如何让底部导航Activity通过滑动改变片段？

Question

我使用适当的 android studio 模板创建了一个新活动：新建->活动->底部导航活动。我向 AppBarConfiguration 添加了 5 个片段，除了一个片段之外一切都工作正常 - 它不提供水平滑动行为。我发现的所有关于使用 ViewPager 或 ViewPager2 作为带有 BottomNavigationView 的片段容器/管理器的示例。但我想有更简单的方法来做到这一点，因为所有导航和片段管理已经由导航组件执行。请指导我这里的正确方法 - 如何添加滑动行为。以防万一 - 我的代码：

活动布局：

<?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"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <!--android:paddingTop="?attr/actionBarSize"-->

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/nav_view"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="0dp"
        android:layout_marginEnd="0dp"
        android:background="?android:attr/windowBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:menu="@menu/bottom_nav_menu" />

    <fragment
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:defaultNavHost="true"
        app:layout_constraintBottom_toTopOf="@+id/nav_view"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:navGraph="@navigation/mobile_navigation" />

</androidx.constraintlayout.widget.ConstraintLayout>

活动.kt：

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(R.layout.activity_main)
        val navView: BottomNavigationView = findViewById(R.id.nav_view)

        val navController = findNavController(R.id.nav_host_fragment)

        // Passing each menu ID as a set of Ids because each
        // menu should be considered as top level destinations.

        val appBarConfiguration = AppBarConfiguration(
            setOf(
                R.id.navigation_whatsNow, R.id.navigation_lessons_schedule,
                R.id.navigation_callsSchedule, R.id.navigation_myTeachers,
                R.id.navigation_subjects
            )
        )
        setupActionBarWithNavController(navController, appBarConfiguration)
        navView.setupWithNavController(navController)
    }

    override fun onSupportNavigateUp(): Boolean {
        val navController = findNavController(R.id.nav_host_fragment)
        return navController.navigateUp()
    }

}

Answer 1

你需要实现SwipeListener，但我只知道java中的方法。我会用JAVA来指导，希望对你有帮助。

OnSwipeListener.java：

import android.content.Context;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;



public class OnSwipeListener implements OnTouchListener {

private final GestureDetector gestureDetector;

public OnSwipeListener (Context ctx){
    gestureDetector = new GestureDetector(ctx, new GestureListener());
}

@Override
public boolean onTouch(View v, MotionEvent event) {
    return gestureDetector.onTouchEvent(event);
}

private final class GestureListener extends SimpleOnGestureListener {

    private static final int SWIPE_THRESHOLD = 100;
    private static final int SWIPE_VELOCITY_THRESHOLD = 100;

    @Override
    public boolean onDown(MotionEvent e) {
        return true;
    }

    @Override
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
        boolean result = false;
        try {
            float diffY = e2.getY() - e1.getY();
            float diffX = e2.getX() - e1.getX();
            if (Math.abs(diffX) > Math.abs(diffY)) {
                if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
                    if (diffX > 0) {
                        onSwipeRight();
                    } else {
                        onSwipeLeft();
                    }
                    result = true;
                }
            }
            else if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
                if (diffY > 0) {
                    onSwipeBottom();
                } else {
                    onSwipeTop();
                }
                result = true;
            }
        } catch (Exception exception) {
            exception.printStackTrace();
        }
        return result;
    }
}

public void onSwipeRight() {
}

public void onSwipeLeft() {
}

public void onSwipeTop() {
}

public void onSwipeBottom() {
}
}

用法如下：

frameLayout.setOnTouchListener(new OnSwipeTouchListener(MyActivity.this) {
public void onSwipeTop() {
    Toast.makeText(MyActivity.this, "top", Toast.LENGTH_SHORT).show();
}
public void onSwipeRight() {

    // todo function to change fragments something like 
    getSupportFragmentManager().beginTransaction()
                                .setCustomAnimations(
                                        R.anim.slide_in,  // enter
                                        R.anim.slide_out // exit
                                )
                                .replace(R.id.fragmentContainer,
                                        selectedFragment).commit();                            

    Toast.makeText(MyActivity.this, "right", Toast.LENGTH_SHORT).show();
}
public void onSwipeLeft() {
    Toast.makeText(MyActivity.this, "left", Toast.LENGTH_SHORT).show();
}
public void onSwipeBottom() {
    Toast.makeText(MyActivity.this, "bottom", Toast.LENGTH_SHORT).show();
}

});

Answer 2

对于Laun的回答，您还可以通过执行BottomNavigationView.setSelectedItemId()而不是片段事务方式来做得更好。