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how to center crop a background image of linear layout?

Hi i had to make a layout with card with recyclerview so for that i set an image as a background to linear layout but now i'm unable to center crop that image
My problem is that i cannot use imageview because using that the height of card increases as well and i don't want that so please if someone can assit me..
my xml
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/primary_card"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="19dp"
android:layout_marginRight="19dp"
android:layout_marginTop="15dp"
app:cardCornerRadius="115dp">
<ImageView
android:id="#+id/background_image_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:visibility="gone" />
<LinearLayout
android:id="#+id/background_image"
android:layout_width="match_parent"
android:layout_height="210dp"
android:background="#drawable/club1"
android:orientation="vertical"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<de.hdodenhof.circleimageview.CircleImageView
android:id="#+id/profile_image"
android:layout_width="56dp"
android:layout_height="56dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="20dp"
android:src="#drawable/ellipse" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="5dp">
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/first_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="18dp"
android:padding="5dp"
android:text="John Doe"
android:textColor="#color/White"
android:textSize="15sp" />
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/second_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="18dp"
android:padding="5dp"
android:text="checked in to"
android:textColor="#color/White"
android:textSize="10sp" />
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/third_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="18dp"
android:padding="5dp"
android:text="W south"
android:textColor="#color/White"
android:textSize="15sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:orientation="horizontal">
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/fourth_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="9dp"
android:text="beach mumbai"
android:textColor="#color/White"
android:textSize="15sp" />
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/fifth_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/second_text"
android:layout_toRightOf="#+id/fourth_text"
android:text="30 mins ago."
android:textColor="#color/White"
android:textSize="10sp" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="85dp">
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/sixth_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerInParent="true"
android:padding="10dp"
android:text="reply to abc............"
android:textColor="#color/White" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerInParent="true">
<ImageView
android:id="#+id/favourite_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="5dp"
android:adjustViewBounds="true"
android:scaleType="fitXY"
android:src="#drawable/ic_favorite_border_black_24dp" />
<com.ct.listrtrial.Custom.CustomTextViewMedium
android:id="#+id/seventh_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="15dp"
android:text="40 likes"
android:textColor="#color/White" />
</LinearLayout>
</RelativeLayout>
</LinearLayout>
</android.support.v7.widget.CardView>

You can't center crop a background image of linear layout,
But you can achieve the same using these changes:
Replace you LinearLayout with RelativeLayout
Place a ImageView as a first child inside relative layout and use property for center crop.
<RelativeLayout
android:id="#+id/background_image"
android:layout_width="match_parent"
android:layout_height="210dp"
android:orientation="vertical">
<ImageView
android:scaleType="centerCrop"
android:src="#drawable/club1"
android:layout_width="match_parent"
android:layout_height="match_parent" />
.....
......
</RelativeLayout>

If you Want to control The Image View Scale
you need to put it in ImageView As Src Not Background
You can use Frame layout To Achieve it
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/primary_card"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="19dp"
android:layout_marginRight="19dp"
android:layout_marginTop="15dp"
app:cardCornerRadius="115dp">
<ImageView
android:id="#+id/background_image_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:visibility="gone" />
<FrameLayout
android:layout_width="match_parent"
android:layout_height="210dp">
<ImageView
android:layout_width="match_parent"
android:src="#mipmap/ic_launcher"
android:layout_height="match_parent" />
<LinearLayout
android:id="#+id/background_image"
android:layout_width="match_parent"
android:layout_height="210dp"
android:orientation="vertical"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:id="#+id/profile_image"
android:layout_width="56dp"
android:layout_height="56dp"
android:layout_marginLeft="10dp"
android:layout_marginTop="20dp"
android:src="#drawable/playstore_icon" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:padding="5dp">
<TextView
android:id="#+id/first_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="18dp"
android:padding="5dp"
android:text="John Doe"
android:textSize="15sp" />
<TextView
android:id="#+id/second_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="18dp"
android:padding="5dp"
android:text="checked in to"
android:textSize="10sp" />
<TextView
android:id="#+id/third_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="18dp"
android:padding="5dp"
android:text="W south"
android:textSize="15sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:orientation="horizontal">
<TextView
android:id="#+id/fourth_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="9dp"
android:text="beach mumbai"
android:textSize="15sp" />
<TextView
android:id="#+id/fifth_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/second_text"
android:layout_toRightOf="#+id/fourth_text"
android:text="30 mins ago."
android:textSize="10sp" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="85dp">
<TextView
android:id="#+id/sixth_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerInParent="true"
android:padding="10dp"
android:text="reply to abc............"
android:textColor="#color/white" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerInParent="true">
<ImageView
android:id="#+id/favourite_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="5dp"
android:adjustViewBounds="true"
android:scaleType="fitXY"
android:src="#drawable/ic_close" />
<TextView
android:id="#+id/seventh_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginRight="15dp"
android:text="40 likes"
android:textColor="#color/white" />
</LinearLayout>
</RelativeLayout>
</LinearLayout>
</FrameLayout>
</android.support.v7.widget.CardView>

