下一篇:《Android ViewPager再探:增加滑動指示條》
ViewPager需要用到適配器PagerAAdapter,以下四個函數需要重寫:
instantiateItem(ViewGroup container, int position):創建指定位置的頁面視圖。適配器增加即將創建的View視圖到這里給定的container中。
destroyItem(ViewGroup container, int position, Object object):移除一個給定位置的頁面。
getCount():返回當前有效視圖的個數。
isViewFromObject(View view, Object object):判斷instantiateItem(ViewGroup, int)函數所返回來的Key與一個頁面視圖是否是代表的同一個視圖。
主界面的布局只要加上
<android.support.v4.view.ViewPager />
即可:
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>
決定ViewPager有3個頁面,每個頁面都要寫布局:
以第一個first_page.xml為例:
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="這是第一頁" 10 android:textSize="20sp"/> 11 12 </RelativeLayout>
MainActivity需要在onCreate里對其初始化,並調用適配器:
1 package com.example.hopecapital.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;//對應 <android.support.v4.view.ViewPager/>控件 16 private List<View> viewList;//View數組 17 18 @Override 19 protected void onCreate(Bundle savedInstanceState) { 20 super.onCreate(savedInstanceState); 21 setContentView(R.layout.activity_main); 22 23 /*初始化*/ 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>();// 將要分頁顯示的View裝入數組中 31 viewList.add(first); 32 viewList.add(second); 33 viewList.add(third); 34 35 /*適配器部分*/ 36 NewPagerAdapter pagerAdapter = new NewPagerAdapter(viewList); 37 viewPager.setAdapter(pagerAdapter); 38 } 39 40 }
最后也是最重要的,繼承自PagerAdapter的適配器:
NewPagerAdapter.java:
1 package com.example.hopecapital.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 /*下面四個函數是一定要重寫的*/ 20 @Override 21 public boolean isViewFromObject(View arg0,Object arg1){ 22 //判斷instantiateItem(ViewGroup, int)函數所返回來的Key與一個頁面視圖是否是代表的同一個視圖(判斷key) 23 // TODO Auto-generated method stub 24 return arg0 == arg1; 25 } 26 27 @Override 28 public int getCount() {//返回要滑動的VIew的個數 29 // TODO Auto-generated method stub 30 return viewList.size(); 31 } 32 33 @Override 34 public void destroyItem(ViewGroup container, int position, 35 Object object) {//從當前container中刪除指定位置(position)的View; 36 // TODO Auto-generated method stub 37 container.removeView(viewList.get(position)); 38 } 39 40 @Override 41 public Object instantiateItem(ViewGroup container, int position) { 42 //實例化:將當前視圖添加到container中,並返回當前View(傳送key) 43 // TODO Auto-generated method stub 44 container.addView(viewList.get(position)); 45 46 return viewList.get(position); 47 } 48 }
以上,便完成了簡單的ViewPager。