Develop Reference

How to make a numpad similar layout in android

How do i make the numpad layout as shown in the uploaded picture.
This is my current code which would not show anything in the design view. I used this code previously on other views which work but this time it does not work and none of the buttons were visible at all in the design view.And also how do i make the 0 button as it is in the picture. This is my 2nd time asking questions in stackoverflow so do let me know if my questions are not clear and also english is not my first language. Thank you in advanced!
Edit: I have to make this layout through xml coding and not the usual thing
where the users click on the textview and the numpad of the phone
shows up. I hope this clarify the doubts of my question. I have to
make the clear, cancel and exit button as well.
<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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="4"
android:layout_weight="4"
android:background="#drawable/background"
tools:context=".insert_amount">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="250dp">
<VideoView
android:id="#+id/videoview1"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
<TextView
android:id="#+id/textview1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Player"
android:textSize="30dp"
android:layout_marginTop="10dp"
android:layout_gravity="center_horizontal"
android:textColor="#color/white"
/>
<TextView
android:id="#+id/textview2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Display ID"
android:textSize="30dp"
android:textStyle="bold"
android:layout_marginTop="20dp"
android:layout_gravity="center_horizontal"
/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="#drawable/content_box"
android:layout_marginTop="10dp"
android:layout_marginStart="50dp"
android:layout_marginEnd="50dp"
android:orientation="vertical">
<ImageView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:src="#drawable/in"
android:layout_gravity="center_horizontal"
android:layout_marginTop="50dp"
/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Top Up Amount (IN)"
android:textSize="30dp"
android:layout_marginTop="10dp"
android:gravity="center_horizontal"
/>
<TextView
android:id="#+id/textviewnumber"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="10dp"
android:hint="0.00"
android:textSize="40dp"
android:textStyle="bold"
android:gravity="center"
/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:weightSum="4"
android:orientation="horizontal">
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_weight="1"
android:background="#drawable/login_signoutbutton"
android:layout_height="fill_parent"
android:text="1"
/>
<Button
android:id="#+id/button2"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="fill_parent"
android:background="#drawable/login_signoutbutton"
android:text="2"
/>'
<Button
android:id="#+id/button3"
android:layout_width="0dp"
android:layout_weight="1"
android:background="#drawable/login_signoutbutton"
android:layout_height="fill_parent"
android:text="3"
/>
<ImageButton
android:id="#+id/buttonclear"
android:layout_width="0dp"
android:layout_weight="1"
android:layout_height="fill_parent"
android:paddingLeft="20dp"
android:paddingRight="20dp"
android:scaleType="fitCenter"
android:background="#drawable/login_signoutbutton"
android:src="#drawable/clear_button"
android:layout_margin="20dp"
/>

Try this
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="Player"
android:textColor="#FFFFFF" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="12345679"
android:textColor="#FFFFFF" />
</LinearLayout>
</android.support.v7.widget.Toolbar>
<ImageView
android:layout_width="50dp"
android:layout_height="50dp"
android:layout_gravity="center"
android:layout_marginTop="10dp"
android:src="#drawable/kid_goku" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="10dp"
android:text="Top up Amount" />
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:hint="Top up Amount" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="20dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="horizontal">
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="1" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="4" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="7" />
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="2" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="5" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="8" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="0" />
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="vertical">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="3" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="6" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="2dp"
android:layout_marginHorizontal="2dp"
android:layout_weight="1"
android:text="9" />
</LinearLayout>
<LinearLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.5"
android:orientation="vertical">
<Button
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_marginHorizontal="2dp"
android:layout_marginTop="8dp"
android:layout_weight="1"
android:background="#9b5006"
android:drawableLeft="#drawable/ic_camera"
android:text="Clear"
android:textColor="#FFFFFF"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="35dp"
android:layout_marginHorizontal="2dp"
android:layout_marginTop="15dp"
android:layout_weight="1"
android:background="#9b5006"
android:drawableLeft="#drawable/ic_camera"
android:text="Cancel"
android:textColor="#FFFFFF"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="35dp"
android:layout_marginHorizontal="2dp"
android:layout_marginTop="12dp"
android:layout_weight="1"
android:background="#9b5006"
android:drawableLeft="#drawable/ic_camera"
android:text="Next"
android:textColor="#FFFFFF" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
</LinearLayout>
OUTPUT