CenterCrop logic is baked inside ImageView. The correct solution is to extract it into a Drawable which wraps another Drawable and centerCrops it.

If you use CoordinatorLayout, then just to put your ImageView with centerCrop parameter to top.
<CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
android:scaleType="centerCrop"
android:background="#drawable/background_main"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<AppBarLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#android:color/transparent"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:elevation="0dp">
<include layout="#layout/header_main" />
<TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabIndicatorColor="#android:color/white"
android:background="#drawable/white_border_background"
app:tabIndicatorHeight="3dp"/>
</AppBarLayout>
<ViewPager
android:id="#+id/view_pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" />
</CoordinatorLayout>

Evenly spacing buttons android

I'm currently working on an android application. I can't get buttons evenly spaced on a screen.
Below is my code.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main_menu"
android:background="#354739"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.cssdapp.MainMenuActivity">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/icon"
/>
<Button
android:text="Log Off"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#6b5847"
android:id="#+id/logOff"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<Button
android:text="Manage Farmers"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#6b5847"
android:id="#+id/button4"
android:layout_above="#+id/button5"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<Button
android:text="My Account"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#6b5847"
android:id="#+id/button5"
android:layout_marginBottom="47dp"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<Button
android:text="Manage Farmers"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#6b5847"
android:id="#+id/button3"
android:layout_above="#+id/button4"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="21dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<Button
android:text="Order History"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#6b5847"
android:id="#+id/button2"
android:layout_above="#+id/button3"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
<Button
android:text="Make an Order"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#6b5847"
android:id="#+id/makeOrder"
android:layout_above="#+id/button2"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="36dp"
android:layout_alignParentRight="true"
android:layout_alignParentEnd="true" />
</RelativeLayout>
I want the buttons evenly spaced down the screen below the image. At the minute the image is where I want to be however I can't get the buttons to where I want them to be. I'm trying to use the gui designer however they won't snap into place. I'm trying to figure out the code way to do it.
Any help appreciated.

In Order to divide the buttons on the whole screen evenly and to maintain synchronization on all devices you need to use a LinearLayout
as your parent View And and another LinearLayout as the parent for each button and apply to it the weight attribute to divide them evenly on the screen Cause you can't just apply the weight attribute on the button itself because the (height or width of it depends on if the layout orintation is horizontal or vertical will gets scaled to fill the whole space) here is a code snippet to demonstrate what am saying
`
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main_menu"
android:layout_marginBottom="#dimen/activity_vertical_margin"
android:layout_marginLeft="#dimen/activity_horizontal_margin"
android:layout_marginRight="#dimen/activity_horizontal_margin"
android:layout_marginTop="#dimen/activity_vertical_margin"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:baselineAligned="false"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/icon" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center">
<Button
android:id="#+id/logOff"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Log Off"
android:textAllCaps="false"
android:textStyle="bold" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center">
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/button4"
android:text="Manage Farmers"
android:textStyle="bold"
android:textAllCaps="false"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center">
<Button
android:text="My Account"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/button5"
android:textAllCaps="false"
android:textStyle="bold"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center">
<Button
android:text="Order History"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/button2"
android:textAllCaps="false"
android:textStyle="bold"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
android:gravity="center">
<Button
android:text="Make an Order"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/makeOrder"
android:textAllCaps="false"
android:textStyle="bold"/>
</LinearLayout>
</LinearLayout>`

