[英]How to work with ViewPager.OnPageChangeListener
As per this accepted answer, I was able to get my tabLyout
as below: 按照这个公认的答案,我能够获得如下所示的
tabLyout
:
What do I need now, is to be able to change the buttons text based on the fragment position, for example if the position is zero, the Back
should not appear, and if the position is the last, the Next
should be replaced by Done
我现在需要的是能够根据片段位置更改按钮文本,例如,如果位置为零,则不应显示“
Back
,如果位置是最后一个,则应将“ Next
替换为Done
I have used the ViewPager.OnPageChangeListener
but did not work for me, below is the full code: 我使用过
ViewPager.OnPageChangeListener
但对我不起作用,下面是完整的代码:
public class Slider extends AppCompatActivity {
private TabLayout tabLayout;
private ViewPager viewPager;
private Button leftBtn, rightBtn;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.start_up);
leftBtn = (Button) findViewById(R.id.left_btn);
rightBtn= (Button) findViewById(R.id.right_btn);
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
tabLayout = (TabLayout) findViewById(R.id.tabLayout);
tabLayout.setupWithViewPager(viewPager);
}
// This is not working, even the `Toast` not appearing
private ViewPager.OnPageChangeListener listener = new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
Toast.makeText(Slider.this, "Current position: "+position, Toast.LENGTH_SHORT).show();
if (position == 0) {
leftBtn.setText("");
}
if (position == 3) {
rightBtn.setText("DONE");
}
}
@Override
public void onPageScrollStateChanged(int state) {
}
};
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFrag(new Tab1(),"");
adapter.addFrag(new Tab2(),"");
adapter.addFrag(new Tab3(),"");
adapter.addFrag(new Tab4(),"");
viewPager.setAdapter(adapter);
}
static class ViewPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager manager) {
super(manager);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
@Override
public int getCount() {
return mFragmentList.size();
}
public void addFrag(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
@Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
public void next_fragment(View view) {
viewPager.setCurrentItem(viewPager.getCurrentItem()+1);
}
public void previous_fragment(View view) {
viewPager.setCurrentItem(viewPager.getCurrentItem()-1);
}
public void start_app(View view) {
startActivity(new Intent(Slider.this, TrustedNumber.class));
finish();
}
}
这是因为您尚未将侦听器添加到viewpager
viewPager.addOnPageChangeListener(listener);
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