小贝子编程

使用默认动画布局更改时滚动视图出现故障



在我的Android应用程序中，我在滚动视图中有一个表单，由一系列通过单选按钮回答的问题组成。每当用户按下单选按钮时，下一个问题都会从底部显示。对于新问题的动画，我使用的是 xml 属性 animateLayoutChanges。问题是，滚动视图不会滚动到显示的下一个问题。

我尝试切换很多属性，但无济于事。唯一有效的方法是将android：layout_gravity：bottom设置为嵌套在滚动视图中的线性布局(ID 为form_container的布局(，但它导致了一个错误，即滚动视图隐藏了顶部的内容离开屏幕并且不允许我向上滚动。

我的 XML

<LinearLayout
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:animateLayoutChanges="true"
    android:clipToPadding="false"
    android:clipChildren="false"
    android:background="@color/colorPrimaryDark">
    <include layout="@layout/progress_bar_container"/>
    <RelativeLayout android:id="@+id/content_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:clipToPadding="false"
        android:clipChildren="false">
        <ScrollView android:id="@+id/form_scroll"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:animateLayoutChanges="true"
            android:padding="20dp"
            android:scrollbars="none"
            android:clipToPadding="false"
            android:clipChildren="false">
            <LinearLayout android:id="@+id/form_container"
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_gravity="bottom"
                android:animateLayoutChanges="true"
                android:layout_height="wrap_content"
                android:clipToPadding="false"
                android:clipChildren="false">
                <LinearLayout
                    android:id="@+id/intro_container"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:clipToPadding="false"
                    android:clipChildren="false">
                    <TextView android:id="@+id/search_title"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:paddingBottom="5dp"
                        android:text="@string/search_title"
                        android:textColor="@android:color/white"
                        android:textSize="24sp"
                        />
                    <TextView
                        android:id="@+id/search_description"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:text="@string/search_description"
                        android:textColor="@android:color/white"
                        android:textSize="22sp"
                        />
                    <ImageView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:paddingBottom="32dp"
                        android:paddingTop="30dp"
                        android:src="@drawable/random" />
                </LinearLayout>
                <LinearLayout android:id="@+id/container1"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:animateLayoutChanges="true"
                    android:orientation="vertical"
                    android:visibility="gone"
                    android:paddingTop="20dp">
                    <TextView
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:paddingBottom="15dp"
                        android:text="whatever"
                        android:textColor="@android:color/white"
                        android:textSize="18sp"
                        />
                    <org.apmem.tools.layouts.FlowLayout android:id="@+id/flow"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:orientation="horizontal" />
                </LinearLayout>
                <LinearLayout android:id="@+id/container2"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:animateLayoutChanges="true"
                    android:visibility="visible"
                    >
                    <TextView
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:paddingBottom="15dp"
                        android:text="whatever2"
                        android:textColor="@android:color/white"
                        android:textSize="18sp"
                        android:typeface="monospace" />
                    <RadioGroup android:id="@+id/radio_group1"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:orientation="horizontal"
                        android:animateLayoutChanges="true"
                        >
                        <android.support.v7.widget.AppCompatRadioButton android:id="@+id/radio1"
                            android:layout_width="0dp"
                            android:layout_weight="1"
                            android:gravity="center"
                            android:paddingStart="20dp"
                            android:layout_height="50dp"
                            android:background="@drawable/radio"
                            android:button="@android:color/transparent"
                            android:text="whatever"
                            android:layout_marginEnd="5dp"
                            />
                        <android.support.v7.widget.AppCompatRadioButton android:id="@+id/radio2"
                            android:layout_marginStart="5dp"
                            android:layout_width="0dp"
                            android:paddingStart="20dp"
                            android:layout_weight="1"
                            android:gravity="center"
                            android:layout_height="50dp"
                            android:background="@drawable/radio"
                            android:button="@android:color/transparent"
                            android:text="whatever"
                            />
                    </RadioGroup>
                </LinearLayout>
                <LinearLayout android:id="@+id/container3"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:visibility="gone"
                    android:orientation="vertical"
                    android:paddingTop="20dp"
                    android:animateLayoutChanges="true"
                    >
                    <TextView
                        android:id="@+id/label"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:paddingBottom="10dp"
                        android:letterSpacing=".07"
                        android:text="@string/confirm"
                        android:textColor="@android:color/white"
                        android:textSize="18sp"
                        android:typeface="monospace" />