I have done some changes, Please check if it works for you
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main_menu"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#354739"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin">
<ImageView
android:id="#+id/iv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_marginTop="23dp"
android:src="#drawable/ic_android_black_24dp"/>
<Button
android:id="#+id/logOff"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/iv"
android:layout_marginTop="23dp"
android:background="#6b5847"
android:text="Log Off"/>
<Button
android:id="#+id/button3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/button5"
android:layout_marginTop="23dp"
android:background="#6b5847"
android:text="Manage Farmers"/>
<Button
android:id="#+id/button4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/logOff"
android:layout_marginTop="23dp"
android:background="#6b5847"
android:text="Manage Farmers"/>
<Button
android:id="#+id/button5"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/button4"
android:layout_marginTop="23dp"
android:background="#6b5847"
android:text="My Account"/>
<Button
android:id="#+id/button2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/button5"
android:layout_marginTop="23dp"
android:background="#6b5847"
android:text="Order History"/>
<Button
android:id="#+id/makeOrder"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#+id/button2"
android:layout_marginTop="23dp"
android:background="#6b5847"
android:text="Make an Order"/>
</RelativeLayout>

Image in layout is not completely on top, where I want it

Edit, it's on top, now it's zoomed in
If it's possible, i would want it to fill the entire screen, width wise, with the image, completely on top, leaving no space between the top and the image. This is not working for me.
This is the main.xml code that I have, it could be completely wrong, please tell me if that's the case.
This is how it looks in the emulator, I want it to fill the entire top side from left to right, completely on the top.
Any help would be appreciated, i'm pretty new to this, so don't be scared to tell me i'm wrong :)
<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:gravity="center"
android:orientation="vertical"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.rodekruis.MainActivity">
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true">
<ImageView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:src="#drawable/rkz_logo"
/>
</RelativeLayout>
<Button
android:id="#+id/button2"
style="?android:attr/buttonStyleSmall"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_above="#+id/button9"
android:layout_alignLeft="#+id/button10"
android:layout_marginBottom="30dp"
android:layout_gravity="top"
android:clickable="true"
android:text="Nieuws" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginBottom="20dp"
android:orientation="horizontal">
<Button
android:id="#+id/button10"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_alignTop="#+id/button8"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Afspraak maken" />
<Button
android:id="#+id/button8"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Bezoek tijden" />
<Button
android:id="#+id/button9"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:text="Contact" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginTop="10dp"
android:layout_marginBottom="20dp"
android:orientation="horizontal">
<Button
android:id="#+id/button3"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Geef je mening!" />
<Button
android:id="#+id/button4"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Route begeleiding" />
<Button
android:id="#+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_alignLeft="#+id/button5"
android:layout_below="#+id/button8"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:text="Specia-listen" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginTop="10dp"
android:orientation="horizontal">
<Button
android:id="#+id/button5"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text="BWC" />
<Button
android:id="#+id/button6"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text="Agenda" />
<Button
android:id="#+id/button7"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:text="Praktische
informatie" />
</LinearLayout>
</LinearLayout>

try this,
<ImageView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:scaleType="centerCrop"
android:src="#drawable/rkz_logo"
/>

just remove your paddings. I hope it will help
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"

