android - ScrollView 只能承载一个直接子级，但它只有一个

Question

每当我开始 Activity 时，我都会收到此错误。

这是完整的堆栈跟踪:

Process: com.example, PID: 28799
                                                                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example/com.example.activity.EditProjectActivity}: java.lang.IllegalStateException: ScrollView can host only one direct child
                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2689)
                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2754)
                                                                    at android.app.ActivityThread.access$900(ActivityThread.java:177)
                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                    at android.os.Looper.loop(Looper.java:145)
                                                                    at android.app.ActivityThread.main(ActivityThread.java:5938)
                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                    at java.lang.reflect.Method.invoke(Method.java:372)
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
                                                                 Caused by: java.lang.IllegalStateException: ScrollView can host only one direct child
                                                                    at android.widget.ScrollView.addView(ScrollView.java:416)
                                                                    at android.view.LayoutInflater.rInflate(LayoutInflater.java:822)
                                                                    at android.view.LayoutInflater.rInflate(LayoutInflater.java:821)
                                                                    at android.view.LayoutInflater.inflate(LayoutInflater.java:511)
                                                                    at android.view.LayoutInflater.inflate(LayoutInflater.java:415)
                                                                    at android.view.LayoutInflater.inflate(LayoutInflater.java:366)
                                                                    at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:280)
                                                                    at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
                                                                    at com.example.activity.EditProjectActivity.onCreate(EditProjectActivity.java:38)
                                                                    at android.app.Activity.performCreate(Activity.java:6288)
                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2642)
                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2754) 
                                                                    at android.app.ActivityThread.access$900(ActivityThread.java:177) 
                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448) 
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                    at android.os.Looper.loop(Looper.java:145) 
                                                                    at android.app.ActivityThread.main(ActivityThread.java:5938) 
                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                    at java.lang.reflect.Method.invoke(Method.java:372) 
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400) 
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195) 

这是布局文件

    <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".activity.EditProjectActivity"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    >
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        >
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            >
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_alignParentTop="true"
                    android:layout_centerHorizontal="true"
                    android:orientation="horizontal"
                    android:id="@+id/ep_layout_name"
                    >
                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Project Name: "/>
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:layout_marginLeft="10dp"
                        android:id="@+id/ep_edit_name"/>
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/ep_layout_name"
                    android:layout_marginTop="20dp"
                    android:layout_centerHorizontal="true"
                    android:orientation="vertical"
                    android:id="@+id/ep_layout_categories"
                    >
                    <ListView
                        android:id="@+id/ep_list_categories"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        />
                    <Button
                        android:id="@+id/ep_btn_add_category"
                        android:layout_width="100dp"
                        android:layout_height="wrap_content"
                        android:layout_gravity="center"
                        android:text="Add"
                        android:onClick="onAddCategoryButtonClick"
                        />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/ep_layout_categories"
                    android:layout_marginTop="20dp"
                    android:layout_centerHorizontal="true"
                    android:orientation="vertical"
                    android:id="@+id/ep_layout_versions"
                    >
                    <ListView
                        android:id="@+id/ep_list_versions"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        />
                    <Button
                        android:id="@+id/ep_btn_add_version"
                        android:layout_width="100dp"
                        android:layout_height="wrap_content"
                        android:layout_gravity="center"
                        android:text="Add"
                        android:onClick="onAddVersionButtonClick"
                        />
                </LinearLayout>
        </RelativeLayout>
    </ScrollView>
</RelativeLayout>

我明白这个错误是什么意思，我已经尝试相应地解决它，但它仍然抛出同样的异常。

ScrollView 只有一个直接 subview ，即 RelativeLayout。我还这样做了，以便 ScrollView 有一个父 View ，而不是基本 View ，以防它导致异常但它不起作用。

Answer 1

可能会尝试在 RelativeLayout 之前再次添加 LinearLayout 和 vertical 方向

  <?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".activity.EditProjectActivity"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    >
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        >
<LinearLayout
                    android:layout_width="match_parent"
                    android:orientation="vertical"
                    android:layout_height="wrap_content">
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            >
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_alignParentTop="true"
                    android:layout_centerHorizontal="true"
                    android:orientation="horizontal"
                    android:id="@+id/ep_layout_name"
                    >
                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="Project Name: "/>
                    <EditText
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:layout_marginLeft="10dp"
                        android:id="@+id/ep_edit_name"/>
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/ep_layout_name"
                    android:layout_marginTop="20dp"
                    android:layout_centerHorizontal="true"
                    android:orientation="vertical"
                    android:id="@+id/ep_layout_categories"
                    >
                    <ListView
                        android:id="@+id/ep_list_categories"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        />
                    <Button
                        android:id="@+id/ep_btn_add_category"
                        android:layout_width="100dp"
                        android:layout_height="wrap_content"
                        android:layout_gravity="center"
                        android:text="Add"
                        android:onClick="onAddCategoryButtonClick"
                        />
                </LinearLayout>
                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_below="@id/ep_layout_categories"
                    android:layout_marginTop="20dp"
                    android:layout_centerHorizontal="true"
                    android:orientation="vertical"
                    android:id="@+id/ep_layout_versions"
                    >
                    <ListView
                        android:id="@+id/ep_list_versions"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        />
                    <Button
                        android:id="@+id/ep_btn_add_version"
                        android:layout_width="100dp"
                        android:layout_height="wrap_content"
                        android:layout_gravity="center"
                        android:text="Add"
                        android:onClick="onAddVersionButtonClick"
                        />
                </LinearLayout>
         </LinearLayout>
        </RelativeLayout>
    </ScrollView>
</RelativeLayout>