Your layout height exceeding the device display. You have to use ScrollView here. Also for making the number keypad using GridLayout link will be better choice and you can easily get '0' button position using this view.

Error parsing XML: not well-formed (invalid token) in Android

I am learning android development and facing problems while building the project.
I am making a calculator app:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:layout_alignParentBottom="true"
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.palakjain.simplecalculator.MainActivity">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="100dp"
android:layout_marginBottom="20dp"
android:id="#+id/textView" />
<!--<Button
android:id="#+id/btnErase"
android:text="<-"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>-->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="#+id/btnClear"
android:text="C"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnPercentage"
android:text="%"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnDivide"
android:text="/"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:id="#+id/btn1"
android:text="1"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn2"
android:text="2"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn3"
android:text="3"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnMul"
android:text="X"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/linearLayout2"
android:layout_below="#+id/linearLayout">
<Button
android:id="#+id/btn4"
android:text="4"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn5"
android:text="5"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn6"
android:text="6"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnSub"
android:text="-"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/linearLayout">
<Button
android:id="#+id/btn7"
android:text="7"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn8"
android:text="8"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn9"
android:text="9"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnAdd"
android:text="+"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="#+id/btnPoint"
android:text="."
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btn0"
android:text="0"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnEquals"
android:text="="
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</LinearLayout>
</LinearLayout>
This is what I have done in my XML file and I am not able to figure out what's wrong. Kindly help.

Use attribute android:layout_width="wrap_content" to btnClear instead of match_parent to show btnPercentage and btnDivide on screen.
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="#+id/btnClear"
android:text="C"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnPercentage"
android:text="%"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<Button
android:id="#+id/btnDivide"
android:text="/"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
Finally, Clean and Rebuild your project and Run again.
UPDATE:
Error parsing XML: not well-formed (invalid token) in Android
I guess this problem is occurring due to android:text="<-". If you want to show "<-" as Text on Button, then use below code:
<Button
android:id="#+id/btnClear"
android:text="<-"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
FYI, here < represents <. Hope this will work~