Remove two line in layout root
android:gravity="center"
android:paddingTop="#dimen/activity_vertical_margin"
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"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
tools:context=".MainActivity">
<ImageView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:src="#mipmap/ic_launcher" />
<Button
android:id="#+id/button2"
style="?android:attr/buttonStyleSmall"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
android:layout_marginBottom="30dp"
android:clickable="true"
android:text="Nieuws" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginBottom="20dp"
android:orientation="horizontal">
<Button
android:id="#+id/button10"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Afspraak maken" />
<Button
android:id="#+id/button8"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Bezoek tijden" />
<Button
android:id="#+id/button9"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:text="Contact" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginBottom="20dp"
android:layout_marginTop="10dp"
android:orientation="horizontal">
<Button
android:id="#+id/button3"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Geef je mening!" />
<Button
android:id="#+id/button4"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text=" Route begeleiding" />
<Button
android:id="#+id/button1"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_alignLeft="#+id/button5"
android:layout_below="#+id/button8"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:text="Specia-listen" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="50dp"
android:layout_marginTop="10dp"
android:orientation="horizontal">
<Button
android:id="#+id/button5"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text="BWC" />
<Button
android:id="#+id/button6"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_marginRight="5dp"
android:layout_weight="1"
android:text="Agenda" />
<Button
android:id="#+id/button7"
style="?android:attr/buttonStyleSmall"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginLeft="5dp"
android:layout_weight="1"
android:text="Praktische informatie" />
</LinearLayout>

android:layout_alignParentTop="true" on the parent of the ImageView is ignored because its parent (the root view) is not a RelativeLayout. Try changing the root view to RelativeLayout, and remove its padding (at least the top one).

layout looks different on real device than how shows in graphical layout of eclipse

