Why is there all this black space between each of the images?

When I run this XML in an android app, it shows perfectly in the emulator. But when ran in the actual device, there are huge blank spaces between each of the images. I'm trying to create a simple social media type app.

Also, I am wondering how I can take user input, such as a new post they create, and upload it into the feed of the app.

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

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="0dp"
        android:minHeight="50dp">

        <Button
            android:onClick="viewBanditos"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="Banditos"
            android:layout_weight="1.0"
            android:layout_gravity="top|fill"
            android:gravity="center"
            android:textStyle="bold"
            android:textColor="#DFCF00"
            android:background="#272727"/>

        <Button
            android:onClick="newPostPage"
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="New Post"
            android:layout_weight="1.0"
            android:textColor="#DFCF00"
            android:background="#272727"/>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:text="Leave The City"
            android:textColor="#DFCF00"
            android:background="#272727"
            android:onClick="leaveTheCity"/>

    </LinearLayout>

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:background="#0E0E0E"
            android:gravity="top">

            <EditText
                android:background="#272727"
                android:ems="10"
                android:layout_height="wrap_content"
                android:inputType="textPassword"
                android:gravity="center"
                android:hint="Whats on your mind?"
                android:typeface="monospace"
                android:layout_width="match_parent"
                android:textColor="#DFCF00"/>

            <LinearLayout
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:gravity="top">

                <LinearLayout
                    android:orientation="vertical"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="top">

                    <ImageView
                        android:src="@drawable/meme1"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:padding="10dp"
                        android:layout_gravity="top"/>

                </LinearLayout>

                <LinearLayout
                    android:orientation="vertical"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:gravity="top">

                    <ImageView
                        android:src="@drawable/meme2"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_gravity="top"/>

                </LinearLayout>

                <LinearLayout
                    android:orientation="vertical"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content">

                </LinearLayout>

            </LinearLayout>

        </LinearLayout>

    </ScrollView>

</LinearLayout>