在ViewPager中正确替换碎片

Question

我试图替换视图中的碎片，但尚未成功。

我有以下类。首先我PagerAdapter：

package com.example.tab1; 

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
public class SectionsPagerAdapter extends FragmentPagerAdapter { 

static final int NUM_ITEMS = 3; 
private final FragmentManager mFragmentManager; 
private Fragment mFragmentAtPos0; 

public SectionsPagerAdapter(FragmentManager fm) { 
    super(fm); 
    mFragmentManager = fm; 
} 

@Override 
public Fragment getItem(int position) { 

    Bundle args = new Bundle(); 


    mFragmentAtPos0= new testFragment(); 
    args.putInt(testFragment.ARG_SECTION_NUMBER, position + 1); 
    mFragmentAtPos0.setArguments(args); 

    return mFragmentAtPos0; 
} 

@Override 
public int getItemPosition(Object object) { 


    return 0; 

} 

@Override 
// liefert die Anzahl der Tabs 
public int getCount() { 
    return NUM_ITEMS; 
} 

@Override 

public CharSequence getPageTitle(int position) { 
    switch (position) { 
    case 0: 

     // return getString(R.string.title_section1).toUpperCase(); 
     // return 
     // Resources.getSystem().getString(R.string.title_section1).toUpperCase(); 

     return "Suche".toUpperCase(); 
    case 1: 
     // return getString(R.string.title_section2).toUpperCase(); 
     // return 
     // Resources.getSystem().getString(R.string.title_section2).toUpperCase(); 
     return "Ergebnis".toUpperCase(); 
    case 2: 

     // return 
     // Resources.getSystem().getString(R.string.title_section3).toUpperCase(); 
     return "Optionen".toUpperCase(); 
    } 
    return null; 
} 

} 

其次我我DatePickerFragment：

package com.example.tab1; 

import android.os.Bundle; 
import android.support.v4.app.DialogFragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 

public class DatePickerFragment extends DialogFragment { 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
    } 

     public static DatePickerFragment newInstance() { 
      DatePickerFragment f = new DatePickerFragment(); 
      return f; 
     } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     //Log.d("DEBUG", "onCreateView"); 
     return inflater.inflate(R.layout.datepickerfrag, container, false); 

    } 

} 

，最后我的MainActivity，在那里我激活的方法onClickSearch，这是我的第一个片段的接口方法的变化，这是应用程序启动时显示的。

package com.example.tab1; 

import android.app.ActionBar; 
import android.app.FragmentTransaction; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentActivity; 
import android.support.v4.view.ViewPager; 
import android.view.Menu; 

public class MainActivity extends FragmentActivity implements 
     ActionBar.TabListener,testFragment.ButtonListenerS{ 

    /** 
    * The {@link android.support.v4.view.PagerAdapter} that will provide 
    * fragments for each of the sections. We use a 
    * {@link android.support.v4.app.FragmentPagerAdapter} derivative, which 
    * will keep every loaded fragment in memory. If this becomes too memory 
    * intensive, it may be best to switch to a 
    * {@link android.support.v4.app.FragmentStatePagerAdapter}. 
    */ 
    SectionsPagerAdapter mSectionsPagerAdapter; 

    /** 
    * The {@link ViewPager} that will host the section contents. 
    */ 
    ViewPager mViewPager; 




    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     // Create the adapter that will return a fragment for each of the three 
     // primary sections 
     // of the app. 
     mSectionsPagerAdapter = new SectionsPagerAdapter(
       getSupportFragmentManager()); 

     // Set up the action bar. 
     final ActionBar actionBar = getActionBar(); 
     actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); 


     // Set up the ViewPager with the sections adapter. 
     mViewPager = (ViewPager) findViewById(R.id.pager); 
     mViewPager.setAdapter(mSectionsPagerAdapter); 

     // When swiping between different sections, select the corresponding 
     // tab. 
     // We can also use ActionBar.Tab#select() to do this if we have a 
     // reference to the 
     // Tab. 
     mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() { 
        @Override 
        public void onPageSelected(int position) { 
         actionBar.setSelectedNavigationItem(position); 
        } 
       }); 

     // For each of the sections in the app, add a tab to the action bar. 
     for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) { 
      // Create a tab with text corresponding to the page title defined by 
      // the adapter. 
      // Also specify this Activity object, which implements the 
      // TabListener interface, as the 
      // listener for when this tab is selected. 
      actionBar.addTab(actionBar.newTab() 
        .setText(mSectionsPagerAdapter.getPageTitle(i)) 
        .setTabListener(this)); 
     } 

     actionBar.selectTab(actionBar.getTabAt(0)); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.activity_main, menu); 
     return true; 
    } 


    /* 
    * Implementierung des "Suchbuttons" (non-Javadoc) 
    * Interaktion zwischen testFragment und MainActivity 
    */ 
    public void OnclickSearchS() { 



      android.support.v4.app.FragmentTransaction ft = getSupportFragmentManager().beginTransaction(); 
      ft.replace(R.id.pager,DatePickerFragment.newInstance()); 
      ft.commit(); 
     //mViewPager.setCurrentItem(1); 
    } 



    public void onTabUnselected(ActionBar.Tab tab, 
      FragmentTransaction fragmentTransaction) { 
    } 

    public void onTabSelected(ActionBar.Tab tab, 
      FragmentTransaction fragmentTransaction) { 
     // When the given tab is selected, switch to the corresponding page in 
     // the ViewPager. 
     mViewPager.setCurrentItem(tab.getPosition()); 
    } 

    public void onTabReselected(ActionBar.Tab tab, 
      FragmentTransaction fragmentTransaction) { 
    } 

    /** 
    * A {@link FragmentPagerAdapter} that returns a fragment corresponding to 
    * one of the primary sections of the app. 
    */ 

} 

当应用程序运行时，我按下按钮在第一时间并没有任何反应，当我做到这一点再其次，我看到一个空的片段，之后得到一个错误：

07-30 21:20:17.800: W/dalvikvm(32553): threadid=1: thread exiting with uncaught exception (group=0x40c671f8) 
07-30 21:20:17.805: E/AndroidRuntime(32553): FATAL EXCEPTION: main 
07-30 21:20:17.805: E/AndroidRuntime(32553): java.lang.NullPointerException 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.support.v4.app.Fragment.setUserVisibleHint(Fragment.java:750) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.support.v4.app.FragmentPagerAdapter.setPrimaryItem(FragmentPagerAdapter.java:130) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.support.v4.view.ViewPager.populate(ViewPager.java:893) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.support.v4.view.ViewPager.populate(ViewPager.java:772) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1539) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:1663) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1631) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1963) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1690) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1963) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1690) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:1963) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1690) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2063) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1399) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.app.Activity.dispatchTouchEvent(Activity.java:2364) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2011) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.View.dispatchPointerEvent(View.java:5861) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3094) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2614) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewRootImpl.processInputEvents(ViewRootImpl.java:978) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:992) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2585) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.os.Handler.dispatchMessage(Handler.java:99) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.os.Looper.loop(Looper.java:137) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at android.app.ActivityThread.main(ActivityThread.java:4507) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at java.lang.reflect.Method.invokeNative(Native Method) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at java.lang.reflect.Method.invoke(Method.java:511) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 
07-30 21:20:17.805: E/AndroidRuntime(32553): at dalvik.system.NativeStart.main(Native Method) 

我不知道怎么回事。

Answer 1

我错过了这个例外getItemId（int position）方法重新实现，它返回默认和替换片段的不同（唯一）ID。请参阅https://stackoverflow.com/a/11974777/685292以获得进一步说明和示例实施。