                    <include android:id="@+id/search_bar"
                        layout="@layout/custom_dummy_search_view"
                        android:layout_height="60dp"
                        android:layout_width="match_parent"/>
                </LinearLayout>
                <LinearLayout android:id="@+id/container4"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:visibility="gone"
                    android:paddingTop="20dp"
                    android:animateLayoutChanges="true"
                    >
                    <TextView
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:paddingBottom="15dp"
                        android:letterSpacing=".07"
                        android:text="whatever"
                        android:textColor="@android:color/white"
                        android:textSize="18sp"
                        android:typeface="monospace" />
                    <org.apmem.tools.layouts.FlowLayout android:id="@+id/flow2"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:orientation="horizontal"
                        android:animateLayoutChanges="true"
                        />
                </LinearLayout>
                <LinearLayout android:id="@+id/container5"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:visibility="gone"
                    android:paddingTop="20dp"
                    android:animateLayoutChanges="true"
                    >
                    <TextView
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:paddingBottom="15dp"
                        android:letterSpacing=".07"
                        android:text="whatever"
                        android:textColor="@android:color/white"
                        android:textSize="18sp"
                        android:typeface="monospace" />
                    <RadioGroup android:id="@+id/radio_group2"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:orientation="horizontal"
                        android:animateLayoutChanges="true"
                        >
                        <android.support.v7.widget.AppCompatRadioButton android:id="@+id/radio3"
                            android:layout_width="0dp"
                            android:layout_weight="1"
                            android:gravity="center"
                            android:paddingStart="20dp"
                            android:layout_height="50dp"
                            android:background="@drawable/radio"
                            android:button="@android:color/transparent"
                            android:text="whatever"
                            android:layout_marginEnd="5dp"
                            />
                        <android.support.v7.widget.AppCompatRadioButton android:id="@+id/radio4"
                            android:layout_marginStart="5dp"
                            android:paddingStart="20dp"
                            android:layout_width="0dp"
                            android:layout_weight="1"
                            android:gravity="center"
                            android:layout_height="50dp"
                            android:background="@drawable/radio"
                            android:button="@android:color/transparent"
                            android:text="whatever"
                            />
                    </RadioGroup>

                </LinearLayout>
                <android.support.constraint.ConstraintLayout android:id="@+id/container6"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:paddingTop="20dp"
                    android:background="@null"
                    android:visibility="gone"
                    android:animateLayoutChanges="true"
                    >
                    <Button android:id="@+id/button"
                        style="?android:attr/borderlessButtonStyle"
                        android:layout_width="match_parent"
                        android:layout_height="60dp"
                        app:layout_constraintBottom_toBottomOf="parent"
                        app:layout_constraintEnd_toEndOf="parent"
                        app:layout_constraintStart_toStartOf="parent" />
                    <ImageView android:id="@+id/search_icon"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_marginStart="16dp"
                        android:layout_marginTop="8dp"
                        android:layout_marginBottom="8dp"
                        android:src="@drawable/search"
                        app:layout_constraintBottom_toBottomOf="parent"
                        app:layout_constraintStart_toStartOf="parent"
                        app:layout_constraintTop_toTopOf="parent" />
                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_marginStart="8dp"
                        android:layout_marginTop="8dp"
                        android:layout_marginBottom="8dp"
                        android:text="whatever"
                        android:textAllCaps="true"
                        android:textSize="18sp"
                        app:layout_constraintBottom_toBottomOf="parent"
                        app:layout_constraintEnd_toEndOf="@+id/button"
                        app:layout_constraintStart_toStartOf="@+id/button"
                        app:layout_constraintTop_toTopOf="parent" />
                </android.support.constraint.ConstraintLayout>
            </LinearLayout>
        </ScrollView>
    </RelativeLayout>
</LinearLayout>

要更改视图的可见性，请使用最简单的代码：

radioButton.setOnCheckedChangeListener { compoundButton, b ->
            mContainer2.visibility = View.VISIBLE

