<android.support.constraint.ConstraintLayout
.....
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_height="wrap_content"
android:layout_width="match_parent"
android:background="@color/colorAccent"
tools:layout_editor_absoluteY="0dp"
tools:layout_editor_absoluteX="8dp">
...
This view is not constrained, it only has designtime positions, so it will jump to (0,0) unless you add constraints
layout_editor_absoluteY 是绝对位置，删除就好了
