content: package com.cy.tablayoutniubility;
  
  import android.os.Bundle;
  import android.os.Parcelable;
  import android.util.Log;
  import android.view.View;
  import android.view.ViewGroup;
  
  import androidx.annotation.IntDef;
  import androidx.annotation.NonNull;
  import androidx.annotation.Nullable;
  import androidx.fragment.app.Fragment;
  import androidx.fragment.app.FragmentManager;
  import androidx.fragment.app.FragmentTransaction;
  import androidx.lifecycle.Lifecycle;
  import androidx.viewpager.widget.PagerAdapter;
  
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.util.ArrayList;
  
  /**
   * @Description:
   * @Author: cy
   * @CreateDate: 2020/10/7 11:52
   * @UpdateUser:
   * @UpdateDate: 2020/10/7 11:52
   * @UpdateRemark:
   * @Version: 1.0
   */
   abstract class CyFragStatePageAdapterVp extends PagerAdapter {
      private static final String TAG = "CyFragStatePageAdapterVp";
      private static final boolean DEBUG = false;
  
      @Retention(RetentionPolicy.SOURCE)
      @IntDef({BEHAVIOR_SET_USER_VISIBLE_HINT, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT})
      private @interface Behavior { }
      @Deprecated
      public static final int BEHAVIOR_SET_USER_VISIBLE_HINT = 0;
  
      public static final int BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT = 1;
  
      private final FragmentManager mFragmentManager;
      private final int mBehavior;
      private FragmentTransaction mCurTransaction = null;
  
      private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<>();
      private ArrayList<Fragment> mFragments = new ArrayList<>();
      private Fragment mCurrentPrimaryItem = null;
      private boolean mExecutingFinishUpdate;
  
      @Deprecated
      public CyFragStatePageAdapterVp(@NonNull FragmentManager fm) {
          this(fm, BEHAVIOR_SET_USER_VISIBLE_HINT);
      }
  
      public CyFragStatePageAdapterVp(@NonNull FragmentManager fm,
                                       @Behavior int behavior) {
          mFragmentManager = fm;
          mBehavior = behavior;
      }
  
      /**
       * Return the Fragment associated with a specified position.
       */
      @NonNull
      public abstract Fragment getItem(int position);
  
      @Override
      public void startUpdate(@NonNull ViewGroup container) {
          if (container.getId() == View.NO_ID) {
              throw new IllegalStateException("ViewPager with adapter " + this
                      + " requires a view id");
          }
      }
  
      @SuppressWarnings("deprecation")
      @NonNull
      @Override
      public Object instantiateItem(@NonNull ViewGroup container, int position) {
          // If we already have this item instantiated, there is nothing
          // to do.  This can happen when we are restoring the entire pager
          // from its saved state, where the fragment manager has already
          // taken care of restoring the fragments we previously had instantiated.
  //        if (mFragments.size() > position) {
  //            Fragment f = mFragments.get(position);
  //            if (f != null) {
  //                return f;
  //            }
  //        }
  
          if (mCurTransaction == null) {
              mCurTransaction = mFragmentManager.beginTransaction();
          }
  
          Fragment fragment = getItem(position);
          if (DEBUG) Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
          if (mSavedState.size() > position) {
              Fragment.SavedState fss = mSavedState.get(position);
              if (fss != null) {
                  fragment.setInitialSavedState(fss);
              }
          }
          while (mFragments.size() <= position) {
              mFragments.add(null);
          }
          fragment.setMenuVisibility(false);
          if (mBehavior == BEHAVIOR_SET_USER_VISIBLE_HINT) {
              fragment.setUserVisibleHint(false);
          }
  
          mFragments.set(position, fragment);
          mCurTransaction.add(container.getId(), fragment);
  
          if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
              mCurTransaction.setMaxLifecycle(fragment, Lifecycle.State.STARTED);
          }
  
          return fragment;
      }
  
      // TODO(b/141958824): Suppressed during upgrade to AGP 3.6.
      @SuppressWarnings("ReferenceEquality")
      @Override
      public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
          Fragment fragment = (Fragment) object;
  
          if (mCurTransaction == null) {
              mCurTransaction = mFragmentManager.beginTransaction();
          }
          if (DEBUG) Log.v(TAG, "Removing item #" + position + ": f=" + object
                  + " v=" + ((Fragment)object).getView());
          while (mSavedState.size() <= position) {
              mSavedState.add(null);
          }
          mSavedState.set(position, fragment.isAdded()
                  ? mFragmentManager.saveFragmentInstanceState(fragment) : null);
          mFragments.set(position, null);
  
          mCurTransaction.remove(fragment);
          if (fragment.equals(mCurrentPrimaryItem)) {
              mCurrentPrimaryItem = null;
          }
      }
  
