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Android实习札记(6)---ViewPager使用详解

本文转载自  xiaoming1430026911  查看原文  2017/06/13  0    view/ 使用/ android/ 实习           

转载自：http://www.2cto.com/kf/201411/353975.html

札记(5)中介绍了Fragment构建简单的底部导航栏,在结尾的时候说要在下一节中,结合Viewpager

实现进入软件时的引导界面,说到ViewPager,很多朋友都用过,不过只知道粘贴复制,连一些基本的

东西都不知道,那是不行的,在本节中就先讲下ViewPager的一些基本概念吧!

 

 

1.首先ViewPager在哪个包下?

\

 

答:如图,就是在v4.view包下,另外,ViewPager也是3.0(api 11)后Google推出的,对于低版本的

可以自行导入v4包来解决低版本兼容的问题!

 

 

2.ViewPager的简单介绍

答:ViewPager就是一个页面切换的组件而已,我们可以往里面填多个view,然后

我们左右滑动切换不同的view而已,和ListView一样,我们也需要一个Adapter(适配器),将要显示

的View和我们的ViewPager进行绑定,而ViewPager有特定的Adapter——PagerAdapter！

另外,Google官方是建议我们使用Fragment来填充ViewPager的,这样可以更加方便的生成

每个Page以及管理每个Page的生命周期!当然也给我们提供了两个不同的Adapter!分别是:

FragmentPageAdapter和FragmentStatePagerAdapter,前者适用于页面较少的情况,后者

适用于页面较多的情况,,对于两个Adapter的区别会在后面进行讲解!

 

\

 

 

3.ViewPager的适配器——PagerAdapter讲解

答:ViewPager和Listview这些组件其实都是类似的,只是前者单位是Page(页面),后者是Item(项)

而PagerAdapter也是特别的!

 

①必须重写的四个方法:

\

 

②方法简介:

先说下简单的两个吧:

getCount( ):获得viewpager中有多少个view

destroyItem( ):移除一个给定位置的页面。适配器有责任从容器中删除这个视图。这是为了确保

在finishUpdate(viewGroup)返回时视图能够被移除。

而另外两个就涉及到一个key的概念了:

instantiateItem( ):①将给定位置的view添加到ViewGroup(容器)中,创建并显示出来

②返回一个代表新增页面的Object(key),通常都是直接返回view本身就可以了,

当然你也可以自定义自己的key,但是key和每个view要一一对应的关系

isViewFromObject( ):判断instantiateItem(ViewGroup, int)函数所返回来的Key与一个页面视图是否是

代表的同一个视图(即它俩是否是对应的，对应的表示同一个View),通常我们直接写

return view == object;就可以了,至于为什么要这样讲起来比较复杂,后面有机会进行了解吧

貌似是ViewPager中有个存储view状态信息的ArrayList,根据View取出对应信息的吧!

③代码示例:

Fragment的简单用法:添加三个View到ViewPager,然后滑动

效果图如下:

\

④实现流程:

step 1:定义三个布局,等下用来填充ViewPager的,例子比较简单,直接用不同TextView与背景颜色来区分

view2,view3只需要copy一下,然后改下颜色与文字就可以了

 

view1.xml

 

?
1234<!--?xml
version=1.0
encoding=utf-8?--><linearlayout
android:background="#FF6666"
android:gravity="center"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android">       <textview android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:text="第一个Page"></textview></linearlayout>

 

step 2:主界面布局文件的编写,一个TextView + ViewPager,注意ViewPager的标签:

 

是这样的:android.support.v4.view.ViewPager

 

activity_main.xml:

 

?
1234567<linearlayout
android:id="@+id/LinearLayout1"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:orientation="vertical"
tools:context=".MainActivity"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">     <textview android:background="#FCBC12/"
android:gravity="center"
android:layout_height="40dp"
android:layout_width="match_parent"
android:text="简单的ViewPager使用">                     </android.support.v4.view.viewpager></textview></linearlayout>

step 3:编写我们的自定义PagerAdapter适配器类,继承PagerAdapter,实现四个基本的方法:

getCount( ),isViewFormObject( ),instantiateItem( ),destoryItem( ),同时还要定义一个View的

集合,用来放viewpager中的view

MyPagerAdapter.java:

 

?
123456789101112131415161718192021222324252627282930313233343536373839404142package
com.jay.example.viewpagerdemo1; import
java.util.ArrayList; import
android.support.v4.view.PagerAdapter;import
android.view.View;import
android.view.ViewGroup; public
class MyPageAdapter extends
PagerAdapter {     private
ArrayList<view> viewLists;       public
MyPageAdapter() {}       public
MyPageAdapter(ArrayList<view> viewLists)    {        super();        this.viewLists = viewLists;    }              @Override    public
int getCount() {             return
viewLists.size();    }     @Override    public
boolean isViewFromObject(View view, Object object) {        return
view == object;    }         @Override    public
Object instantiateItem(ViewGroup container, int
position) {        container.addView(viewLists.get(position));        return
viewLists.get(position);    }     @Override    public
void destroyItem(ViewGroup container, int
position, Object object) {        container.removeView(viewLists.get(position));    }}</view></view>

