android - CollapsingToolbarLayout 折叠时滚动停止

Question

我将 CoordinatorLayout 与 AppBarLayout 和 CollapsingToolbarLayout 一起使用。内容还有一个 NestedScrollView。当我在 CollapsingToolbarLayout 上滚动时，当 CollapsingToolbarLayout 折叠时滚动停止。我想要的是继续滚动 NestedScrollView 的内容。当我在 NestedScrollView 上滚动时，它一直滚动到内容的末尾。 CollapsingToolbarLayout 按预期折叠。

视频链接:http://sendvid.com/m7d0mq2q

在视频中，正如您在第一次滚动中看到的那样，当 CollapsingToolbarLayout 折叠时它停止滚动。

我的布局:

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.journaldev.collapsingtoolbarlayout.ScrollingActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/app_bar"
        android:layout_width="match_parent"
        android:layout_height="400dp"
        android:fitsSystemWindows="true"
        android:theme="@style/AppTheme.AppBarOverlay">

        <com.google.android.material.appbar.CollapsingToolbarLayout
            android:id="@+id/toolbar_layout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">


            <ImageView
                android:id="@+id/expandedImage"
                android:layout_width="match_parent"
                android:layout_height="400dp"
                android:scaleType="centerCrop"
                android:src="@drawable/photo"/>

            <androidx.appcompat.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/AppTheme.PopupOverlay" />

        </com.google.android.material.appbar.CollapsingToolbarLayout>
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="@dimen/text_margin"
            android:text="@string/large_text" />

    </androidx.core.widget.NestedScrollView>

</androidx.coordinatorlayout.widget.CoordinatorLayout>

我的 Activity :

package com.journaldev.collapsingtoolbarlayout;

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;

import com.google.android.material.appbar.AppBarLayout;

public class ScrollingActivity extends AppCompatActivity {


    private Menu menu;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scrolling);
        final Toolbar mToolbar = this.findViewById(R.id.toolbar);
        setSupportActionBar(mToolbar);

        AppBarLayout mAppBarLayout = (AppBarLayout) findViewById(R.id.app_bar);
        mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            boolean isShow = false;
            int scrollRange = -1;

            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                if (scrollRange == -1) {
                    scrollRange = appBarLayout.getTotalScrollRange();
                }
                if (scrollRange + verticalOffset == 0) {
                    isShow = true;
                    showOption(R.id.action_info);
                } else if (isShow) {
                    isShow = false;
                    hideOption(R.id.action_info);
                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        this.menu = menu;
        getMenuInflater().inflate(R.menu.menu_scrolling, menu);
        hideOption(R.id.action_info);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        } else if (id == R.id.action_info) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    private void hideOption(int id) {
        MenuItem item = menu.findItem(id);
        item.setVisible(false);
    }

    private void showOption(int id) {
        MenuItem item = menu.findItem(id);
        item.setVisible(true);
    }
}

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.journaldev.collapsingtoolbarlayout"
        minSdkVersion 21
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    implementation "androidx.appcompat:appcompat:1.0.2"
    implementation "com.google.android.material:material:1.1.0-alpha04"
    testCompile 'junit:junit:4.12'
}

Answer 1

当我们在 ScrollView (即 RecyclerView)上执行 fling 操作时，一切都按预期进行。所以我的解决方案的想法是忽略 AppBarLayout 的一闪而过并将完全相同的参数传递给 ScrollView (在我的例子中是 RecyclerView)。因此，我们只需要为此类提供适当的 ScrollView (很可能它也适用于其他 View ，即 NestedScrollView)。作为奖励，我的自定义行为还不仅解决了大多数华为设备上出现的丑陋抖动问题(如果不感兴趣，只需删除 onNestedPreFling 方法)。有关此问题的更多详细信息:CollapsingToolbarLayout flickers while scrolling down

/**
 * Customized app bar provides 2 features:
 * 1. Force AppBarLayout to stop fling when nested view starts fling, otherwise scrolling view fling collides with AppBarLayout fling
 * 2. Ignore AppBarLayout fling and transfer it to scrolling view. This is done in order to continue page scroll when AppBarLayout
 * fully collapses (now after collapse scroll stops)
 */

class SmoothAppBarBehavior : AppBarLayout.Behavior() {

    companion object {
        private const val FLING_UNITS = 1000 //copied from base class
    }

    var recyclerView: RecyclerView? = null
    private var overScroller: OverScroller? = null
    private var pointerId = -1
    private var velocityTracker: VelocityTracker? = null

    override fun onNestedPreFling(coordinatorLayout: CoordinatorLayout,
                                  child: AppBarLayout,
                                  target: View,
                                  velocityX: Float,
                                  velocityY: Float): Boolean {
        stopAppBarLayoutFling()
        return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY)
    }

    override fun onInterceptTouchEvent(parent: CoordinatorLayout,
                                       child: AppBarLayout,
                                       ev: MotionEvent): Boolean {
        val consumed = super.onInterceptTouchEvent(parent, child, ev)
        when (ev.actionMasked) {
            MotionEvent.ACTION_DOWN -> {
                ensureVelocityTracker()              
                recyclerView?.stopScroll()
                pointerId = ev.getPointerId(0)
            }
            MotionEvent.ACTION_CANCEL -> {
                velocityTracker?.recycle()
                velocityTracker = null
                pointerId = -1
            }
            else -> {}
        }
        return consumed
    }

    override fun onTouchEvent(parent: CoordinatorLayout,
                              child: AppBarLayout,
                              ev: MotionEvent): Boolean {
        val consumed = super.onTouchEvent(parent, child, ev)
        recyclerView?.let {
            when (ev.actionMasked) {
                MotionEvent.ACTION_DOWN -> {
                    ensureVelocityTracker()
                    pointerId = ev.getPointerId(0)
                }
                MotionEvent.ACTION_UP -> {
                    stopAppBarLayoutFling()
                    recyclerView?.fling(0, getYVelocity(ev))
                }
                MotionEvent.ACTION_CANCEL -> {
                    velocityTracker?.recycle()
                    velocityTracker = null
                    pointerId = -1
                }
                else -> {}
            }
            velocityTracker?.addMovement(ev)
        }
        return consumed
    }

    private fun ensureVelocityTracker() {
        if (velocityTracker == null) {
            velocityTracker = VelocityTracker.obtain()
        }
    }

    private fun getYVelocity(event: MotionEvent): Int {
        velocityTracker?.let {
            it.addMovement(event)
            it.computeCurrentVelocity(FLING_UNITS)
            return - it.getYVelocity(pointerId).toInt()
        }
        return 0
    }

    private fun stopAppBarLayoutFling() {
        if (overScroller == null) {
            val scrollerField = javaClass.superclass.superclass.superclass.getDeclaredField("scroller")
            scrollerField.isAccessible = true
            overScroller = scrollerField.get(this) as? OverScroller
        }
        overScroller?.forceFinished(true)
    }
}