LifecycleModel 分享

这里写目录标题

• 源码地址
• 使用
• 粘贴使用的代码
• 源码类分析

源码地址

源码地址：https://github.com/JessYanCoding/LifecycleModel
作者解读：https://juejin.im/post/6844903529094578189

使用

一直都想用ViewModel，但是又不想用MVVM，偶然看到了大神的实现，使用简单而且方便
注意最好下载代码，因为源码没有更新到 AndroidX，下载下来改改就好，主要是思想哦！

粘贴使用的代码

自定义 LifecycleModel

public class UserLifecycleModel implements LifecycleModel {

    private Subject<String> mSubject = PublishSubject.create();

    public void doAction(String s) {
        mSubject.onNext(s);
    }

    public void addAction(Consumer<String> consumer) {
        mSubject.subscribe(consumer);
    }

    @Override
    public void onCleared() {

    }

}

创建

LifecycleModelProviders.of(this).put(UserLifecycleModel.class.getName(), new UserLifecycleModel());

收

        UserLifecycleModel lifecycleModel = LifecycleModelProviders.of(getActivity()).get(UserLifecycleModel.class.getName());
        lifecycleModel.addAction(new Consumer<String>() {
            @Override
            public void accept(String s) throws Exception {
                // Update the UI.
                Log.d("AFragment", s);
            }

        });

发

        UserLifecycleModel lifecycleModel = LifecycleModelProviders.of(getActivity()).get(UserLifecycleModel.class.getName());
        lifecycleModel.doAction("JessYan");

源码类分析

/*
 * Copyright 2017 JessYan
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package me.jessyan.lifecyclemodel;

import android.app.Activity;
import android.app.Application.ActivityLifecycleCallbacks;
import android.os.Bundle;

import android.util.Log;

import androidx.annotation.Nullable;
import androidx.annotation.RestrictTo;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.fragment.app.FragmentManager;

import java.util.HashMap;
import java.util.Map;

/**
 * @hide 此类为实现 {@link LifecycleModel} 的核心类
 * <p>
 * Created by JessYan on 21/11/2017 16:57
 * <a href="mailto:[e-mail]">Contact me</a>
 * <a href="https://github.com/JessYanCoding">Follow me</a>
 */
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
public class HolderFragment extends Fragment {
    private static final String LOG_TAG = "LifecycleModelStores";

    private static final HolderFragmentManager sHolderFragmentManager = new HolderFragmentManager();

    /**
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public static final String HOLDER_TAG =
            "me.jessyan.lifecyclemodel.state.StateProviderHolderFragment";

    private final LifecycleModelStore mLifecycleModelStore = new LifecycleModelStore();

    public HolderFragment() {
        setRetainInstance(true);//Fragment 在 Activity 重建的时候存活下来
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        sHolderFragmentManager.holderFragmentCreated(this);//初始化内部类
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mLifecycleModelStore.clear();
    }

    public LifecycleModelStore getLifecycleModelStore() {
        return mLifecycleModelStore;
    }

    /**
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public static HolderFragment holderFragmentFor(FragmentActivity activity) {
        return sHolderFragmentManager.holderFragmentFor(activity);
    }

    /**
     * @hide
     */
    @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
    public static HolderFragment holderFragmentFor(Fragment fragment) {
        return sHolderFragmentManager.holderFragmentFor(fragment);
    }

    @SuppressWarnings("WeakerAccess")
    static class HolderFragmentManager {
        private Map<Activity, HolderFragment> mNotCommittedActivityHolders = new HashMap<>();
        private Map<Fragment, HolderFragment> mNotCommittedFragmentHolders = new HashMap<>();

        //Activity销毁的时候移除掉
        private ActivityLifecycleCallbacks mActivityCallbacks =
                new EmptyActivityLifecycleCallbacks() {
                    @Override
                    public void onActivityDestroyed(Activity activity) {
                        HolderFragment fragment = mNotCommittedActivityHolders.remove(activity);
                        if (fragment != null) {
                            Log.e(LOG_TAG, "Failed to save a LifecycleModel for " + activity);
                        }
                    }
                };

        private boolean mActivityCallbacksIsAdded = false;

        //Fragment销毁的时候移除掉
        private FragmentManager.FragmentLifecycleCallbacks mParentDestroyedCallback =
                new FragmentManager.FragmentLifecycleCallbacks() {
                    @Override
                    public void onFragmentDestroyed(FragmentManager fm, Fragment parentFragment) {
                        super.onFragmentDestroyed(fm, parentFragment);
                        HolderFragment fragment = mNotCommittedFragmentHolders.remove(
                                parentFragment);
                        if (fragment != null) {
                            Log.e(LOG_TAG, "Failed to save a LifecycleModel for " + parentFragment);
                        }
                    }
                };

        void holderFragmentCreated(Fragment holderFragment) {
            Fragment parentFragment = holderFragment.getParentFragment();//getParentFragment() 方法可以获取到fragment的宿主fragment.
            if (parentFragment != null) {
                mNotCommittedFragmentHolders.remove(parentFragment);//移除 Fragment KEY
                parentFragment.getFragmentManager().unregisterFragmentLifecycleCallbacks(
                        mParentDestroyedCallback);
            } else {
                mNotCommittedActivityHolders.remove(holderFragment.getActivity());//移除 Activity KEY
            }
        }

        //通过 HOLDER_TAG 找到我们的 Fragment
        private static HolderFragment findHolderFragment(FragmentManager manager) {
            if (manager.isDestroyed()) {
                throw new IllegalStateException("Can't access LifecycleModels from onDestroy");
            }

            Fragment fragmentByTag = manager.findFragmentByTag(HOLDER_TAG);
            if (fragmentByTag != null && !(fragmentByTag instanceof HolderFragment)) {
                throw new IllegalStateException("Unexpected "
                        + "fragment instance was returned by HOLDER_TAG");
            }
            return (HolderFragment) fragmentByTag;
        }

        //创建 Fragment 携带 HOLDER_TAG ，提交
        private static HolderFragment createHolderFragment(FragmentManager fragmentManager) {
            HolderFragment holder = new HolderFragment();
            fragmentManager.beginTransaction().add(holder, HOLDER_TAG).commitAllowingStateLoss();
            return holder;
        }

        //通过 FragmentActivity 找到我们的 记录的 Fragment
        HolderFragment holderFragmentFor(FragmentActivity activity) {
            FragmentManager fm = activity.getSupportFragmentManager();
            HolderFragment holder = findHolderFragment(fm);//找到 Fragment
            if (holder != null) {
                return holder;
            }
            holder = mNotCommittedActivityHolders.get(activity);//看看列表有没有 Fragment
            if (holder != null) {
                return holder;
            }

            if (!mActivityCallbacksIsAdded) { //没有加入 Fragment
                mActivityCallbacksIsAdded = true;
                activity.getApplication().registerActivityLifecycleCallbacks(mActivityCallbacks);
            }
            holder = createHolderFragment(fm);//创建 （带TAG）
            mNotCommittedActivityHolders.put(activity, holder);// 加入列表
            return holder;//返回
        }

        //通过 Fragment 找到我们的 记录的 Fragment
        HolderFragment holderFragmentFor(Fragment parentFragment) {
            FragmentManager fm = parentFragment.getChildFragmentManager();
            HolderFragment holder = findHolderFragment(fm);
            if (holder != null) {
                return holder;
            }
            holder = mNotCommittedFragmentHolders.get(parentFragment);
            if (holder != null) {
                return holder;
            }

            parentFragment.getFragmentManager()
                    .registerFragmentLifecycleCallbacks(mParentDestroyedCallback, false);
            holder = createHolderFragment(fm);
            mNotCommittedFragmentHolders.put(parentFragment, holder);
            return holder;
        }
    }
}

主要是利用 Fragment 的重建保存数据。

本文地址：https://blog.csdn.net/weixin_35691921/article/details/109614661