ScrollView Still comes Behind out of it's Area

This Is My Xml.
.
<RelativeLayout 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"
tools:context="com.xxx.xxx.MyActivity" >
<LinearLayout
android:id="#+id/viewFromDateToDate"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_gravity="center"
android:layout_marginBottom="10dp"
android:layout_marginTop="10dp"
android:gravity="center"
android:orientation="horizontal" >
<EditText
android:id="#+id/txtFromDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableRight="#drawable/timesheet_icon"
android:editable="false"
android:focusableInTouchMode="false"
android:hint="#string/txtFromDate"
android:inputType="date"
android:onClick="selectDate"
android:textSize="#dimen/generalTextSize" />
<TextView
android:id="#+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:text="#string/lblFromTo"
android:textAppearance="?android:attr/textAppearanceMedium"
android:textSize="#dimen/generalTextSize" />
<EditText
android:id="#+id/txtToDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:drawableRight="#drawable/timesheet_icon"
android:editable="false"
android:focusableInTouchMode="false"
android:hint="#string/txtToDate"
android:inputType="date"
android:onClick="selectDate"
android:textSize="#dimen/generalTextSize" />
<Button
android:layout_width="100dp"
android:layout_height="wrap_content"
android:layout_marginLeft="15dp"
android:background="#drawable/green_button_department"
android:text="#string/btnShowData"
android:textColor="#color/white" />
</LinearLayout>
<View
android:id="#+id/upperSeparator"
android:layout_width="fill_parent"
android:layout_height="1dp"
android:layout_below="#id/viewFromDateToDate"
android:layout_marginTop="15dp"
android:background="#android:color/darker_gray" />
<LinearLayout
android:id="#+id/viewTimeOffDetailsHeader"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#id/upperSeparator"
android:orientation="horizontal"
android:padding="10dp" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="3"
android:text="#string/txtHeaderTimeOff"
android:textSize="#dimen/generalTextSize" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="2"
android:text="#string/txtHeaderDate"
android:textSize="#dimen/generalTextSize" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="#string/txtHeaderHours"
android:textSize="#dimen/generalTextSize" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/txtHeaderAction"
android:textSize="#dimen/generalTextSize" />
</LinearLayout>
<View
android:id="#+id/lowerSeparator"
android:layout_width="fill_parent"
android:layout_height="1dp"
android:layout_below="#id/viewTimeOffDetailsHeader"
android:background="#android:color/darker_gray" />
<ScrollView
android:id="#+id/scrollDiv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#id/lowerSeparator" >
<LinearLayout
android:id="#+id/viewTimeOffDetailsArea"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
</ScrollView>
<LinearLayout
android:id="#+id/viewTimeOffDetailsFooter"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_gravity="center"
android:gravity="center"
android:orientation="vertical" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="5dp"
android:layout_marginLeft="15dp"
android:background="#drawable/green_button_department"
android:text="#string/btnSubmitTimeOff"
android:textColor="#color/white"
android:textSize="20sp" />
</LinearLayout>
</RelativeLayout>
I want my LinerLayout scrollDiv to Be in Between of lowerSeparator and viewTimeOffDetailsFooter But the problem is ScrolView is still displaying it's Elements After viewTimeOffDetailsFooter Starts.
.
Here is an output.
Of XML Layout
Here you can see the Buttons of scrollDiv Still Displays after viewTimeOffDetailsFooter Buttons. I know that i should not put whole File But i am not getting proper solution that's why. Thanks.

you just need to place it above the viewTimeOffDetailsFooter, by adding below attribute to your scrollDiv
android:layout_above="#+id/viewTimeOffDetailsFooter"

Your viewTimeOffDetailsFooter doesn't have any positional link with scrollDiv, so add to it new rule android:layout_below="#id/scrollDiv". It can work only without android:layout_alignParentBottom="true" rule - need to try.

Custom Alert button overlapping

Ok i successfully created a custom alert and when i ran it the format is the same as in xml but after re-running it for the nth time suddenly the buttons overlap and I dont know how to fix it so can you pls help me out on this?.
alert.xml(output should be):
wrong output:
xml code:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#595959">
<EditText
android:id="#+id/orderQuantity"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignRight="#+id/b3"
android:background="#FFFFFF"
android:ems="10"
android:inputType="number" />
<Button
android:id="#+id/b1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/b4"
android:layout_alignParentLeft="true"
android:text="1" />
<Button
android:id="#+id/b2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/orderQuantity"
android:layout_toRightOf="#+id/b4"
android:text="2" />
<Button
android:id="#+id/b3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/b4"
android:layout_centerHorizontal="true"
android:text="3" />
<Button
android:id="#+id/b4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="#+id/b2"
android:text="4" />
<Button
android:id="#+id/b5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/b2"
android:layout_toLeftOf="#+id/b3"
android:text="5" />
<Button
android:id="#+id/b6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="#+id/b5"
android:layout_alignBottom="#+id/b5"
android:layout_alignLeft="#+id/b3"
android:text="6" />
<Button
android:id="#+id/b7"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/b4"
android:layout_toLeftOf="#+id/b5"
android:text="7" />
<Button
android:id="#+id/b8"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/b4"
android:layout_toRightOf="#+id/b4"
android:text="8" />
<Button
android:id="#+id/b9"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="#+id/b6"
android:layout_below="#+id/b6"
android:text="9" />
<Button
android:id="#+id/b0"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/b8"
android:layout_toLeftOf="#+id/b9"
android:text="0" />
<Button
android:id="#+id/addCart"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/b0"
android:layout_alignParentLeft="true"
android:layout_below="#+id/b7"
android:layout_toLeftOf="#+id/b0"
android:text="ADD" />
<Button
android:id="#+id/cancel"
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="#+id/b0"
android:layout_alignRight="#+id/b9"
android:layout_below="#+id/b9"
android:layout_toRightOf="#+id/b0"
android:text="BACK" />
</RelativeLayout>