 

step 4:最后就是MainActivity了,也很简单,实例化ViewPager对象以及View集合,然后通过LayoutInflater动态

加载三个view,通过add方法添加到View集合中,接着把View集合作为参数传递给MyPagerAdapter对象,

最后 调用setAdapter(mAdapter);就可以了

MainActivity.java

 

?
12345678910111213141516171819202122232425262728293031323334353637383940package
com.jay.example.viewpagerdemo1; import
java.util.ArrayList;import
android.os.Bundle;import
android.app.Activity;import
android.support.v4.view.ViewPager;import
android.view.LayoutInflater;import
android.view.View; public
class MainActivity extends
Activity {     //定义相关变量    private
View v1,v2,v3;    private
ViewPager vPager;    private
ArrayList<view> aList;    private
MyPageAdapter mAdapter;         @Override    protected
void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        vPager = (ViewPager) findViewById(R.id.viewpager);                 //动态加载三个View        LayoutInflater li = getLayoutInflater();        v1 = li.inflate(R.layout.view1, null);        v2 = li.inflate(R.layout.view2, null);        v3 = li.inflate(R.layout.view3, null);        aList = new
ArrayList<view>();        aList.add(v1);        aList.add(v2);        aList.add(v3);        mAdapter = new
MyPageAdapter(aList);                vPager.setAdapter(mAdapter);         }          }</view></view>


代码还是比较简单的,自己看看应该能明白的~大笑

 

 

 

4.ViewPager标题栏——PagerTitleStrip与PagerTabStrip

就是跟随着ViewPager滑动而滑动的标题咯,这两个是官方提供的,一个是普通文字,一个是带有下划线,以及可以

点击文字可切换页面,当然官方的肯定是满足不了我们的,不过还是得学习下哈,关于自定义标题等下再讲

 

先看下两个的效果:

height=584height=584

 

 

效果如图所示,

PagerTitleStrip只是一个普通的标题,会跟随Page切换进行切换,

而PagerTabStrip不仅有标题,还有下划线,另外点击标题也可以进行页面的切换,和TabHost有点相似

代码的话3个view就直接复用上面demo1的东西,然后修改一下布局文件和MainActivity就可以了:

 

①PagerTitleStrip的代码:

activity_main.xml:

 

?
123456789101112<linearlayout
android:id="@+id/LinearLayout1"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:orientation="vertical"
android:paddingbottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">         <textview android:background="#CCFF99"
android:gravity="center"
android:layout_height="35dp"
android:layout_width="match_parent"
android:text="PagerTitleStrip效果演示">                                                      </android.support.v4.view.pagertitlestrip></android.support.v4.view.viewpager> </textview></linearlayout>

MainActivity.java

 

 

?
12345678910111213141516171819202122232425262728293031323334353637383940414243444546package
com.jay.example.viewpagerdemo2; import
java.util.ArrayList; import
com.jay.example.viewpagerdemo2.MyPageAdapter;import
android.os.Bundle;import
android.app.Activity;import
android.support.v4.view.ViewPager;import
android.view.LayoutInflater;import
android.view.View; public
class MainActivity extends
Activity {         //定义相关变量        private
View v1,v2,v3;        private
ViewPager vPager;        private
ArrayList<view> aList;        private
ArrayList<string> sList;        private
MyPageAdapter mAdapter;                 @Override        protected
void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            vPager = (ViewPager) findViewById(R.id.viewpager);                                      LayoutInflater li = getLayoutInflater();            v1 = li.inflate(R.layout.view1, null);            v2 = li.inflate(R.layout.view2, null);            v3 = li.inflate(R.layout.view3, null);            aList = new
ArrayList<view>();            aList.add(v1);            aList.add(v2);            aList.add(v3);            sList = new
ArrayList<string>();            sList.add(红色);            sList.add(蓝色);            sList.add(黄色);            mAdapter = new
MyPageAdapter(aList,sList);                  vPager.setAdapter(mAdapter);                 } }</string></view></string></view>


 

②PagerTabStrip的代码:

activity_main.xml:

 

?
1234567891011<linearlayout
android:id="@+id/LinearLayout1"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:orientation="vertical"
android:paddingbottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">         <textview android:background="#C0C080"
android:gravity="center"
android:layout_height="35dp"
android:layout_width="match_parent"
android:text="PagerTabStrip效果演示">                                                   </android.support.v4.view.pagertabstrip></android.support.v4.view.viewpager> </textview></linearlayout>

MainActivity.java

 

 

