Android match_parent on child not reaches weight from parent

Question

Like in title. Layout looks great on Android Studio, but when I get it on real device it looks bad. The JavaCameraView takes only half of the screen while in Android Studio takes about 3/4 as it should be. JavaCameraView should reach horizontal bar shown on screen.

Here are my screenshots.

On Android Studio:

On real device:

Layout Inspector shows that this RelativeLayout that hosts JavaCameraView occupies all that space but JavaCameraView with height:match_parent not behaves like that:

Why is that so?

Here is my layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:opencv="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="5"
    android:layout_above="@+id/scroll_view">


    <org.opencv.android.JavaCameraView
        android:id="@+id/java_surface_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true"
        opencv:camera_id="any"
        opencv:show_fps="true" />

</RelativeLayout>

<ScrollView
    android:id="@+id/scroll_view"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    android:layout_marginBottom="?actionBarSize">

    <RelativeLayout
        android:id="@+id/rl"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <View
            android:id="@+id/View1"
            android:layout_width="wrap_content"
            android:layout_height="2dp"
            android:layout_marginTop="5dp"
            android:layout_marginBottom="5dp"
            android:background="@android:color/darker_gray" />

        <TextView
            android:id="@+id/alert_pxcm_too_small"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/View1"
            android:layout_centerHorizontal="true"
            android:gravity="center_horizontal"
            android:textColor="#FF0000"
            android:textSize="@dimen/text_size_rest"
            android:visibility="visible" />

        <Spinner
            android:id="@+id/spinner"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:layout_marginTop="10dp"
            android:layout_below="@id/alert_pxcm_too_small"/>
        <TextView
            android:id="@+id/measurements_width_converter"
            android:layout_marginTop="15dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/spinner"
            android:layout_centerHorizontal="true"
            android:gravity="center_horizontal"
            android:textColor="#0000FF"
            android:text="@string/width_info"
            android:textSize="@dimen/text_size_rest"
            android:visibility="visible" />

        <TextView
            android:id="@+id/measurements_height_converter"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/measurements_width_converter"
            android:layout_centerHorizontal="true"
            android:gravity="center_horizontal"
            android:textColor="#0000FF"
            android:text="@string/width_info"
            android:textSize="@dimen/text_size_rest"
            android:visibility="visible" />

    </RelativeLayout>
</ScrollView>

If you need something more just ask. Probably you will need also some Java code of classes, this fragment etc. Thank you in advance! :)

Answer 1

Here is the working correctly layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:opencv="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_marginBottom="?actionBarSize">


    <org.opencv.android.JavaCameraView
        android:id="@+id/java_surface_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/scroll_view"
        android:layout_alignParentTop="true"
        opencv:camera_id="any"
        opencv:show_fps="true" />

    <ScrollView
        android:id="@+id/scroll_view"
        android:layout_width="match_parent"
        android:layout_height="150dp"
        android:layout_alignParentBottom="true">

        <RelativeLayout
            android:id="@+id/rl"
            android:layout_width="match_parent"
            android:layout_height="150dp">

            <View
                android:id="@+id/View1"
                android:layout_width="wrap_content"
                android:layout_height="2dp"
                android:layout_marginTop="5dp"
                android:layout_marginBottom="5dp"
                android:background="@android:color/darker_gray" />

            <TextView
                android:id="@+id/alert_pxcm_too_small"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/View1"
                android:layout_centerHorizontal="true"
                android:gravity="center_horizontal"
                android:textColor="#FF0000"
                android:textSize="@dimen/text_size_rest"
                android:visibility="visible" />

            <Spinner
                android:id="@+id/spinner"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_below="@id/alert_pxcm_too_small"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="10dp" />

            <TextView
                android:id="@+id/measurements_width_converter"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/spinner"
                android:layout_centerHorizontal="true"
                android:layout_marginTop="15dp"
                android:gravity="center_horizontal"
                android:text="@string/width_info"
                android:textColor="#0000FF"
                android:textSize="@dimen/text_size_rest"
                android:visibility="visible" />

            <TextView
                android:id="@+id/measurements_height_converter"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_below="@id/measurements_width_converter"
                android:layout_centerHorizontal="true"
                android:gravity="center_horizontal"
                android:text="@string/width_info"
                android:textColor="#0000FF"
                android:textSize="@dimen/text_size_rest"
                android:visibility="visible" />

        </RelativeLayout>
    </ScrollView>
</RelativeLayout>

Answer 2

Your problem is on the value you're using in android:layout_weight and how you're set the android:layout_width and android:layout_height.

<LinearLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  ...
  >
  <RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="0.3"
   ..
   >
   <org.opencv.android.JavaCameraView
     android:layout_width="match_parent"
     android:layout_height="match_parent"
    ..
    />
  </RelativeLayout>

  <ScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="0.7"

    <!-- Other views here -->

  </ScrollView>
</LinearLayout>