在 android 选项卡滑动或 select 上更改按钮文本

Question

我在选项卡 activity 上有一个按钮，现在每次滑动 activity 或选择另一个选项卡时，我想根据片段的索引更改按钮文本。我怎么做？

我刚刚按照本教程创建了 android 选项卡： https://www.youtube.com/watch?v=00LLd7qr9sA 它基本上是默认选项卡 activity，它只是为每个片段创建了一个 java 和 xml 文件。

这是我的 main_activity.java

import android.support.design.widget.TabLayout;
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.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;


public class MainActivity extends AppCompatActivity{

    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;
    Button buttonChangeMyText;


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

        buttonChangeMyText= (Button)findViewById(R.id.btnChange);


        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);


        anoNa=mViewPager.getCurrentItem();


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

    }


    @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_screen, 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);
    }

/*
    @Override
    public void onPageSelected(View v) {
        TextView tv = (TextView) v.getRootView().findViewById(R.id.textViewSaUna);
        tv.setText("Welcome To Android");
    }*/


    /**
     * 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) {
            switch (position){
                case 0:
                    Tab1_First tab1 = new Tab1_First();
                    return tab1;
                case 1:
                    Tab2_Second tab2 = new Tab2_Second();
                    return tab2;
                case 2:
                    Tab3_Third tab3 = new Tab3_Third();
                    return tab3;
                default:
                    return null;

            }

        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "ONE";
                case 1:
                    return "TWO";
                case 2:
                    return "THREE";
            }
            return null;
        }
    }//end ng fragment adapter
}

这是片段的java代码。

import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;

public class Tab1_Una extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
       View rootView = inflater.inflate(R.layout.tab1_una, container, false);

        return rootView;
    }

}

这是 main_activity 的 xml。

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.example.lat.sampletabs.MainScreen">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="@dimen/appbar_padding_top"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|enterAlways"
            app:popupTheme="@style/AppTheme.PopupOverlay"


            >

        </android.support.v7.widget.Toolbar>

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

    </android.support.design.widget.AppBarLayout>

    <Button
        android:id="@+id/btnChange"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="120dp"
        android:layout_marginTop="500dp"
        android:text="Change the text"/>


    <android.support.v4.view.ViewPager
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />


</android.support.design.widget.CoordinatorLayout>

Answer 1

您需要将 OnPageChangeListener 添加到您的 mViewPager 中，如下所示：

mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
            // position = Current tab index being scrolled from

        }

        @Override
        public void onPageSelected(int position) {
            // position = New tab index
            switch (position) {
                case 0:
                    buttonChangeMyText.setText("Some text");
                    break;
                case 1:
                    buttonChangeMyText.setText("Some other text");
                    break;
                case 2:
                    buttonChangeMyText.setText("Some other other text");
                    break;
                // ...
            }
        }

        @Override
        public void onPageScrollStateChanged(int state) {
            // state = Tells when the user begins dragging, when the pager is 
            // automatically settling to the current page, or when it is fully stopped/idle.

        }
    });

在 android 选项卡滑动或 select 上更改按钮文本

Change a button text on android tab swipe or select

android

android-fragments

tabs

android-tablayout

android-tabs