Hey there! Let's get those online/offline icons behaving exactly how you want them to. It sounds like you've already got the layout set up and core functionality working—great start! The key here is properly referencing and controlling the icons within your friend list's adapter (since it's a list, I’m assuming you’re using a RecyclerView). Here’s how to tackle it step by step:

1. Double-Check Your Layout IDs #

First, confirm the android:id values for your online/offline icons in the list item layout are correct and match what you’re using in code. A tiny typo here is the most common culprit! Example layout snippet:

<!-- In your friend list item layout -->
<ImageView
    android:id="@+id/iv_online_status"
    android:layout_width="16dp"
    android:layout_height="16dp"
    android:src="@drawable/ic_green_dot" />

<ImageView
    android:id="@+id/iv_offline_status"
    android:layout_width="16dp"
    android:layout_height="16dp"
    android:src="@drawable/ic_grey_dot"
    android:visibility="gone" /> <!-- Start with one hidden by default -->

2. Control Visibility in Your RecyclerView Adapter #

Each friend item needs its own status toggle, so handle this in your adapter’s onBindViewHolder method. Here are examples for both Kotlin and Java:

Kotlin Example #

// Define your ViewHolder with references to the icons
class FriendViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    val onlineIcon: ImageView = itemView.findViewById(R.id.iv_online_status)
    val offlineIcon: ImageView = itemView.findViewById(R.id.iv_offline_status)
    val fullNameText: TextView = itemView.findViewById(R.id.tv_full_name)
}

// In your adapter's onBindViewHolder
override fun onBindViewHolder(holder: FriendViewHolder, position: Int) {
    val currentFriend = friendList[position]
    holder.fullNameText.text = currentFriend.fullName

    // Toggle icons based on the friend's online status
    if (currentFriend.isOnline) {
        holder.onlineIcon.visibility = View.VISIBLE
        holder.offlineIcon.visibility = View.GONE
    } else {
        holder.onlineIcon.visibility = View.GONE
        holder.offlineIcon.visibility = View.VISIBLE
    }
}

Java Example #

// ViewHolder class
public class FriendViewHolder extends RecyclerView.ViewHolder {
    ImageView onlineIcon;
    ImageView offlineIcon;
    TextView fullNameText;

    public FriendViewHolder(View itemView) {
        super(itemView);
        onlineIcon = itemView.findViewById(R.id.iv_online_status);
        offlineIcon = itemView.findViewById(R.id.iv_offline_status);
        fullNameText = itemView.findViewById(R.id.tv_full_name);
    }
}

// In onBindViewHolder
@Override
public void onBindViewHolder(FriendViewHolder holder, int position) {
    Friend currentFriend = friendList.get(position);
    holder.fullNameText.setText(currentFriend.getFullName());

    if (currentFriend.isOnline()) {
        holder.onlineIcon.setVisibility(View.VISIBLE);
        holder.offlineIcon.setVisibility(View.GONE);
    } else {
        holder.onlineIcon.setVisibility(View.GONE);
        holder.offlineIcon.setVisibility(View.VISIBLE);
    }
}

3. Bonus: Use Data Binding for Simpler Control #

If you’re using Android Data Binding, you can skip manual visibility checks in code and bind directly in your layout. This keeps your adapter cleaner:

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="friend"
            type="com.yourpackage.Friend" />
    </data>

    <!-- Your existing layout elements -->
    <TextView
        android:id="@+id/tv_full_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@{friend.fullName}" />

    <ImageView
        android:id="@+id/iv_online_status"
        android:layout_width="16dp"
        android:layout_height="16dp"
        android:src="@drawable/ic_green_dot"
        android:visibility="@{friend.isOnline ? View.VISIBLE : View.GONE}" />

    <ImageView
        android:id="@+id/iv_offline_status"
        android:layout_width="16dp"
        android:layout_height="16dp"
        android:src="@drawable/ic_grey_dot"
        android:visibility="@{friend.isOnline ? View.GONE : View.VISIBLE}" />
</layout>

Quick Troubleshooting Tips #

• If icons still don’t toggle, verify your friend.isOnline flag is correctly updated and passed to the adapter.
• Remember to call notifyItemChanged(position) (or notifyDataSetChanged()) when a friend’s status updates to refresh the UI.
• Check that your icon drawables are properly added to the drawable folders and aren’t missing or corrupted.

Hope this gets your status icons working perfectly! 🚀

内容的提问来源于stack exchange，提问作者Eng