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希望SDK不会出错：BottomSheetBehavior中的嵌套滚动问题

也许每个人都喜欢欣赏美丽的窗口，工具栏和其他视图，并且可以顺畅地朝不同的方向移动，思考它的工作原理，甚至还可以阅读有关CoordianatorLayout，各种Behaivor的内容，从而可以在android视图上创建字面上的魔术。当然，您可以编写具有所需行为的自定义视图，这只能受您的想象力或对Android开发的了解所限制。但是除此之外，还有一个限制-时间，您将不会在有时间限制的项目中在黑客马拉松上编写自定义视图，并且使用自定义视图预先编写的决策不能在短时间内被团队成员掌握。到那时，最简单，最合乎逻辑的问题解决方案就来了-不要炫耀，请使用标准的Android工具，聪明的人坐在那里，一切都会用巧克力（好吧，或者其他Android糖果）。


但是，并非所有事情都那么简单，这就是我与CoordinatorLayout，BottomSheetBehavior之类的魔术师的熟识开始的地方，或者是开发人员在编写它们时忽略的错误。本文将介绍使用BottomSheetBehavior的行为识别与视图组件内部的嵌套滚动相关的错误的过程，以及解决该错误的方法。


协调器布局动画


首次见面


我的任务是使用包含水平RecyclerView，ScrollView和CoordinatorLayout的嵌套滚动来使功能简单，正是他允许在Behavior的嵌套视图的引导下执行特技飞行，例如平滑各种视图的任意移动。


目的动画


: CoordinatorLayout, , RecyclerView, android.material BottomSheetBehavior, , . item- , TextView — item-, NestedScrollView, ( TextView).


NestedScrollViewMeme


activity_main.xml


<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.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_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:nestedScrollingEnabled="false"
        app:behavior_hideable="false"
        app:behavior_peekHeight="80dp"
        app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>

recycler_item.xml


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/item_bottom_sheet"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?attr/colorControlHighlight"
    android:orientation="vertical">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:background="@color/colorAccent"
        android:text="@string/head_text"
        android:textAlignment="center"
        android:textColor="@android:color/white"
        android:textSize="24sp" />

    <androidx.core.widget.NestedScrollView
        android:id="@+id/scroll_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:id="@+id/item_text_view"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textAlignment="center"
            android:textSize="24sp" />
    </androidx.core.widget.NestedScrollView>
</LinearLayout>

NestedScrollView? , Android, , ScrollView, , , , .


layout, RecyclerView.Adapter RecyclerView.ViewHolder, , , ...


RecyclerViewAdapter.kt


import android.content.Context
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView

class RecyclerViewAdapter(private val context: Context, private val itemList: List<ItemModel>) :
    RecyclerView.Adapter<RecyclerViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerViewHolder {
        return RecyclerViewHolder.create(context, parent)
    }

    override fun getItemCount() = itemList.size

    override fun onBindViewHolder(holder: RecyclerViewHolder, position: Int) {
        holder.bind(itemList[position])
    }
}

RecyclerViewHolder.kt


import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.core.widget.NestedScrollView
import androidx.recyclerview.widget.RecyclerView

class RecyclerViewHolder(view: View) : RecyclerView.ViewHolder(view) {

    fun bind(model: ItemModel) {
        val textView: TextView = itemView.findViewById(R.id.item_text_view)
        val scrollView = itemView.findViewById(R.id.scroll_view) as NestedScrollView
        textView.text = ""
        for (i in 1..50) {
            textView.append(model.number.toString() + "\n")
        }
    }

    companion object {
        fun create(context: Context, parent: ViewGroup): RecyclerViewHolder {
            return RecyclerViewHolder(
                LayoutInflater.from(context).inflate(
                    R.layout.recycler_item,
                    parent,
                    false
                )
            )
        }
    }
}

ItemModel.kt


data class ItemModel(val number: Int)

MainActvity.kt


import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private val itemList = arrayListOf<ItemModel>().apply {
        for (i in 0..100) {
            this.add(ItemModel(i))
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        recycler_view.layoutManager =
            LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false)
        recycler_view.adapter = RecyclerViewAdapter(this, itemList)
    }
}

, , , … ? , NestedScrollView , ? recycler item, … … item- , , item-. RecyclerView, — View, Recycler , . , - NestedScrollView, .



, — item- . onScrollChange:


scrollView.setOnScrollChangeListener { v: NestedScrollView?, scrollX: Int, scrollY: Int, oldScrollX: Int, oldScrollY: Int ->
    Log.i("TAG", "OnScrollChange")
}

item , … , - , :


scrollView.setOnTouchListener { view, motionEvent ->
    Log.i("TAG", motionEvent.toString())
    false
}

, , , , , , , , , , - - , , .



截距


, , . ? , NestedScrollView OnTouch. item-:


itemView.setOnTouchListener { view, motionEvent ->
    Log.i("TAG", motionEvent.toString())
    false
}

. , recycler, , . : CoordinatorLayout, — item-, .


, CoordinatorLayout, , , — CoordinatorLayout, , FrameLayout. , RecyclerView material — BottomSheetBehavior. , , .


BottomSheetBehavior


BottomSheetBehavior — java , CoordinatorLayout.Behavior, (CoordinatorLayout). , , . ? BottomSheetBehavior TestBehavior, , , -. RecyclerView .

