如何在Android应用中实现响应式UI更新：LiveData实践指南

import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel

// 假设这是一个ViewModel，用于管理UI相关的数据
class GameViewModel : ViewModel() {
    // 声明一个MutableLiveData来持有isPlayerNearby状态，并初始化为false
    val isPlayerNearby = MutableLiveData(false)

    // 其他ViewModel逻辑...
}

import android.content.Context
import android.widget.Toast
import androidx.lifecycle.ViewModelProvider
import com.google.android.gms.nearby.Nearby
import com.google.android.gms.nearby.connection.DiscoveredEndpointInfo
import com.google.android.gms.nearby.connection.EndpointDiscoveryCallback

// 假设您的Activity或Fragment持有GameViewModel实例
class MyGameActivity : AppCompatActivity() {
    private lateinit var viewModel: GameViewModel
    // ... 其他成员变量和方法

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_my_game) // 假设您的布局文件
        viewModel = ViewModelProvider(this).get(GameViewModel::class.java)
        // ... 初始化其他组件
    }

    private var endpointDiscoveryCallback: EndpointDiscoveryCallback = object :
        EndpointDiscoveryCallback() {
        override fun onEndpointFound(endpointId: String, info: DiscoveredEndpointInfo) {
            // ... 其他连接逻辑
            Nearby.getConnectionsClient(applicationContext)
                .requestConnection(getLocalUserName(), endpointId, connectionLifeCycleCallback)
                .addOnSuccessListener {
                    run {
                        // endpointFound()
                        // 在这里更新isPlayerNearby的LiveData值
                        viewModel.isPlayerNearby.postValue(true) // 使用postValue确保在主线程更新
                        Toast.makeText(applicationContext, endpointId, Toast.LENGTH_SHORT).show()
                    }
                }
                .addOnFailureListener { _ ->
                    // 连接失败处理
                }
        }

        override fun onEndpointLost(endpointId: String) {
            // 当端点丢失时，更新LiveData为false
            viewModel.isPlayerNearby.postValue(false)
            Toast.makeText(applicationContext, "Endpoint Lost", Toast.LENGTH_SHORT).show()
        }
    }
    // ... 其他方法
}

import android.os.Bundle
import android.view.View
import android.widget.Button
import android.widget.ImageView
import android.widget.TextView
import androidx.fragment.app.Fragment
import androidx.lifecycle.ViewModelProvider

class GameFragment : Fragment(R.layout.fragment_game) { // 假设您的布局文件是fragment_game.xml

    private lateinit var viewModel: GameViewModel
    private lateinit var statusTextView: TextView
    private lateinit var playerImageView: ImageView
    private lateinit var eliminateButton: Button

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)

        // 初始化ViewModel
        viewModel = ViewModelProvider(requireActivity()).get(GameViewModel::class.java)

        // 假设您已经通过ViewBinding或findViewById获取了这些视图组件
        statusTextView = view.findViewById(R.id.statusText)
        playerImageView = view.findViewById(R.id.playerImage)
        eliminateButton = view.findViewById(R.id.eliminateButton)

        // 观察isPlayerNearby的LiveData变化
        viewModel.isPlayerNearby.observe(viewLifecycleOwner) { isPlayerNearby ->
            if (isPlayerNearby) {
                statusTextView.text = "Player $playerName is within range!" // 假设playerName已定义
                playerImageView.setImageResource(R.drawable.player_nearby_image) // 替换为您的资源ID
                eliminateButton.isEnabled = true // 启用按钮
                eliminateButton.text = "ELIMINATE"
                eliminateButton.setOnClickListener { attack() } // 设置点击事件
            } else {
                statusTextView.text = "No players nearby. Keep searching."
                playerImageView.setImageResource(R.drawable.no_player_image) // 替换为您的资源ID
                eliminateButton.isEnabled = false // 禁用按钮
                eliminateButton.text = "ELIMINATE"
                eliminateButton.setOnClickListener(null) // 移除点击事件或设置为不执行任何操作
            }
        }
    }

    private fun attack() {
        // 执行攻击逻辑
        Toast.makeText(requireContext(), "Attacking!", Toast.LENGTH_SHORT).show()
    }

    // 假设playerName是一个可访问的变量
    private val playerName = "Enemy"
}