我们经常看到使用了ViewPager的App，在每页上面都会有一个滑块来标志当前处于哪一页。在PagerView包里有android.support.v4.view.PagerTitleStrip和android.support.v4.view.PagerTabStrip两个组件，可以在布局文件中，作为ViewPager的子标签，并设定相对与ViewPager的位置(比如顶部)。但这两个组件都很丑，并且标题会随着页面一起滑动，所以一般都不用。

其实实现一个滑块标志当前页面也很简单，大概需要两步：

第一步 在布局文件ViewPager的上方放置一个ImageView组件，组件可以是图片或是shape资源。注意需要把ImageView的scaleType属性设为matrix，就是说该组件的位置和大小由一个变换矩阵来控制；

第二步 在Activity中为ViewPager组件添加OnPageChangeListener监听器。在OnPageChangeListener里设定matrix，用于控制指示滑块ImageView的位置。该监听器需要实现三个方法：

onPageScrollStateChanged：用于监听滑动状态的改变

onPageScrolled：用于监听滑动的动作

onPageSeleted:用于监听页面的切换，即某个页面被选中了作为当前页面。

一般实现onPageSelected方法就可以，其他两个方法可以空着。另外为了使页面切换时滑块也是平滑地滑动，可以给滑块的ImageView指定一个TranslateAnimation动画，指定动画用setAnimation，TranlateAnimation也很简单，有个构造函数是TranslateAnimation(int beginX,int endX,int beginY,int endY)，将运动矢量的起始位置和终止位置传给它就好了。

下面我们来看五个具体的例子：

一 实现ViewPager（数据源为List<View>）

1.先在main.xml文件中添加一个ViewPager:

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

2.创建三个View:

<"1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/txt1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:textSize="25dp" android:text="第一页" > </TextView> </LinearLayout>

<"1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/txt2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="第二页" > </TextView> </LinearLayout>

<"1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > <TextView android:id="@+id/txt3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="第三页" > </TextView> </LinearLayout>

3.创建一个ViewPager适配器类：

package com.yayun.viewpagerdemo; import java.util.ArrayList; import java.util.List; import android.support.v4.view.PagerAdapter; import android.view.View; import android.view.ViewGroup; public class ViewPagerAdapter extends PagerAdapter { private List<View> lViews=new ArrayList<View>(); public ViewPagerAdapter(List<View> lViews){ this.lViews=lViews; } @Override public int getCount() { return lViews.size(); } @Override public boolean isViewFromObject(View arg0, Object arg1) { return arg0==arg1; } @Override public Object instantiateItem(ViewGroup container, int position) { container.addView(lViews.get(position)); return lViews.get(position); } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView(lViews.get(position)); } }

4.MainActivity.java:

package com.yayun.viewpagerdemo; import java.util.ArrayList; import java.util.List; import android.support.v7.app.ActionBarActivity; import android.support.v7.app.ActionBar; import android.support.v4.app.Fragment; import android.support.v4.view.PagerAdapter; import android.support.v4.view.ViewPager; import android.os.Bundle; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.view.Window; import android.os.Build; public class MainActivity extends ActionBarActivity { private ViewPager viewPager; private List<View> listViews=null; ViewPagerAdapter pagerAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.activity_main); viewPager=(ViewPager) findViewById(R.id.pager); listViews=new ArrayList<View>(); /** * 为Adapter创建数据源 */ View view1=View.inflate(this, R.layout.view1, null); View view2=View.inflate(this, R.layout.view2, null); View view3=View.inflate(this, R.layout.view3, null); listViews.add(view1); listViews.add(view2); listViews.add(view3); pagerAdapter=new ViewPagerAdapter(listViews) ; viewPager.setAdapter(pagerAdapter); } }

5.运行实例：

可以实现翻页效果。

二 添加标题

1.我们需要更改main.xml文件：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" > <android.support.v4.view.ViewPager android:id="@+id/pager" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" > <android.support.v4.view.PagerTabStrip android:id="@+id/strip" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="top" > </android.support.v4.view.PagerTabStrip> </android.support.v4.view.ViewPager> </LinearLayout>

2.需要更改适配器文件：

package com.yayun.viewpagerdemo; import java.util.ArrayList; import java.util.List; import android.support.v4.view.PagerAdapter; import android.view.View; import android.view.ViewGroup; public class ViewPagerAdapter extends PagerAdapter { private List<View> lViews=new ArrayList<View>(); private List<String> titleList=new ArrayList<String>(); public ViewPagerAdapter(List<View> lViews,List<String> titleList){ this.lViews=lViews; this.titleList=titleList; } @Override public int getCount() { return lViews.size(); } @Override public boolean isViewFromObject(View arg0, Object arg1) { return arg0==arg1; } @Override public Object instantiateItem(ViewGroup container, int position) { container.addView(lViews.get(position)); return lViews.get(position); } @Override public void destroyItem(ViewGroup container, int position, Object object) { container.removeView(lViews.get(position)); } /** * 标题 */ @Override public CharSequence getPageTitle(int position) { // TODO Auto-generated method stub return titleList.get(position); } }