I am working on the UI of my app.
The graphical layout I get in Eclipse while coding looks perfect and as that should be.
But when I launch the app either on an emulator or on a device, it gets distorted.
Every UI component, like Buttons, EditTexts and TextViews.
All the margins and paddings just get lost.
<LinearLayout
android:id="#+id/ll_grand_parent"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:gravity="fill_horizontal"
android:orientation="vertical"
android:weightSum="10" >
<LinearLayout
android:id="#+id/ll_button_signin_create_account"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="fill"
android:layout_marginLeft="7dp"
android:layout_marginTop="29dp"
android:layout_weight="2"
android:orientation="horizontal"
android:visibility="visible"
>
<Button
android:id="#+id/button_common_singin"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/transparent_button"
android:gravity="center"
android:text="Sign In"
android:textColor="#FFFFFF"
android:textSize="13sp" />
<Button
android:id="#+id/button_common_create_account"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/colored_button"
android:gravity="center"
android:text="Create Account"
android:textColor="#FFFFFF"
android:textSize="13sp" />
</LinearLayout>
<LinearLayout
android:id="#+id/signin_main"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="5.24"
android:orientation="vertical"
android:visibility="gone" >
<LinearLayout
android:id="#+id/ll_parent_signin_email_password"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="20sp"
android:layout_weight=".8"
android:background="#drawable/border"
android:orientation="vertical"
android:visibility="visible" >
<LinearLayout
android:id="#+id/ll_signin_email"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_space_signin_email"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="2" />
<TextView
android:id="#+id/textview_signin_email"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3"
android:gravity="center"
android:text="Email"
android:textColor="#FFFFFF" />
<EditText
android:id="#+id/edittext_signin_email"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="3"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="john#hotmail.com"
android:textColorHint="#FFFFFF"
android:textSize="13dp" />
</LinearLayout>
<View
android:id="#+id/view_line_signin_email_password"
android:layout_width="fill_parent"
android:layout_height="1dip"
android:background="#FFFFFF" />
<LinearLayout
android:id="#+id/ll_signin_password"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_space_signin_password"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1" />
<TextView
android:id="#+id/textview_signin_password"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3"
android:gravity="center"
android:text="Password"
android:textColor="#FFFFFF" />
<EditText
android:id="#+id/edittext_signin_password"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="4.49"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="*********"
android:password="true"
android:textColorHint="#FFFFFF" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:id="#+id/ll_signin_logme_parent_button"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_marginTop="20dp"
android:layout_weight="1"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_space_signin_loginme_button_lhs"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1" />
<Button
android:id="#+id/button_signin_loginme"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="7"
android:background="#219AC7"
android:gravity="center"
android:text="Login Me"
android:textColor="#FFFFFF" />
<ImageView
android:id="#+id/textview_space_signin_logmebutton_rhs"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight=".7" />
</LinearLayout>
<RelativeLayout
android:id="#+id/relative_layout_signin_parent_forgetpassword"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="right"
android:layout_marginLeft="14dp"
android:layout_marginTop="9dp"
android:visibility="visible" >
<TextView
android:id="#+id/textview_signin_forget_password"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="forget password"
android:textColor="#000000" />
</RelativeLayout>
<LinearLayout
android:id="#+id/ll_signin_orline_draw_parent"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="1"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<View
android:layout_width="fill_parent"
android:layout_height="1dip"
android:layout_gravity="center"
android:layout_weight="4"
android:background="#000000"
android:padding="20dp" />
<ImageView
android:id="#+id/imageview_signin_or_drawline"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_weight="2"
android:src="#drawable/or" />
<View
android:layout_width="fill_parent"
android:layout_height="1dip"
android:layout_gravity="center"
android:layout_weight="4"
android:background="#000000"
android:padding="20dp" />
</LinearLayout>
<LinearLayout
android:id="#+id/ll_signin_parent_loginwith_facebook"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_marginTop="13dp"
android:layout_weight="1"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_space_signin_facebook_lhs"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1" />
<ImageView
android:id="#+id/imageview_signin_facebook_logo"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="2"
android:background="#drawable/fb" />
<Button
android:id="#+id/button_singin_facebook"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="6"
android:background="#3B5998"
android:text="login with facebook"
android:textColor="#FFFFFF" />
<TextView
android:id="#+id/textview_space_sigin_facebook_rhs"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:id="#+id/signup_main"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_weight="6"
android:orientation="vertical"
android:visibility="visible" >
<LinearLayout
android:id="#+id/ll_signup_parentlayout_name"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="20sp"
android:layout_weight=".8"
android:background="#drawable/border"
android:orientation="vertical"
android:visibility="visible" >
<LinearLayout
android:id="#+id/ll_singnup_firstname"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_signup_firstname"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3"
android:gravity="center"
android:text="First Name"
android:textColor="#FFFFFF" />
<EditText
android:id="#+id/edittext_signup_firstname"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="3"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="John"
android:singleLine="true"
android:textColor="#FFFFFF"
android:textColorHint="#FFFFFF"
/>
<EditText
android:id="#+id/edittext_singup_email"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_weight="3"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="john#xyz.com"
android:singleLine="true"
android:textColor="#FFFFFF"
android:textColorHint="#FFFFFF"
android:textSize="13dp"
android:visibility="gone" >
</EditText>
</LinearLayout>
<View
android:id="#+id/view_signup_line_draw_name_first_last_name"
android:layout_width="fill_parent"
android:layout_height="1dip"
android:background="#FFFFFF" />
<LinearLayout
android:id="#+id/ll_signup_lastname"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_signup_lastname"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3"
android:gravity="center"
android:text="Last Name"
android:textColor="#FFFFFF" />
<EditText
android:id="#+id/edittext_signup_lastname"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="4.47"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="Smith"
android:password="false"
android:singleLine="true"
android:textColor="#FFFFFF"
android:textColorHint="#FFFFFF" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:id="#+id/ll_singnup_email_parent"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"
android:layout_marginTop="20sp"
android:layout_weight=".8"
android:background="#drawable/border"
android:orientation="vertical"
android:visibility="visible" >
<LinearLayout
android:id="#+id/ll_signup_email_address"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2"
android:orientation="horizontal"
android:weightSum="10" >
<TextView
android:id="#+id/textview_signup_email"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3"
android:gravity="center"
android:text="Email Address"
android:textColor="#FFFFFF" />
<EditText
android:id="#+id/edittext_signup_enteremail"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="4.49"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="john#xyz.com"
android:password="false"
android:singleLine="true"
android:textColor="#FFFFFF"
android:textColorHint="#FFFFFF" />
</LinearLayout>
<View
android:id="#+id/view_signup_draw_line_email"
android:layout_width="fill_parent"
android:layout_height="1dip"
android:background="#FFFFFF" />
<LinearLayout
android:id="#+id/ll_signup_reenter_email"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_gravity="center"
android:layout_weight="2"
android:orientation="horizontal"
android:visibility="visible"
android:weightSum="10" >
<TextView
android:id="#+id/textview_signup_reenteremail"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="3"
android:gravity="center"
android:singleLine="true"
android:text="Re Enter Email Address"
android:textColor="#FFFFFF" />
<EditText
android:id="#+id/edittext_signup_reenteremail"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="4.49"
android:background="#android:color/transparent"
android:gravity="center"
android:hint="john#xyz.com"
android:password="false"
android:singleLine="true"
android:textColor="#FFFFFF"
android:textColorHint="#FFFFFF" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:id="#+id/ll_signup_dob_button_parent"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="13dp"
android:divider="#drawable/divider"
android:gravity="center"
android:orientation="horizontal"
android:showDividers="middle"
android:visibility="visible"
android:weightSum="3" >
<Button
android:id="#+id/button_signup_day"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/round_button"
android:text="BirthDate"
android:textColor="#000000"
android:textSize="10sp" />
<Button
android:id="#+id/button_signup_month"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/round_button"
android:divider="#drawable/divider"
android:showDividers="middle"
android:text="BirthMonth"
android:textColor="#000000"
android:textSize="10sp" />
<Button
android:id="#+id/button_singup_year"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/round_button"
android:singleLine="true"
android:text="BirthYear"
android:textColor="#000000"
android:textSize="10sp" />
</LinearLayout>
<LinearLayout
android:id="#+id/ll_singup_radio_gender_parent"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="left"
android:layout_marginTop="10dp"
android:orientation="horizontal"
android:visibility="visible" >
<RadioGroup
android:id="#+id/radio_signup_radiogroup"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<RadioButton
android:id="#+id/radiobutton_signup_male"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:cursorVisible="true"
android:text="male "
android:textColor="#FFFFFF"
android:textColorHighlight="#ED933E" />
<RadioButton
android:id="#+id/radiobutton_signup_female"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="female"
android:textColor="#FFFFFF" />
</RadioGroup>
</LinearLayout>
<Button
android:id="#+id/button_signup_createaccount"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="13dp"
android:layout_marginRight="13dp"
android:layout_weight=".003"
android:background="#drawable/colored_button"
android:text="Create My Account"
android:visibility="visible" />
</LinearLayout>

