LifecycleRegistry 未初始化，在 MVP 架构的 BaseActivity 中

Question

我为我的 Activity 和 Fragment、Presenter、ViewHolder 和 ViewModel 定义了几个 Base classes，并定义了一个接口和 Presenter，所有其他继承这些基础的活动 classes，在我的 BaseActivity class 和 BaseFragmentClass 中，我正在创建 lifecycleRegistry 对象并对其进行初始化，但是当应用程序启动时它崩溃并出现错误 getLifecycle() returned null in ComponentActivity's constructor. Please make sure you are lazily constructing your Lifecycle in the first call to getLifecycle() rather than relying on field initialization.

文件：BaseFragment.java

package com.example.myapp.data.helper.base;


import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.CallSuper;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.databinding.DataBindingUtil;
import androidx.databinding.ViewDataBinding;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleRegistry;
import androidx.lifecycle.ViewModelProviders;

public abstract class BaseFragment<V extends MvpView, P extends BasePresenter<V>>
        extends Fragment implements MvpView, View.OnClickListener {
    private  final LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this);
    protected P presenter;
    private int defaultValue = -1;
    private ViewDataBinding viewDataBinding;
    private View rootView;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

    @SuppressWarnings("unchecked")
    @CallSuper
    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        BaseViewModel<V, P> viewModel = ViewModelProviders.of(this).get(BaseViewModel.class);
        boolean isPresenterCreated = false;
        if (viewModel.getPresenter() == null) {
            viewModel.setPresenter(initPresenter());
            isPresenterCreated = true;
        }
        presenter = viewModel.getPresenter();
        presenter.attachLifecycle(getLifecycle());
        presenter.attachView((V) this);
        if (isPresenterCreated)
            presenter.onPresenterCreated();
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        startUI();
    }

    @Override
    public void onClick(View view) {

    }

    @NonNull
    @Override
    public LifecycleRegistry getLifecycle() {
        return lifecycleRegistry;
    }

    protected abstract void startUI();

    protected abstract void stopUI();

    protected ViewDataBinding getViewDataBinding() {
        return viewDataBinding;
    }

    @CallSuper
    @Override
    public void onDestroyView() {
        super.onDestroyView();

        if (presenter != null) {
            presenter.detachLifecycle(getLifecycle());
            presenter.detachView();
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        if (presenter != null) {
            presenter.detachLifecycle(getLifecycle());
            presenter.detachView();
        }

        stopUI();
    }

    private BaseActivity<V,P> getBaseActivity() {
        return ((BaseActivity<V,P>) getActivity());
    }

    private boolean isBaseActivityInstance() {
        return getActivity() instanceof BaseActivity;
    }

    protected void setTitle(String title) {
        if (isBaseActivityInstance()) {
            getBaseActivity().setTitle(title);
        }
    }

    protected void setClickListener(View... views) {
        for (View view : views) {
            view.setOnClickListener(this);
        }
    }

    protected abstract P initPresenter();
}

文件：BaseActivity.java

package com.example.data.helper.base;

import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.ActionBar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.core.content.ContextCompat;
import androidx.databinding.DataBindingUtil;
import androidx.databinding.ViewDataBinding;
import androidx.lifecycle.LifecycleOwner;
import androidx.lifecycle.LifecycleRegistry;
import androidx.lifecycle.ViewModelProviders;

public abstract class BaseActivity<V extends MvpView, P extends BasePresenter<V>>
        extends AppCompatActivity implements MvpView, View.OnClickListener, LifecycleOwner {


    private final LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this) ;
    protected P presenter;
    private ViewDataBinding viewDataBinding;
    private Menu menu;
    private int defaultValue = -1;

    @NonNull
    @Override
    public LifecycleRegistry getLifecycle() {
        return lifecycleRegistry;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState, @Nullable PersistableBundle persistentState) {
        super.onCreate(savedInstanceState, persistentState);
        int layoutId = getLayoutId();
        if (layoutId > defaultValue) {

            try {
                viewDataBinding = DataBindingUtil.setContentView(this, layoutId);
            } catch (Exception e) {
                if (viewDataBinding == null) {
                    setContentView(layoutId);
                }
            }

