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网站建设接外包流程,app怎么推广运营,网站维护中 html,集团网站设计建设参考 8、在初始化ViewPager时，应先给Adapter初始化内容后再将该adapter传给ViewPager，如果不这样处理，在更新adapter的内容后，应该调用一下adapter的notifyDataSetChanged方法，否则在ADT22以上使用会报The applicatio…

参考

8、在初始化ViewPager时，应先给Adapter初始化内容后再将该adapter传给ViewPager，如果不这样处理，在更新adapter的内容后，应该调用一下adapter的notifyDataSetChanged方法，否则在ADT22以上使用会报The application's PagerAdapter changed the adapter's contents without calling PagerAdapter#notifyDataSetChanged的异常，具体原因可参考：http://stackoverflow.com/questions/16756131/fragmentstatepageradapter-stopped-working-after-updating-to-adt-22

问题

使用viewpager及fragment的代码如下：
test_tab1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"><LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:id="@+id/main_tabs" android:orientation="vertical"><android.support.v4.view.ViewPager android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/viewpager"></android.support.v4.view.ViewPager></LinearLayout><LinearLayout android:layout_width="fill_parent" android:layout_height="wrap_content" android:orientation="horizontal"><Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btn_tab_1" android:text="tab 1"/><Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btn_tab_2" android:text="tab 2"/><Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btn_tab_3" android:text="tab 3"/><Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/btn_tab_4" android:text="tab 4"/></LinearLayout></LinearLayout>

四个fragment的layout如下：
fragment_1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent">
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="这是标签1"/>
</LinearLayout>

fragment_2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent">
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="这是标签2"/>
</LinearLayout>

fragment_3.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent">
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="这是标签3"/>
</LinearLayout>

fragment_4.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent">
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="这是标签4"/>
</LinearLayout>

四个fragment类：
fragment_1.java

package com.app.activities;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;public class fragment_1 extends Fragment
{@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){return  inflater.inflate(R.layout.fragment_1, container, false);}}

fragment_2.java

package com.app.activities;import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;public class fragment_2 extends Fragment
{@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){return  inflater.inflate(R.layout.fragment_2, container, false);}}

fragment_3.java

package com.app.activities;import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;public class fragment_3 extends Fragment
{@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){return  inflater.inflate(R.layout.fragment_3, container, false);}}

fragment_4.java

package com.app.activities;import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;public class fragment_4 extends Fragment
{@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){return  inflater.inflate(R.layout.fragment_4, container, false);}}

运行结果如下：
这里写图片描述

解释

出现这个问题的最基本原因是因为初始化adapter的时候，已经将fragments的数量定死了，在后面将fragment添加上去的话，需要通知adapter数据变更了；
第二种解决方案是先将fragments都添加完毕再初始化adapter，即两种方案为：
方案1：

package com.app.activities;import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.Button;import java.util.ArrayList;/*** Created by Administrator on 2015/8/28.*/
public class test_tab1 extends ActionBarActivity {private ViewPager viewPager;private Button btn_tab1;private Button btn_tab2;private Button btn_tab3;private Button btn_tab4;private FragmentPagerAdapter pagerAdapter;private ArrayList<Fragment> fragments=new ArrayList<Fragment>();private void initUI(){viewPager=(ViewPager)findViewById(R.id.viewpager);btn_tab1=(Button)findViewById(R.id.btn_tab_1);btn_tab2=(Button)findViewById(R.id.btn_tab_2);btn_tab3=(Button)findViewById(R.id.btn_tab_3);btn_tab4=(Button)findViewById(R.id.btn_tab_4);pagerAdapter=new FragmentPagerAdapter(getSupportFragmentManager()) {@Overridepublic Fragment getItem(int position) {return fragments.get(position);}@Overridepublic int getCount() {return fragments.size();}};viewPager.setAdapter(pagerAdapter);viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {Log.e("TAG-",""+position);}@Overridepublic void onPageSelected(int position) {}@Overridepublic void onPageScrollStateChanged(int state) {}});fragment_1 tab1=new fragment_1();fragment_2 tab2=new fragment_2();fragment_3 tab3=new fragment_3();fragment_4 tab4=new fragment_4();fragments.add(tab1);fragments.add(tab2);fragments.add(tab3);fragments.add(tab4);pagerAdapter.notifyDataSetChanged();}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.test_tab1);initUI();}
}

方案2：

package com.app.activities;import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import android.widget.Button;import java.util.ArrayList;/*** Created by Administrator on 2015/8/28.*/
public class test_tab1 extends ActionBarActivity {private ViewPager viewPager;private Button btn_tab1;private Button btn_tab2;private Button btn_tab3;private Button btn_tab4;private FragmentPagerAdapter pagerAdapter;private ArrayList<Fragment> fragments=new ArrayList<Fragment>();private void initUI(){viewPager=(ViewPager)findViewById(R.id.viewpager);btn_tab1=(Button)findViewById(R.id.btn_tab_1);btn_tab2=(Button)findViewById(R.id.btn_tab_2);btn_tab3=(Button)findViewById(R.id.btn_tab_3);btn_tab4=(Button)findViewById(R.id.btn_tab_4);fragment_1 tab1=new fragment_1();fragment_2 tab2=new fragment_2();fragment_3 tab3=new fragment_3();fragment_4 tab4=new fragment_4();fragments.add(tab1);fragments.add(tab2);fragments.add(tab3);fragments.add(tab4);        pagerAdapter=new FragmentPagerAdapter(getSupportFragmentManager()) {@Overridepublic Fragment getItem(int position) {return fragments.get(position);}@Overridepublic int getCount() {return fragments.size();}};viewPager.setAdapter(pagerAdapter);viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {@Overridepublic void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {Log.e("TAG-",""+position);}@Overridepublic void onPageSelected(int position) {}@Overridepublic void onPageScrollStateChanged(int state) {}});}@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.test_tab1);initUI();}
}