如何计算碎片？

Question

我有一个显示 3 个片段的活动和寻呼机适配器。碎片被打乱。当我浏览它们时，我需要知道每页的编号，并且该编号需要显示在 textView 中。比如我在第一页时显示1号，第二页-号2以此类推。

PagerAdapter.java

public class PagerAdapter extends FragmentPagerAdapter {

    private List<Fragment> fragments;

    public PagerAdapter(FragmentManager fm, List<Fragment> fragments) {
        super(fm);
        this.fragments = fragments;
    }

    @Override
    public Fragment getItem(int arg0) {
        return this.fragments.get(arg0);
    }

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

    public void setFragments(List<Fragment> fragments) {
        this.fragments = fragments;
    }
}

ma​​inActivity.java

    public class testActivity extends FragmentActivity {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_pager_adapter);
            initialisePaging();
        }

        private  void initialisePaging() {
            List<Fragment> fragments = new Vector<Fragment>();
            fragments.add(Fragment.instantiate(this,fragment1.class.getName()));
            fragments.add(Fragment.instantiate(this,fragment2.class.getName()));
            fragments.add(Fragment.instantiate(this,fragment3.class.getName()));
            PagerAdapter mPagerAdapter = new PagerAdapter(this.getSupportFragmentManager(), fragments);
        Collections.shuffle(fragments, new Random(System.nanoTime()));

            ViewPager pager = (ViewPager) findViewById(R.id.viewpager);
            pager.setAdapter(mPagerAdapter);

        }


        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            getMenuInflater().inflate(R.menu.menu_test, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            int id = item.getItemId();

            //noinspection SimplifiableIfStatement
            if (id == R.id.action_settings) {
                return true;
            }

            return super.onOptionsItemSelected(item);
        }

    }

Answer 1

如果您想在片段中显示数字，请使用此

在您的活动中

@Override
public Fragment getItem(int position) {
    // Here you can add an argument that will be passed to the fragment
    // In your case you need to pass the page number
    Fragment fragment = this.fragments.get(arg0);
    Bundle b = new Bundle();
    b.putInt("page_number", position);
    fragment.setArguments(b);
    return fragment;
}

在你的片段中这样做

int number;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // Read the data that Activity passed to us
    if (savedInstanceState == null) {
        Bundle args = getArguments();
        if (args != null) {
            number = args.getInt("page_number") + 1;
        }
    }
    else {
        number = savedInstanceState.getInt("page_number");
    }
}

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    // Here you need to find your TextView and show the number
    View v = inflater.inflate(R.layout.some_layout, container, false);
    ((TextView) v.findViewById(R.id.someTextView)).setText(String.format("%d", number));
    return v;
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("page_number", number);
}

如果您想在 Activity 中显示数字，请使用此

private  void initialisePaging() {
    List<Fragment> fragments = new Vector<Fragment>();
    fragments.add(Fragment.instantiate(this,fragment1.class.getName()));
    fragments.add(Fragment.instantiate(this,fragment2.class.getName()));
    fragments.add(Fragment.instantiate(this,fragment3.class.getName()));
    PagerAdapter mPagerAdapter = new PagerAdapter(this.getSupportFragmentManager(), fragments);
    Collections.shuffle(fragments, new Random(System.nanoTime()));

    // !!! Change ME!!!!!
    textView = (TextView) findViewById(R.id.someTextView);

    ViewPager pager = (ViewPager) findViewById(R.id.viewpager);

    pager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int i, float v, int i2) {

        }

        @Override
        public void onPageSelected(int i) {
            textView.setText("Position: " + i);
        }

        @Override
        public void onPageScrollStateChanged(int i) {

        }
    });

    pager.setAdapter(mPagerAdapter);


}

Answer 2

将PageChangeListener 用作：

yourPager.setOnPageChangeListener(new OnPageChangeListener() {

     @Override
     public void onPageSelected(int position)
     {
         yourTextView.setText("Page: " + position); 
     }

     ... ... 

  });