ViewPager+Fragmrnt最简单结合方法

Fragment和ViewPager

本博文系本菜鸟第一次博文展示,有错误之处请尽管提出

FragmentPagerAdapter

谷歌官方提供了这么一个adapter(FragmentPagerAdapter),

• 与正常的PagerAdapter相比:
  用FragmentPagerAdapter时:只需要复写getItem(int position),getCount()两个方法

public MyPagerAdapter(FragmentManager fm) {    super(fm)}@Overridepublic Fragment getItem(int position) {    return null;}@Overridepublic int getCount() {    return 0;}

• 用PagerAdapter时:通常要复写大部分方法:

@Overridepublic int getCount() {    return 0;}@Overridepublic boolean isViewFromObject(View view, Object object) {    return false;}public MyPagerAdapter() {    super();}@Overridepublic Object instantiateItem(ViewGroup container, int position) {    return super.instantiateItem(container, position);}@Overridepublic void destroyItem(ViewGroup container, int position, Object object) {    super.destroyItem(container, position, object);}

下面附上FragmentPagerAdapter的代码

/* * 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 android.support.v4.app;import android.os.Parcelable;import android.support.v4.view.PagerAdapter;import android.util.Log;import android.view.View;import android.view.ViewGroup;/** * 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. * * <p>This version of the pager is best for use when there are a handful of * typically more static fragments to be paged through, such as a set of tabs. * The fragment of each page the user visits will be kept in memory, though its * view hierarchy may be destroyed when not visible.  This can result in using * a significant amount of memory since fragment instances can hold on to an * arbitrary amount of state.  For larger sets of pages, consider * {@link FragmentStatePagerAdapter}. * * <p>When using FragmentPagerAdapter the host ViewPager must have a * valid ID set.</p> * * <p>Subclasses only need to implement {@link #getItem(int)} * and {@link #getCount()} to have a working adapter. * * <p>Here is an example implementation of a pager containing fragments of * lists: * * {@sample development/samples/Support4Demos/src/com/example/android/supportv4/app/FragmentPagerSupport.java *      complete} * * <p>The <code>R.layout.fragment_pager</code> resource of the top-level fragment is: * * {@sample development/samples/Support4Demos/res/layout/fragment_pager.xml *      complete} * * <p>The <code>R.layout.fragment_pager_list</code> resource containing each * individual fragment's layout is: * * {@sample development/samples/Support4Demos/res/layout/fragment_pager_list.xml *      complete} */public abstract class FragmentPagerAdapter 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;    public FragmentPagerAdapter(FragmentManager fm) {        mFragmentManager = fm;    }    /**     * 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 (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();        }    }    @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>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;    }    private static String makeFragmentName(int viewId, long id) {        return "android:switcher:" + viewId + ":" + id;    }}

在代码中可以看出来,谷歌官方的api已经对Fragment的生命周期进行了一定的管理 大大的方便了有这种需要的程序猿们

本菜鸟在开发过程中同时用了ViewPager和Fragment打造首页展示页面 但是之前封装的Fragmrnt在使用过程中发生了一些错误
之前封装过一个BaseFragment来帮助自己减轻代码负担, 封装的时候并没有用v4包的Fragment

注意事项:该api对应的Fragment必须是v4包的Fragment 如果不是的话会报错,请注意.

                本人博文:转载请注明  http://blog.csdn.net/qq_25436769/article/details/50765557