我使用可滑动标签作为活动的一部分，共有3个部分。我提供了向右和向左箭头以导航到滑动视图的其他部分。
当我在最左边的部分时，我希望我的左箭头消失，当我在最右边的部分时，我的右箭头消失。
这是我正在尝试的东西，但没有得到理想的结果：
public class MainActivity extends AppCompatActivity {
private SectionsPagerAdapter mSectionsPagerAdapter;
static Button rightButton;
static Button leftButton;
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
rightButton = (Button)findViewById(R.id.buttonRight);
leftButton = (Button)findViewById(R.id.buttonLeft);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "SECTION 1";
case 1:
return "SECTION 2";
case 2:
return "SECTION 3";
}
return null;
}
}
public static class PlaceholderFragment extends Fragment {
private static final String ARG_SECTION_NUMBER = "section_number";
// Returns a new instance of this fragment for the given section number.
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
int sectionNumber = getArguments().getInt(ARG_SECTION_NUMBER);
String text = instructions(sectionNumber);
textView.setText(text);
return rootView;
}
private String instructions(int sectionNumber) {
if (sectionNumber == 1) {
leftButton.setVisibility(View.INVISIBLE);
rightButton.setVisibility(View.VISIBLE);
Log.i("Welcome"," to section 1");
return "All questions are mandatory. Each question carries 1 mark. There is no negative marking";
}
else if(sectionNumber == 2) {
leftButton.setVisibility(View.VISIBLE);
rightButton.setVisibility(View.VISIBLE);
Log.i("Welcome", " to section 2");
return "Color the bubble besides the option you think is best for the answer.";
}
else {
leftButton.setVisibility(View.VISIBLE);
rightButton.setVisibility(View.INVISIBLE);
Log.i("Welcome", " to section 3");
return "Click on the skip button above to start the test. Timer will start as soon as you'll click that button!";
}
}
}
}
正如您在方法instructions中看到的那样，我尝试使用日志查看发生了什么，但却发现我从未得到过＃34;欢迎来到第2部分＆＃34;甚至在多次滑过标签后也是如此。尽管如此，正确返回与给定部分相关的文本。我在这里缺少什么？
答案 0 :(得分：1)
问题是您在getItem中返回了一个新片段
这样做：
public class SectionsPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragments = new ArrayList<Fragment>();
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
mFragments.add(PlaceholderFragment.newInstance(1));
mFragments.add(PlaceholderFragment.newInstance(2));
mFragments.add(PlaceholderFragment.newInstance(3));
}
@Override
public Fragment getItem(int position) {
return mFragments.get(position);
}
}
同时将按钮更改为fragment_main布局＆＃34;不是＆＃34;在activity_main中并像这样使用它。
public static class PlaceholderFragment extends Fragment {
private static final String ARG_SECTION_NUMBER = "section_number";
private Button rightButton;
private Button leftButton;
// Returns a new instance of this fragment for the given section number.
public static PlaceholderFragment newInstance(int sectionNumber) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
TextView textView = (TextView) rootView.findViewById(R.id.section_label);
rightButton = (Button)rootView.findViewById(R.id.buttonRight);
leftButton = (Button)rootView.findViewById(R.id.buttonLeft);
int sectionNumber = getArguments().getInt(ARG_SECTION_NUMBER);
String text = instructions(sectionNumber);
textView.setText(text);
return rootView;
}
编辑，如果你想知道你必须实现的cuurent页面。
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
Log.i("Welcome", "page "+ position+1);
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
同时添加以下行，以便系统只创建一次片段：
mViewPager.setOffscreenPageLimit(3);
您遇到的问题是您现在获得的系统位置不是当前页面。