ViewPager包含GridView的片段

Question

我有一个带有两个片段的ViewPager，每个片段都有一个GridView

Frag1.java

public class Frag1 extends Fragment{
GridView grid;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    return inflater.inflate(R.layout.frag1, container, false);
}

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    grid = (GridView) getActivity().findViewById(R.id.gridView1);
    grid.setAdapter(new MyAdapter());

}

private class MyAdapter extends BaseAdapter {
    private int ar []={R.drawable.ch1,R.drawable.ch2,R.drawable.ch3,R.drawable.ch4};
    private LayoutInflater inflater;


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

    @Override
    public Object getItem(int i) {
        return ar[i];
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        View v = view;
        ViewHolder holder = null;

        if(v == null) {
            inflater = (LayoutInflater) getActivity().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = inflater.inflate(R.layout.grid_layout, viewGroup, false);
            holder = new ViewHolder();
            v.setTag(holder);

        }else{
            holder = (ViewHolder) v.getTag();
        }

        holder.img = (ImageView)v.findViewById(R.id.imageView1);
        holder.img.setBackgroundResource(ar[i]);
        return v;
    }

    private class ViewHolder{
        ImageView img;
    }
}

Frag2与Frag1相同，但有两个不同的东西

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    return inflater.inflate(R.layout.frag, container, false);
}
private class MyAdapter extends BaseAdapter {
    private int ar []={R.drawable.gmc1,R.drawable.gmc2,R.drawable.gmc3,R.drawable.gmc4};
     ......
   }

这是包含ViewPager

的SecondActivity

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_second);
    pager = (ViewPager) findViewById(R.id.pager);
    FragmentManager fm = getSupportFragmentManager();
    adapter = new MyPagerAdapter(fm);
    pager.setAdapter(adapter);

}

 class MyPagerAdapter extends FragmentStatePagerAdapter {

    public MyPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {

        Fragment frag;
        if (position == 0) {
            frag = new Frag1();
        } else {
            frag = new Frag2();
        }
        return frag;

    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return 2;
    }
}

问题是ViewPage只能查看一个页面（Frag2），滚动页面时会得到一个空白页面

Answer 1

这很奇怪......

@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    grid = (GridView) getActivity().findViewById(R.id.gridView1);
    grid.setAdapter(new MyAdapter());

}

为什么要在Activity中查找gridView？可能你应该在onCreateView中执行此操作而不会弄乱onActivityCreated

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
    Bundle savedInstanceState) {
        ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.frag, container, false);
        grid = (GridView) rootView.findViewById(R.id.gridView1);
        grid.setAdapter(new MyAdapter());
        return rootView;
}

一些解释：

您正在致电

getActivity().findViewById(R.id.gridView1);

在其子图片（片段布局）中的ViewPager（以及它是扩展的ViewGroup）中的Activity中搜索。两者都调用gridView1，假设此网格仅附加到Frag1，您正在使用此视图创建Frag1并使用ch drawables设置Adapter。然后创建第二个片段Frag2，从早先在Frag1中膨胀的Activity GridView获取并仍然出现在屏幕上（alive，not null）并设置gmc adapter