These are the causes of your issue
android:weightSum="10"
You have to fill parent on every view and give each one a weight to just to make this work. You can achieve a good looking app that way but it is quite labor intensive and we have not even discussed text size among different devices.
Also other stuff like
android:layout_marginLeft="7dp"
Imagine a 10 inch tablet and a normal sized phone. Think of the different dimensions of the two and how your application will stretch . What happens if your turn your app sideways? How would it look then?
Go here and when your done reading it read it again.
http://developer.android.com/training/basics/supporting-devices/screens.html

layout_weight not adjusting size properly

I am trying to make a calculator app. I have a outer linearlayout which is vertical orientation and then have nested linear layouts which have a horizontal orientation where my buttons will go. Only the last nested linear layout is not adjusting the width properly of the buttons as I want the '0' button to take half the width and the '.' and '=' button to take a quarter of the width. I gave the '=' button a layout weight of 0.5 and the '.' & '=' button a layout weight of 0.25 but it still won't work properly.
Here is a screenshot of the graphical layout:
XML code:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:background="#000000"
android:weightSum="1">
<TextView
android:text="0"
android:layout_width="wrap_content"
android:layout_weight = "0.25"
android:layout_height="0dp"
android:textSize="40sp"
android:layout_gravity="right"
android:textColor="#FFFFFF"
android:id="#+id/tvDisplay"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:orientation="horizontal"
android:layout_weight="0.15"
android:weightSum="1">
<Button
android:id="#+id/bClear"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="C"
android:textSize="30sp" />
<Button
android:id="#+id/bChangeSign"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="+/-"
android:textSize="30sp" />
<Button
android:id="#+id/bPercent"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="%"
android:textSize="30sp" />
<Button
android:id="#+id/bDivide"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="/"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:orientation="horizontal"
android:layout_weight="0.15">
<Button
android:text="7"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b7"/>
<Button
android:text="8"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b8"/>
<Button
android:text="9"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b9"/>
<Button
android:id="#+id/bMultiply"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="x"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:orientation="horizontal"
android:layout_weight="0.15">
<Button
android:text="4"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b4"/>
<Button
android:text="5"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b5" />
<Button
android:text="6"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b6" />
<Button
android:text="-"
android:background="#FF9900"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/bSubtract"
/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:orientation="horizontal"
android:layout_weight="0.15">
<Button
android:text="1"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b1" />
<Button
android:text="2"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b2" />
<Button
android:text="3"
android:background="#FFFFFF"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/b3" />
<Button
android:text="+"
android:background="#FF9900"
android:textSize="30sp"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:id="#+id/bPlus" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.15"
android:orientation="horizontal"
<Button
android:id="#+id/b0"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.5"
android:background="#FFFFFF"
android:text="0"
android:textSize="30sp" />
<Button
android:id="#+id/bDecimal"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="."
android:textSize="30sp" />
<Button
android:id="#+id/bEquals"
android:layout_width="wrap_content"
android:layout_height="fill_parent"
android:layout_margin="0.2dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="="
android:textSize="30sp" />
</LinearLayout>

