I came across this link :
Assign width to half available screen width declaratively
How to do the same in relative layout? Here's the code: Trying linearlayout inside relative layout. But this doesn't work.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/bg" >
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<Button
android:id="@+id/button5"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="14dp"
android:layout_weight="1"
android:text="Button" />
<Button
android:id="@+id/button6"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
android:layout_weight="1"
android:text="Button" />
<Button
android:id="@+id/button4"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_weight="1"
android:text="UID"
android:textColor="#ffe5f1f1" />
<EditText
android:id="@+id/editText1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:background="#ffe5f1f1"
android:hint="Enter UID"
android:inputType="number"
android:shadowColor="5"
android:textColor="#ff009999"
android:textStyle="bold"
android:typeface="monospace" >
<requestFocus />
</EditText>
<Button
android:id="@+id/button7"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:layout_alignParentLeft="true"
android:layout_marginTop="18dp"
android:text="Button" />
<Button
android:id="@+id/button8"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/button7"
android:layout_weight="1"
android:layout_marginTop="16dp"
android:text="Button" />
<Button
android:id="@+id/button9"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:layout_alignParentLeft="true"
android:layout_below="@+id/button8"
android:layout_marginTop="17dp"
android:text="Button" />
<EditText
android:id="@+id/editText2"
android:layout_width="50"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_weight="1"
android:background="#ffe5f1f1"
android:ems="10"
android:hint="Enter Name"
android:inputType="number"
android:inputType="textPersonName"
android:textColor="#ff009999"
android:textStyle="bold"
android:layout_weight="1"
android:typeface="monospace" />
<EditText
android:id="@+id/editText3"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:ems="10"
android:layout_weight="1"
android:inputType="number" />
<EditText
android:id="@+id/editText4"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button7"
android:layout_alignBottom="@+id/button7"
android:layout_alignParentRight="true"
android:ems="10"
android:layout_weight="1"
android:inputType="phone" />
<EditText
android:id="@+id/editText5"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button8"
android:layout_alignBottom="@+id/button8"
android:layout_alignParentRight="true"
android:ems="10"
android:layout_weight="1"
android:inputType="textPersonName" />
<RadioButton
android:id="@+id/radioButton2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button9"
android:layout_alignBottom="@+id/button9"
android:layout_alignLeft="@+id/editText5"
android:layout_weight="1"
android:text="Male" />
<RadioButton
android:id="@+id/radioButton1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/radioButton2"
android:layout_alignBottom="@+id/radioButton2"
android:layout_alignParentRight="true"
android:layout_weight="1"
android:text="Female" />
<Button
android:id="@+id/button10"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/button9"
android:layout_marginTop="31dp"
android:layout_weight="1"
android:text="Button" />
<Spinner
android:id="@+id/spinDept"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button10"
android:layout_alignBottom="@+id/button10"
android:layout_alignLeft="@+id/radioButton2"
android:layout_alignParentRight="true"
android:layout_weight="1"
android:background="#ff009999" />
</LinearLayout>
</RelativeLayout>
This is a nice workaround if you precisely need half, when using RelativeLayout. What you do is, make a fake invisible view centered in parent, and have left button be alignParentLeft and alignRight to that fake view and the right button vice-versa
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<View android:id="@+id/fakeView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_centerInParent="true"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@id/fakeView"
android:layout_alignParentLeft="true"
android:text="Left"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@id/fakeView"
android:layout_alignParentRight="true"
android:text="Right"/>
</RelativeLayout>
Its really clever.
Wrap the same thing with Relative layout which should work for you.
<LinearLayout android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="somebutton">
<TextView android:layout_width="fill_parent"
android:layout_height="Wrap_content"
android:layout_weight="1">
</LinearLayout>
In addition to urSus's answer, it's better to use a Space class instead of View:
<Space android:id="@+id/fakeView"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_centerInParent="true"/>
Display display = getWindowManager().getDefaultDisplay();
int width = display.getWidth();
int height = display.getHeight();
plannerEditLayout = (RelativeLayout) findViewById(R.id.plannerLayoutEdit);
plannerEditLayout.setGravity(Gravity.CENTER_VERTICAL);
plannerEditLayout.setLayoutParams(new RelativeLayout.LayoutParams(
(width / 2), height));
I use the same code for LinearLayout. Havent tried it out myslef for RelativeLayout. Give it a shot. Comment if it doesn't work.
<LinearLayout android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button android:layout_width="match_parent"
android:id="@+id/button"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="somebutton">
<TextView android:layout_width="match_parent"
android:id="@+id/textview"
android:layout_height="Wrap_content"
android:layout_weight="1">
</LinearLayout>
In above example used LinearLayout, set widget layout_width to "match_parent" and provide weight(to specify area to be occupy).
This solves your problem.
来源：https://stackoverflow.com/questions/11244326/adjust-width-to-half-screen