3.需要更改MainActivity.java文件：

package com.yayun.viewpagerdemo; import java.util.ArrayList; import java.util.List; import android.support.v7.app.ActionBarActivity; import android.support.v7.app.ActionBar; import android.support.v4.app.Fragment; import android.support.v4.view.PagerAdapter; import android.support.v4.view.PagerTabStrip; import android.support.v4.view.ViewPager; import android.os.Bundle; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.view.Window; import android.os.Build; public class MainActivity extends ActionBarActivity { private ViewPager viewPager; private List<View> listViews=null; ViewPagerAdapter pagerAdapter; PagerTabStrip pagerTabStrip; private List<String> titleList; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.activity_main); viewPager=(ViewPager) findViewById(R.id.pager); pagerTabStrip=(PagerTabStrip) findViewById(R.id.strip); listViews=new ArrayList<View>(); titleList=new ArrayList<String>(); titleList.add("第一页"); titleList.add("第二页"); titleList.add("第三页"); /** * 为Adapter创建数据源 */ View view1=View.inflate(this, R.layout.view1, null); View view2=View.inflate(this, R.layout.view2, null); View view3=View.inflate(this, R.layout.view3, null); listViews.add(view1); listViews.add(view2); listViews.add(view3); pagerAdapter=new ViewPagerAdapter(listViews,titleList) ; viewPager.setAdapter(pagerAdapter); } }

4.运行实例如下：

三 实现ViewPager(数据源为List<Fragment>)

1.首先我们要创建三个Fragment:

package com.yayun.viewpagerdemo; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; public class Fragment1 extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.view1, container, false); } } package com.yayun.viewpagerdemo; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; public class Fragment2 extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.view2, container, false); } } package com.yayun.viewpagerdemo; import android.os.Bundle; import android.support.v4.app.Fragment; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; public class Fragment3 extends Fragment { @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { return inflater.inflate(R.layout.view3, container, false); } }

2.设置Adapter:

package com.yayun.viewpagerdemo; import java.util.List; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentPagerAdapter; public class MyFragmentPagerAdapter extends FragmentPagerAdapter { List<Fragment> fragmentsList; List<String> titleList; public MyFragmentPagerAdapter(FragmentManager fm,List<Fragment> fragmentsList,List<String> titleList) { super(fm); this.fragmentsList=fragmentsList; this.titleList=titleList; } @Override public Fragment getItem(int arg0) { // TODO Auto-generated method stub return fragmentsList.get(arg0); } @Override public int getCount() { // TODO Auto-generated method stub return fragmentsList.size(); } @Override /** * 添加标题 */ public CharSequence getPageTitle(int position) { // TODO Auto-generated method stub return titleList.get(position); } }

3.MainActivity.java:

package com.yayun.viewpagerdemo; import java.util.ArrayList; import java.util.List; import android.graphics.Color; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.view.PagerTabStrip; import android.support.v4.view.ViewPager; import android.support.v4.view.ViewPager.PageTransformer; import android.support.v7.app.ActionBarActivity; import android.view.View; import android.view.Window; public class MainActivity extends ActionBarActivity { private ViewPager viewPager; private List<View> listViews=null; ViewPagerAdapter pagerAdapter; PagerTabStrip pagerTabStrip; private List<String> titleList; private List<Fragment> fragmentsList; MyFragmentPagerAdapter myFragmentPagerAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.activity_main); viewPager=(ViewPager) findViewById(R.id.pager); pagerTabStrip=(PagerTabStrip) findViewById(R.id.strip); /** * 设置PagerTabStrip属性 */ pagerTabStrip.setBackgroundColor(Color.GREEN); pagerTabStrip.setDrawFullUnderline(false); pagerTabStrip.setTextColor(Color.WHITE); listViews=new ArrayList<View>(); titleList=new ArrayList<String>(); fragmentsList=new ArrayList<Fragment>(); fragmentsList.add(new Fragment1()); fragmentsList.add(new Fragment2()); fragmentsList.add(new Fragment3()); titleList.add("第一页"); titleList.add("第二页"); titleList.add("第三页"); /** * 为Adapter创建数据源 */ View view1=View.inflate(this, R.layout.view1, null); View view2=View.inflate(this, R.layout.view2, null); View view3=View.inflate(this, R.layout.view3, null); listViews.add(view1); listViews.add(view2); listViews.add(view3); pagerAdapter=new ViewPagerAdapter(listViews,titleList) ; myFragmentPagerAdapter=new MyFragmentPagerAdapter(getSupportFragmentManager(), fragmentsList, titleList); //viewPager.setAdapter(pagerAdapter); viewPager.setAdapter(myFragmentPagerAdapter); } }