The solution to this problem is remarkably simple.
Android is great, and the tools for developing it are great, but then you come across behaviors like this and you realize that it certainly isn't perfect yet.
Go ahead and change the android:layout_width in your 3 buttons at the bottom to
android:layout_width="0dp"
Now, this was the way this was explained to me. The layout_weight attribute tries to balance out the widths to be in the correct ratios, but it takes into account the widths of the buttons it is trying to balance. By setting the width to absolutely nothing (0dp), you're taking away any sort of widths that may have interfered with layout_weigth's attempts to balance the ratios. Basically, so that there are no other values that could throw off the shifting of the widths.
I hope that helps. Good luck :)

test well
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#000000"
android:orientation="vertical"
android:weightSum="1" >
<TextView
android:id="#+id/tvDisplay"
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_gravity="right"
android:layout_weight="0.25"
android:text="0"
android:textColor="#FFFFFF"
android:textSize="40sp" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.15"
android:orientation="horizontal"
android:weightSum="1" >
<Button
android:id="#+id/bClear"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="C"
android:textSize="30sp" />
<Button
android:id="#+id/bChangeSign"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="+/-"
android:textSize="30sp" />
<Button
android:id="#+id/bPercent"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="%"
android:textSize="30sp" />
<Button
android:id="#+id/bDivide"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="/"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.15"
android:orientation="horizontal"
android:weightSum="1" >
<Button
android:id="#+id/b7"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="7"
android:textSize="30sp" />
<Button
android:id="#+id/b8"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="8"
android:textSize="30sp" />
<Button
android:id="#+id/b9"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="9"
android:textSize="30sp" />
<Button
android:id="#+id/bMultiply"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="x"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.15"
android:orientation="horizontal"
android:weightSum="1" >
<Button
android:id="#+id/b4"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="4"
android:textSize="30sp" />
<Button
android:id="#+id/b5"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="5"
android:textSize="30sp" />
<Button
android:id="#+id/b6"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="6"
android:textSize="30sp" />
<Button
android:id="#+id/bSubtract"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="-"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.15"
android:orientation="horizontal"
android:weightSum="1" >
<Button
android:id="#+id/b1"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="1"
android:textSize="30sp" />
<Button
android:id="#+id/b2"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="2"
android:textSize="30sp" />
<Button
android:id="#+id/b3"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="3"
android:textSize="30sp" />
<Button
android:id="#+id/bPlus"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="+"
android:textSize="30sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="0.15"
android:orientation="horizontal"
android:weightSum="1" >
<Button
android:id="#+id/b0"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.5"
android:background="#FFFFFF"
android:text="0"
android:textSize="30sp" />
<Button
android:id="#+id/bDecimal"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FFFFFF"
android:text="."
android:textSize="30sp" />
<Button
android:id="#+id/bEquals"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_margin="0.1dp"
android:layout_weight="0.25"
android:background="#FF9900"
android:text="="
android:textSize="30sp" />
</LinearLayout>