            BaseViewModel<V,P> viewModel = ViewModelProviders.of(this).get(BaseViewModel.class);
            boolean isPresenterCreated = false;

            if (viewModel.getPresenter() == null) {
                viewModel.setPresenter(initPresenter());
                isPresenterCreated = true;
            }

            presenter = viewModel.getPresenter();
            presenter.attachLifecycle(getLifecycle());
            presenter.attachView((V) this);
            if (isPresenterCreated) {
                presenter.onPresenterCreated();
            }
        }

        startUI();
    }

    @Override
    protected void onResume() {
        super.onResume();
        onResumeUI();
    }
    protected abstract void onResumeUI();
    */

    protected abstract void startUI();

    protected abstract void stopUI();

    protected ViewDataBinding getViewDataBinding() {
        return viewDataBinding;
    }

    protected static void runCurrentActivity(Context context, Intent intent) {
        context.startActivity(intent);
    }

    @Override
    public void onClick(View view) {

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        this.stopUI();
        presenter.detachLifecycle(getLifecycle());
        presenter.detachView();
    }

    protected abstract P initPresenter();

    protected void setTitle(String title) {
        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.setTitle(title);
        }
    }

    protected void setClickListener(View... views) {
        for (View view : views) {
            view.setOnClickListener(this);
        }
    }

    protected BaseFragment<?, ?> mBaseCurrentFragment;

    protected void commitFragment(int parentId, BaseFragment<?, ?> baseFragment) {
        getSupportFragmentManager()
                .beginTransaction()
                .replace(parentId, baseFragment, baseFragment.getClass().getName())
                .commit();

        setCurrentFragment(baseFragment);
    }

    protected void setCurrentFragment(BaseFragment<?, ?> baseFragment) {
        this.mBaseCurrentFragment = baseFragment;
    }

    protected BaseFragment<?, ?> getBaseCurrentFragment() {
        return mBaseCurrentFragment;
    }
}

**文件：MvpView

public interface MvpView{

}

文件：BasePresenter.java

public abstract class BasePresenter<V extends MvpView> implements LifecycleObserver, Presenter<V> {

    private V myMvpView;
    private Bundle stateBundle;

    @Override
    public void attachView(V mvpView) {
        myMvpView = mvpView;
    }

    @Override
    public void detachView() {
        mMvpView = null;
    }

    @Override
    public void attachLifecycle(Lifecycle lifecycle) {
        if (lifecycle != null) {
            lifecycle.addObserver(this);
        }
    }

    @Override
    public void detachLifecycle(Lifecycle lifecycle) {
        if (lifecycle != null) {
            lifecycle.removeObserver(this);
        }
    }

    public boolean isViewAttached() {
        return myMvpView != null;
    }

    public V getMvpView() {
        return myMvpView;
    }

    public Bundle getStateBundle() {
        return stateBundle == null ?
                stateBundle = new Bundle() : stateBundle;
    }

    public void checkViewAttached() {
        if (!isViewAttached()) throw new MvpViewNotAttachedException();
    }

    public static class MvpViewNotAttachedException extends RuntimeException {
        public MvpViewNotAttachedException() {
            super("Please call Presenter.attachView(MvpView) before" +
                    " requesting data to the Presenter");
        }
    }

    @Override
    public void onPresenterDestroy() {
        if (stateBundle != null && !stateBundle.isEmpty()) {
            stateBundle.clear();
        }
    }
}

更新： 我尝试通过将 lifeCycleRegistry 设为 Non Final 来更新 BaseActivity.java 和 BaseFragment.java 的代码。并在 getLifecycle 中初始化它（如果它为 null ），但是我只能看到一个空白屏幕，不知道为什么？

public abstract class BaseActivity<V extends MvpView, P extends BasePresenter<V>>
        extends AppCompatActivity implements MvpView, View.OnClickListener {
      private LifecycleRegistry = new LifeCycleRegistry(this);

    @NonNull
    @Override
    public LifecycleRegistry getLifecycle() {
        if (lifecycleRegistry==null){

            lifecycleRegistry= new LifecycleRegistry(this);
        }
        return lifecycleRegistry;
    }

}

所有其他代码相同。

Answer 1

删除对 getLifecycle() 和您自己的 LifecycleRegistry 的覆盖。在 Architecture Components 变得稳定并直接集成到 AppCompatActivity 和 Fragment 之前，这是必需的，但现在不再需要了。

LifecycleRegistry 未初始化，在 MVP 架构的 BaseActivity 中

LifecycleRegistry not getting initialized, in the BaseActivity for MVP architecture

java

android

androidx

android-lifecycle

android-mvp