Android:ViewPager 不尊重 WRAP_CONTENT？

Question

我想创建一个 ViewPager，其宽度环绕其内容，并在其父项中水平居中。第一个代码 fragment 使用 LinearLayout 来创建此效果，如第一个屏幕截图所示。第二个代码 fragment 是我尝试使用 ViewPager 而不是 LinearLayout 来执行此操作，但结果不是所需的行为，如第二个屏幕截图所示。

关于我如何创建第一个效果但使用 ViewPager 有什么建议吗？

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

        textView = new TextView(this);
        textView.setLayoutParams(new ViewGroup.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT));
        textView.setText("abcabcabcabcabc");
        textView.setBackgroundColor(Color.YELLOW);

        LinearLayout llayout = new LinearLayout(this);
        llayout.setBackgroundColor(Color.BLUE);
        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.MATCH_PARENT);
        layoutParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        llayout.setLayoutParams(layoutParams);
        llayout.addView(textView);

        layout = new RelativeLayout(this);
        layout.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
        layout.setBackgroundColor(Color.GREEN);
        layout.addView(llayout);

        setContentView(layout);
    }


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

        textView = new TextView(this);
        textView.setLayoutParams(new ViewGroup.LayoutParams(ViewPager.LayoutParams.WRAP_CONTENT, ViewPager.LayoutParams.WRAP_CONTENT));
        textView.setText("abcabcabcabcabc");
        textView.setBackgroundColor(Color.YELLOW);

        ViewPager pager = new ViewPager(this);
        pager.setBackgroundColor(Color.BLUE);
        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.FILL_PARENT);
        layoutParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        pager.setLayoutParams(layoutParams);
        pager.setAdapter(new ViewPagerAdapter());

        layout = new RelativeLayout(this);
        layout.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
        layout.setBackgroundColor(Color.GREEN);
        layout.addView(pager);

        setContentView(layout);
    }

    class ViewPagerAdapter extends PagerAdapter
    {
        @Override
        public int getCount() 
        {
            return 1;
        }

        public Object instantiateItem(ViewGroup collection, int position) 
        {
            collection.addView(textView, 0);
            return textView;
        }

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

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

        @Override
        public void finishUpdate(ViewGroup arg0) {}


        @Override
        public void restoreState(Parcelable arg0, ClassLoader arg1) {}

        @Override
        public Parcelable saveState() 
        {
            return null;
        }

        @Override
        public void startUpdate(ViewGroup arg0) {}
    }

Answer 1

如果您查看适配器调用 instantiateItem()

的代码

public Object instantiateItem(ViewGroup collection, int position) 
{
    collection.addView(textView, 0)
    return textView;
}

您正在返回一个 TextView 作为页面和您想要显示的唯一内容。

文档的相关部分在这里: http://developer.android.com/reference/android/support/v4/view/PagerAdapter.html

A very simple PagerAdapter may choose to use the page Views themselves as key objects, returning them from instantiateItem(ViewGroup, int) after creation and adding them to the parent ViewGroup. A matching destroyItem(ViewGroup, int, Object) implementation would remove the View from the parent ViewGroup and isViewFromObject(View, Object) could be implemented as return view == object;.

使用您想要的布局创建一个 View 并将其返回到那里以获得您想要的效果。

见底部: http://android-developers.blogspot.com/2011/08/horizontal-view-swiping-with-viewpager.html