实现左右滑动—ViewPager

   还记得在前几期我用模板生成了一个导航标签，那里面有个viewPager控件。今天我想来着重看一下这个android官方版实现的左右滑动效果—viewPager

这是官方android API对viewPager的解释

Layout manager that allows the user to flip left and right through pages of data. You supply an implementation of a PagerAdapter to generate the pages that the view shows.

Note this class is currently under early design and development. The API will likely change in later updates of the compatibility library, requiring changes to the source code of apps when they are compiled against the newer version.

ViewPager is most often used in conjunction with Fragment, which is a convenient way to supply and manage the lifecycle of each page. There are standard adapters implemented for using fragments with the ViewPager, which cover the most common use cases. These are FragmentPagerAdapter and FragmentStatePagerAdapter; each of these classes have simple code showing how to build a full user interface with them.

允许用户翻转左和右通过数据页的布局管理器。 您提供的 PagerAdapter 生成的视图显示页的实现。
请注意此类目前正在早期设计和发展。 API 可能会改变以后的更新兼容性库，他们针对新版本在编译时需要更改的应用程序的源代码。
ViewPager 是最常与Fragment联合使用的，是一种供应和管理生命周期的每个页面的简便方法的结合。 有标准适配器使用Fragment的 ViewPager，实施包括最常见的使用情况。这些都是 FragmentPagerAdapter 和 FragmentStatePagerAdapter ；每个类有简单的代码展示了如何构建一个完整的用户界面与他们。
参照官方给出的例子，写了个小例子。

package com.example.viewpager_01;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.PagerTitleStrip;
import android.support.v4.view.ViewPager;

import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {

	private ViewPager mViewPager;
	private PagerTitleStrip mPagerTitleStrip;
	private View view1 =null;
	private View view2 = null;
	private View view3 = null;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		mViewPager = (ViewPager)findViewById(R.id.viewpager);
		mPagerTitleStrip = (PagerTitleStrip)findViewById(R.id.pagertitle);
		
		LayoutInflater inflater = LayoutInflater.from(this);
		 view1 = inflater.inflate(R.layout.view1, null);
		 view2 = inflater.inflate(R.layout.view2, null);
		 view3 = inflater.inflate(R.layout.view3, null);
		
		final List<View> views = new ArrayList<View>();
		views.add(view1);
		views.add(view2);
		views.add(view3);
		
		final List<String> titles = new ArrayList<String>();
		titles.add("tabl");
		titles.add("tab2");
		titles.add("tab3");
		PagerAdapter adapter = new PagerAdapter() {
			
			@Override
			public boolean isViewFromObject(View arg0, Object arg1) {
				return arg0 == arg1;
			}
			
			@Override
			public int getCount() {
				return views.size();
			}
			
			@Override
			public void destroyItem(View container, int position, Object object) {
				((ViewPager)container).removeView(views.get(position));
			}
			
			@Override
			public CharSequence getPageTitle(int position) {
				return titles.get(position);
			}
			
			@Override
			public Object instantiateItem(View container, int position) {
				((ViewPager)container).addView(views.get(position));
				return views.get(position);
			}
		};
		mViewPager.setAdapter(adapter);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

布局文件

<android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center" >

        <android.support.v4.view.PagerTitleStrip
            android:id="@+id/pagertitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="top" />
    </android.support.v4.view.ViewPager>

下面是我之前用Tabs模板创建的Android工程，这个实现了ViewPager的用法

package com.example.addnavigationtab_02;

import java.util.Locale;

import android.app.ActionBar;
import android.app.FragmentTransaction;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.app.NavUtils;
import android.support.v4.view.ViewPager;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class AddNavigationTabActivity extends FragmentActivity implements
		ActionBar.TabListener {

	/**
	 * The {@link android.support.v4.view.PagerAdapter} that will provide
	 * fragments for each of the sections. We use a
	 * {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
	 * will keep every loaded fragment in memory. If this becomes too memory
	 * intensive, it may be best to switch to a
	 * {@link android.support.v4.app.FragmentStatePagerAdapter}.
	 */
	SectionsPagerAdapter mSectionsPagerAdapter;

