java - 单击选项卡布局项目时选项卡未更改

Question

单击选项卡布局(选项卡按钮)时 fragment (选项卡)不会更改

我尝试过以下代码

MainActivity.java

package com.kunal.flightstatus;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;

import android.net.Uri;
import android.os.Bundle;

import com.google.android.material.tabs.TabLayout;

public class MainActivity extends AppCompatActivity {

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

        TabLayout tabLayout = findViewById(R.id.tablayout);
        tabLayout.addTab(tabLayout.newTab().setText("Home"));
        tabLayout.addTab(tabLayout.newTab().setText("Favourite"));
        tabLayout.addTab(tabLayout.newTab().setText("Search"));
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);

        final ViewPager viewPager = findViewById(R.id.viewpager);
        PageAdapter adapter = new PageAdapter(getSupportFragmentManager());
        viewPager.setAdapter(adapter);

    }

}

PagerAdapter.java

package com.kunal.flightstatus;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;


public class PageAdapter extends FragmentPagerAdapter {


    public PageAdapter(@NonNull FragmentManager fm) {
        super(fm);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 0 :
                Tab1 tab1 = new Tab1();
                position +=1;
                Bundle bundle = new Bundle();
                bundle.putString("message","fragment :"+position);
                tab1.setArguments(bundle);
                return tab1;
            case 1 :
                Tab2 tab2 = new Tab2();
                position +=1;
                Bundle bundl = new Bundle();
                bundl.putString("message","fragment :"+position);
                tab2.setArguments(bundl);
                return tab2;
            case 2 :
                Tab3 tab3 = new Tab3();
                position +=1;
                Bundle bundlee = new Bundle();
                bundlee.putString("message","fragment :"+position);
                tab3.setArguments(bundlee);
                return tab3;
            default:
                return null;
        }
    }

    @Override
    public int getCount() {
        return 3;
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <com.google.android.material.tabs.TabLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tablayout"
        android:background="@color/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    </com.google.android.material.tabs.TabLayout>

    <androidx.viewpager.widget.ViewPager
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:id="@+id/viewpager">

    </androidx.viewpager.widget.ViewPager>

</LinearLayout>

选项卡( fragment )应在单击选项卡布局项目时更改

Answer 1

需要链接 ViewPager 和 TabLayout 才能进行选项卡切换。

tabLayout.setupWithViewPager(viewPager);

应该可以解决问题。

这样 TabLayout 将连接到 ViewPager 并自动填充。在 FragmentPagerAdapter 中实现 CharSequence getPageTitle (intposition) 来填充标题，而不是手动调用 tabLayout.addTab():

@NonNull
private List<String> titles = Arrays.asList("Home", "Favourite", "Search");

@Override
public CharSequence getPageTitle (int position) {
    return titles.get(position);
}

整个设置如下所示:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <com.google.android.material.tabs.TabLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tablayout"
        android:background="@color/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:tabGravity="fill" />

    <androidx.viewpager.widget.ViewPager
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:id="@+id/viewpager" />

</LinearLayout>

Activity :

package com.kunal.flightstatus;

import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;

import android.os.Bundle;

import com.google.android.material.tabs.TabLayout;

public class MainActivity extends AppCompatActivity {

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

        final ViewPager viewPager = findViewById(R.id.viewpager);
        PageAdapter adapter = new PageAdapter(getSupportFragmentManager());
        viewPager.setAdapter(adapter);

        TabLayout tabLayout = findViewById(R.id.tablayout);
        tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
        tabLayout.setupWithViewPager(viewPager);
    }

}

寻呼机适配器:

package com.kunal.flightstatus;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;

import java.util.Arrays;
import java.util.List;


public class PageAdapter extends FragmentPagerAdapter {
    @NonNull
    private List<String> titles = Arrays.asList("Home", "Favourite", "Search");

    public PageAdapter(@NonNull FragmentManager fm) {
        super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
    }

    @Override
    public CharSequence getPageTitle (int position) {
        return titles.get(position);
    }

    @NonNull
    @Override
    public Fragment getItem(int position) {
        switch (position){
            case 0 :
                Tab1 tab1 = new Tab1();
                position +=1;
                Bundle bundle = new Bundle();
                bundle.putString("message","fragment :"+position);
                tab1.setArguments(bundle);
                return tab1;
            case 1 :
                Tab2 tab2 = new Tab2();
                position +=1;
                Bundle bundl = new Bundle();
                bundl.putString("message","fragment :"+position);
                tab2.setArguments(bundl);
                return tab2;
            case 2 :
                Tab3 tab3 = new Tab3();
                position +=1;
                Bundle bundlee = new Bundle();
                bundlee.putString("message","fragment :"+position);
                tab3.setArguments(bundlee);
                return tab3;
            default:
                throw new IllegalStateException();
        }
    }

    @Override
    public int getCount() {
        return 3;
    }
}