不在 androidx.viewpager2.widget.ViewPager2 中显示片段并且不滑动：

Question

在我的 app/build.gradle 中：

android {
    viewBinding.enabled = true
    dataBinding {
        enabled = true
    }

在我的活动中：

import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import androidx.viewpager2.widget.ViewPager2

import com.myproject.BuildConfig
import com.myproject.R
import com.myproject.adapter.CustomFragmentStateAdapter
import com.myproject.databinding.QrBluetoothSwipeActivityBinding
import com.myproject.ui.fragment.BluetoothPageFragment
import com.myproject.ui.fragment.QrPageFragment
import androidx.databinding.DataBindingUtil
import androidx.databinding.ObservableInt

class QRBluetoothSwipeActivity : AppCompatActivity() {

    private lateinit var viewBinding: QrBluetoothSwipeActivityBinding

    var positionObservable = ObservableInt()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewBinding = QrBluetoothSwipeActivityBinding.inflate(layoutInflater)
        setContentView(viewBinding.root)
        val customFragmentStateAdapter = CustomFragmentStateAdapter(this)
        customFragmentStateAdapter.addFragment(QrPageFragment())
        customFragmentStateAdapter.addFragment(BluetoothPageFragment())
        viewBinding.viewPager2.adapter = customFragmentStateAdapter
    }
}

我的自定义适配器： CustomFragmentStateAdapter

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;

public class CustomFragmentStateAdapter extends FragmentStateAdapter {

    private ArrayList<Fragment> arrayList = new ArrayList<>();

    public CustomFragmentStateAdapter(FragmentActivity fa) {
        super(fa);
    }

    public void addFragment(Fragment fragment) {
        arrayList.add(fragment);
    }

    @Override
    public int getItemCount() {
        return arrayList.size();
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        // return your fragment that corresponds to this 'position'
        return arrayList.get(position);
    }
}

并在qr_bluetooth_swipe_activity.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    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:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager2"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toTopOf="@+id/bottonContainer"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</layout>

结果 viewPager2 成功初始化和成功滑动。 第一个屏幕是我的第一个片段QrPageFragment ，第二个屏幕是BluetoothPageFragment 。

好的。 它工作正常。

现在我想使用数据绑定。 所以这里改变了我的活动：

class QRBluetoothSwipeActivity : AppCompatActivity() {
    private lateinit var viewBinding: QrBluetoothSwipeActivityBinding
    var positionObservable = ObservableInt()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewBinding = QrBluetoothSwipeActivityBinding.inflate(layoutInflater)
        setContentView(viewBinding.root)
        val binding = DataBindingUtil.setContentView<QrBluetoothSwipeActivityBinding>(this, R.layout.qr_bluetooth_swipe_activity)
        binding.setHandler(this)

        val customFragmentStateAdapter = CustomFragmentStateAdapter(this)
        customFragmentStateAdapter.addFragment(QrPageFragment())
        customFragmentStateAdapter.addFragment(BluetoothPageFragment())
        viewBinding.viewPager2.adapter = customFragmentStateAdapter
    }
}

在 xml 中：

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <data>

        <import type="android.view.View" />

        <variable
            name="handler"
            type="com.myproject.android.ui.actviity.QRBluetoothSwipeActivity" />

    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <androidx.viewpager2.widget.ViewPager2
            android:id="@+id/viewPager2"
            android:layout_width="0dp"
            android:layout_height="0dp"
            app:layout_constraintBottom_toTopOf="@+id/bottonContainer"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</layout>

但现在viewPager2显示，但不显示我的片段。 而且我不能刷卡。 为什么？

Answer 1

请试试这个

    class QRBluetoothSwipeActivity : AppCompatActivity() {
    private lateinit var viewBinding: QrBluetoothSwipeActivityBinding
    var positionObservable = ObservableInt()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        viewBinding = DataBindingUtil.setContentView<QrBluetoothSwipeActivityBinding>(this, R.layout.qr_bluetooth_swipe_activity)
        binding.setHandler(this)

        val customFragmentStateAdapter = CustomFragmentStateAdapter(this)
        customFragmentStateAdapter.addFragment(QrPageFragment())
        customFragmentStateAdapter.addFragment(BluetoothPageFragment())
        viewBinding.viewPager2.adapter = customFragmentStateAdapter
    }
}