tw.com.ischool.dominator.util.ViewPagerAdapter.java Source code

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Here is the source code for tw.com.ischool.dominator.util.ViewPagerAdapter.java

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/*
 * 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 tw.com.ischool.dominator.util;

import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.util.Log;
import android.util.SparseArray;
import android.view.View;

/**
 * Implementation of {@link android.support.v4.view.PagerAdapter} that
 * represents each page as a {@link Fragment} that is persistently kept in the
 * fragment manager as long as the user can return to the page.
 */
public abstract class ViewPagerAdapter extends PagerAdapter {
    private static final String TAG = "FragmentPagerAdapter";
    private static final boolean DEBUG = false;

    private final FragmentManager mFragmentManager;
    private FragmentTransaction mCurTransaction = null;
    private Fragment mCurrentPrimaryItem = null;
    private SparseArray<Fragment> mRegisteredFragments = null;

    public ViewPagerAdapter(FragmentManager fm) {
        mFragmentManager = fm;
        mRegisteredFragments = new SparseArray<Fragment>();
    }

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

    @Override
    public void startUpdate(View container) {
    }

    @Override
    public Object instantiateItem(View container, int position) {
        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }

        // Do we already have this fragment?
        String name = makeFragmentName(container.getId(), position);
        Fragment fragment = mFragmentManager.findFragmentByTag(name);
        if (fragment != null) {
            if (DEBUG)
                Log.v(TAG, "Attaching item #" + position + ": f=" + fragment);
            mCurTransaction.attach(fragment);
        } else {
            fragment = getItem(position);
            if (DEBUG)
                Log.v(TAG, "Adding item #" + position + ": f=" + fragment);
            mCurTransaction.add(container.getId(), fragment, makeFragmentName(container.getId(), position));
        }
        if (fragment != mCurrentPrimaryItem) {
            fragment.setMenuVisibility(false);
        }

        // save register fragment
        mRegisteredFragments.put(position, fragment);

        return fragment;
    }

    @Override
    public void destroyItem(View container, int position, Object object) {
        mRegisteredFragments.remove(position);

        if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
        if (DEBUG)
            Log.v(TAG, "Detaching item #" + position + ": f=" + object + " v=" + ((Fragment) object).getView());
        mCurTransaction.detach((Fragment) object);
    }

    @Override
    public void setPrimaryItem(View container, int position, Object object) {
        Fragment fragment = (Fragment) object;
        if (fragment != mCurrentPrimaryItem) {
            if (mCurrentPrimaryItem != null) {
                mCurrentPrimaryItem.setMenuVisibility(false);
            }
            if (fragment != null) {
                fragment.setMenuVisibility(true);
            }
            mCurrentPrimaryItem = fragment;
            onPrimaryItemChanged(position);
        }
    }

    @Override
    public void finishUpdate(View 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) {
    }

    protected abstract void onPrimaryItemChanged(int position);

    public Fragment getRegisteredFragment(int position) {
        return mRegisteredFragments.get(position);
    }

    public static String makeFragmentName(int viewId, int index) {
        return "android:switcher:" + viewId + ":" + index;
    }
}