我是android的新手，有线性布局并在其中滚动。即使滚动发生，我也希望我的Button固定在底部，不知道该怎么做。下面是我的代码，按钮是最后一个。有人可以帮忙吗我试过＆＃34; android_gravity＆＃34;和＆＃34; layout_bottom = true＆＃34;我在stackoverflow中读到的几个答案，当我使用LinearLayout时，我应该使用它们
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:card_view="http://schemas.android.com/tools"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/colorWhite"
android:orientation="vertical"
tools:ignore="ContentDescription|MissingPrefix">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="@dimen/action_bar_height"
android:background="@android:color/transparent"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light">
<RelativeLayout
android:id="@+id/toolbar_layout"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:id="@+id/title_text"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_centerVertical="true"
android:textStyle="bold"
android:gravity="center"
android:text="@string/registration_string"
android:textColor="@color/eula_body_text_color"
android:textSize="19sp" />
</RelativeLayout>
</android.support.v7.widget.Toolbar>
<TextView
android:id="@+id/tool_border"
android:layout_width="match_parent"
android:layout_height="1dp"
android:layout_below="@id/toolbar"
android:background="@color/tool_border_color" />
<ScrollView
android:id="@+id/scrollView_layout"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@color/colorWhite"
android:fitsSystemWindows="true"
android:visibility="visible">
<LinearLayout
android:id="@+id/registration_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="@dimen/_20sdp"
android:background="@color/colorWhite"
android:orientation="vertical"
android:visibility="visible">
<View
android:id="@+id/profileFocus"
android:layout_width="1dp"
android:layout_height="1dp"
android:focusable="true"
android:focusableInTouchMode="true" />
<LinearLayout
android:id="@+id/addPictureImageLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_horizontal"
>
<ImageView
android:id="@+id/addPictureImage"
android:layout_width="140dip"
android:layout_height="140dip"
android:layout_marginBottom="22.5dp"
android:background="@drawable/uploadidphoto"
android:visibility="visible" />
</LinearLayout>
<TextView
android:id="@+id/imagephotorequired"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginBottom="@dimen/_11sdp"
android:text="@string/image_photo_required"
android:textColor="#ffe7181c"
android:visibility="invisible"
android:textSize="@dimen/_9sdp" />
<LinearLayout
android:id="@+id/card_view2"
android:layout_width="@dimen/_110sdp"
android:layout_height="@dimen/_110sdp"
android:layout_below="@+id/profile_layout"
android:layout_gravity="center"
android:layout_marginBottom="@dimen/_32sdp"
android:layout_marginTop="@dimen/_25sdp"
android:visibility="gone"
card_view:cardCornerRadius="@dimen/_2sdp">
<com.honeywell.hbs.visitormanagement.utils.CircleImage
android:id="@+id/profileImage"
android:layout_width="@dimen/_87sdp"
android:layout_height="@dimen/_87sdp"
android:layout_gravity="center"
android:foregroundGravity="center_vertical"
android:scaleType="fitCenter" />
</LinearLayout>
<!-- <TextView
android:id="@+id/vectorText"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="left"
android:layout_marginBottom="@dimen/_20sdp"
android:gravity="left"
android:text="@string/registrationDetails"
android:textColor="@color/gray606060"
android:textSize="@dimen/_15sdp" />
-->
<TextView
android:id="@+id/nameText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/_11sdp"
android:text="@string/first_name"
android:textColor="@color/blackText"
android:textSize="@dimen/_12sdp" />
<LinearLayout
android:id="@+id/addIdProofPictureImageLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginBottom="10dip"
android:orientation="vertical">
<ImageView
android:id="@+id/id_proof_document"
android:layout_width="140dip"
android:layout_height="140dip"
android:layout_gravity="center"
android:background="@drawable/uploadidproof"
android:visibility="visible" />
</LinearLayout>
<TextView
android:id="@+id/id_proof_number_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/_10sdp"
android:layout_marginTop="10dip"
android:text="@string/id_proof_number"
android:textColor="@color/blackText"
android:textSize="@dimen/_12sdp" />
<EditText
android:id="@+id/id_proof_number"
android:layout_width="fill_parent"
android:layout_height="@dimen/_34sdp"
android:layout_marginTop="1dip"
android:maxLength="4"
android:background="@drawable/edit_text_border"
android:drawableRight="@drawable/asterix"
android:paddingEnd="@dimen/_5sdp"
android:paddingRight="@dimen/_5sdp"
android:paddingStart="@dimen/_5sdp"
android:textColor="@color/black"
android:singleLine="true" />
<TextView
android:id="@+id/proofnumberrequired"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/_11sdp"
android:text="@string/proofnumber_required"
android:textColor="#ffe7181c"
android:visibility="invisible"
android:textSize="@dimen/_9sdp" />
<TextView
android:id="@+id/id_proof_type_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/_10sdp"
android:text="@string/id_proof_type"
android:textColor="@color/blackText"
android:textSize="@dimen/_12sdp" />
<EditText
android:id="@+id/id_proof_type"
android:layout_width="fill_parent"
android:layout_height="@dimen/_34sdp"
android:layout_marginTop="1dip"
android:background="@drawable/edit_text_border"
android:drawableRight="@drawable/asterix"
android:paddingEnd="@dimen/_5sdp"
android:paddingRight="@dimen/_5sdp"
android:paddingStart="@dimen/_5sdp"
android:textColor="@color/black"
android:singleLine="true" />
<TextView
android:id="@+id/prooftyperequired"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="@dimen/_11sdp"
android:text="@string/prooftype_required"
android:textColor="#ffe7181c"
android:visibility="invisible"
android:textSize="@dimen/_9sdp" />
<!--<Spinner
android:id="@+id/id_proof_spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/idProofcard_view"
android:layout_marginTop="5dp"
android:layout_marginBottom="@dimen/_10sdp"
android:entries="@array/id_proof_type"
android:popupBackground="#FFF"
android:spinnerMode="dropdown" />
<View
android:layout_width="match_parent"
android:layout_below="@+id/id_proof_spinner"
android:layout_height="1dp"
android:layout_marginBottom="@dimen/_24sdp"
android:background="#ffa0a0a0" />-->
<Button
android:id="@+id/btn_login"
style="?android:attr/borderlessButtonStyle"
android:layout_marginTop="15dip"
android:layout_width="fill_parent"
android:layout_height="@dimen/_34sdp"
android:layout_marginBottom="@dimen/_24sdp"
android:background="@drawable/button_state"
android:gravity="center"
android:text="@string/confirm"
android:textColor="@color/colorWhite"
android:textSize="@dimen/_16sdp" />
</LinearLayout>
</ScrollView>
<ProgressBar
android:id="@+id/progressbar"
android:visibility="invisible"
android:layout_centerInParent="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>