Develop Reference

Align checkbox to the right side in LinearLayout android

I am trying to make some text views with checkboxes in LinearLayout. I want for result like this:
TextView Ckeckbox
TextViewwwwww Ckeckbox
TextV Ckeckbox
But currently I have this:
TextView Checkbox
TextViewwwww Checkbox
TextView Checkbox
Here is my xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentTop="true"
android:orientation="horizontal">
<TextView
android:id="#+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</LinearLayout>
And this xml gives me same result:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentTop="true"
android:orientation="horizontal">
<TextView
android:id="#+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="start"/>
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="end"/>
</LinearLayout>

You can use the layout_weight attribute on your TextView only to automatically designate the TextView to fill any space which the CheckBox does not occupy. For example, the following will set your checkboxes to the end (provided they have no text associated with them) and then lets the TextView fill the rest of the layout.
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentTop="true"
android:orientation="horizontal">
<TextView
android:id="#+id/itemTitle"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1" />
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
Additionally, you should use match_parent instead of fill_parent as fill_parent is deprecated.

Try this:
<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="com.example.ipdemo.MainActivity" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:id="#+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="TextView" />
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1" />
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="TextView" />
<CheckBox
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1" />
</LinearLayout>
</LinearLayout>

Use layout weights and try this:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentTop="true"
android:orientation="horizontal"
android:weightSum="5">
<TextView
android:id="#+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="wdjhwdjwo"/>
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="4"/>
</LinearLayout>

You should be using layout_weight attribute to achieve the effect
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal">
<TextView
android:id="#+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1" />
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1" />
</LinearLayout>
So horizontally both the views will be occupying half of the screen size. You could adjust layout_weight to achieve the desired outcome.
There maybe other ways to do this, but I think this method is the best way.

Use layout_gravity="right" instead of gravity="end" if you're working with vertical layouts.
Your CheckBox tag should look like:
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right"/>
EDIT: On horizontal layouts, try layout_weight="1", that will make both of your elements fill half of the layout space.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentTop="true"
android:orientation="horizontal">
<TextView
android:id="#+id/itemTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"/>
<CheckBox
android:id="#+id/checkItem"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"/>
</LinearLayout>

check the following use android:layout_weight="1" in both view
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentTop="true"
android:orientation="horizontal">
<TextView
android:id="#+id/itemTitle"
android:layout_width="fill_parent"
android:layout_weight="1"
android:layout_height="wrap_content"
/>
<CheckBox
android:id="#+id/checkItem"
android:layout_width="fill_parent"
android:layout_weight="1"
android:layout_height="wrap_content"
/>
</LinearLayout>

Alignment of two Relative layout within a main relative layout

<RelativeLayout
android:id="#+id/OtherWeatherInfo_main"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="#dimen/margin_space"
android:layout_marginLeft="#dimen/margin_space"
android:layout_marginRight="#dimen/margin_space" >
<RelativeLayout
android:id="#+id/OtherWeatherInfo"
android:layout_width="#dimen/weather_space"
android:layout_height="wrap_content"
android:layout_centerVertical="true"
android:gravity="center_vertical"
android:layout_alignParentLeft="true"
android:background="#drawable/rect_block" >
<LinearLayout
android:id="#+id/humidityLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="#+id/humidityTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="#string/str_humidity"
android:textSize="#dimen/weather_size"
android:textStyle="bold" >
</TextView>
<TextView
android:id="#+id/humidityValue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="#string/str_no_data"
android:textColor="#color/color_white"
android:textStyle="bold" >
</TextView>
</LinearLayout>
</RelativeLayout>
<RelativeLayout
android:id="#+id/OtherWeatherInfo2"
android:layout_width="#dimen/weather_space"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:gravity="center_vertical"
android:layout_toRightOf="#+id/OtherWeatherInfo"
android:background="#drawable/rect_block" >
<LinearLayout
android:id="#+id/visiLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<TextView
android:id="#+id/visiTitle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="#string/str_visi"
android:textSize="#dimen/weather_size"
android:textStyle="bold" />
<TextView
android:id="#+id/visiValue"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:text="#string/str_no_data"
android:textColor="#color/color_white"
android:textStyle="bold" />
</LinearLayout>
</RelativeLayout>
</RelativeLayout>
The above code is written by me to achieve the following figure:.But what I am achieving is this: or this:.
I have absolutely no clue about what is the mistake I am doing here??I am just using a main relative layout
OtherWeatherInfo_main and within that I am embedding two relative layouts to represent the two weather attributes. #dimen/weather_space is 145 dp.I am unable to align the two relative layout within the main layout equally.Any help will be appreciated.

