带有 dagger、JetPack 组件的 Android Kotlin MVVM

Question

目前我正在从事 Kotlin android 开发。在编写 MVVM 架构时，我被 ViewModel Creation 困住了 错误：类文字的左侧只允许使用类

相关类是

详情

BaseViewModel 类，在创建这个类的对象时，我们得到了错误

package com.logicipher.mvvm.ui.base

import androidx.databinding.ObservableBoolean
import androidx.lifecycle.ViewModel
import com.logicipher.mvvm.data.DataManager
import com.logicipher.mvvm.utils.rx.SchedulerProvider
import io.reactivex.disposables.CompositeDisposable
import java.lang.ref.WeakReference

/**
 * Created by Shamji N S on 20-08-2020.
 */
abstract class BaseViewModel<N>(
    dataManager: DataManager,
    schedulerProvider: SchedulerProvider
) : ViewModel() {
    private val mDataManager: DataManager
    private val mIsLoading = ObservableBoolean()
    private val mSchedulerProvider: SchedulerProvider
    private val mCompositeDisposable: CompositeDisposable
    private var mNavigator: WeakReference<N>? = null
    override fun onCleared() {
        mCompositeDisposable.dispose()
        super.onCleared()
    }

    fun getCompositeDisposable(): CompositeDisposable {
        return mCompositeDisposable
    }

    fun getDataManager(): DataManager {
        return mDataManager
    }

    fun getIsLoading(): ObservableBoolean {
        return mIsLoading
    }

    fun setIsLoading(isLoading: Boolean) {
        mIsLoading.set(isLoading)
    }

    fun getNavigator(): N? {
        return mNavigator!!.get()
    }

    fun setNavigator(navigator: N) {
        mNavigator = WeakReference(navigator)
    }

    fun getSchedulerProvider(): SchedulerProvider {
        return mSchedulerProvider
    }

    init {
        mDataManager = dataManager
        mSchedulerProvider = schedulerProvider
        mCompositeDisposable = CompositeDisposable()
    }
}

基础活动

package com.logicipher.mvvm.ui.base

import android.annotation.TargetApi
import android.app.ProgressDialog
import android.content.Context
import android.content.pm.PackageManager
import android.os.Build
import android.os.Bundle
import android.view.inputmethod.InputMethodManager
import androidx.annotation.LayoutRes
import androidx.appcompat.app.AppCompatActivity
import androidx.databinding.DataBindingUtil
import androidx.databinding.ViewDataBinding
import com.logicipher.mvvm.utils.CommonUtils
import com.logicipher.mvvm.utils.NetworkUtils
import dagger.android.AndroidInjection

/**
 * Created by Shamji N S on 20-08-2020.
 */

abstract class BaseActivity<T : ViewDataBinding?, V : BaseViewModel<*>?> :
    AppCompatActivity(), BaseFragment.Callback {
    // TODO
    // this can probably depend on isLoading variable of BaseViewModel,
    // since its going to be common for all the activities
    private var mProgressDialog: ProgressDialog? = null
    private var mViewDataBinding: T? = null
    private var mViewModel: V? = null

    /**
     * Override for set binding variable
     *
     * @return variable id
     */
    abstract fun getBindingVariable(): Int

    /**
     * @return layout resource id
     */
    @LayoutRes
    abstract fun getLayoutId(): Int

    /**
     * Override for set view model
     *
     * @return view model instance
     */
    abstract fun getViewModel(): V

    override fun onFragmentAttached() {

    }


    override fun onFragmentDetached(tag: String?) {

    }

    override fun onCreate(savedInstanceState: Bundle?) {
        performDependencyInjection()
        super.onCreate(savedInstanceState)
        performDataBinding()
    }

    fun getViewDataBinding(): T? {
        return mViewDataBinding
    }

    @TargetApi(Build.VERSION_CODES.M)
    fun hasPermission(permission: String?): Boolean {
        return Build.VERSION.SDK_INT < Build.VERSION_CODES.M ||
                checkSelfPermission(permission!!) == PackageManager.PERMISSION_GRANTED
    }

    fun hideKeyboard() {
        val view = this.currentFocus
        if (view != null) {
            val imm =
                getSystemService(Context.INPUT_METHOD_SERVICE) as InputMethodManager
            imm?.hideSoftInputFromWindow(view.windowToken, 0)
        }
    }

