Android ViewPager与碎片获取错误

Question

我正试图用两个片段创建一个简单的ViewPager。我正在使用两个片段并将它们添加到viewPager中，以测试简单的viewPager。但我错了。请帮我

主要类别为：

public class MainActivity extends FragmentActivity {
private MyPagerAdapter adapter;
ViewPager viewpager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
adapter=new MyPagerAdapter(getSupportFragmentManager());
viewpager=(ViewPager)findViewById(R.id.pager);
viewpager.setAdapter(adapter);
}
public class MyPagerAdapter extends FragmentPagerAdapter
{
public MyPagerAdapter(android.support.v4.app.FragmentManager fm) {
super(fm);
// TODO Auto-generated constructor stub
}
@Override
public int getCount() {
// TODO Auto-generated method stub
//return fragments.size();
return 2;
}
@Override
public boolean isViewFromObject(View arg0, Object arg1) {
// TODO Auto-generated method stub
return false;
}
@Override
public Fragment getItem(int position) {
// TODO Auto-generated method stub
//return fragments.get(position);
switch (position) {
case 0:
//return new AboutUs();
return new Programs();
case 1:
return new fragment2Activity();
}
return null;
}   
}

}

第一个片段是：

public class fragment2Activity extends Fragment {
@Override
public void onPause() {
// TODO Auto-generated method stub
super.onPause();
onDestroyView();
}
private String mContent = "???";
private static final String KEY_CONTENT = "TestFragment:Content";

@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
if ((savedInstanceState != null)
&& savedInstanceState.containsKey(KEY_CONTENT)) {
mContent = savedInstanceState.getString(KEY_CONTENT);
}
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString(KEY_CONTENT, mContent);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
return inflater.inflate(R.layout.fragment2_layout, container, true);
}

}

SecondFragment是：

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Programs extends Fragment 
{
@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
}
private String mContent = "???";
private static final String KEY_CONTENT = "TestFragment:Content";
@Override
public void onPause() {
// TODO Auto-generated method stub
super.onPause();
onDestroyView();
}
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
if ((savedInstanceState != null)
&& savedInstanceState.containsKey(KEY_CONTENT)) {
mContent = savedInstanceState.getString(KEY_CONTENT);
}
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString(KEY_CONTENT, mContent);
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View inf = inflater.inflate(R.layout.fragment1_layout, container, false);
return inf;
}

}

我得到以下信息错误：

02-27 10:54:05.157: E/AndroidRuntime(21364): FATAL EXCEPTION: main
02-27 10:54:05.157: E/AndroidRuntime(21364): java.lang.IllegalStateException: The specified child     already has a parent. You must call removeView() on the child's parent first.
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewGroup.addViewInner(ViewGroup.java:3345)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewGroup.addView(ViewGroup.java:3216)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewGroup.addView(ViewGroup.java:3173)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewGroup.addView(ViewGroup.java:3153)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.NoSaveStateFrameLayout.wrap(NoSaveStateFrameLayout.java:40)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:931)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.View.measure(View.java:13011)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.View.measure(View.java:13011)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.View.measure(View.java:13011)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2162)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.View.measure(View.java:13011)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1091)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2505)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.os.Looper.loop(Looper.java:154)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at android.app.ActivityThread.main(ActivityThread.java:4945)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at java.lang.reflect.Method.invokeNative(Native Method)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at java.lang.reflect.Method.invoke(Method.java:511)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
02-27 10:54:05.157: E/AndroidRuntime(21364):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

试试这个，把它添加到MainActivity中

Vector<Fragment> fragments = new Vector<Fragment>();
fragments.add(Fragment.instantiate(this, Programs.class.getName()));
fragments.add(Fragment.instantiate(this, fragment2Activity.class.getName()));
adapter=new MyPagerAdapter(getSupportFragmentManager(),fragments);

并在MyPagerAdapter中进行更改

private List<Fragment> fragments;
public MyPagerAdapter(FragmentManager fm, List<Fragment> fragments) {
super(fm);
this.fragments = fragments;
}

@Override
public Fragment getItem(int position)
{
return this.fragments.get(position);
}

并去除CCD_ 3。

Answer 2

两件事：

1. 在您的适配器中，改为执行以下操作：

   @Override
   public boolean isViewFromObject(View arg0, Object arg1) {
   return **arg0==arg1**;
   }
   

2. 在您的onCreateView中，改为执行以下操作：

   return inflater.inflate(R.layout.fragment2_layout, container, **false**);
   

3. 如果仍然不起作用，请尝试在适配器中重写destroyItem()：

   @Override
   public void destroyItem(ViewGroup container, int position, Object object) {
   ((ViewPager) container).removeView((View) object);
   }
   

Answer 3

请参阅下面的链接，在这里您可以获得具有正确布局的简单示例。如何实现具有不同片段/布局的ViewPager