Android ViewPager: slide the page, androidviewpager

Android ViewPager: slide the page, androidviewpager

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The adapter PagerAAdapter is required for ViewPager. The following four functions need to be rewritten:

InstantiateItem (ViewGroup container, int position): Creates a page view at a specified position. The adapter adds the View to the container specified here.
DestroyItem (ViewGroup container, int position, Object object): removes a page at a given position.
GetCount (): returns the number of valid views.
IsViewFromObject (View view, Object object): determines whether the Key returned by the instantiateItem (ViewGroup, int) function is the same View as that of a page view.

 

You only need to add the layout of the main interface

<Android. support. v4.view. ViewPager/>

You can:

Activity_main.xml:

 1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 2                 xmlns:tools="http://schemas.android.com/tools" 3                 android:layout_width="match_parent" 4                 android:layout_height="match_parent" 5                 tools:context=".MainActivity"> 6  7     <android.support.v4.view.ViewPager 8         android:id="@+id/viewpager" 9         android:layout_width="wrap_content"10         android:layout_height="wrap_content"11         android:layout_gravity="center"/>12 13 </RelativeLayout>

 

It is determined that ViewPager has three pages, and each page must have a layout:

Take the first first_page.xml as an example:

1 <? Xml version = "1.0" encoding = "UTF-8"?> 2 <RelativeLayout xmlns: android = "http://schemas.android.com/apk/res/android" 3 android: layout_width = "match_parent" 4 android: layout_height = "match_parent"> 5 <TextView 6 android: layout_width = "match_parent" 7 android: layout_height = "match_parent" 8 android: gravity = "center" 9 android: text = "This is the first page" 10 android: textSize = "20sp"/> 11 12 </RelativeLayout>

 

MainActivity needs to initialize it in onCreate and call the adapter:

1 package com. example. hopecaploud. myapplication; 2 3 import android. app. activity; 4 import android. OS. bundle; 5 import android. support. v4.view. viewPager; 6 import android. view. layoutInflater; 7 import android. view. view; 8 9 import java. util. arrayList; 10 import java. util. list; 11 12 13 public class MainActivity extends Activity {14 private View first, second, third; 15 private ViewPager viewPager; // corresponds to <android. support. v4.view. viewPager/> Control 16 private List <View> viewList; // View array 17 18 @ Override19 protected void onCreate (Bundle savedInstanceState) {20 super. onCreate (savedInstanceState); 21 setContentView (R. layout. activity_main); 22 23/* initialize */24 viewPager = (ViewPager) findViewById (R. id. viewpager); 25 LayoutInflater inflater = getLayoutInflater (); 26 first = inflater. inflate (R. layout. first_page, null); 27 second = inflater. inflate (R. layout. second_page, null); 28 third = inflater. inflate (R. layout. third_page, null); 29 30 viewList = new ArrayList <View> (); // Mount 31 viewList in the array to be displayed by page. add (first); 32 viewList. add (second); 33 viewList. add (third); 34 35/* adapter part */36 NewPagerAdapter pagerAdapter = new NewPagerAdapter (viewList); 37 viewPager. setAdapter (pagerAdapter); 38} 39 40}

 

The last and most important, inherited from PagerAdapter adapter:

NewPagerAdapter. java:

1 package com. example. hopecaploud. myapplication; 2 3 import android. support. v4.view. pagerAdapter; 4 import android. view. view; 5 import android. view. viewGroup; 6 7 import java. util. list; 8 9/** 10 * Created by LT on 2015/7/27. 11 */12 public class NewPagerAdapter extends PagerAdapter {13 public List <View> viewList; 14 15 public NewPagerAdapter (List <View> viewList) {16 this. viewList = viewList; 17} 18 19/* the following four functions must be overwritten */20 @ Override21 public boolean isViewFromObject (View arg0, Object arg1) {22 // judge whether the Key returned by the instantiateItem (ViewGroup, int) function is the same view as that returned by a page view (judge the key) 23 // TODO Auto-generated method stub24 return arg0 = arg1; 25} 26 27 @ Override28 public int getCount () {// return the number of views to slide 29 // TODO Auto-generated method stub30 return viewList. size (); 31} 32 33 @ Override34 public void destroyItem (ViewGroup container, int position, 35 Object object) {// Delete the View at the specified position from the current container; 36 // TODO Auto-generated method stub37 container. removeView (viewList. get (position); 38} 39 40 @ Override41 public Object instantiateItem (ViewGroup container, int position) {42 // instantiate: add the current view to the container, and return the current View (transfer key) 43 // TODO Auto-generated method stub44 container. addView (viewList. get (position); 45 46 return viewList. get (position); 47} 48}

 

Then, a simple ViewPager is completed.