    fun hideLoading() {
        if (mProgressDialog != null && mProgressDialog!!.isShowing) {
            mProgressDialog!!.cancel()
        }
    }

    fun isNetworkConnected(): Boolean {
        return NetworkUtils.isNetworkConnected(applicationContext)
    }

    fun openActivityOnTokenExpire() {

    }

    fun performDependencyInjection() {
        AndroidInjection.inject(this)
    }

    @TargetApi(Build.VERSION_CODES.M)
    fun requestPermissionsSafely(
        permissions: Array<String?>?,
        requestCode: Int
    ) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            requestPermissions(permissions!!, requestCode)
        }
    }

    fun showLoading() {
        hideLoading()
        mProgressDialog = CommonUtils.showLoadingDialog(this)
    }

    private fun performDataBinding() {
        mViewDataBinding = DataBindingUtil.setContentView<T>(this, getLayoutId())
        mViewModel = if (mViewModel == null) getViewModel() else mViewModel
        mViewDataBinding!!.setVariable(getBindingVariable(), mViewModel)
        mViewDataBinding!!.executePendingBindings()
    }
}

主活动

package com.logicipher.mvvm.ui.main
import android.os.Bundle
import android.util.Log
import androidx.lifecycle.ViewModelProviders
import com.logicipher.mvvm.BR
import com.logicipher.mvvm.R
import com.logicipher.mvvm.ViewModelProviderFactory
import com.logicipher.mvvm.databinding.ActivityMainBinding
import com.logicipher.mvvm.ui.base.BaseActivity
import javax.inject.Inject

/**
 * Created by Shamji N S on 21-08-2020.
 */
class MainActivity : BaseActivity<ActivityMainBinding?, MainViewModel<MainNavigator>?>(),
    MainNavigator /*, HasSupportFragmentInjector*/ {
    /*   @Inject
    DispatchingAndroidInjector<Fragment> fragmentDispatchingAndroidInjector;*/

    @set:Inject
    internal var factory: ViewModelProviderFactory? = null
    var mViewModel: MainViewModel<MainNavigator>? = null
    var mBinding: ActivityMainBinding? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.d(TAG, "onCreate: ")
        mBinding = getViewDataBinding()
        mViewModel?.setNavigator(this)
    }

    override fun getBindingVariable(): Int {
        return BR.viewModel
    }

    override fun getLayoutId(): Int {
        return R.layout.activity_main
    }

    override fun getViewModel(): MainViewModel<MainNavigator>? {
        mViewModel =
            ViewModelProviders.of(this, factory).get<MainViewModel<MainNavigator>>(MainViewModel<MainNavigator>::class.java)
        return mViewModel
    }

    /*
    @Override
    public AndroidInjector<Fragment> supportFragmentInjector() {
        return fragmentDispatchingAndroidInjector;
    }
*/

    companion object {
        private const val TAG = "MainActivity"
    }
}

ViewModelProviderFactory

package com.logicipher.mvvm

import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider.NewInstanceFactory
import com.logicipher.mvvm.data.DataManager
import com.logicipher.mvvm.ui.main.MainNavigator
import com.logicipher.mvvm.ui.main.MainViewModel
import com.logicipher.mvvm.utils.rx.SchedulerProvider
import java.lang.IllegalArgumentException
import javax.inject.Inject

/**
 * Created by Shamji N S on 25-08-2020.
 */
public class ViewModelProviderFactory @Inject constructor(
    dataManager: DataManager,
    schedulerProvider: SchedulerProvider
) : NewInstanceFactory() {
    private val dataManager: DataManager
    private val schedulerProvider: SchedulerProvider



    override fun <T : ViewModel?> create(modelClass: Class<T>): T {
        return super.create(modelClass)

        if (modelClass.isAssignableFrom(MainViewModel::class.java)) {
            return MainViewModel<T>(dataManager, schedulerProvider) as T
        }

        throw IllegalArgumentException("Unknown view model" + modelClass.name)
    }

    init {
        this.dataManager = dataManager
        this.schedulerProvider = schedulerProvider
    }
}

Answer 1

您的BaseViewModel 是抽象的，您不能创建抽象类的对象或实例。 创建ViewModelFactory 之后，创建（或获取）ViewModel 实例的方法如下：

val viewModel = ViewModelProvider(this, viewModelFactory).get(ViewModelName::class.java)

不过，我会考虑使用Kotlin Property Delegate from here，这有助于减少代码。