编辑：

重现问题的示例代码：

.XML

<ScrollView android:id="@+id/form_scroll"
        xmlns:android="http://schemas.android.com/apk/res/android"
            android:background="@color/colorPrimaryDark"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:animateLayoutChanges="true"
        android:padding="20dp"
        android:scrollbars="none">
    <RelativeLayout
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:animateLayoutChanges="true"
            android:gravity="bottom"
            android:clipChildren="false"
            android:layout_height="wrap_content">
    <TextView android:id="@+id/text1"
            android:layout_width="wrap_content"
              android:visibility="visible"
              android:text="text1text1text1text1text1text1text1text1text1text1text1text1text1text1text1text1text1text1"
              android:textSize="40sp"
              android:background="@color/colorPrimary"
              android:layout_height="wrap_content"/>
    <TextView android:id="@+id/text2"
              android:layout_below="@id/text1"
              android:layout_width="wrap_content"
              android:text="text2text2text2text2text2text2text2text2text2text2text2text2text2text2text2text2text2text2text2"
              android:textSize="40sp"
              android:visibility="gone"
              android:background="@color/colorPrimary"
              android:layout_height="wrap_content"/>
    <TextView android:id="@+id/text3"
              android:layout_below="@id/text2"
              android:layout_width="wrap_content"
              android:text="text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3text3"
              android:textSize="40sp"
              android:visibility="gone"
              android:background="@color/colorPrimary"
              android:layout_height="wrap_content"/>
    <TextView android:id="@+id/text4"
              android:layout_below="@id/text3"
              android:layout_width="wrap_content"
              android:text="text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4text4"
              android:textSize="40sp"
              android:visibility="gone"
              android:background="@color/colorPrimary"
              android:layout_height="wrap_content"/>
    </RelativeLayout>
</ScrollView>

活动：

class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    val mScroll = findViewById<ScrollView>(R.id.form_scroll)
    val mText1 = findViewById<TextView>(R.id.text1)
    val mText2 = findViewById<TextView>(R.id.text2)
    val mText3 = findViewById<TextView>(R.id.text3)
    val mText4 = findViewById<TextView>(R.id.text4)
    mText1.setOnClickListener {
        mText2.visibility = View.VISIBLE
    }
    mText2.setOnClickListener {
        mText3.visibility = View.VISIBLE
    }
    mText3.setOnClickListener {
        mText4.visibility = View.VISIBLE
    }
}
}

您需要等待布局更改，然后再滚动滚动视图。为此，您可以使用 viewTreeObserver 和 addOnGlobalLayoutListener。为避免听众泄漏，请在使用后直接将其销毁。我在这里使用Antonio Leiva提供的扩展，看看他的文章，以更好地了解viewTreeObserver和监听器是如何工作的

。

测量完成后，您需要知道滚动视图完整内容的大小。您需要找到 scrollView 的第一个子项才能找到高度：getChildAt(0(.height

不幸的是，我无法使用 smoothScroll 而不在之后调用它两次，我无法解释这种行为......

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val mScroll = findViewById<ScrollView>(R.id.form_scroll)
        val mText1 = findViewById<TextView>(R.id.text1)
        val mText2 = findViewById<TextView>(R.id.text2)
        val mText3 = findViewById<TextView>(R.id.text3)
        val mText4 = findViewById<TextView>(R.id.text4)
        mText1.setOnClickListener {
            mText2.visibility = View.VISIBLE
            mText2.afterMeasured {
                mScroll.scrollTo(0, mScroll.getChildAt(0).height)
            }
        }
        mText2.setOnClickListener {
            mText3.visibility = View.VISIBLE
            mText3.afterMeasured {
                mScroll.scrollTo(0, mScroll.getChildAt(0).height)
            }
        }
        mText3.setOnClickListener {
            mText4.visibility = View.VISIBLE
            mText4.afterMeasured {
                mScroll.scrollTo(0, mScroll.getChildAt(0).height)
            }
        }
    }
}
inline fun View.afterMeasured(crossinline f: View.() -> Unit) {
    viewTreeObserver.addOnGlobalLayoutListener(object : ViewTreeObserver.OnGlobalLayoutListener {
        override fun onGlobalLayout() {
            if (measuredWidth > 0 && measuredHeight > 0) {
                println(measuredHeight)
                f()
                viewTreeObserver.removeOnGlobalLayoutListener(this)
            }
        }
    })
}

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