TestBehavior.java


import android.content.Context;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.coordinatorlayout.widget.CoordinatorLayout;

import com.google.android.material.bottomsheet.BottomSheetBehavior;

public class TestBehavior<V extends View> extends BottomSheetBehavior<V> {

    public TestBehavior(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onInterceptTouchEvent(@NonNull CoordinatorLayout parent, @NonNull V child, @NonNull MotionEvent event) {
        Log.i("TAG", "onInterceptTouchEvent");
        return super.onInterceptTouchEvent(parent, child, event);
    }

    @Override
    public void onRestoreInstanceState(
            @NonNull CoordinatorLayout parent, @NonNull V child, @NonNull Parcelable state) {
        Log.i("TAG", "onRestoreInstanceState");
        super.onRestoreInstanceState(parent, child, state);
    }

    @Override
    public void onAttachedToLayoutParams(@NonNull CoordinatorLayout.LayoutParams layoutParams) {
        Log.i("TAG", "onAttachedToLayoutParams");
        super.onAttachedToLayoutParams(layoutParams);
    }

    @Override
    public void onDetachedFromLayoutParams() {
        Log.i("TAG", "onDetachedFromLayoutParams");
        super.onDetachedFromLayoutParams();
    }

    @Override
    public boolean onLayoutChild(
            @NonNull CoordinatorLayout parent, @NonNull V child, int layoutDirection) {
        Log.i("TAG", "onLayoutChild");
        return super.onLayoutChild(parent, child, layoutDirection);
    }

    @Override
    public boolean onTouchEvent(
            @NonNull CoordinatorLayout parent, @NonNull V child, @NonNull MotionEvent event) {
        Log.i("TAG", "onTouchEvent " + event.toString());
        return super.onTouchEvent(parent, child, event);
    }

    @Override
    public boolean onStartNestedScroll(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View directTargetChild,
            @NonNull View target,
            int axes,
            int type) {
        Log.i("TAG", "onStartNestedScroll");
        return super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, axes, type);
    }

    @Override
    public void onNestedPreScroll(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View target,
            int dx,
            int dy,
            @NonNull int[] consumed,
            int type) {
        Log.i("TAG", "onNestedPreScroll");
        super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
    }

    @Override
    public void onStopNestedScroll(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View target,
            int type) {
        Log.i("TAG", "onStopNestedScroll");
        super.onStopNestedScroll(coordinatorLayout, child, target, type);
    }

    @Override
    public void onNestedScroll(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View target,
            int dxConsumed,
            int dyConsumed,
            int dxUnconsumed,
            int dyUnconsumed,
            int type,
            @NonNull int[] consumed) {
        Log.i("TAG", "onNestedScroll");
        super.onNestedScroll(coordinatorLayout, child, target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type, consumed);
    }

    @Override
    public boolean onNestedPreFling(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View target,
            float velocityX,
            float velocityY) {
        Log.i("TAG", "onNestedPreFling");
        return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
    }
}

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:nestedScrollingEnabled="false"
        app:behavior_hideable="false"
        app:behavior_peekHeight="80dp"
        app:layout_behavior=".TestBehavior" />

. item- : onInterceptTouchEvent, onStartNestedScroll, onNestedPreScroll, onNestedScroll, onStopNestedScroll. : onInterceptTouchEvent, onStartNestedScroll, onNestedPreScroll, onStopNestedScroll. , onNestedPreScroll . onNestedPreScroll BottomSheetBehavior , , , :


View scrollingChild = nestedScrollingChildRef != null ? nestedScrollingChildRef.get() : null;
if (target != scrollingChild) {
  return;
}

, nestedScrollingChildRef? View, View, CoordinatorLayout View, .


  @Nullable WeakReference<View> nestedScrollingChildRef;

, onLayoutChild:


  @Override
  public boolean onLayoutChild(
      @NonNull CoordinatorLayout parent, @NonNull V child, int layoutDirection) {
      ...
      nestedScrollingChildRef = new WeakReference<>(findScrollingChild(child));
      return true;
  }

Recycler, , item, View, BottomSheetBehavior, , , View , , — . , .



, ? - view Recycler-, , , BottomSheetBehavior , , : (: , ) Java Reflection API. , .


Java Reflection API


反思模因


Java Reflection API, TestBeahvior, Runtime , , , onStartNestedScroll, onNestedPreScroll.


import android.content.Context;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.coordinatorlayout.widget.CoordinatorLayout;

import com.google.android.material.bottomsheet.BottomSheetBehavior;

import java.lang.ref.WeakReference;
import java.lang.reflect.Field;

public class TestBeahvior<V extends View> extends BottomSheetBehavior<V> {

    public TestBeahvior(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onStartNestedScroll(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View directTargetChild,
            @NonNull View target,
            int axes,
            int type) {
        try {
            Field nestedScrollingChildRefField = this.getClass().getSuperclass().getDeclaredField("nestedScrollingChildRef");
            nestedScrollingChildRefField.setAccessible(true);
            nestedScrollingChildRefField.set(this, new WeakReference<>(target));
        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }
        return super.onStartNestedScroll(coordinatorLayout, child, directTargetChild, target, axes, type);
    }
}


这里的一切都很简单，复制BottomSheetBehavior类，添加私有方法refreshNestedScrollingChildRef，这将更新链接对象的内容，并在onStartNestedScroll方法中调用此方法。完成，一切正常。


private void refreshNestedScrollingChildRef(View view) {
    nestedScrollingChildRef = new WeakReference<>(view);
}

    @Override
    public boolean onStartNestedScroll(
            @NonNull CoordinatorLayout coordinatorLayout,
            @NonNull V child,
            @NonNull View directTargetChild,
            @NonNull View target,
            int axes,
            int type) {
        refreshNestedScrollingChildRef(target);
        ...
    }

结论


Android开发人员提供了许多出色且功能良好的工具，但这并不意味着它们都能完美运行。在我的情况下，您总能找到标准工具无法使用的情况。


所有有趣的案例！

Source: https://habr.com/ru/post/undefined/

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