Android ViewPager setAdapter 无法更新 View 和 fragment

Question

我有一个包含输入按钮的 FragmentActivity 和一个 viewpager。
当点击入口按钮时，它会设置一个图像 url 到一个新的 FragmentPagerAdapter 并将适配器设置为 viewpager。
FragmentPagerAdpater 持有显示图像的 fragment 。
然后按后退按钮，并再次单击该输入按钮。
它会将一个新的图像 url 设置为一个新的 FragmentPagerAdapter，并将适配器设置为 viewpager。

我的问题 fragment 一直显示第一张图片，但在单击输入按钮时不显示其他图片。好像有些东西更新不了。

会出现什么问题？

TestGallery.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.season.test.TestGalleryFragment;

import java.util.ArrayList;


public class TestGallery extends FragmentActivity {
    private ArrayList<Integer> imgURLs;
    private GalleryPagerAdapter mAdapter;
    private Button btnEntry;
    private ViewPager viewPager;
    private int curr = 0;
    private int[] resourceIDs = {R.drawable.abc_btn_check_material, R.drawable.abc_ic_go_search_api_mtrl_alpha, R.drawable.ic_launcher};

    @Override
    public void onBackPressed() {
        if (viewPager.getVisibility() == View.VISIBLE) {
            btnEntry.setVisibility(View.VISIBLE);
            viewPager.setVisibility(View.GONE);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test_gallery);
        btnEntry = (Button) findViewById(R.id.btnEntry);
        viewPager = (ViewPager) findViewById(R.id.viewPager);
        btnEntry.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (curr >= resourceIDs.length) {
                    curr = 0;
                }
               if (imgURLs == null) {
                imgURLs = new ArrayList<>();
            }
            imgURLs.clear();
            imgURLs.add(resourceIDs[curr]);

            if (mAdapter == null) {
                mAdapter = new GalleryPagerAdapter(getSupportFragmentManager(), imgURLs);
                viewPager.setAdapter(mAdapter);
            }
            mAdapter.notifyDataSetChanged();

                btnEntry.setVisibility(View.GONE);
                viewPager.setVisibility(View.VISIBLE);

                curr++;
                btnEntry.setText("Click For Next Image: " + curr % resourceIDs.length);
                Toast.makeText(TestGallery.this,"Press Back Button",Toast.LENGTH_SHORT).show();
            }
        });

    }

    class GalleryPagerAdapter extends FragmentPagerAdapter {
        ArrayList<Integer> imgURLs;


        GalleryPagerAdapter(FragmentManager fm, ArrayList<Integer> imgURLs) {
            super(fm);
            this.imgURLs = imgURLs;
        }

        @Override
        public Fragment getItem(int position) {
            return TestGalleryFragment.newInstance(imgURLs.get(position));
        }

        @Override
        public int getCount() {
            return imgURLs.size();
        }


    }

}

activity_test_gallery.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/layoutDetails">

        <Button
            android:id="@+id/btnEntry"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="Click to show next"
            android:textSize="30sp"
           />

        <android.support.v4.view.ViewPager
            android:background="#0000"
            android:id="@+id/viewPager"
            android:visibility="gone"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />
    </FrameLayout>


</FrameLayout>

TestGalleryFragment.java

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.season.test.R;

public class TestGalleryFragment extends Fragment {

    public static String KEY_IMG_URL = "imgURL";

    private Integer imgURL = R.drawable.ic_launcher;

    public static TestGalleryFragment newInstance(Integer imgURL) {
        Log.i("url", "frag url: " + imgURL);
        TestGalleryFragment fragment = new TestGalleryFragment();
        Bundle args = new Bundle();
        args.putInt(KEY_IMG_URL, imgURL);
        fragment.setArguments(args);
        return fragment;
    }

    public TestGalleryFragment() {
        // Required empty public constructor
    }

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

        if (getArguments() != null) {
            imgURL = getArguments().getInt(KEY_IMG_URL);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View root = inflater.inflate(R.layout.fragment_gallery, container, false);
        ImageView imgPhoto = (ImageView) root.findViewById(R.id.imgPhoto);
        imgPhoto.setImageResource(imgURL);
        return root;
    }


}

fragment_test_gallery.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#0000">

    <ImageView
        android:id="@+id/imgPhoto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center" />


</FrameLayout>

Answer 1

我发现了为什么会出现这个问题。
这是因为在调用 notifyDataSetChanged 后 fragment 不会重新
刷新/重新创建。为了在每次数据更改时制作新的 fragment 。最好将 FragmentPagerAdapter 修改为来自
https://stackoverflow.com/a/26944013/2080233 的建议答案