	/**
	 * The {@link ViewPager} that will host the section contents.
	 */
	ViewPager mViewPager;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_add_navigation_tab);

		// Set up the action bar. 设置ActionBar为导航模式
		final ActionBar actionBar = getActionBar();
		actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

		// Create the adapter that will return a fragment for each of the three
		// primary sections of the app.
		mSectionsPagerAdapter = new SectionsPagerAdapter(
				getSupportFragmentManager());

		// Set up the ViewPager with the sections adapter.
		mViewPager = (ViewPager) findViewById(R.id.pager);
		mViewPager.setAdapter(mSectionsPagerAdapter);

		// When swiping between different sections, select the corresponding
		// tab. We can also use ActionBar.Tab#select() to do this if we have
		// a reference to the Tab.
		mViewPager
				.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
					@Override
					public void onPageSelected(int position) {
						//显示当前的Tab标签
						actionBar.setSelectedNavigationItem(position);
					}
				});

		// For each of the sections in the app, add a tab to the action bar.
		for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
			// Create a tab with text corresponding to the page title defined by
			// the adapter. Also specify this Activity object, which implements
			// the TabListener interface, as the callback (listener) for when
			// this tab is selected.
			actionBar.addTab(actionBar.newTab()
					.setText(mSectionsPagerAdapter.getPageTitle(i))
					.setTabListener(this));
		}
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.add_navigation_tab, menu);
		return true;
	}

	@Override
	public void onTabSelected(ActionBar.Tab tab,
			FragmentTransaction fragmentTransaction) {
		// When the given tab is selected, switch to the corresponding page in
		// the ViewPager.
		mViewPager.setCurrentItem(tab.getPosition());
	}

	@Override
	public void onTabUnselected(ActionBar.Tab tab,
			FragmentTransaction fragmentTransaction) {
	}

	@Override
	public void onTabReselected(ActionBar.Tab tab,
			FragmentTransaction fragmentTransaction) {
	}

	/**
	 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
	 * one of the sections/tabs/pages.
	 */
	public class SectionsPagerAdapter extends FragmentPagerAdapter {

		public SectionsPagerAdapter(FragmentManager fm) {
			super(fm);
		}

		@Override
		public Fragment getItem(int position) {
			// getItem is called to instantiate the fragment for the given page.
			// Return a DummySectionFragment (defined as a static inner class
			// below) with the page number as its lone argument.
			Fragment fragment = new DummySectionFragment();
			Bundle args = new Bundle();
			args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
			fragment.setArguments(args);
			return fragment;
		}

		@Override
		public int getCount() {
			// Show 3 total pages.
			return 3;
		}

		@Override
		public CharSequence getPageTitle(int position) {
			Locale l = Locale.getDefault();
			switch (position) {
			case 0:
				return getString(R.string.title_section1).toUpperCase(l);
			case 1:
				return getString(R.string.title_section2).toUpperCase(l);
			case 2:
				return getString(R.string.title_section3).toUpperCase(l);
			}
			return null;
		}
	}

	/**
	 * A dummy fragment representing a section of the app, but that simply
	 * displays dummy text.
	 */
	public static class DummySectionFragment extends Fragment {
		/**
		 * The fragment argument representing the section number for this
		 * fragment.
		 */
		public static final String ARG_SECTION_NUMBER = "section_number";

		public DummySectionFragment() {
		}

		@Override
		public View onCreateView(LayoutInflater inflater, ViewGroup container,
				Bundle savedInstanceState) {
			View rootView = inflater.inflate(
					R.layout.fragment_add_navigation_tab_dummy, container,
					false);
			TextView dummyTextView = (TextView) rootView
					.findViewById(R.id.section_label);
			dummyTextView.setGravity(Gravity.CENTER);
			dummyTextView.setText("第"+Integer.toString(getArguments().getInt(
					ARG_SECTION_NUMBER))+"页");
			return rootView;
		}
	}

}

布局文件

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".AddNavigationTabActivity" />

目前我只了解这么多的ViewPager的知识点，渴望跟大家交流来获得更深的理解。