ViewPager 没有显示任何东西 - android

Question

我需要一些建议。 ViewPager 只显示白页。我进行了很多搜索，但找不到适合我的案例的解决方案。
我试图制作简单的按钮，但我得到了相同的输出。我认为这不是图像问题。 这是我的代码。

public class IntroduceArticleFragment extends Fragment {

    View view;
    String depart;
    String path;
    int num;

    CustomPagerAdapter customPagerAdapter;
    ViewPager viewPager;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_introduce_article, container, false);
        view.setBackgroundColor(Color.WHITE);

        depart = getArguments().getString("depart");
        create();

        //customPagerAdapter = new CustomPagerAdapter(getActivity());
        viewPager = (ViewPager)view.findViewById(R.id.pager);
        viewPager.setAdapter(customPagerAdapter);


        return view;
    }

    void create(){
        DBHelper dbHelper = new DBHelper(getActivity());
        path = dbHelper.getContentsPath(depart);
        num = dbHelper.getNum(depart);

        customPagerAdapter = new CustomPagerAdapter(getActivity());
        customPagerAdapter.mResources = new int[num];
        for(int i=0;i<num;i++) {
            String uri = "@drawable/" + path + "_" + Integer.toString(i);
            int imageResource = getActivity().getResources().getIdentifier(uri, "drawabale", getActivity().getPackageName());
            customPagerAdapter.mResources[i] = imageResource;
        }
    }
}


public class CustomPagerAdapter extends PagerAdapter {
    Context mContext;

    public int[] mResources;

    public CustomPagerAdapter(Context context) {
        super();
        mContext = context;
    }

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

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

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        LayoutInflater mLayoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View itemView = mLayoutInflater.inflate(R.layout.pager_item_0, container, false);

        ImageView imageView = (ImageView) itemView.findViewById(R.id.pagerimageView_0);
        imageView.setImageResource(mResources[position]);

        container.addView(itemView);

        return itemView;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((LinearLayout) object);
    }

    @Override
    public void startUpdate(ViewGroup container) {
        super.startUpdate(container);
    }

    @Override
    public void finishUpdate(ViewGroup container) {
        super.finishUpdate(container);
    }
}

这里是 ArticleFragment 的 xml 代码

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

        <ScrollView
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="vertical" >

                <android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
                    android:id="@+id/pager"
                    android:layout_width="match_parent"
                    android:layout_height="0dp"
                    android:visibility="visible">
                </android.support.v4.view.ViewPager>


            </LinearLayout>
        </ScrollView>
    </LinearLayout>

这里是

的 xml 代码

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

        <Button
            android:text="Button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/button" />

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scaleType="fitCenter"
            android:id="@+id/pagerimageView_0" />
    </LinearLayout>

Answer 1

好的...首先您必须将ScrollView 的孩子的android:layout_height 设置为wrap_content。

其次，考虑到不能将ViewPager 的android:layout_height 设置为wrap_content。除非您使用自定义 ViewPager。例如，您可以查看this answer

通过在ScrollView 中将android:fillViewport 设置为true，ScrollView 的Child 的高度会自动设置为match_parent，直到其高度高于屏幕。

我不明白你为什么将ViewPager 的高度设置为0dp 并期望它显示一些东西！

现在你的布局应该是这样的：

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

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport="true">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
                android:id="@+id/pager"
                android:layout_width="match_parent"
                android:layout_height="match_pranet"
                android:visibility="visible">
            </android.support.v4.view.ViewPager>


        </LinearLayout>
    </ScrollView>
</LinearLayout>

Answer 2

我花了半天时间解决它，并发现我的 ViewPager 与我应用程序中另一个模块中的另一个 ViewPager 具有相同的 id，所以我只是给了它另一个 id。我不知道为什么它很重要，但就是这样。

Answer 3

你错了，使用这个代码

    import android.support.v4.app.Fragment;
    import android.support.v4.app.FragmentManager;
    import android.support.v4.app.FragmentStatePagerAdapter;


    public class CustomPagerAdapter extends FragmentStatePagerAdapter {

       public int[] mResources;

        public NewsAdapter(FragmentManager fm, int[] mResources) {
            super(fm);

            this.mNumOfTabs = mResources.length();
            this.mResources = mResources;
        }



        @Override
        public Fragment getItem(int position) {
            return ContentFragment.newInstance(mResources[position]);
        } 

        @Override
        public int getCount() {
            return mNumOfTabs;
        }
    }



public class ContentFragment extends Fragment  {


    private Context context;

    private int resource_id;

    public static ContentFragment newInstance(int resourdid) {
        Bundle args = new Bundle();
        args.putInt("resource_id", resourdid);
        ContentFragment fragment = new ContentFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        resource_id   = getArguments().getInt("resource_id");

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return inflater.inflate(in.newswallet.R.layout.content_row, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        initalize();
    }


    private void initalize(){
        View itemView = getView();
        ImageView imageView = (ImageView) itemView.findViewById(R.id.pagerimageView_0);
        imageView.setImageResource(resource_id);    
    }



    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        this.context=context;
    }





}

Answer 4

<android.support.v4.view.ViewPager     xmlns:android="http://schemas.android.com/apk/res/android"
                android:id="@+id/pager"
                android:layout_width="match_parent"
                android:layout_height="0dp"
                android:visibility="visible">
            </android.support.v4.view.ViewPager>

尝试将 android:layout_height = "0dp" 更改为类似 android:layout_height = "50dp" 或

的值

赋予布局权重 android:layout_weight = "1"

Answer 5

变化：

container.removeView((LinearLayout) object);

与：

container.removeView((ConstraintLayout) object);