      @Override
      @SuppressWarnings({"ReferenceEquality", "deprecation"})
      public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
          Fragment fragment = (Fragment)object;
          if (fragment != mCurrentPrimaryItem) {
              if (mCurrentPrimaryItem != null) {
                  mCurrentPrimaryItem.setMenuVisibility(false);
                  if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
                      if (mCurTransaction == null) {
                          mCurTransaction = mFragmentManager.beginTransaction();
                      }
                      mCurTransaction.setMaxLifecycle(mCurrentPrimaryItem, Lifecycle.State.STARTED);
                  } else {
                      mCurrentPrimaryItem.setUserVisibleHint(false);
                  }
              }
              fragment.setMenuVisibility(true);
              if (mBehavior == BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
                  if (mCurTransaction == null) {
                      mCurTransaction = mFragmentManager.beginTransaction();
                  }
                  mCurTransaction.setMaxLifecycle(fragment, Lifecycle.State.RESUMED);
              } else {
                  fragment.setUserVisibleHint(true);
              }
  
              mCurrentPrimaryItem = fragment;
          }
      }
  
      @Override
      public void finishUpdate(@NonNull ViewGroup container) {
          if (mCurTransaction != null) {
              // We drop any transactions that attempt to be committed
              // from a re-entrant call to finishUpdate(). We need to
              // do this as a workaround for Robolectric running measure/layout
              // calls inline rather than allowing them to be posted
              // as they would on a real device.
              if (!mExecutingFinishUpdate) {
                  try {
                      mExecutingFinishUpdate = true;
                      mCurTransaction.commitNowAllowingStateLoss();
                  } finally {
                      mExecutingFinishUpdate = false;
                  }
              }
              mCurTransaction = null;
          }
      }
  
      @Override
      public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
          return ((Fragment)object).getView() == view;
      }
  
      @Override
      @Nullable
      public Parcelable saveState() {
          Bundle state = null;
          if (mSavedState.size() > 0) {
              state = new Bundle();
              Fragment.SavedState[] fss = new Fragment.SavedState[mSavedState.size()];
              mSavedState.toArray(fss);
              state.putParcelableArray("states", fss);
          }
          for (int i=0; i<mFragments.size(); i++) {
              Fragment f = mFragments.get(i);
              if (f != null && f.isAdded()) {
                  if (state == null) {
                      state = new Bundle();
                  }
                  String key = "f" + i;
                  mFragmentManager.putFragment(state, key, f);
              }
          }
          return state;
      }
  
      @Override
      public void restoreState(@Nullable Parcelable state, @Nullable ClassLoader loader) {
          if (state != null) {
              Bundle bundle = (Bundle)state;
              bundle.setClassLoader(loader);
              Parcelable[] fss = bundle.getParcelableArray("states");
              mSavedState.clear();
              mFragments.clear();
              if (fss != null) {
                  for (int i=0; i<fss.length; i++) {
                      mSavedState.add((Fragment.SavedState)fss[i]);
                  }
              }
              Iterable<String> keys = bundle.keySet();
              for (String key: keys) {
                  if (key.startsWith("f")) {
                      int index = Integer.parseInt(key.substring(1));
                      Fragment f = mFragmentManager.getFragment(bundle, key);
                      if (f != null) {
                          while (mFragments.size() <= index) {
                              mFragments.add(null);
                          }
                          f.setMenuVisibility(false);
                          mFragments.set(index, f);
                      } else {
                          Log.w(TAG, "Bad fragment at key " + key);
                      }
                  }
              }
          }
      }
  }
  