Wrap the two RelativeLayouts inside a LinearLayout with horizontal orientation and then assign both the RelativeLayouts equal weight.
In general, something like this:
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="1" >
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:weight="0.5" />
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:weight="0.5" />
</LinearLayout>

Remove either this
android:layout_alignParentRight="true"
or this
android:layout_toRightOf="#+id/OtherWeatherInfo"
from your second layout.
Also you can wrap both your RelativeLayouts to the horizontal LinearLayout and use android:layout_weight attribute

Try this way,if you wan achieved your design using LinearLayout.
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:gravity="center">
<TextView
android:id="#+id/txtCityName"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Kolkata"/>
<ImageView
android:id="#+id/imgWeather"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/ic_launcher"
android:layout_marginTop="20dp"/>
<TextView
android:id="#+id/txtTemprature"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="28 C"
android:layout_margin="10dp"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp">
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical"
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Humidity"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="29"/>
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical"
android:layout_marginLeft="20dp"
android:gravity="center">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Humidity"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="29"/>
</LinearLayout>
</LinearLayout>
<TextView
android:id="#+id/txtDateTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Fri 28"
android:layout_margin="10dp"/>
</LinearLayout>

Textview center-aligned based on percentage of screenwidth

I thought this will be a common question, but I couldn't find any answers......
Is it possible to center-aligned a (variable length) textview based on a percentage of the screen width?
In my case, I have 2 textview and I want to achieve something like this:
Another example:
The first textview is center-aligend 30% of the screenwidth, width=wrap_content, while the second textview takes up the rest of the space. The first textview's size should NOT be fixed (see picture above)
I do not want to do that programatically, as it will be expensive on my program. If possible it's better be in an xml layout file :)
Right now I can only achieve a "left-aligned" textview using layout_weight of LinearLayout (by putting a 30% dummy on the left), but I want center-alignment.
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<View
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_weight="3" >
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="7"
android:orientation="horizontal" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="textview" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="end"
android:singleLine="true"
android:text="another textview"
android:textColor="#FFFF0000"/>
</LinearLayout>
</LinearLayout>

With almost an hour testing this "..." layout, I succeeded with this :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="100" >
<RelativeLayout
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="40"
android:background="#android:color/transparent">
<RelativeLayout
android:id="#+id/left_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_margin="0dp"
android:gravity="center"
android:padding="0dp"
android:singleLine="true"
android:text="first textview"
android:textColor="#FFFF0000" >
<View
android:layout_width="1dp"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:background="#0000FF" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:background="#00FF00"
android:gravity="center"
android:text="textview"
android:textColor="#FFF" />
</RelativeLayout>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_toLeftOf="#id/left_layout"
android:background="#0000FF"
android:gravity="center"
android:text="textview"
android:textColor="#FFF" />
</RelativeLayout>
<TextView
android:layout_width="0dip"
android:layout_height="wrap_content"
android:layout_weight="60"
android:background="#FFFF0000"
android:gravity="right"
android:singleLine="true"
android:text="another textview"
android:textColor="#FFF" />
</LinearLayout>
Outputs
Finally in your Java, according to the green textview width or content length, you can change the layout_weight for other textviews programmatically.
This should help you
Have a nice day.

// try this way hope this will help you...
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<View
android:layout_width="0dp"
android:layout_height="1dp"
android:layout_weight="0.15"/>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="0.85">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="left"
android:text="first Textview"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="second textview demo text "/>
</LinearLayout>
</LinearLayout>
</LinearLayout>

try this one
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="3"
android:gravity="center_horizontal"
android:orientation="vertical" >
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="7"
android:gravity="center_horizontal"
android:orientation="vertical" >
<TextView
android:id="#+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Large Text"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
Work perfect checked by me.

