在MVP架构的BaseActivity中，LifecycleRegistry未初始化 [英] LifecycleRegistry not getting initialized, in the BaseActivity for MVP architecture

问题描述

我为我的Activity和Fragment，Presenter和ViewHolder和ViewModel定义了几个基类，并定义了一个接口和Presenter，所有其他活动都继承了这些基类，并且在我的BaseActivity类和BaseFragmentClass中，我是创建 lifecycleRegistry 对象并对其进行初始化，但是在启动应用程序时，它崩溃，并出现错误 getLifecycle()在ComponentActivity的构造函数中返回null.请确保在第一次调用getLifecycle()时延迟构建生命周期，而不是依赖字段初始化.

I have the few Base classes defined for my Activity and Fragment, Presenter, and ViewHolder, and ViewModel, and an interface and Presenter being defined, All other activities inheriting these base classes, and In my BaseActivity class and BaseFragmentClass, i am creating lifecycleRegistry object and initializing it, but when the App is launched it crashes with error 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

**File: 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设置为Non Final来更新BaseActivity.java和BaseFragment.java的代码.并在getLifecycle中将其初始化为null，但是我只能看到一个空白屏幕，不确定为什么吗?

Updates: I try to update the code of BaseActivity.java and BaseFragment.java by making lifeCycleRegistry as Non Final. and initializing it in getLifecycle if it is null , but then i can only see a blank screen, Not sure Why?

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;
    }

}

所有其他代码都相同.

推荐答案

将替代项移至 getLifecycle()和您自己的 LifecycleRegistry .在Architecture Components稳定并直接集成到AppCompatActivity和Fragment中之前，这是必需的，但现在不再需要.

Remove the override to getLifecycle() and your own LifecycleRegistry. This was neccessary before Architecture Components became stable and directly integrated into AppCompatActivity and Fragment, but is not necessary anymore.

这篇关于在MVP架构的BaseActivity中，LifecycleRegistry未初始化的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！