FragmentCacheManager.java

package com.konka.music.fragmentcontrol;

import java.util.ArrayList;

import com.konka.music.R;

import android.os.Bundle;
import android.os.Parcelable;
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;

public abstract class FragmentCacheManager extends PagerAdapter {
	private static final String TAG = "FragmentCacheManager";
	private static final boolean DEBUG = false;

	private final FragmentManager mFragmentManager;
	private FragmentTransaction mCurTransaction = null;

	private ArrayList<Fragment.SavedState> mSavedState = new ArrayList<Fragment.SavedState>();
	private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();
	private Fragment mCurrentPrimaryItem = null;

	public FragmentCacheManager(FragmentManager fm) {
		mFragmentManager = fm;
	}

 
	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();
			mCurTransaction.setCustomAnimations(R.anim.slide_right_in, R.anim.slide_out_left, R.anim.slide_in_left, R.anim.slide_right_out);
		}
		Fragment fragment = null;
		if (mFragments.size() > position) {
			fragment = mFragments.get(position);
		}
		if (fragment == null) {
			fragment = getItem(position);
			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);
		fragment.setUserVisibleHint(false);
		mFragments.set(position, fragment);
		mCurTransaction.replace(container.getId(), fragment);
		mCurTransaction.addToBackStack(null);
		return fragment;
	}

	@Override
	public void destroyItem(ViewGroup container, int position, 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, mFragmentManager.saveFragmentInstanceState(fragment));
		mFragments.set(position, null);
		System.out.println("销毁了");
		mCurTransaction.remove(fragment);
	}

	@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 (fragment != null) {
				fragment.setMenuVisibility(true);
				fragment.setUserVisibleHint(true);
			}
			
			mCurrentPrimaryItem = fragment;
		}
	}

	@Override
	public void finishUpdate(ViewGroup container) {
		if (mCurTransaction != null) {
			mCurTransaction.commitAllowingStateLoss();
			mCurTransaction = null;
			mFragmentManager.executePendingTransactions();
		}
	}
//	public void finishUpdate() {
//		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() {
		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) {
				if (state == null) {
					state = new Bundle();
				}
				String key = "f" + i;
				mFragmentManager.putFragment(state, key, f);
			}
		}
		return state;
	}

	@Override
	public void restoreState(Parcelable state, 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);
					}
				}
			}
		}
	}
}