Linearlayout for different screen sizes

I have a linearLayout which is surrounded by a scrollView in order to make it for smaller screens scrollable. In the linear layout I have 3 childs which are also linearlayout.
This is working fine. But I also want to support larger screens. At the moment I get with a larger screen space left on the bottom of the screen. I want to have the buttons (navigation bar) be always at the bottom. for larger screens (height) I would like to add at the top of the screen an empty view which fills out the space that is more provided by the larger screen.
How can I achieve that? i tried a lot with weight attribute but didnt get it working.
Here the layout:
<?xml version="1.0" encoding="utf-8"?>
<ScrollView
xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#8db9f6"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#8db9f6">
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_marginTop="8dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:text="test"
android:id="#+id/test"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textSize="20dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</TextView>
<View
android:layout_width="wrap_content"
android:layout_height="0dip"
android:layout_weight="1"/>
<ImageButton
android:id="#+id/btnName"
android:scaleType="center"
android:layout_width="60dp"
android:layout_height="48dp"
android:src="#android:drawable/ic_menu_edit">
</ImageButton>
</LinearLayout>
<EditText
android:id="#+id/edittest"
android:editable="false"
android:hint="#string/test"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
</EditText>
<TextView
android:text="#string/optionalText"
android:id="#+id/test1"
android:paddingLeft="10dp"
android:textSize="12dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</TextView>
<TextView
android:id="#+id/space"
android:layout_width="fill_parent"
android:layout_marginTop="4dp"
android:layout_height="3sp"
android:background="#333142">
</TextView>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_marginTop="5dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:text="TEST TESt"
android:id="#+id/test2"
android:paddingLeft="10dp"
android:layout_marginTop="5dp"
android:textStyle="bold"
android:textSize="20dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</TextView>
<View
android:layout_width="wrap_content"
android:layout_height="0dip"
android:layout_weight="1"/>
<ProgressBar
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:visibility="gone"
android:id="#+id/progressbar"/>
<ImageButton
android:id="#+id/btnPicture"
android:scaleType="center"
android:layout_width="60dp"
android:layout_height="48dp"
android:src="#android:drawable/ic_menu_edit">
</ImageButton>
</LinearLayout>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:background="#ffffff"
android:layout_gravity="center"
android:layout_width="fill_parent"
android:layout_height="150dip">
<ImageView
android:id="#+id/test3"
android:layout_width="400dip"
android:layout_height="150dip"
android:layout_gravity="center"
android:scaleType="fitCenter"
android:src="#drawable/test1"/>
<TextView
android:id="#+id/text"
android:layout_gravity="bottom"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="8dp"
android:text="test test"/>
</FrameLayout>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_gravity="bottom"
android:layout_marginTop="3dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/scaleMinus"
android:textSize="14dp"
android:layout_weight="1"
android:layout_gravity="bottom"
android:layout_width="fill_parent"
android:layout_height="40dp"
android:text="#string/zoomOut"/>
<Button
android:id="#+id/scalePlus"
android:textSize="14dp"
android:layout_weight="1"
android:layout_gravity="bottom"
android:layout_width="fill_parent"
android:layout_height="40dp"
android:text="#string/zoomIn"/>
</LinearLayout>
<TextView
android:id="#+id/balken"
android:layout_width="fill_parent"
android:layout_marginTop="4dp"
android:layout_height="3sp"
android:background="#333142">
</TextView>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_marginTop="5dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView
android:text="test test"
android:id="#+id/test3"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textSize="20dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</TextView>
<View
android:layout_width="wrap_content"
android:layout_height="0dip"
android:layout_weight="1"/>
<EditText
android:id="#+id/test4"
android:editable="false"
android:layout_width="100dp"
android:layout_height="wrap_content">
</EditText>
<TextView
android:text="test"
android:id="#+id/mtest4"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textSize="20dp"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
</TextView>
<View
android:layout_width="wrap_content"
android:layout_height="0dip"
android:layout_weight="1"/>
<ImageButton
android:id="#+id/test5"
android:scaleType="center"
android:layout_width="60dp"
android:layout_height="48dp"
android:src="#android:drawable/ic_menu_edit">
</ImageButton>
</LinearLayout>
<TextView
android:id="#+id/balken"
android:layout_width="fill_parent"
android:layout_marginTop="4dp"
android:layout_height="3sp"
android:background="#333142">
</TextView>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_gravity="bottom"
android:background="#000000"
android:paddingTop="5dp"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/save"
android:textSize="18dp"
android:layout_weight="1"
android:layout_gravity="bottom"
android:layout_width="fill_parent"
android:layout_height="60dp"
android:text="#string/save"/>
<Button
android:id="#+id/cancel"
android:textSize="18dp"
android:layout_weight="1"
android:layout_gravity="bottom"
android:layout_width="fill_parent"
android:layout_height="60dp"
android:text="#string/abort"/>
</LinearLayout>
</LinearLayout>
</ScrollView>

Wrap the entire layout in a Relative Layout. Use a relative layout as your root element and set the Linear Layout containing your buttons to layout_alignParentBottom="true" and the ScrollView set to layout_alignParentTop="true".
The LinearLayout containing the buttons and the ScrollView should be direct children of the RelativeLayout.
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout <-- containing the layout minus the buttons
android:id="#+id/SV"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true">
<The Rest Of The Layout>
</LinearLayout>
<LinearLayout
android:id="#+id/LLButtons"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true">
<Buttons>
</LinearLayout>
</ScrollView>
If you want the buttons to be always at the bottom of the screen alignParentBottom. If you want the buttons to always be at the bottom of the scrollview alignBelow="#id/SV"

android:layout_height="wrap_content" in your inner LinearLayout is your trouble here, changing it to 'fill_parent' should help. In general, you may want to use hierarchyviewer to help troubleshoot layout issues like this.

