Develop Reference

How to set background color of an image, but within the border?

My goal is to display a circular image, and allow the user to set its foreground and background colors respectively, for example:
My attempt was to create an image asset with transparent background, then use ImageView::setColorFilter to change its foreground, and use ImageView::setBackgroundColor to set its background. The image asset looks like this:
My problem is that pixels outside of what we humans call 'border' are also transparent, so the result looks like this:
How do people usually deal with this issue? Although I was doing Android development, but any ideas or code snippets in any language are appreciated!

at the first, you must create a new drawable file and write below code for creating the circle with yellow color with blue border:
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="oval">
<solid android:color="#cab816" />
<size android:width="50dp"
android:height="50dp"/>
<stroke android:width="2dp"
android:color="#color/darkBlue"/>
</shape>
and now you must set this drawable to the background of your imageview and set your image with src.
if your image covered all of this circle, use padding for decrease image size.

Is it ok to use png as a button background?

Is there is any drawback of using png as a background for a Button or EditText. Or should I write a code for XML for background of Button or EditText. I want to know which is the better way.

You can use color,drawable file or image as background
Color
android:background="#2F6699"
Drawable
android:background="#drawable/edittext_background"
Image
android:background="#drawable/ic_launcher"
Drawable file
<?xml version="1.0" encoding="utf-8" ?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:thickness="0dp"
android:shape="rectangle">
<stroke android:width="2dp"
android:color="#2F6699"/>
<corners android:radius="3dp" />
<gradient android:startColor="#C8C8C8"
android:endColor="#FFFFFF"
android:type="linear"
android:angle="270"/>
</shape>

I think you can try 9 patch image for button and edittext background.
9 Patch:
9-Patch images are stretchable, repeatable images reduced to their
smallest size; users draw a right and bottom, solid black 1 pixel
border to tell the system how to place the content within the image.
For more information visit this post:
Utility of android nine patch

just put png image into drawable, and than set it in xml via android:background="#drawable/image.png"

Use it in button properties
android:background="#drawable/imageName"

Draw rectangle with empty partial fill

Here's what I want to do: Click
I have a progressBar and I want to overlay this onto it so that I can achieve rounded corners. Problem is, if I use a 9patch image, it doesn't scale down, and scaling up pixelates the corners. Also, the corners when I increase the size of the progressBar, don't look sharp enough.
So I thought maybe drawing such a rectangle on top would make it 100% precise with crisp quality. Unfortunately, I've never used that before and there's no tutorial similar to what I want to achieve.
Thanks for all the help.

If you apply a shape drawable, you should be able to achieve what you want. You reference it just like any other drawable (android:src/android:background).
Let's name this file rounded_rect.xml:
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<corners android:radius="20dp" />
<solid android:color="#80ffffff" />
</shape>
The radius can be more or less than 20dp, it will actually scale down if the container that it's drawn in requires less for the sides to be perfectly rounded; the color is white with a bit of transparency (#80).
Save it to your drawable folder and refer to it as you usually would with any png/jpg/etc drawable:
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/rounded_rect" />

Android 9 patch images are only useful for single coloured square shape images?

Android 9 patch images are only useful for single coloured square shape images. I have button with circle shape,
how to use 9 patch for this image?

You need to create a shape drawable in the drawable folder that looks something like:
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="oval" >
<gradient android:startColor="#FFFF0000" android:endColor="#80FF00FF"
android:angle="270"/>
</shape>
Modify color code that you want.
(For this example I have saved the drawable as circle.xml and it will have a gradient fill)
Then in your layout you need to define a view and set the shape as the background:
<View android:layout_width="50dp"
android:layout_height="50dp"
android:background="#drawable/circle"/>
The View defines the size and dimensions of the shape.
Edit - Screenshots of the result of the code

How to add corners to a view

I added a full border around a view but I need to add just the corner as shown image below :
I mean the red corner only .
I tried to adjust the below border xml , but it didn't work :
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<stroke android:width="10dp" android:height="10dp" android:color="#B22222" />
<solid android:color="#FCE6C9" />
<corners android:radius="20dp" />
</shape>
Any help will be appreciated

I don't think it's possible to do this using a ShapeDrawable, as it would require you to use some sort of margin or padding on the drawable itself. There actually is a padding attribute, but unfortunately that only has effect on the content of the View, and not the drawable itself.
That being said, an easy solution would be to create a 9-patch in stead and apply that as background to the TextView. Just for demonstration purposes: make the 9-patch look somewhat like this:
Edit:
On second thought, there's actually another option that relies on using a LayerDrawable to create the desired effect. It's a bit tedious to create and I have my doubts it'll be more efficient than using a 9-patch, but at least you don't have to render out images, which means that if you need to make e.g. a change in colours, it's more straightforward.
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="#drawable/rounded" />
<item android:drawable="#android:color/white" android:left="30dp"
android:right="30dp" />
<item android:bottom="30dp" android:drawable="#android:color/white"
android:top="30dp" />
<item android:bottom="30dp" android:left="10dp" android:right="10dp"
android:drawable="#color/pink" android:top="30dp" />
<item android:bottom="10dp" android:left="30dp" android:right="30dp"
android:drawable="#color/pink" android:top="10dp" />
</layer-list>
Some details: #drawable/rounded is the code snippet you posted yourself. The following two items are simply white rectangles with an offset, to create the white edges. Now, since these will also overlay the pink surface, we need two more pink rectangles (again with specific offsets) to counter that. The result is a background that looks exactly like what you're showing in your question.
Note that you might want to see if you can optimise this a bit. At the least I'd recommend not hardcoding the offsets (like I did for simplicity), but store them in a dimens.xml file so you can keep these values centralized and consistent by referencing them from both the ShapeDrawable and LayerDrawable.
Addendum: On pre-ICS (or perhaps pre-Honeycomb) devices, there appears to be an issue with directly referencing colours with the android:drawable attribute. You can however easily get around this by setting up another drawable (be it either a 9-patch or ShapeDrawable) to represent this colour. For example, in the snippet above, you would replace android:drawable="#color/pink" with android:drawable="#drawable/color_pink", where color_pink can simply be an xml file containing:
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<solid android:color="#FCE6C9" />
</shape>
Obviously you will need to do the same for all other colours referenced in the LayerDrawable. Tested on Gingerbread 2.3.7.

I would create a 9-patch file and set it to be the background of the main container. The steps to do that would be.
You create the background you would like roughly in fireworks, illustrator, or whatever image editing software you prefer.
Then crop the artwork so that there is only a 1 pixel border around the artwork. Save it as a png.
Open the draw9patch.bat file in your android sdk folder on your computer C:\Program Files (x86)\Android\android-sdk\tools.
Open your png file. You can then use your mouse to click on the outer 1 pixel border which will turn the clicked pixels black. The areas that you have black pixels on both the top and bottom or on the left and right will be the area that is stretched. In your case you just want to have the middle area where there is no red stretched.
My personal preference is to just open the file above and save it as a 9 patch file. Then open it in my photo editing software to create a 1 pixel thick line in the same fashion as above. It is quicker and more precise.
Finally add the file to your drawable folder. Then set the background of your main view container to the drawable.
That should be it. Hope that helps.