如何通过单击Android当前选项卡中的按钮来转到其他选项卡？

Question

我尝试在Android中编写代码,通过单击按钮从一个选项卡切换到另一个选项卡.

我知道通过单击选项卡我们可以从一个选项卡切换到另一个选项卡但是可以通过单击一个按钮从一个选项卡切换到另一个选项卡.

我尝试了以下教程.

http://www.androidhive.info/2013/10/android-tab-layout-with-swipeable-views-1/

在本教程中,我以下列方式编辑了MovieFragment.java文件.

MovieFragment.java

package info.androidhive.tabsswipe;

import info.androidhive.tabsswipe.R;
import android.annotation.SuppressLint;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager; 
import android.support.v4.view.ViewPager; 
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;

public class MoviesFragment extends Fragment {

ViewPager viewPager;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle    savedInstanceState) 
{

   View rootView = inflater.inflate(R.layout.fragment_movies, container, false);

   Button btn = (Button) rootView.findViewById(R.id.btn);

   btn.setOnClickListener(new View.OnClickListener() 
   {

       @Override
      public void onClick(View v) 
      {

          viewPager.setCurrentItem(0);

      }
  }); 


 return rootView;
}}

XML代码:

<?xml version="1.0" encoding="utf-8"?>
  <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical" 
     android:background="#17df0d">

<android.support.v4.view.ViewPager
    android:id="@+id/myfivepanelpager"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />


<TextView android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="Design Movies Screen"
    android:textSize="20dp"
    android:layout_centerInParent="true"/>

<Button 
    android:id="@+id/btn"
    android:layout_width="100dp"
    android:layout_height="80dp"
    android:text="Click"
    />


</RelativeLayout>

我已经在xml布局中创建了一个按钮并尝试切换到选项卡-1但我得到了空指针异常.

错误代码:

05-20 09:07:10.995: E/AndroidRuntime(1117): FATAL EXCEPTION: main
05-20 09:07:10.995: E/AndroidRuntime(1117): java.lang.NullPointerException
05-20 09:07:10.995: E/AndroidRuntime(1117):     at info.androidhive.tabsswipe.MoviesFragment$1.onClick(MoviesFragment.java:33)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at android.view.View.performClick(View.java:4240)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at  android.view.View$PerformClick.run(View.java:17721)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at android.os.Handler.handleCallback(Handler.java:730)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at android.os.Handler.dispatchMessage(Handler.java:92)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at android.os.Looper.loop(Looper.java:137)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at android.app.ActivityThread.main(ActivityThread.java:5103) 
05-20 09:07:10.995: E/AndroidRuntime(1117):     at java.lang.reflect.Method.invokeNative(Native Method)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at java.lang.reflect.Method.invoke(Method.java:525) 
05-20 09:07:10.995: E/AndroidRuntime(1117):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-20 09:07:10.995: E/AndroidRuntime(1117):     at dalvik.system.NativeStart.main(Native Method)

请建议我一些解决方案或一些好的技术来做到这一点.

Answer 1

您必须在片段内调用父视图.

public class MoviesFragment extends Fragment {

     ViewPager viewPager;
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_movies, container, false);

        Button btn = (Button) rootView.findViewById(R.id.btn);
        viewPager = (ViewPager) getActivity().findViewById(R.id.pager);

           btn.setOnClickListener(new View.OnClickListener() 
           {

               @Override
              public void onClick(View v) 
              {
                   viewPager.setCurrentItem(0);


              }
          }); 

        return rootView;
    }

}