Android linear layout align center and right

This is what I have:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:background="#FFFFFF">
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:background="#E30000"
android:layout_gravity="center_horizontal|center_vertical"
android:gravity="center_horizontal|center_vertical">
<TextView
android:id="#+id/TextView00"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#FFFFFF"
android:textSize="20px"
android:textStyle="bold"
android:text="Something"
android:gravity="right|center_vertical"
/>
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:gravity="right|center_vertical"
android:layout_gravity="center_vertical"
android:background="#E30000">
<Button
android:id="#+id/btnCalls"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableLeft="#drawable/icon"
android:gravity="right|center_vertical"
/>
</LinearLayout>
</LinearLayout>
</LinearLayout>
And I want this:
So horizontal center align the text and vertical center align the button.
What am I missing? I haven't tried RelativeLayout and I would prefer LinearLayout to work this out.

android:gravity="right|center_vertical"
aligns your TextView to the right. How about center_horizontal?
And your LinearLayouts have the same ID, if there is not more code, then I would delete one of them.

try this one
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:background="#FFFFFF">
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:background="#E30000"
android:layout_gravity="center_horizontal|center_vertical"
android:gravity="center_vertical">
<TextView
android:id="#+id/TextView00"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#FFFFFF"
android:textSize="20px"
android:textStyle="bold"
android:text="Something"
android:layout_weight="1"
android:gravity="center"/>
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:gravity="right|center_vertical"
android:layout_gravity="center_vertical"
android:background="#E30000"
android:layout_width="wrap_content">
<Button
android:id="#+id/btnCalls"
android:layout_width="wrap_content"
android:drawableLeft="#drawable/icon"
android:gravity="right|center_vertical"
android:layout_height="wrap_content"
android:layout_margin="5dip"/>
</LinearLayout>
</LinearLayout>
</LinearLayout>

I found none of the answers work exactly as the OP intended, but the RelativeLayout solution was the closest one. Except that the TextView wasn't centered. But, with layout_centerInParent=true, works like a charm:
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/TextView00"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#FFFFFF"
android:textSize="20px"
android:textStyle="bold"
android:text="Something"
android:layout_centerInParent="true" />
<Button
android:id="#+id/btnCalls"
android:drawableLeft="#drawable/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"/>
</RelativeLayout>

you have used android:gravity="right|center_vertical" in your textview. Use android:gravity="center".

Try to add empty View inside horizontal LinearLayout between element that you want see left and element that you want to see right, e.g.:
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<View
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_weight="1"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>

define layout weight for TextView and LinearLayout
set android:layout_weight="1" to TextView
set android:layout_weight="0" to LinearLayout
and also change the layout_width="wrap_content" to LinearLayout
and set layout_gravity="center" to TextView

I think,gravity means the position of things inside the component(for textview,it means the text you have given)in component where layout_gravity means position of component itself in the whole layout.So...
Try Using:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:background="#FFFFFF"
>
<LinearLayout android:id="#+id/LinearLayout01"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:background="#E30000"
android:layout_gravity="right"
android:gravity="center_vertical|right"
>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right|center_vertical"
android:gravity="center_vertical|center"
android:layout_weight="0.9"
>
<TextView
android:id="#+id/TextView00"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#FFFFFF"
android:textSize="20px"
android:textStyle="bold"
android:text="Something"
android:gravity="center_horizontal"
android:layout_gravity="center_horizontal|center_vertical"
/>
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right|center_vertical"
android:gravity="center_vertical|right"
android:paddingTop="5dip"
android:layout_weight="0.1"
>
<Button
android:id="#+id/btnCalls"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableLeft="#drawable/icon"
android:layout_gravity="center_vertical"
android:gravity="center"
/>
</LinearLayout>
</LinearLayout>
</LinearLayout>

Just use RelativeLayout, and wallaaa!!!
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="#+id/TextView00"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#FFFFFF"
android:textSize="20px"
android:textStyle="bold"
android:text="Something"
android:gravity="center" />
<Button
android:id="#+id/btnCalls"
android:drawableLeft="#drawable/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"/>
</RelativeLayout>

The solution for this is-
android:gravity="center_vertical"
Normally you'll also have to take care of its parent's position too to make sure it works.