?
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748package
com.jay.example.viewpagerdemo3; import
java.util.ArrayList; import
com.jay.example.viewpagerdemo2.R;import
com.jay.example.viewpagerdemo3.MyPageAdapter; import
android.os.Bundle;import
android.app.Activity;import
android.support.v4.view.ViewPager;import
android.view.LayoutInflater;import
android.view.View; public
class MainActivity extends
Activity {         //定义相关变量        private
View v1,v2,v3;        private
ViewPager vPager;        private
ArrayList<view> aList;        private
ArrayList<string> sList;        private
MyPageAdapter mAdapter;                 @Override        protected
void onCreate(Bundle savedInstanceState) {            super.onCreate(savedInstanceState);            setContentView(R.layout.activity_main);            vPager = (ViewPager) findViewById(R.id.viewpager);                                      LayoutInflater li = getLayoutInflater();            v1 = li.inflate(R.layout.view1, null);            v2 = li.inflate(R.layout.view2, null);            v3 = li.inflate(R.layout.view3, null);            aList = new
ArrayList<view>();            aList.add(v1);            aList.add(v2);            aList.add(v3);            sList = new
ArrayList<string>();            sList.add(红色);            sList.add(蓝色);            sList.add(黄色);            mAdapter = new
MyPageAdapter(aList,sList);                  vPager.setAdapter(mAdapter);                 } }</string></view></string></view>

 

 

ps:两个的实现代码都是类似的,这里就不多说了,而且这两个东西用的也不多,通常情况下都是按

实际需求自己写一个的,下面给大家演示一个Viewpager实现Tabhost效果的示例吧!

 

 

 

 

5.ViewPager实现TabHost效果:

先来看看效果图咯,正所谓没图你说个XX:

\

 

 

下面就来通过代码来实现上面的效果:

step 1:先完成我们的主界面布局,三个并列的TextView + 作为底部移动条的ImageView+ViewPager

 

activity_main.xml:

 

?
12345678910111213141516<linearlayout
android:id="@+id/LinearLayout1"
android:layout_height="match_parent"
android:layout_width="match_parent"
android:orientation="vertical"
tools:context=".MainActivity"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools">     <linearlayout android:background="#FFFFFF"
android:id="@+id/linearLayout1"
android:layout_height="60dp"
android:layout_width="fill_parent">         <textview android:gravity="center"
android:id="@+id/text1"
android:layout_height="fill_parent"
android:layout_weight="1.0"
android:layout_width="fill_parent"
android:text="红色">         <textview android:gravity="center"
android:id="@+id/text2"
android:layout_height="fill_parent"
android:layout_weight="1.0"
android:layout_width="fill_parent"
android:text="蓝色/">         <textview android:gravity="center"
android:id="@+id/text3"
android:layout_height="fill_parent"
android:layout_weight="1.0"
android:layout_width="fill_parent"
android:text="黄色">    </textview></textview></textview></linearlayout>     <imageview android:id="@+id/cursor"
android:layout_height="wrap_content"
android:layout_width="fill_parent"
android:scaletype="matrix"
android:src="@drawable/a">       </android.support.v4.view.viewpager></imageview></linearlayout>

ps:上面的一些属性可能不理解,那就先放一放,那些是关于动画的,

 

后续会专门对Android中的动画进行一个总结!

 

 

Step 2:自定义一个PageAdapter的适配器,和前面的是一样的

MyPageAdapter.java

 

?
123456789101112131415161718192021222324252627282930313233343536373839package
com.jay.example.viewpagerdemo4; import
java.util.List; import
android.support.v4.view.PagerAdapter;import
android.support.v4.view.ViewPager;import
android.view.View; public
class MyPagerAdapter extends
PagerAdapter {     public
List<view> mListViews;     public
MyPagerAdapter(List<view> mListViews) {        this.mListViews = mListViews;    }     @Override    public
void destroyItem(View arg0, int
arg1, Object arg2) {        ((ViewPager) arg0).removeView(mListViews.get(arg1));    }     @Override    public
int getCount() {        return
mListViews.size();    }     @Override    public
Object instantiateItem(View arg0, int
arg1) {        ((ViewPager) arg0).addView(mListViews.get(arg1), 0);        return
mListViews.get(arg1);    }     @Override    public
boolean isViewFromObject(View arg0, Object arg1) {        return
arg0 == (arg1);    } }</view></view>

step 3.创建三个填充到ViewPager中的view,这里直接用前面的就可以了

 

step 4:主Activity的编写,要完成的事有:

1)相关组件的初始化

2)定义TextView点击事件的方法,Pager.setCurrentItem(index);设置当前显示的页面

3)定义一个初始化移动条位置的方法,移动条的起始位置offset = (屏幕宽度/3 - 移动条宽度)/2;

