HIGH
                )
                notifChannel.enableLights(true)
                notifChannel.lightColor = Color.RED
                notifChannel.enableVibration(true)
  
                notifManager.createNotificationChannel(notifChannel)
  
                notifBuilder = Notification.Builder(this, channelID)
                    .setContentTitle("Some Title")
                    .setContentText("Some Content Text")
                    .setSmallIcon(R.mipmap.ic_launcher_round)
  
                    // Command to Insert Image in the Notification
                    .setStyle(
                        Notification.BigPictureStyle() // <---- Look here
                            .bigPicture(myBitmap)
                    ) // <---- Look here
                    .setContentIntent(pendingIntent)
            }
            // Else the Android device would give out default UI attributes
            else {
                notifBuilder = Notification.Builder(this)
                    .setContentTitle("Some Title")
                    .setContentText("Some Content Text")
                    .setContentIntent(pendingIntent)
            }
  
            // Everything is done now and the Manager is to be notified about
            // the Builder which built a Notification for the application
            notifManager.notify(1234, notifBuilder.build())
        }
    }
}

Note: If you have previously searched for the code for expandable notifications, then you must have seen this particular line of code:

 “.setStyle(NotificationCompat.BigPictureStyle().bigPicture(myBitmap)”

As “NotificationCompat” is currently deprecated and your code would always crash whenever an attempt is made to build a notification (on button click in our case). Instead, just use “Notification”.

输出：在模拟器上运行