如何检查 viewpager 中的页面是否在 java 中可见

Question

我已经在互联网上搜索了一个小时，并为 viewPager 创建了自定义视图。我看到的每个解决方案都是针对 Fragments 的。我的问题是如何使用 if 语句检查我的页面是否可见。我想这样做是出于一个原因。我有一些位于相机屏幕顶部的视图，我想根据视图保存每张照片。例如：如果正在使用"TOPS"衣服对象和"tops_view"，我想将它保存到android中的"tops"文件夹中。我已经知道如何保存到不同的文件夹，所以我想在我的 cameraAPI 文件中进行 if 语句。 if语句就是我要实现的伪代码：

if (ClothesPagerView == TOPS)

final File file = new File(Environment.getExternalStorageDirectory() + "/OutfitMatcher/tops/img" + System.currentTimeMillis () +".jpg");

else if (ClothesPagerView == BOTTOMS)

final File file = new File(Environment.getExternalStorageDirectory() + "/OutfitMatcher/bottoms/img" + System.currentTimeMillis () +".jpg");

CustomPagerAdapater.java

public class CustomPagerAdapter1 extends PagerAdapter{
    private Context mContext;

    public CustomPagerAdapter1(Context context) {
        mContext = context;
    }

    @Override
    public Object instantiateItem(ViewGroup collection, int position) {
        ClothesObject clothesObject = ClothesObject.values()[position];
        LayoutInflater inflater = LayoutInflater.from(mContext);
        ViewGroup layout = (ViewGroup) inflater.inflate(clothesObject.getLayoutResId(), collection, false);
        collection.addView(layout);
        return layout;
    }

    @Override
    public void destroyItem(ViewGroup collection, int position, Object view) {
        collection.removeView((View) view);
    }

    @Override
    public int getCount() {
        return ClothesObject.values().length;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        ClothesObject customPagerEnum = ClothesObject.values()[position];
        return mContext.getString(customPagerEnum.getTitleResId());
    }
}

ClothesObject.jaca（我与适配器一起使用）

public enum ClothesObject {
    TOPS(R.string.tops_camera, R.layout.tops_view),
    BOTTOMS(R.string.bottoms_camera, R.layout.bottoms_view),
    ACCESSORIES(R.string.accessories_camera, R.layout.accessories_view),
    SHOES(R.string.shoes_camera, R.layout.shoes_view),
    OUTERWEAR(R.string.outerwear_camera, R.layout.outerwear_view),
    DRESSES(R.string.dresses_camera, R.layout.dresses_view);

    private int mTitleResId;
    private int mLayoutResId;

    ClothesObject(int titleResId, int layoutResId) {
        mTitleResId = titleResId;
        mLayoutResId = layoutResId;
    }

    public int getTitleResId() {
        return mTitleResId;
    }

    public int getLayoutResId() {
        return mLayoutResId;
    }
}

Answer 1

为此，您必须将 fragment 与 Viewpager 一起使用。那么您可以在片段中使用 getUserVisibleHint() 来检查页面是否处于活动状态

即

    if(getUserVisibleHint()){
    //Your fragment is visible
    }else{
      // Not visible
}

如何检查 viewpager 中的页面是否在 java 中可见

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