如何在选项卡式活动中设置片段从右到左开始

Posted 2023-04-19

【中文标题】如何在选项卡式活动中设置片段从右到左开始

【英文标题】：How to set fragments in a tabbed activity to begin from right to left

【发布时间】：2016-03-23 02:30:23

【问题描述】：

我是一名初级安卓开发者。我一直在尝试使用选项卡式活动中的一组片段来开发图书应用程序。问题是，我看不到在哪里可以将第一个片段设置为最后一个片段，然后使片段可以从右向左滑动。

可以通过android:layoutDirection="rtl" 命令在activity_main 中轻松地将文本设置为rtl，但我无法找到将片段设置为任何地方的rtl 的方法。

我假设需要在MainActivity.Java 中实现一些代码，因此我将在下面发布预定义的代码。

package com.silenceofwinds.goldeneagle.silenceofwinds;

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);


    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 @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;
    


/**
 * 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";

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

例如，如果我正在使用这个应用程序，我希望它从第三个片段开始，然后向右滑动以转到片段 2，依此类推。

感谢阅读:)

【参考方案1】：

设置适配器后，只需在 mViewPager 中设置当前项目。

 // Set up the ViewPager with the sections adapter. 
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mSectionsPagerAdapter);
//set the default item to be # 3
    mViewPager.setCurrentItem(3);