可嵌套使用的 FragmentPagerAdapter 主要修复 FragmentPagerAdapter 处理 {@link Fragment#setMenuVisibility(boolean)} 的 bug

HierarchyFragmentPagerAdapter.java

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * 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 com.dstech.huishou;

import android.os.Parcelable;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v4.view.PagerAdapter;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;

/**
 *
 * 可嵌套使用的 FragmentPagerAdapter
 * 主要修复 FragmentPagerAdapter 处理 {@link Fragment#setMenuVisibility(boolean)} 的 bug
 * Created by Tiou on 6/20/16.
 */
public abstract class HierarchyFragmentPagerAdapter extends PagerAdapter {
    private static final String TAG = "HierarchyFragmentPager";
    private static final boolean DEBUG = false;
    private final FragmentManager mFragmentManager;
    private FragmentTransaction mCurTransaction = null;
    private Fragment mCurrentPrimaryItem = null;
    private boolean currentPrimary;
    private AdapterHolder mHolder;
    private HierarchyFragmentPagerAdapter mParent;

    public HierarchyFragmentPagerAdapter(FragmentManager fm, @Nullable HierarchyFragmentPagerAdapter parent, @NonNull AdapterHolder holder) {
        mFragmentManager = fm;
        mParent = parent;
        if (parent == null || parent.mCurrentPrimaryItem == holder) {
            // 1. 根节点始终是主要的
            // 2. Holder Fragment 构造 Adapter 时已经是 currentPrimaryItem
            currentPrimary = true;
        }
        mHolder = holder;

    }

    private static String makeFragmentName(int viewId, long id) {
        return "android:switcher:" + viewId + ":" + id;
    }
//
//    public void addChild(HierarchyFragmentPagerAdapter child) {
//        mChildren.add(child);
//    }

    /**
     * Return the Fragment associated with a specified position.
     */
    public abstract Fragment getItem(int position);

    @Override
    public void startUpdate(ViewGroup container) {
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        final long itemId = getItemId(position);
        // Do we already have this fragment?
        String name = makeFragmentName(container.getId(), itemId);
        Fragment fragment = mFragmentManager.findFragmentByTag(name);
        if (fragment != null) {
            if (DEBUG) Log.v(TAG, "Attaching item #" + itemId + ": f=" + fragment);
            mCurTransaction.attach(fragment);
        } else {
            fragment = getItem(position);
            if (DEBUG) Log.v(TAG, "Adding item #" + itemId + ": f=" + fragment);
            mCurTransaction.add(container.getId(), fragment,
                    makeFragmentName(container.getId(), itemId));
        }

        if (fragment != mCurrentPrimaryItem) {
            fragment.setMenuVisibility(false);
            fragment.setUserVisibleHint(false);
        }

        return fragment;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        if (DEBUG) Log.v(TAG, "Detaching item #" + getItemId(position) + ": f=" + object
                + " v=" + ((Fragment) object).getView());
        mCurTransaction.detach((Fragment) object);
    }


    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        Fragment fragment = (Fragment) object;
        if (fragment != mCurrentPrimaryItem) {
            if (mCurrentPrimaryItem != null) {
                mCurrentPrimaryItem.setMenuVisibility(false);
                mCurrentPrimaryItem.setUserVisibleHint(false);
                if (mCurrentPrimaryItem instanceof AdapterHolder) {
                    notifyHolderParentPrimaryChanged((AdapterHolder) mCurrentPrimaryItem, false);
                }
            }
            if (fragment != null) {
                if (mHolder != null && isHolderCurrentPrimary()) {
                    fragment.setMenuVisibility(true);
                    fragment.setUserVisibleHint(true);
                }
                if (fragment instanceof AdapterHolder) {
                    Log.d(TAG, "Holder:" + mHolder.getClass());
                    Log.d(TAG, "Fragment:" + fragment.getClass());
                    notifyHolderParentPrimaryChanged((AdapterHolder) fragment, true);
                }
            }
            mCurrentPrimaryItem = fragment;
        }
    }

    private void notifyHolderParentPrimaryChanged(AdapterHolder fragment, boolean primary) {
        if (fragment.getAdapter() != null) {
            fragment.getAdapter().onParentPrimaryChanged(primary);
        }
    }

    private boolean isHolderCurrentPrimary() {
        if (mHolder.getAdapter() != null) {
            return mHolder.getAdapter().isCurrentPrimary();
        } else {
            return false;
        }
    }


    /**
     * 表示当前 Adapter 是否是首要的，如果 adapter 标记首要，当其父 Adapter 不是首要，仍返回非首要
     *
     * @return
     */
    public boolean isCurrentPrimary() {
        return currentPrimary && (mParent == null || mParent.isCurrentPrimary());
    }

    /**
     * 容器 Fragment 是否是首要页发生变化
     *
     * @param primary 父 fragment 是否是首要的
     */
    protected void onParentPrimaryChanged(boolean primary) {
        Log.d(TAG, "Holder:" + mHolder.getClass());
        currentPrimary = primary;
        if (mCurrentPrimaryItem != null) {
            Log.d(TAG, "onParentPrimaryChanged:" + mCurrentPrimaryItem.getClass() + ":" + primary);
            if (primary) {
                mCurrentPrimaryItem.setMenuVisibility(true);
                mCurrentPrimaryItem.setUserVisibleHint(true);
            } else {
                mCurrentPrimaryItem.setMenuVisibility(false);
                mCurrentPrimaryItem.setUserVisibleHint(false);
            }
            // 递归传递消息
            if (mCurrentPrimaryItem instanceof AdapterHolder) {
                ((AdapterHolder) mCurrentPrimaryItem).getAdapter().onParentPrimaryChanged(primary);
            }
        }

    }

    @Override
    public void finishUpdate(ViewGroup container) {
        if (mCurTransaction != null) {
            mCurTransaction.commitAllowingStateLoss();
            mCurTransaction = null;
            mFragmentManager.executePendingTransactions();
        }
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return ((Fragment) object).getView() == view;
    }

    @Override
    public Parcelable saveState() {
        return null;
    }

    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {
    }

    /**
     * Return a unique identifier for the item at the given position.
     * <p>
     * <p>The default implementation returns the given position.
     * Subclasses should override this method if the positions of items can change.</p>
     *
     * @param position Position within this adapter
     * @return Unique identifier for the item at position
     */
    public long getItemId(int position) {
        return position;
    }


    public interface AdapterHolder {
        HierarchyFragmentPagerAdapter getAdapter();
    }


}