Question

更新： Logcat has been added to the question 我实际上想要在button Click上更改视图（从一个片段到另一个片段。）我尝试了很多东西，但我无法做到。我还写了一个CustomViewPager来停止在刷屏幕时更改页面。它工作正常。

这是我的代码：

MyFragment

 public CustomViewPager mViewPager;
 public Button next;
 public static int count=0;

 public static final MyFragment newInstance(String message,ArrayList<String> a)

 {

   MyFragment f = new MyFragment();

   Bundle bdl = new Bundle(1);

   bdl.putString(EXTRA_MESSAGE, message);
   bdl.putStringArrayList(EXTRA_ARRAY, a);

   f.setArguments(bdl);

   return f;

 }



 @Override

 public View onCreateView(LayoutInflater inflater, ViewGroup container,

   Bundle savedInstanceState) {

   String message = getArguments().getString(EXTRA_MESSAGE);
   View v = inflater.inflate(R.layout.myfragment_layout, container, false);

   spinner = (Spinner)v.findViewById(R.id.spinoptions);
   answer = (EditText)v.findViewById(R.id.answer);
   next = (Button)v.findViewById(R.id.next);

   next.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        mViewPager.setCurrentItem(1, true);//getItem(-1) for previous  

// it is not working

    }
});

   ArrayList<String> list = new ArrayList<String>();
    list.add("list 1");
    list.add("list 2");
    list.add("list 3");
    Builtprofile.q.get(0).getOptions();


        answer.setVisibility(View.INVISIBLE);
        spinner.setVisibility(View.VISIBLE);
    ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(Builtprofile.context,
        android.R.layout.simple_spinner_item,getArguments().getStringArrayList(EXTRA_ARRAY));
    dataAdapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line); 
       spinner.setAdapter(dataAdapter);



   TextView messageTextView = (TextView)v.findViewById(R.id.textView);


   messageTextView.setText(message);



   return v;

 }
 private int getItem() {
       return mViewPager.getCurrentItem();
}

我的PageAdapter代码

class MyPageAdapter extends FragmentPagerAdapter {

      private List<Fragment> fragments;


      public MyPageAdapter(FragmentManager fm, List<Fragment> fragments) {

        super(fm);

        this.fragments = fragments;

      }

      @Override 

      public Fragment getItem(int position) {

        return this.fragments.get(position);

      }


      @Override

      public int getCount() {

        return this.fragments.size();

      }

    }

ActivityClass代码

  public List<Fragment> getFragments(){

      List<Fragment> fList = new ArrayList<Fragment>();

     for(i=0;i<q.size();i++)
     {
      fList.add(MyFragment.newInstance(q.get(i).getText(),q.get(i).getOptions()));

     }


      return fList;

    }

  public void fragmentopener()
  {
      List<Fragment> fragments = getFragments();

        pageAdapter = new MyPageAdapter(getSupportFragmentManager(), fragments);

        ViewPager pager = (ViewPager)findViewById(R.id.viewpager);

        pager.setAdapter(pageAdapter);
  }

myCustomViewPager的代码

public class CustomViewPager extends ViewPager {

    private boolean isPagingEnabled;


    public CustomViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.isPagingEnabled = false;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (this.isPagingEnabled) {
            return super.onTouchEvent(event);
        }

        return false;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent event) {
        if (this.isPagingEnabled) {
            return super.onInterceptTouchEvent(event);
        }

        return false;
    }

    public void setPagingEnabled(boolean b) {
        this.isPagingEnabled = b;
    }
}

logcat的：

04-07 15:55:53.254: E/AndroidRuntime(17379): FATAL EXCEPTION: main
04-07 15:55:53.254: E/AndroidRuntime(17379): java.lang.NullPointerException
04-07 15:55:53.254: E/AndroidRuntime(17379):    at adapters.MyFragment$1.onClick(MyFragment.java:71)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at android.view.View.performClick(View.java:3574)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at android.view.View$PerformClick.run(View.java:14293)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at android.os.Handler.handleCallback(Handler.java:605)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at android.os.Handler.dispatchMessage(Handler.java:92)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at android.os.Looper.loop(Looper.java:137)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at android.app.ActivityThread.main(ActivityThread.java:4448)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at java.lang.reflect.Method.invokeNative(Native Method)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at java.lang.reflect.Method.invoke(Method.java:511)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:823)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:590)
04-07 15:55:53.254: E/AndroidRuntime(17379):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

