Develop Reference

How to set my Child Layout also starts from parent's position?

I try to set my LinearLayout starts from screen edge(like Parent layout).I dont want the White Space between two layouts.
i need to start from left side from screen edge and top also edge . or follow the parent left and top properties.
NOTE:
suppose i dont want to change the Relative layout properties only changes in linear layout means how to fix it?
<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"
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.zd.MainActivity" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:id="#+id/preview"
android:focusable="true">
<requestFocus />
</LinearLayout>
</RelativeLayout>

DO LIKE BELOW.
<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.example.zd.MainActivity" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:id="#+id/preview"
android:focusable="true">
<requestFocus />
</LinearLayout>
</RelativeLayout>

remove these lines.. these are creating padding for the child.
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
But according your question.
<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"
android:background="#color/gray"
android:clipToPadding="false" // this will do the trick here
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin" >
// suppose you have 16dp padding
<LinearLayout
android:layout_marginTop="-16dp"
android:layout_marginBottom="-16dp"
android:layout_marginLeft="-16dp"
android:layout_marginRight="-16dp"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"
android:id="#+id/preview"
android:background="#color/green"
android:focusable="true">
<requestFocus />
</LinearLayout>
</RelativeLayout>

Remove space between app border and a List view

I'm developing an android app which uses a list view using android studio.But when i use it a space is being displayed between list view and app borders.how can i remove that space?? Like in this pic I need my app to be designed .The following code is XML code for listview i got in my editor.Suggest the changes for space removal.
<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" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity">
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/listView"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true"
android:layout_alignParentBottom="true" />
</RelativeLayout>

The padding is due to the padding provided to RelativeLayout
From your XML code remove padding by making you code look like
<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=".MainActivity">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/listView"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true"
android:layout_alignParentStart="true" />
</RelativeLayout>

Textview not skipping to next line android

I am a complete beginner in android programming, and I am working with TextViews. I want two TextViews with one on top and one on bottom. But it doesn't work, and I am not sure why. Here is the xml
<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:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivity">
<TextView
android:text="#string/hello_world"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<TextView
android:text="#string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
So I have the first TextView as fill_parent for width to skip a line, but instead it just takes it out. I can't add a picture as a I just made this account for this question, but it just displays the first TextView and not the next. What is the mistake I made?

In a LinearLayout, you need to set the orientation.
android:orientation="vertical"

Use this code, here orientation was missing in your code
<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:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".MainActivity">
<TextView
android:text="#string/hello_world"
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<TextView
android:text="#string/hello_world"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>

How to generate background images?

I have the layout like below -
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#drawable/background"
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"
android:scrollbars="vertical"
tools:context="com.example.MainActivity$FragmentRegister" >
...
and the following image - (download link).
How should I generate valid backgrounds from this image? What should be their sizes? Should I generate separate images for landscape mode? Should I use 9-patches somehow there?

Use ImageView with ScaleType property.
<ImageView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:src="#drawable/background"
android:scaleType="fitXY"
/>

Background image at the right bottom corner?

I have the following simple layout:
<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"
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=".MainActivity" >
<TextView
android:id="#+id/textview_app_description"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/app_description" />
</RelativeLayout>
How could I add there background image at the right bottom corner (it should be semi-transparent, since may be behind the text - I've tried to use ImageView, but it doesn't work with such scenario)?

Would this work?
<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"
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=".MainActivity" >
<ImageView
android:id="#+id/xxx"
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:layout_alignParentRight="true"
android:layout_alignParentBottom="true"
android:alpha="0.4"
android:src="#drawable/xxx"/>
<TextView
android:id="#+id/textview_app_description"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/app_description" />
</RelativeLayout>

You can use an XML Bitmap drawable as a background. Say the image (with desired transparency) is stored in bg.png. If you just use it as the background, it will stretch to fill the view; however, you can define an XML bitmap drawable with a gravity attribute. Let's put it in /res/drawable/bottom_right_bg.xml:
<?xml version="1.0" encoding="utf-8"?>
<bitmap
xmlns:android="http://schemas.android.com/apk/res/android"
android:src="#drawable/bg"
android:gravity="bottom|right" />
Then you can add an android:background attribute to the RelativeLayout:
<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"
android:background="#drawable/bottom_right_bg"
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=".MainActivity" >
<TextView
android:id="#+id/textview_app_description"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/app_description" />
</RelativeLayout>