ViewPager和Toast

Question

我有一个从远程服务器加载图像的ViewPager。我的问题是，一旦选择了一个特定的位置(而不是点击)，我不知道如何给它一个函数。比方说，我滑动视图页面，直到它到达特定的图像，比如图像5，我想显示一些Toast，上面写着“图像5”。

pager.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View arg1, int position,long id) {  





 public class ImagePagerActivity extends BaseActivity {

    private ViewPager pager;

    private DisplayImageOptions options;

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.ac_image_pager);
    Bundle bundle = getIntent().getExtras();
    String[] imageUrls = bundle.getStringArray(Extra.IMAGES);
    int pagerPosition = bundle.getInt(Extra.IMAGE_POSITION, 0);

    options = new DisplayImageOptions.Builder()
                .showImageForEmptyUri(R.drawable.image_for_empty_url)
                .cacheOnDisc()
                .imageScaleType(ImageScaleType.IN_SAMPLE_INT)
                .build();

    pager = (ViewPager) findViewById(R.id.pager);
    pager.setAdapter(new ImagePagerAdapter(imageUrls));
    pager.setCurrentItem(pagerPosition);

    }

    protected void onStop() {
    imageLoader.stop();
    super.onStop();
    }

    private class ImagePagerAdapter extends PagerAdapter {

    private String[] images;
    private LayoutInflater inflater;

    ImagePagerAdapter(String[] images) {
    this.images = images;
    inflater = getLayoutInflater();
    }

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

    public void finishUpdate(View container) {
    }

    public int getCount() {
    return images.length;
    }

    public Object instantiateItem(View view, int position) {
                final View imageLayout = inflater.inflate(R.layout.item_pager_image, null);
                final ImageView imageView = (ImageView) imageLayout.findViewById(R.id.image);
                final ProgressBar spinner = (ProgressBar) imageLayout.findViewById(R.id.loading);

    imageLoader.displayImage(images[position], imageView, options, new ImageLoadingListener() {

    public void onLoadingStarted() {
    spinner.setVisibility(View.VISIBLE);
    }


    public void onLoadingFailed(FailReason failReason) {
    String message = null;
    switch (failReason) {
    case IO_ERROR:
    message = "Input/Output error";
    break;
    case OUT_OF_MEMORY:
    message = "Out Of Memory error";
    break;
    case UNKNOWN:
    message = "Unknown error";
    break;
    }
    Toast.makeText(ImagePagerActivity.this, message, Toast.LENGTH_SHORT).show();

    spinner.setVisibility(View.GONE);
                              imageView.setImageResource(android.R.drawable.ic_delete);
                    }


    public void onLoadingComplete(Bitmap loadedImage) {
    spinner.setVisibility(View.GONE);
    Animation anim = AnimationUtils.loadAnimation(ImagePagerActivity.this, R.anim.fade_in);
    imageView.setAnimation(anim);
    anim.start();
    }

    public void onLoadingCancelled() {
    // Do nothing
    }
    });

    ((ViewPager) view).addView(imageLayout, 0);
    return imageLayout;
    }

    public boolean isViewFromObject(View view, Object object) {
    return view.equals(object);
    }

    public void restoreState(Parcelable state, ClassLoader loader) {
    }
    public Parcelable saveState() {
    return null;
    }

    public void startUpdate(View container) {
    }
    }
    }

Answer 1

您可以实现onPageChangeListener，然后可以使用(setOnPageChangeListener()) ...将此pageChageListener设置为您的ViewPager。

public class ImagePagerActivity extends BaseActivity implements onPageChangeListener {
    private ViewPager pager;
    // other variables here

    public void onCreate(Bundle savedInstanceState) {
        // create view Pager 
        // other variables 
        pager.setOnPageChangeListener(this);
    }

    // methods for Page Change Listener
    @Override
    public void onPageSelected(int pos) {
        if (pos==5) {
          //show Toast here 
        }
    }

    @Override
    public void onPageScrollStateChanged(int arg0) {
        // do Nothing
    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        // do Noting
    }

}// class def ends here

编辑..

使用此速记版本

Pager.setOnPageChangeListener(new OnPageChangeListener() {

    @Override
    public void onPageSelected(int arg0) {
        if (pos==5) {
            //show Toast here 
        }
    }

    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {
        // TODO Auto-generated method stub
    }

    @Overridee3public void onPageScrollStateChanged(int arg0) {
        // TODO Auto-generated method stub
    }
});

Answer 2

您应该使用OnPageChangeListener。

您可以使用as onPageSelected(int position)方法来获取当前位置。

就像这样

pager.setOnPageChangeListener(this);

然后让您的ImagePagerActivity实现OnPageChangeListener接口：

public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}

public void onPageSelected(int position) {
    Toast.makeText(getApplicationContext(), "image " + position, Toast.LENGTH_SHORT).show();
}

public void onPageScrollStateChanged(int state) {
}