ViewPager是android擴展包v4包中的類，這個類可以讓用戶左右切換當前的view。我們首先來看看API對於這個類的表述：
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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 andFragmentStatePagerAdapter; each of these classes have simple code showing how to build a full user interface with them. |
從這個描述中我們知道幾點：
1）ViewPager類直接繼承了ViewGroup類，所有它是一個容器類，可以在其中添加其他的view類。
2）ViewPager類需要一個PagerAdapter適配器類給它提供數據。
3）ViewPager經常和Fragment一起使用，並且提供了專門的FragmentPagerAdapter和FragmentStatePagerAdapter類供Fragment中的ViewPager使用。
在編寫ViewPager的應用的使用，還需要使用兩個組件類分別是PagerTitleStrip類和PagerTabStrip類，PagerTitleStrip類直接繼承自ViewGroup類，而PagerTabStrip類繼承PagerTitleStrip類，所以這兩個類也是容器類。但是有一點需要注意，在定義XML的layout的時候，這兩個類必須是ViewPager標籤的子標籤，不然會出錯。
layout.xml:
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity" > <android.support.v4.view.ViewPager android:id="@+id/viewpager" android:layout_width="wrap_content" android:layout_height="wrap_content" > <android.support.v4.view.PagerTabStrip android:id="@+id/tabstrip" android:layout_width="wrap_content" android:layout_height="50dip" android:gravity="center" /> </android.support.v4.view.ViewPager></RelativeLayout> |
MainActivity.java
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package com.example.android_viewpager1;import java.util.ArrayList;import android.annotation.SuppressLint;import android.app.Activity;import android.os.Bundle;import android.support.v4.view.PagerAdapter;import android.support.v4.view.PagerTabStrip;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.OnPageChangeListener;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;public class MainActivity extends Activity { ViewPager pager = null; PagerTabStrip tabStrip = null; ArrayList<View> viewContainter = new ArrayList<View>(); ArrayList<String> titleContainer = new ArrayList<String>(); public String TAG = "tag"; @SuppressLint("ResourceAsColor") @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); pager = (ViewPager) this.findViewById(R.id.viewpager); tabStrip = (PagerTabStrip) this.findViewById(R.id.tabstrip); //取消tab下面的長橫線 tabStrip.setDrawFullUnderline(false); //設置tab的背景色 tabStrip.setBackgroundColor(this.getResources().getColor(R.color.bg)); //設置當前tab頁籤的下劃線顏色 tabStrip.setTabIndicatorColor(this.getResources().getColor(R.color.red)); tabStrip.setTextSpacing(200); View view1 = LayoutInflater.from(this).inflate(R.layout.tab1, null); View view2 = LayoutInflater.from(this).inflate(R.layout.tab2, null); View view3 = LayoutInflater.from(this).inflate(R.layout.tab3, null); View view4 = LayoutInflater.from(this).inflate(R.layout.tab4, null); //viewpager開始添加view viewContainter.add(view1); viewContainter.add(view2); viewContainter.add(view3); viewContainter.add(view4); //頁籤項 titleContainer.add("網易新聞"); titleContainer.add("網易體育"); titleContainer.add("網易財經"); titleContainer.add("網易女人"); pager.setAdapter(new PagerAdapter() { //viewpager中的組件數量 @Override public int getCount() { return viewContainter.size(); } //滑動切換的時候銷燬當前的組件 @Override public void destroyItem(ViewGroup container, int position, Object object) { ((ViewPager) container).removeView(viewContainter.get(position)); } //每次滑動的時候生成的組件 @Override public Object instantiateItem(ViewGroup container, int position) { ((ViewPager) container).addView(viewContainter.get(position)); return viewContainter.get(position); } @Override public boolean isViewFromObject(View arg0, Object arg1) { return arg0 == arg1; } @Override public int getItemPosition(Object object) { return super.getItemPosition(object); } @Override public CharSequence getPageTitle(int position) { return titleContainer.get(position); } }); pager.setOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageScrollStateChanged(int arg0) { Log.d(TAG, "--------changed:" + arg0); } @Override public void onPageScrolled(int arg0, float arg1, int arg2) { Log.d(TAG, "-------scrolled arg0:" + arg0); Log.d(TAG, "-------scrolled arg1:" + arg1); Log.d(TAG, "-------scrolled arg2:" + arg2); } @Override public void onPageSelected(int arg0) { Log.d(TAG, "------selected:" + arg0); } }); }} |
實現的效果如下：
對於PagerAdapter類，android的文檔已經說的很清楚了，必須至少實現如下的4個方法，如果需要更好的擴展也可以實現更多的方法。
public Object instantiateItem(ViewGroup container, int position)
public void destroyItem(ViewGroup container, int position,Object object)
public int getCount()
public boolean isViewFromObject(View arg0, Object arg1)
