Question

我正在创建一个标签式应用程序，需要一种方法来在我更改标签时执行操作。问题是我能找到的只是TabHost，它依赖于已弃用的TabActivity类。即使它没有被弃用，预先生成的选项卡式活动代码甚至不使用它，所以我必须从头开始构建我的主要活动类。所以我想知道是否有另一种方法来获得该功能

代码的粗略骨架

公共类MainActivity扩展AppCompatActivity实现TabHost.OnTabChangeListener {

公共类SectionsPagerAdapter扩展了FragmentPagerAdapter {

}

Answer 1

让我们假装您使用的是Android Studio 1.5.1。

当我使用新项目向导创建项目并接受默认值时，除了选择“选项卡式活动”作为模板外，在向导的活动配置页面上，还有一个“导航样式”下拉列表”。有三个选项：“滑动视图”，“操作栏选项卡”和“Action Bar Spinner”。

让我们假装你选择了“Action Bar Tabs”。

结果活动没有implements TabHost.OnTabChangeListener，我不知道他们的任何模板都有。相反，你得到这个：

import android.support.design.widget.TabLayout;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;

import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

  /**
   * The {@link android.support.v4.view.PagerAdapter} that will
   * provide
   * fragments for each of the sections. We use a
   * {@link FragmentPagerAdapter} derivative, which will keep
   * every
   * loaded fragment in memory. If this becomes too memory
   * intensive, it
   * may be best to switch to a
   * {@link android.support.v4.app.FragmentStatePagerAdapter}.
   */
  private SectionsPagerAdapter mSectionsPagerAdapter;

  /**
   * The {@link ViewPager} that will host the section contents.
   */
  private ViewPager mViewPager;

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

    Toolbar toolbar=(Toolbar)findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    // 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);

    TabLayout tabLayout=(TabLayout)findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(mViewPager);

    FloatingActionButton fab=
      (FloatingActionButton)findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        Snackbar.make(view, "Replace with your own action",
          Snackbar.LENGTH_LONG)
          .setAction("Action", null).show();
      }
    });

  }


  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
  }

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id=item.getItemId();

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

    return super.onOptionsItemSelected(item);
  }

  /**
   * A placeholder fragment containing a simple view.
   */
  public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for
     * this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER=
      "section_number";

    public PlaceholderFragment() {
    }

    /**
     * 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;
    }

    @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);
      textView.setText(getString(R.string.section_format,
        getArguments().getInt(ARG_SECTION_NUMBER)));
      return rootView;
    }
  }

  /**
   * 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;
    }
  }
}

如果这是您开始使用的地方，那么“正确解释您正在使用的内容”的正确回答应为“AppCompatActivity，ViewPager和TabLayout”。

让我们假装这是你拥有的，或多或少。

在这种情况下，call addOnPageChangeListener() on the ViewPager，传入OnPageChangeListener实施。当用户切换标签时，无论是通过TabLayout还是通过ViewPager本身的滑动手势，都会调用该标签。

现在，完全有可能这不是你所拥有的，因为我必须做出一些猜测，因为你的问题解释有限。

像TabHost.onTabChanged（）之类的东西

1 个答案: