Android 创建一个全局通用的ViewModel

（推荐）使用ViewModelStore

代码示例：

class MyApplication : Application(), ViewModelStoreOwner {
    private val mViewModelStore = ViewModelStore()

    override fun onCreate() {
        super.onCreate()
    }

    override val viewModelStore: ViewModelStore
        get() = mViewModelStore


    /**
     * 手动清理 ViewModelStore
     */
    fun clearViewModelStore() {
        mViewModelStore.clear()
    }
}

ShareViewModel:

class SharedViewModel: ViewModel() {
    val mShareData = MutableLiveData<String>()
}

ActivityA & ActivityB

class MainActivity : AppCompatActivity() {
    private val TAG = "MainActivity"
    private lateinit var mShareViewMode: SharedViewModel
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContentView(R.layout.activity_main)
        mShareViewMode =
            ViewModelProvider(application as MyApplication)[SharedViewModel::class.java]
        
        val tvTest = findViewById<TextView>(R.id.tvTest)
        tvTest.setOnClickListener {
            mShareViewMode.mShareData.value = "我是MainActivity更新的数据"
            startActivity(Intent(this,BActivity::class.java))
        }
        mShareViewMode.mShareData.observe(this){
            Log.i(TAG, "MainActivity shareData:$it")
        }
    }
}

class BActivity : AppCompatActivity() {
    private val TAG = "BActivity"
    private lateinit var mShareViewMode: SharedViewModel
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContentView(R.layout.activity_bactivity)
        // 这里传入MyApplication的
        mShareViewMode =
            ViewModelProvider(application as MyApplication)[SharedViewModel::class.java]
        mShareViewMode.mShareData.observe(this) {
            Log.e(TAG, "BActivity onCreate shareData:$it")
        }
    }
}