android studioUI控件位置全在左上角,该怎么解决
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".MainActivity"
tools:layout_editor_absoluteY="56dp"
tools:showIn="@layout/activity_main">
<TextView
android:id="@+id/textView"
android:layout_width="0dp"
android:layout_height="35dp"
android:layout_marginStart="78dp"
android:layout_marginLeft="78dp"
android:layout_marginEnd="20dp"
android:layout_marginRight="20dp"
android:gravity="center"
android:text="用户名"
android:textSize="20dp"
app:layout_constraintBaseline_toBaselineOf="@+id/editText"
app:layout_constraintEnd_toStartOf="@+id/editText"
app:layout_constraintStart_toStartOf="parent" />
<TextView
android:id="@+id/textView2"
android:layout_width="0dp"
android:layout_height="35dp"
android:layout_marginStart="78dp"
android:layout_marginLeft="78dp"
android:layout_marginEnd="20dp"
android:layout_marginRight="20dp"
android:gravity="center"
android:text="密码"
android:textSize="20dp"
app:layout_constraintBaseline_toBaselineOf="@+id/editText2"
app:layout_constraintEnd_toStartOf="@+id/editText2"
app:layout_constraintStart_toStartOf="parent" />
<Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="登录"
app:layout_constraintBaseline_toBaselineOf="@+id/button2"
app:layout_constraintEnd_toEndOf="@+id/textView2" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="46dp"
android:layout_marginEnd="21dp"
android:layout_marginRight="21dp"
android:text="注册"
app:layout_constraintEnd_toEndOf="@+id/editText2"
app:layout_constraintTop_toBottomOf="@+id/editText2" />
<EditText
android:id="@+id/editText"
android:layout_width="0dp"
android:layout_height="35dp"
android:layout_marginTop="144dp"
android:layout_marginEnd="67dp"
android:layout_marginRight="67dp"
android:ems="10"
android:inputType="textPersonName"
android:text=""
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/textView"
app:layout_constraintTop_toTopOf="parent" />
<EditText
android:id="@+id/editText2"
android:layout_width="0dp"
android:layout_height="35dp"
android:layout_marginTop="70dp"
android:layout_marginEnd="67dp"
android:layout_marginRight="67dp"
android:ems="10"
android:inputType="numberPassword"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="@+id/textView2"
app:layout_constraintTop_toBottomOf="@+id/editText" />
</android.support.constraint.ConstraintLayout>