为什么在横向，线性布局，按钮下降，我只看到一个空白屏幕？

Question

I have a problem that when i rotate my phone, screen is blank, I can only see a title of the application. In landscape mode some buttons go below the screen, and I don't know how to resolve this problem. I'm using one linear layout with two linear layouts inside.

I have tried to move the buttons, but I can't move them.

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


    <TextView
        android:id="@+id/tvQuestion"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|center_horizontal"
        android:layout_marginLeft="20dp"
        android:layout_marginTop="300dp"
        android:layout_marginRight="20dp"
        android:gravity="center"
        android:padding="24dp"
        android:text="@string/textview"
        android:textSize="18sp" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:gravity="top"
        android:measureWithLargestChild="true"
        android:orientation="horizontal">


        <Button
            android:id="@+id/btnTrue"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/true_button" />

        <Button
            android:id="@+id/btnFalse"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/false_button" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:orientation="horizontal">

        <ImageButton
            android:id="@+id/imgBtnBack"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="3dp"
            android:adjustViewBounds="true"
            android:maxWidth="168dp"
            android:maxHeight="42dp"
            android:scaleType="fitCenter"
            android:src="@drawable/left_arrow" />

        <ImageButton
            android:id="@+id/imgBtnNext"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="3dp"
            android:adjustViewBounds="true"
            android:maxWidth="168dp"
            android:maxHeight="42dp"
            android:scaleType="fitCenter"
            android:src="@drawable/right_arrow" />
    </LinearLayout>

</LinearLayout>

Answer 1

Just removed android:layout_marginTop="300dp" from textview and added android:gravity="center" in parent LinearLayout. See the following layout, it will work for landscape also.

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


    <TextView
            android:id="@+id/tvQuestion"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|center_horizontal"
            android:layout_marginLeft="20dp"
            android:layout_marginRight="20dp"
            android:gravity="center"
            android:padding="24dp"
            android:text="textview"
            android:textSize="18sp" />

    <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:layout_marginLeft="20dp"
            android:layout_marginRight="20dp"
            android:gravity="top"
            android:measureWithLargestChild="true"
            android:orientation="horizontal">


        <Button
                android:id="@+id/btnTrue"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="true_button" />

        <Button
                android:id="@+id/btnFalse"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="false_button" />
    </LinearLayout>

    <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:orientation="horizontal">

        <ImageButton
                android:id="@+id/imgBtnBack"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="3dp"
                android:adjustViewBounds="true"
                android:maxWidth="168dp"
                android:maxHeight="42dp"
                android:scaleType="fitCenter"
                android:src="left_arrow" />

        <ImageButton
                android:id="@+id/imgBtnNext"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="3dp"
                android:adjustViewBounds="true"
                android:maxWidth="168dp"
                android:maxHeight="42dp"
                android:scaleType="fitCenter"
                android:src="right_arrow" />
    </LinearLayout>

</LinearLayout>