你在@ NPE的第71行得到MyFragment，正如你在评论中说的那样，这一行是：

 mViewPager.setCurrentItem(1, true);

所以mViewPager为空，您需要在使用

之前初始化它

使用以下代码代替您的代码：

mViewPager.setCurrentItem(getItem(+1), true);

和getItem()是：

private int getItem(int i) {
       return mViewPager.getCurrentItem() + i;
}

Answer 2

虽然不是答案，但请继续阅读

我可能会迟到，我从online resource找到了一个非常简单的解决方案：

在片段xml中，您要实现下一个/上一个按钮，将此行添加到按钮xml：

机器人：的onClick =＆＃34; jumpToPage＆＃34;

将光标放在＆＃34; jumpToPage＆＃34;之间。 - 按Alt + Enter：

在PagerActivity中添加相关功能 - 不在片段中

现在将功能修改为：

public void jumpToPage(View view) {

        viewPager.setCurrentItem(viewPager.getCurrentItem() + 1, true);
    }

现在给我买nunchai :)

Answer 3

我希望这会对你有所帮助：

只需点击按钮输入此代码：

pager.setCurrentItem(1, true);

注意：在 1 的位置，您可以传递您的号码

Answer 4

我就是这样做的

    if (viewPager.getCurrentItem() < 4) {   
        viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
      }

Answer 5

只需执行此操作

下一个和上一个是两个按钮。

 previous.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (viewPager.getCurrentItem() != 0)
                viewPager.setCurrentItem(viewPager.getCurrentItem() - 1);
        }
    });

    next.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (viewPager.getCurrentItem() < viewPager.getAdapter().getCount())
                viewPager.setCurrentItem(viewPager.getCurrentItem() + 1);
        }
    });

Answer 6

我的代码是针对kotlin的，我认为我可以为很多人提供帮助，所以我不得不在这里编写它。

        val fragments: ArrayList<Fragment> =
        arrayListOf(
            HomeFragment(),
            SearchFragment(),
            AddFragment(),
            NotificationsFragment(),
            ProfileFragment()
        )
    binding.viewpager.adapter = FragmentViewPagerAdapter(supportFragmentManager, fragments)
    binding.viewpager.offscreenPageLimit = 5
    binding.viewpager.currentItem = 1


    binding.viewpager.addOnPageChangeListener(object : ViewPager.OnPageChangeListener{
        override fun onPageScrollStateChanged(state: Int) {

        }

        override fun onPageScrolled(
            position: Int,
            positionOffset: Float,
            positionOffsetPixels: Int
        ) {

        }

        override fun onPageSelected(position: Int) {
            when(position){
                0 -> binding.navigation.selectedItemId = position
                1 -> binding.navigation.selectedItemId = position
                2 -> binding.navigation.selectedItemId = position
                3 -> binding.navigation.selectedItemId = position
                4 -> binding.navigation.selectedItemId = position

            }


        }
    })
    binding.navigation.setOnNavigationItemSelectedListener { it
        it.let {
            when(it.itemId){
                R.id.nav_home -> {
                    binding.viewpager.currentItem = 0
                    return@setOnNavigationItemSelectedListener true
                }
                R.id.nav_search-> {
                    binding.viewpager.currentItem = 1
                    return@setOnNavigationItemSelectedListener true
                }
                R.id.nav_add -> {
                    binding.viewpager.currentItem = 2
                    return@setOnNavigationItemSelectedListener true
                }
                R.id.nav_notifications -> {
                    binding.viewpager.currentItem = 3
                    return@setOnNavigationItemSelectedListener true
                }
                R.id.nav_profile -> {
                    binding.viewpager.currentItem = 4
                    return@setOnNavigationItemSelectedListener true
                }
                else -> {
                    binding.viewpager.currentItem = 0
                    return@setOnNavigationItemSelectedListener true
                }
            }
        }

Answer 7

最好和最简单的答案是

viewPager.setCurrentItem(viewPager.getCurrentItem() + 1, true);

按钮上的更改页面单击ViewPager Android

7 个答案:

只需点击按钮输入此代码：

注意：在 1 的位置，您可以传递您的号码