Android 事件分发与滑动冲突全解：从原理到 Tab + ViewPager + RecyclerView 实战

// frameworks/base/core/java/android/view/View.java（语义简化）
public boolean dispatchTouchEvent(MotionEvent event) {
    // 1. OnTouchListener.onTouch
    // 2. onTouchEvent
    // 返回 true：本 View 消费，事件链在此终止（对当前 dispatch 路径而言）
    // 返回 false：未消费，事件向上回溯，交给父 View 的 onTouchEvent
}

// frameworks/base/core/java/android/view/ViewGroup.java（语义简化）
public boolean onInterceptTouchEvent(MotionEvent ev) {
    // 返回 false：不拦截，事件继续传给子 View
    // 返回 true：拦截，后续 MOVE/UP 不再给子 View，改由本 ViewGroup 处理
    //            子 View 会收到 ACTION_CANCEL
}

public boolean onTouchEvent(MotionEvent event) {
    // 返回 true：本 View 声明消费该事件序列
    // 返回 false：不消费，事件继续向上冒泡
}

// ViewGroup.dispatchTouchEvent 逻辑骨架（AOSP 简化）
public boolean dispatchTouchEvent(MotionEvent ev) {
    final int action = ev.getActionMasked();
    boolean intercept = false;
 
    if (action == ACTION_DOWN) {
        cancelTouchTarget();           // 新手势，清空旧状态
    } else if (action == ACTION_MOVE) {
        intercept = onInterceptTouchEvent(ev);
    }
 
    TouchTarget target = mFirstTouchTarget;
 
    if (!intercept && target != null) {
        // 分发给已捕获 DOWN 的子 View
        return dispatchTransformedTouchEvent(ev, false, target.child, target.pointerId);
    }
 
    // 无子 View 消费，或已拦截 → 自己处理
    return onTouchEvent(ev);
}

<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
 
    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tabLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
 
    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/viewPager"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />
</LinearLayout>

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/rvHorizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

fun RecyclerView.setupHorizontalNestedScrollWithViewPager() {
    var initialX = 0f
    var initialY = 0f
 
    addOnItemTouchListener(object : RecyclerView.SimpleOnItemTouchListener() {
        override fun onInterceptTouchEvent(rv: RecyclerView, e: MotionEvent): Boolean {
            when (e.actionMasked) {
                MotionEvent.ACTION_DOWN -> {
                    initialX = e.x
                    initialY = e.y
                    // 默认先不让 ViewPager2 抢
                    rv.parent?.requestDisallowInterceptTouchEvent(true)
                }
                MotionEvent.ACTION_MOVE -> {
                    val dx = e.x - initialX
                    val dy = e.y - initialY
                    if (abs(dx) <= abs(dy)) {
                        // 纵向为主：交给外层（若外层有竖滑容器）
                        rv.parent?.requestDisallowInterceptTouchEvent(false)
                        return false
                    }
                    val canScrollLeft = rv.canScrollHorizontally(-1)
                    val canScrollRight = rv.canScrollHorizontally(1)
                    val scrollingLeft = dx > 0   // 手指右滑，内容向左
                    val scrollingRight = dx < 0
 
                    val innerCanConsume = when {
                        scrollingLeft && canScrollLeft -> true
                        scrollingRight && canScrollRight -> true
                        else -> false
                    }
                    rv.parent?.requestDisallowInterceptTouchEvent(innerCanConsume)
                }
                MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
                    rv.parent?.requestDisallowInterceptTouchEvent(false)
                }
            }
            return false  // 不拦截，让 RV 自己滚
        }
    })
}

class NestedHorizontalRecyclerView @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0
) : RecyclerView(context, attrs, defStyleAttr) {
 
    private var lastX = 0f
    private var lastY = 0f
 
    override fun dispatchTouchEvent(ev: MotionEvent): Boolean {
        when (ev.actionMasked) {
            MotionEvent.ACTION_DOWN -> {
                lastX = ev.x
                lastY = ev.y
                parent.requestDisallowInterceptTouchEvent(true)
            }
            MotionEvent.ACTION_MOVE -> {
                val dx = ev.x - lastX
                val dy = ev.y - lastY
                if (abs(dx) > abs(dy)) {
                    val canScroll = if (dx > 0) canScrollHorizontally(-1)
                                    else canScrollHorizontally(1)
                    parent.requestDisallowInterceptTouchEvent(canScroll)
                } else {
                    parent.requestDisallowInterceptTouchEvent(false)
                }
            }
            MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
                parent.requestDisallowInterceptTouchEvent(false)
            }
        }
        return super.dispatchTouchEvent(ev)
    }
}

class NestedScrollViewPager2 @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null
) : ViewPager2(context, attrs) {
 
    private var initialX = 0f
    private var initialY = 0f
 
    override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {
        when (ev.actionMasked) {
            MotionEvent.ACTION_DOWN -> {
                initialX = ev.x
                initialY = ev.y
                parent?.requestDisallowInterceptTouchEvent(true)
            }
            MotionEvent.ACTION_MOVE -> {
                val dx = ev.x - initialX
                val dy = ev.y - initialY
                if (abs(dx) <= abs(dy)) return false
 
                val innerRv = findInnerRecyclerView()
                val innerCanScroll = innerRv?.let { rv ->
                    if (dx > 0) rv.canScrollHorizontally(-1) else rv.canScrollHorizontally(1)
                } ?: false
 
                if (innerCanScroll) return false  // 不 intercept，留给内层
            }
        }
        return super.onInterceptTouchEvent(ev)
    }
 
    private fun findInnerRecyclerView(): RecyclerView? {
        // 当前页 Fragment 根布局中的横向 RV，按 id 查找或接口回调
        return (getChildAt(0) as? RecyclerView)
            ?.findViewById(R.id.rvHorizontal)
    }
}

viewPager.isUserInputEnabled = false

override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {
    val intercept = super.onInterceptTouchEvent(ev)
    Log.d("Touch", "${this::class.simpleName}.onIntercept ${ev.actionToString()} → $intercept")
    return intercept
}