setOnPageChangeListener does not call onPageSelected

Question

我使用以下示例设置了一个simpleonpagechangelistener：

Android SimpleOnPageChangeListener-确定滑动方向

然而，当我执行代码然后滑动视图寻呼机时，我希望调用以下行：

public void onPageSelected(int position) {

然而，它似乎从来没有这样做过——这导致了一个不起作用的viewPager。

有什么建议吗？

   public class Home extends YouTubeBaseActivity implements VideoClickListener {
    ...
    private int mCurrentTabPosition = NO_CURRENT_POSITION;
    private static final int NO_CURRENT_POSITION = -1;
    private ViewPager mPager;
    ...
    int imageArray[];
    String[] stringArray;
    private OnPageChangeListener mPageChangeListener;
    ImagePagerAdapter adapter = new ImagePagerAdapter();
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.home);
        final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
        viewPager.setAdapter(adapter);
...
        setOnPageChangeListener(mPageChangeListener);

        mPageChangeListener = new ViewPager.SimpleOnPageChangeListener() {

            @Override
            public void onPageSelected(int position) {
                onTabChanged(mPager.getAdapter(), mCurrentTabPosition, position);
                position = mCurrentTabPosition;
                int oldPos = viewPager.getCurrentItem();
                if (position > oldPos) {
                    System.out.print(position);
                    // Moving to the right
                    String playlist = "TheMozARTGROUP‎";
                    new GetYouTubeUserVideosTask(responseHandler, playlist)
                            .execute();
                    View vg = findViewById(R.layout.home);
                    vg.invalidate();
                } else if (position < oldPos) {
                    // Moving to the Left
                    System.out.print(position);
                    String playlist = "TheMozARTGROUP‎";
                    new GetYouTubeUserVideosTask(responseHandler, playlist)
                            .execute();
                    View vg = findViewById(R.layout.home);
                    vg.invalidate();
                }
                viewPager.setOnPageChangeListener(mPageChangeListener);
            }
            private void onTabChanged(PagerAdapter adapter,
                    int mCurrentTabPosition, int position) {
                // TODO Auto-generated method stub
            }
        };
    }
    private void setOnPageChangeListener(
            OnPageChangeListener mPageChangeListener2) {
        // TODO Auto-generated method stub
    }
    ...

    private class ImagePagerAdapter extends PagerAdapter {
        public ImagePagerAdapter(Activity act, int[] mImages,
                String[] stringArra) {
            imageArray = mImages;
            activity = act;
            stringArray = stringArra;
        }

        public ImagePagerAdapter() {
            super();
        }
        private int[] mImages = new int[] { R.drawable.selstation_up_btn,
                R.drawable.classical_up_btn, R.drawable.country_up_btn,
                R.drawable.dance_up_btn, R.drawable.hiphop_up_btn,
                R.drawable.island_up_btn, R.drawable.latin_up_btn,
                R.drawable.pop_up_btn, R.drawable.samba_up_btn };
        private String[] stringArray = new String[] { "vevo",
                "TheMozARTGROUP‎", "TimMcGrawVEVO‎", "TiestoVEVO‎",
                "EminemVEVO‎" };
        @Override
        public int getCount() {
            return mImages.length;
        }
        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view == ((ImageView) object);
        }
        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            Context context = Home.this;
            ImageView imageView = new ImageView(context);
            imageView.setScaleType(ScaleType.FIT_XY);
            imageView.setImageResource(mImages[position]);
            ((ViewPager) container).addView(imageView, 0);
            return imageView;
        }
        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            ((ViewPager) container).removeView((ImageView) object);
        }
        protected void onTabChanged(final PagerAdapter adapter,
                final int oldPosition, final int newPosition) {
            // Calc if swipe was left to right, or right to left
            if (oldPosition > newPosition) {
                // left to right
            } else {
                // right to left

            }
            final ViewPager viewPager = (ViewPager) findViewById(R.id.view_pager);
        }
    }
}

XML：

 <android.support.v4.view.ViewPager
  android:id="@+id/view_pager"
  android:layout_width="wrap_content"
  android:layout_height="fill_parent" />

Answer 1

我使用的是ViewPagerIndicator，事实证明，当你这样做时，你应该在指示器上而不是在viewpager上设置OnPageChangeListener。（如文件所示）

那么做：

    mIndicator.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
            doYourThing();
        }
    });

而不是：

    mPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
            doYourThing();
        }
    });

如果您使用SlidingTabLayout

Answer 2

使用

 viewPager.setOnPageChangeListener(mPageChangeListener);

删除

 private void setOnPageChangeListener(
        OnPageChangeListener mPageChangeListener2) {
    // TODO Auto-generated method stub
}

和

 setOnPageChangeListener(mPageChangeListener);

Answer 3

您是否尝试使用ViewPager.setOnPageChangeListener而不是SimpleChangeListener？试试看：

mPager.setOnPageChangeListener(new OnPageChangeListener() {
        @Override
        public void onPageSelected(int pos) {
        }
        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
            // TODO Auto-generated method stub
        }
        @Override
        public void onPageScrollStateChanged(int pos) {
        }
    });

Answer 4

我现在遇到了同样的问题-我还将一个变量设置为等于：

 mPageChangeListener =  new ViewPager.OnPageChangeListener() {<methods>}

然后通过将其分配给我的视图寻呼机

 mPager.setOnPageChangeListener(mPageChangeListener)

代码不起作用的原因是您正在onCreate方法中创建本地变量。有两种方法可以解决这个问题：

1. 您可以在setter中为onPageChangeListener分配代码，以便：

mPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {<methods>})

2. 您可以为"mPageChangeListener"创建一个成员变量，以便在调用onCreate之前对其进行初始化。因此，将mPageChangeListener代码复制到onCreate方法之上，并在那里进行初始化

Answer 5

        viewPager.setOnPageChangeListener(new OnPageChangeListener() {
            public void onPageSelected(int currentPage) {
                // work here after changing page
            }
        });