为什么我的应用程序在实现 ViewModel 和弹出对话框后不断停止？

Question

我开始了这个新项目，用于跟踪山羊农场的山羊信息。这是我第一次使用 ViewModel 来弹出对话框，我假设这就是出错的地方，在 viewModel 和对话框实现之前，一切都很顺利。

现在，没有错误，gradle 构建运行顺利，但应用程序不断停止。

这是代码，可能是我错过的一个愚蠢的问题：

import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.viewModels
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.foundation.Image
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.lazy.grid.GridCells
import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
import androidx.compose.foundation.lazy.grid.items
import androidx.compose.material3.Button
import androidx.compose.material3.ButtonDefaults
import androidx.compose.material3.Card
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Surface
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.layout.ContentScale
import androidx.compose.ui.res.painterResource
import androidx.compose.ui.res.stringResource
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontStyle
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.googlefonts.Font
import androidx.compose.ui.text.googlefonts.GoogleFont
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import com.example.goats.ui.theme.CustomDialog
import com.example.goats.ui.theme.DataSource
import com.example.goats.ui.theme.DataSource.goats
import com.example.goats.ui.theme.Goats
import com.example.goats.ui.theme.GoatsTheme
import com.example.goats.ui.theme.MainViewModel
import androidx.fragment.app.activityViewModels
import androidx.fragment.app.Fragment
import androidx.lifecycle.viewmodel.compose.viewModel


class MainActivity : AppCompatActivity() {
    private val viewModel by viewModels<MainViewModel>()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            GoatsTheme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {

                    GoatsApp()
                    
                }
            }
        }
    }
}

@Composable
fun GoatsApp() {
    val provider = GoogleFont.Provider(
        providerAuthority = "com.google.android.gms.fonts",
        providerPackage = "com.google.android.gms",
        certificates = R.array.com_google_android_gms_fonts_certs

    )
    val fontName = GoogleFont("Lato")

    val fontFamily = FontFamily(
        Font(googleFont = fontName, fontProvider = provider)
    )
Column(modifier = Modifier.padding(16.dp)) {
    Text(text = "Does", modifier = Modifier
        .background(color = Color.LightGray)
        .fillMaxWidth()
        .padding(12.dp),
        fontStyle = FontStyle.Italic,
        textAlign = TextAlign.Center,
        fontFamily = fontFamily,
        fontWeight = FontWeight.ExtraLight
    )


    GoatList(goatList = DataSource.goats, modifier = Modifier.padding(8.dp))
    

}
}

@Composable
fun GoatCard(allgoats: Goats, viewModel: MainViewModel) {
val years = allgoats.age.toString()



Card(modifier = Modifier) {
    Row{

     Image(painter = painterResource(allgoats.image), contentDescription = (allgoats.name.toString()),
         modifier = Modifier.size(68.dp),
        contentScale = ContentScale.Crop)

Column(Modifier.width(120.dp)) {

        Text(text = stringResource(allgoats.name), modifier = Modifier.padding(8.dp),
            style = MaterialTheme.typography.titleSmall)
    Row{
        Text(text = stringResource(allgoats.breed), modifier = Modifier.padding(8.dp), style = MaterialTheme.typography.bodySmall)
        Text(years, modifier = Modifier.padding(8.dp), style = MaterialTheme.typography.bodySmall)

       Box {
        Button(onClick = { viewModel.isGoatClick() },
            modifier = Modifier.fillMaxWidth(), colors = ButtonDefaults.buttonColors(Color.LightGray)) { }
            Text(text = "More",
                style = MaterialTheme.typography.bodySmall,
                textAlign = TextAlign.End,
                fontWeight = FontWeight.Bold,
                modifier = Modifier
                    .fillMaxWidth()
                    .padding(end = 6.dp, top = 12.dp))

           



       }
    }

    if(viewModel.isDialogShown) {
        CustomDialog(onDismiss = {viewModel.onDismissDialog()}, myGoats = Goats(name = allgoats.name, age = allgoats.age, breed = allgoats.breed, image = allgoats.image))
    }

}
    }
}
}


@Composable
fun GoatList(goatList: List<Goats>, modifier: Modifier = Modifier.padding(8.dp)) {

    LazyVerticalGrid(columns = GridCells.Fixed(1), modifier.padding(8.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
        items(goats) { allgoats ->
            GoatCard(allgoats = allgoats, viewModel = MainViewModel())
        }
        
    }
    
}

和MainViewModel代码：

import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue
import androidx.lifecycle.ViewModel

class MainViewModel : ViewModel() {
    var isDialogShown by mutableStateOf(false)
        private set

    fun isGoatClick() {
        isDialogShown = true
    }

    fun onDismissDialog() {
        isDialogShown = false
    }



}```

Answer 1

通过将

class MainActivity : AppCompatActivity()

更改为

解决了这个问题

class MainActivity : ComponentActivity()