Use LinearLayout instead of RelativeLayout. And remove these in Buttons:
android:layout_alignParentLeft="true"
after that it should be fine.
EDIT: Not just left alignment directives, but all alignment directives.

i would suggest you to use TableLayout ... very easy to understand and fits what you want perfectly and its easy to reuse or modify later ... your code ...
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/tableLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TableRow
android:id="#+id/tableRow1"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<EditText
android:id="#+id/orderQuantity"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignRight="#+id/b3"
android:background="#FFFFFF"
android:ems="10"
android:inputType="number" />
</TableRow>
<TableRow
android:id="#+id/tableRow1"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="1" />
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="2" />
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="3" />
</TableRow>
<TableRow
android:id="#+id/tableRow1"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="4" />
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="5" />
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="6" />
</TableRow>
<TableRow
android:id="#+id/tableRow1"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="7"/>
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="8"/>
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="9" />
</TableRow>
<TableRow
android:id="#+id/tableRow1"
android:layout_width="fill_parent"
android:layout_height="0dp"
android:layout_weight="1" >
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="Add"/>
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="0"/>
<Button
android:id="#+id/button1"
android:layout_width="0dp"
android:layout_height="fill_parent"
android:layout_weight="1"
android:text="OK"/>
</TableRow>
</TableLayout>

Organize each row as below...
<Button
android:id="#+id/b1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/b4"
android:layout_alignParentLeft="true"
android:text="1" />
<Button
android:id="#+id/b2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/orderQuantity"
android:layout_toLeftOf="#+id/b3"
android:layout_toRightOf="#+id/b1"
android:text="2" />
<Button
android:id="#+id/b3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/b4"
android:layout_toRightOf="#+id/b2"
android:layout_centerHorizontal="true"
android:text="3" />

Ok after analyzing i was able to see whats wrong.
This
<Button
android:id="#+id/b3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/b4"
android:layout_centerHorizontal="true"
android:text="3" />
Should be :
<Button
android:id="#+id/b3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/b4"
android:text="3" />

I would do something like 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="vertical"
android:background="#595959">
<EditText
android:id="#+id/orderQuantity"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignRight="#+id/b3"
android:background="#FFFFFF"
android:ems="10"
android:inputType="number"/>
<LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="1">
<Button
android:id="#+id/b1"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="1"/>
<Button
android:id="#+id/b2"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="2"/>
<Button
android:id="#+id/b3"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="3"/>
</LinearLayout>
<LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="1">
<Button
android:id="#+id/b4"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="4"/>
<Button
android:id="#+id/b5"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="5"/>
<Button
android:id="#+id/b6"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="6"/>
</LinearLayout>
<LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="1">
<Button
android:id="#+id/b7"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="7"/>
<Button
android:id="#+id/b8"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="8"/>
<Button
android:id="#+id/b9"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="9"/>
</LinearLayout>
<LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="1">
<Button
android:id="#+id/b0"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="0"/>
<Button
android:id="#+id/addCart"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="ADD"/>
<Button
android:id="#+id/cancel"
android:layout_width="0dp"
android:layout_weight=".3333"
android:layout_height="match_parent"
android:text="BACK"/>
</LinearLayout>
</LinearLayout>

How to stretch the component to match the width of parent components in Android layout?

