如何在bottomNavigationView android项目上显示徽章？

Question

我看到了这个问题 - Display badge on top of bottom navigation bar's icon并决定将我自己的自定义徽章添加到我的bottomNavigationView中。首先，我创建了徽章的特殊布局：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/counter_badge"
        android:layout_width="wrap_content"
        android:layout_height="20dp"
        android:layout_gravity="top|center_horizontal"
        android:layout_marginStart="20dp"
        android:gravity="center"
        android:textSize="12sp"
        android:textStyle="bold"
        android:ellipsize="end"
        android:textAlignment="center"
        android:textColor="@color/white"
        android:padding="3dp"
        android:background="@drawable/badge"/>
</FrameLayout>

然后我在我的活动中为徽章textView添加了一些信息：

BottomNavigationMenuView menuView = (BottomNavigationMenuView) bottomNavigationView.getChildAt(0);
BottomNavigationItemView itemView = (BottomNavigationItemView) menuView.getChildAt(0);

notificationBadge = LayoutInflater.from(this).inflate(R.layout.notification_badge, menuView, false);
TextView textView = notificationBadge.findViewById(R.id.counter_badge);

textView.setText("15");

itemView.addView(notificationBadge);

但是当我看到我只能使用我的视图中的一个项目时，当我尝试从0更改为1项时，我收到此错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.design.internal.BottomNavigationMenuView.getChildAt(int)' on a null object reference

然后我尝试使用特殊的项目ID，但我收到类似的错误。也许smb知道如何为我想要的物品添加徽章？

Answer 1

您应该将代码更改为此

BottomNavigationMenuView menuView = (BottomNavigationMenuView) bottomNavigationView.getChildAt(0);
BottomNavigationItemView itemView = (BottomNavigationItemView) menuView.getChildAt(1);

编辑

要拥有更多具有徽章的项目，您需要创建另一个布局，依此类推

BottomNavigationMenuView menuView = (BottomNavigationMenuView) bottomNavigationView.getChildAt(0);
BottomNavigationItemView itemView = (BottomNavigationItemView) menuView.getChildAt(0);

notificationBadge = LayoutInflater.from(this).inflate(R.layout.notification_badge, menuView, false);
TextView textView = notificationBadge.findViewById(R.id.counter_badge);
textView.setText("15");
itemView.addView(notificationBadge);

BottomNavigationMenuView menuView1 = (BottomNavigationMenuView) bottomNavigationView.getChildAt(0);
BottomNavigationItemView itemView1 = (BottomNavigationItemView) menuView1.getChildAt(1);

notificationBadgeOne = LayoutInflater.from(this).inflate(R.layout.notification_badge_one, menuView1, false);
TextView textView = notificationBadgeOne.findViewById(R.id.counter_badge);
textView.setText("15");
itemView1.addView(notificationBadgeOne);

Answer 2

只需在BottomNavigationView上添加徽章即可：

 private lateinit var bottomNavItemView: BottomNavigationItemView
 private var messageBadgeView: View? = null

 val mBottomNavigationMenuView = getChildAt(0) as BottomNavigationMenuView
 val view = mBottomNavigationMenuView.getChildAt(1)
 bottomNavItemView = view as BottomNavigationItemView

 messageBadgeView = LayoutInflater.from(this@Activity)
          .inflate(R.layout.item_message_count_badge,
                        mBottomNavigationMenuView, false)

 messageBadgeView!!.badgeCount.text = "99+"

 //Add badge
 bottomNavItemView.addView(messageBadgeView)

 //Or Remove badge
 bottomNavItemView.removeView(messageBadgeView)