4.运行实例：

这种方法不会销毁不在当前页面的页面，不能实现页卡的创建和销毁。

四 实现ViewPager(数据源为List<Fragment>实现FargmentStatePagerAdapter)常用

改变Adapter:

package com.yayun.viewpagerdemo; import java.util.List; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentPagerAdapter; import android.support.v4.app.FragmentStatePagerAdapter; import android.view.View; public class MyFragmentPagerAdapter2 extends FragmentStatePagerAdapter { List<Fragment> fragmentsList; List<String> titleList; public MyFragmentPagerAdapter2(FragmentManager fm,List<Fragment> fragmentsList,List<String> titleList) { super(fm); this.fragmentsList=fragmentsList; this.titleList=titleList; } @Override public Fragment getItem(int arg0) { // TODO Auto-generated method stub return fragmentsList.get(arg0); } @Override public int getCount() { // TODO Auto-generated method stub return fragmentsList.size(); } @Override /** * 添加标题 */ public CharSequence getPageTitle(int position) { // TODO Auto-generated method stub return titleList.get(position); } @Override public Object instantiateItem(View container, int position) { // TODO Auto-generated method stub return super.instantiateItem(container, position); } @Override public void destroyItem(View container, int position, Object object) { // TODO Auto-generated method stub super.destroyItem(container, position, object); } }

将MainActivity.java中的Adapter换一下即可，它可以实现页卡的创建和销毁。

五 onPagerChangeListener 监听使用

只需要修改MainActivity.java:

package com.yayun.viewpagerdemo; import java.util.ArrayList; import java.util.List; import android.graphics.Color; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.view.PagerTabStrip; import android.support.v4.view.ViewPager; import android.support.v4.view.ViewPager.OnPageChangeListener; import android.support.v4.view.ViewPager.PageTransformer; import android.support.v7.app.ActionBarActivity; import android.view.View; import android.view.Window; import android.widget.Toast; public class MainActivity extends ActionBarActivity implements OnPageChangeListener { private ViewPager viewPager; private List<View> listViews=null; ViewPagerAdapter pagerAdapter; PagerTabStrip pagerTabStrip; private List<String> titleList; private List<Fragment> fragmentsList; MyFragmentPagerAdapter myFragmentPagerAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.activity_main); viewPager=(ViewPager) findViewById(R.id.pager); pagerTabStrip=(PagerTabStrip) findViewById(R.id.strip); /** * 设置PagerTabStrip属性 */ pagerTabStrip.setBackgroundColor(Color.GREEN); pagerTabStrip.setDrawFullUnderline(false); pagerTabStrip.setTextColor(Color.WHITE); listViews=new ArrayList<View>(); titleList=new ArrayList<String>(); fragmentsList=new ArrayList<Fragment>(); fragmentsList.add(new Fragment1()); fragmentsList.add(new Fragment2()); fragmentsList.add(new Fragment3()); titleList.add("第一页"); titleList.add("第二页"); titleList.add("第三页"); /** * 为Adapter创建数据源 */ View view1=View.inflate(this, R.layout.view1, null); View view2=View.inflate(this, R.layout.view2, null); View view3=View.inflate(this, R.layout.view3, null); listViews.add(view1); listViews.add(view2); listViews.add(view3); pagerAdapter=new ViewPagerAdapter(listViews,titleList) ; myFragmentPagerAdapter=new MyFragmentPagerAdapter(getSupportFragmentManager(), fragmentsList, titleList); //viewPager.setAdapter(pagerAdapter); viewPager.setAdapter(myFragmentPagerAdapter); viewPager.setOnPageChangeListener(this);//加载监听器 } @Override public void onPageScrollStateChanged(int arg0) { // TODO Auto-generated method stub } @Override public void onPageScrolled(int arg0, float arg1, int arg2) { // TODO Auto-generated method stub } @Override public void onPageSelected(int arg0) { Toast.makeText(this, "当前页面为"+(arg0+1), Toast.LENGTH_SHORT).show(); } }

运行实例即可以显示当前页面标签。