Below is the layout I designed.
Here is my code:
<LinearLayout
android:id="#+id/digitRow1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/button1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/login_button_1" />
<Button
android:id="#+id/button2"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/login_button_2" />
<Button
android:id="#+id/button3"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="#string/login_button_3" />
</LinearLayout>
<LinearLayout
android:id="#+id/digitRow2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/button4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_4" />
<Button
android:id="#+id/button5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_5" />
<Button
android:id="#+id/button6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_6" />
</LinearLayout>
<LinearLayout
android:id="#+id/digitRow3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/button7"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_7" />
<Button
android:id="#+id/button8"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_8" />
<Button
android:id="#+id/button9"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_9" />
</LinearLayout>
<LinearLayout
android:id="#+id/digitRow4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<Button
android:id="#+id/buttonClear"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_clear" />
<Button
android:id="#+id/button0"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_0" />
<Button
android:id="#+id/buttonBack"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_back" />
</LinearLayout>
<LinearLayout
android:id="#+id/buttonRow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="horizontal"
android:padding="5dp" >
<Button
android:id="#+id/buttonChange"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_dhange" />
<Button
android:id="#+id/buttonDisable"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/login_button_disable" />
</LinearLayout>
The problem is that I want to stretch the bottom two buttons, "Change" and "Back", to match the width of the buttons above.

You can use weight on both of them, like this:
<LinearLayout
android:id="#+id/buttonRow"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="horizontal"
android:padding="5dp" >
<Button
android:id="#+id/buttonChange"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.0"
android:text="#string/login_button_dhange" />
<Button
android:id="#+id/buttonDisable"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.0"
android:text="#string/login_button_disable" />

You probably want something like the code below.
I used a hard coded button width, but you probably want to put this in dimen.xml and reference it. I centered everything with gravity.
I tried this with weights as well, but the re-sizing is funny. As your screen gets wider the buttons get two wide.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:gravity="center_horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:id="#+id/digitRow1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/button1"
android:layout_width="100dp"
android:layout_height="match_parent"
android:text="1" />
<Button
android:id="#+id/button2"
android:layout_width="100dp"
android:layout_height="match_parent"
android:text="2" />
<Button
android:id="#+id/button3"
android:layout_width="100dp"
android:layout_height="match_parent"
android:text="3" />
</LinearLayout>
<LinearLayout
android:id="#+id/digitRow2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/button4"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="4" />
<Button
android:id="#+id/button5"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="5" />
<Button
android:id="#+id/button6"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="6" />
</LinearLayout>
<LinearLayout
android:id="#+id/digitRow3"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/button7"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="7" />
<Button
android:id="#+id/button8"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="8" />
<Button
android:id="#+id/button9"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="9" />
</LinearLayout>
<LinearLayout
android:id="#+id/digitRow4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:orientation="horizontal" >
<Button
android:id="#+id/buttonClear"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="Clear" />
<Button
android:id="#+id/button0"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="0" />
<Button
android:id="#+id/buttonBack"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="Back" />
</LinearLayout>
<LinearLayout
android:id="#+id/buttonRow"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="horizontal"
android:padding="5dp"
android:gravity="center_horizontal"
>
<Button
android:id="#+id/buttonChange"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:text="Change" />
<Button
android:id="#+id/buttonDisable"
android:layout_width="150dp"
android:layout_height="wrap_content"
android:text="Disable" />
</LinearLayout>

Try to use weight like below. Also use margins to tweak the positions of the buttons.
<LinearLayout
android:id="#+id/buttonRow"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:orientation="horizontal"
android:padding="5dp" >
<Button
android:id="#+id/buttonChange"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.0"
android:text="#string/login_button_dhange" />
<Button
android:id="#+id/buttonDisable"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1.0"
android:text="#string/login_button_disable" />