Android Studio 如何为片段内的视图设置约束

Question

Attempting to attach a view to the bottom left of a fragment and it is not obeying my commands:(

The code compiles and runs but the button is very much in the top left of the screen.

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/map"
    android:name="com.google.android.gms.maps.SupportMapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MapsActivity">


    <ImageButton
        android:id="@+id/searchBtn"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:adjustViewBounds="true"
        android:background="@null"
        android:scaleType="centerInside"
        map:layout_constraintBottom_toBottomOf="parent"
        map:layout_constraintStart_toStartOf="parent"
        map:srcCompat="@drawable/loupe"/>
</fragment>

New to android studio and don't yet completely understand all the patterns, so I feel like I might be attempting to do something the wrong way.

Should I be defining some sort of container and then putting the map fragment and the button inside of that?

But if I do that it brakes the map code in my main.

Answer 1

Not sure what you are asking but from what I understand is that you want to position your ImageButton on top of fragment. You can add this to your button android:layout_gravity="bottom|start" to position your button.

Answer 2

Using LinearLayout is better. It puts elements horizontally next to each other or vertically, depend on what you say in android:orientation=""

<LinearLayout
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"
android:orientation="vertical"
tools:context=".MapsActivity">
    <ImageButton
    android:id="@+id/searchBtn"
    android:layout_width="150dp"
    android:layout_height="150dp"
    android:background="@null"/>
</LinearLayout>

Then, if you want it to be at bottom left corner, you can add android:layout_marginBottom="0dp" and android:layout_marginLeft="0dp" in the ImageButton . This means ImageButton should be 0dp away from bottom of the screen, also should be 0dp away from left of the screen, which makes it sits at bottom left.

Answer 3

Thanks @Tyler for your comment which i cannot accept as an answer because it is a comment.

"The commands layout_constraintBottom_toBottomOf and layout_constraintStart_toStartOf are for a ConstraintLayout. If you want them to be used, you need to put the view inside a ConstraintLayout. However, check out this question on how to lay out a fragment. The fragment layout shouldn't go inside the tag, it should be its own file."

The fixed xml code looks like this (no need to change any of the other code) -

<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MapsActivity">

    <fragment
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/map_fragment"
        android:name="com.google.android.gms.maps.SupportMapFragment" />

    <ImageButton
        android:id="@+id/searchBtn"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:adjustViewBounds="true"
        android:background="@null"
        android:scaleType="centerInside"
        map:layout_constraintBottom_toBottomOf="@id/map"
        map:layout_constraintStart_toStartOf="@id/map"
        map:srcCompat="@drawable/loupe"/>

</androidx.constraintlayout.widget.ConstraintLayout>