然后通过Matrix的相关方法设置ImageView的位置

4)定义ViewPager页面切换事件,先计算出移动一页与两页的偏移量:

一页 = offset * 2 + 图片宽度

两页 = 一页 * 2

然后根据哪页跳哪页,通过TranslateAnimation设置跳转动画即可

代码如下:

MainActivity.java

 

?
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141package
com.jay.example.viewpagerdemo4; import
java.util.ArrayList;import
java.util.List;import
android.os.Bundle;import
android.support.v4.view.ViewPager;import
android.support.v4.view.ViewPager.OnPageChangeListener;import
android.util.DisplayMetrics;import
android.view.LayoutInflater;import
android.view.View;import
android.view.View.OnClickListener;import
android.view.animation.Animation;import
android.view.animation.TranslateAnimation;import
android.widget.ImageView;import
android.widget.TextView;import
android.app.Activity;import
android.graphics.BitmapFactory;import
android.graphics.Matrix;  public
class MainActivity extends
Activity {     private
ViewPager mPager;    private
List<view> listViews;     private
ImageView cursor;    private
TextView t1, t2, t3;    private
int offset = 0;//移动条图片的偏移量    private
int currIndex = 0;//当前页面的编号    private
int bmpWidth;// 移动条图片的长度              @Override    protected
void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initCursorPos();        initView();        }         //完成View组件的初始化,并将三个view动态地添加到Adapter对象中    //然后调用setAdapter将view集合与ViewPager绑定,设置进去的页面    //指向第一个页面setCurrentItem(0),最后设置onclick和onPageChange监听器    public
void initView()    {        mPager = (ViewPager) findViewById(R.id.vPager);        t1 = (TextView) findViewById(R.id.text1);        t2 = (TextView) findViewById(R.id.text2);        t3 = (TextView) findViewById(R.id.text3);                    listViews = new
ArrayList<view>();        LayoutInflater mInflater = getLayoutInflater();        listViews.add(mInflater.inflate(R.layout.view1,null));        listViews.add(mInflater.inflate(R.layout.view2,null));        listViews.add(mInflater.inflate(R.layout.view3,null));        mPager.setAdapter(new
MyPagerAdapter(listViews));        mPager.setCurrentItem(0);                          t1.setOnClickListener(new
MyClickListener(0));        t2.setOnClickListener(new
MyClickListener(1));        t3.setOnClickListener(new
MyClickListener(2));        mPager.setOnPageChangeListener(new
MyOnPageChangeListener());    }         //初始化指示器的位置,就是下面那个移动条一开始放的地方    public
void initCursorPos() {         cursor = (ImageView) findViewById(R.id.cursor);        bmpWidth = BitmapFactory.decodeResource(getResources(), R.drawable.a)                .getWidth();// 获取图片宽度        DisplayMetrics dm = new
DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(dm);        int
screenW = dm.widthPixels;// 获取分辨率宽度        offset = (screenW / 3
- bmpWidth) / 2;// 计算偏移量        Matrix matrix = new
Matrix();        matrix.postTranslate(offset,0);        cursor.setImageMatrix(matrix);// 设置动画初始位置    }          //设置点击事件,点击上面文字切换页面的    public
class MyClickListener implements
OnClickListener    {        private
int index = 0;        public
MyClickListener(int
i)        {            index = i;        }                 @Override        public
void onClick(View arg0) {            mPager.setCurrentItem(index);                  }             }              //监听页面切换时间,主要做的是动画处理,就是移动条的移动    public
class MyOnPageChangeListener implements
OnPageChangeListener {        int
one = offset * 2
+ bmpWidth;// 移动一页的偏移量,比如1->2,或者2->3        int
two = one * 2;// 移动两页的偏移量,比如1直接跳3         @Override        public
void onPageSelected(int
index) {            Animation animation = null;            switch
(index) {            case
0:                if
(currIndex == 1) {                    animation = new
TranslateAnimation(one, 0,0,0);                }else
if (currIndex == 2) {                    animation = new
TranslateAnimation(two, 0,0,0);                }                break;            case
1:                if
(currIndex == 0) {                    animation = new
TranslateAnimation(offset, one, 0,0);                }else
if (currIndex == 2) {                    animation = new
TranslateAnimation(two, one, 0,0);                }                break;            case
2:                if
(currIndex == 0) {                    animation = new
TranslateAnimation(offset, two, 0,0);                }else
if (currIndex == 1) {                    animation = new
TranslateAnimation(one, two, 0,0);                }                break;            }            currIndex = index;            animation.setFillAfter(true);// true表示图片停在动画结束位置            animation.setDuration(300);//设置动画时间为300毫秒            cursor.startAnimation(animation);//开始动画        }         @Override        public
void onPageScrollStateChanged(int
arg0) {}         @Override        public
void onPageScrolled(int
arg0, float
arg1, int
arg2) {}         }}</view></view>

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