Develop Reference

Programmatically setting TextView background

I've defined a background for my TextView:
<?xml version="1.0" encoding="utf-8"?>
<shape
xmlns:android="http://schemas.android.com/apk/res/android"
android:shape= "rectangle" >
<solid android:color="#000"/>
<stroke android:width="1dp" android:color="#ff9"/>
</shape>
Now I'm trying to set it to my TextView programmatically:
textview.setBackground((Drawable)findViewById(R.drawable.cellborder));
This isn't working though, it's telling me it can't cast a View as a Drawable. Is there another way to do this?

If you want backwards compatibility then use the following:
textView.setBackground(ContextCompat.getDrawable(MainActivity.this, R.drawable.cellborder));
Replace MainActivity.this with the name of the activity from where are you calling these methods.
If you call textView.setBackground(...) from Pijamas activity then do the following:
textView.setBackground(ContextCompat.getDrawable(Pijamas.this, R.drawable.cellborder));

You have to use
getResources().getDrawable(R.drawable.cellborder);
which will return a Drawable.
If you use findViewById() it will try to find a View in the View Hierarchy and return that. A View is not a Drawable, so you can't cast it.

try to set drawable like this
textview.setBackgroundDrawable( getResources().getDrawable(R.drawable.cellborder) );
visit for more help.
set background drawable programmatically in Android

Dynamically change drawable colors

In my application I have a lot of drawables defined with xml files. For example I have a button defined like that:
button.xml
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<!-- Bottom 3dp Shadow -->
<item android:top="3dp">
<shape android:shape="rectangle">
<corners android:radius="3dp" />
<solid android:color="#color/black_30" />
</shape>
</item>
<!-- green top color -->
<item android:top="3dp" android:bottom="3dp" android:id="#+id/background">
<shape android:shape="rectangle">
<corners android:radius="3dp" />
<solid android:color="#color/green1" />
</shape>
</item>
</layer-list>
and then I display a button like that:
layout.xml
<Button
android:id="#+id/button"
android:layout_gravity="center"
android:layout_height="60dp"
android:layout_width="fill_parent"
android:textSize="17sp"
android:gravity="center"
android:background="#drawable/button" />
When I navigate in the app, I want to "theme" some views (some colors are changing in function of the context) and to do that I would like to be able to change dynamically the color of the button (green1) at runtime.
1) One first nice approach would be to change the color definition in button.xml with an ?attr/my_color. And then define the different color values I need in the theme file style.xml. Then at runtime, I can switch to the desired theme and that will work. The complete steps are here:
How to reference colour attribute in drawable?
The issue is that it works on Android 5 but not on Android 4 ( and I need to support this version) (we get an android.view.InflateException: Binary XML file line #2: Error inflating class <unknown>)
2) The second approach is to load the drawable in the code and then use setColorto change the color of the drawable: (written in Xamarin.Android but I am sure that you will understand the corresponding Java version)
LayerDrawable button = (LayerDrawable)Resources.GetDrawable(Resource.Drawable.normal_question_button);
GradientDrawable background = (GradientDrawable)button.FindDrawableByLayerId(Resource.Id.background);
background.SetColor(Android.Graphics.Color.Red.ToArgb());
The good things is that it's works... but randomly... Sometimes when I am displaying the button again, it's still the original green that is displayed. Sometimes, it's the new color... And once I have one of the both behaviour, the same color can stay many time and suddenly it changes again to the correct one.
Someone could explain this? Is there some caching on drawables that can gives that kind of issue?
3) I was thinking about a third solution: dynamically change the color defined in colors.xml (where green1 is defined) but it doesn't seem possible

In fact for 2) one really simple solution is:
instead of trying to customize the drawable coming from the xml file:
LayerDrawable button = (LayerDrawable)Resources.GetDrawable(Resource.Drawable.normal_question_button);
GradientDrawable background = (GradientDrawable)button.FindDrawableByLayerId(Resource.Id.background);
background.SetColor(Android.Graphics.Color.Red.ToArgb());
We can change directly the color on each button once we have an instance for them:
LayerDrawable buttonDrawable = _button.Background;
GradientDrawable background = (GradientDrawable)buttonDrawable.FindDrawableByLayerId(Resource.Id.background);
background.SetColor(Android.Graphics.Color.Red.ToArgb());

Simple gradient in Android

I'm kinda new to Android, and I'm looking to create a really simple gradient of 2 colors, from top to bottom, display it on the view, and maybe save it as an image. I really didn't find an answer that suits my needs, I'm really looking for the simplest and most straight-forward way.
Thanks!

I think the easiest way is to create a simple Shape template in XML, and then use it in any view you want, like this:
shape.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
<gradient
android:type= "linear"
android:startColor="#474946"
android:endColor="#181818"
android:angle="270"/>
</shape>
then in your view tag just add:
android:background="#drawable/shape"

I will answer in two parts creating gradient and the displaying it.
To create gradient Create a new xml file in your drawable folder and name it whatever you want. In this case i will call it myGradient.xml.
Open myGradient.xml file and paste the code below which will help create two color gradient. You can change the values of color to what you need.
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:bottom="6px" android:right="4dp">
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient
android:startColor="#d7009482"
android:endColor="#ad1c4e9b"
android:centerX="100%"
android:centerY="150%"
android:type="linear"
android:angle="135"/>
</shape>
</item>
</layer-list>
This will give you output below.
Gradient with two colors
The second part will be to display this gradient in view.
Open your view and set background to be the gradient.
android:background="#drawable/myGradient
Hope that will help you

Highlight selected items in ListFragment (MultiChoiceModeListener)?

I want to be able to see what items that have been selected in my list. Before turning ListView into ListFragment, the selected items had a blue background color (Holo Dark), but now I can only see the blue color while pressing the items - then it disappears. I do not have a problem with the items getting "checked", because they are. You just can't see it.
Here's what I do in onActivityCreated():
getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE_MODAL);
getListView().setItemsCanFocus(false);
getListView().setMultiChoiceModeListener(new LongPress());
LongPress() is a private class implementing ListView.MultiChoiceModeListener. It opens up a contextual action bar when holding finger on an item. The user can then select more items, and this is where the problem occurs. You can not see which items are checked or not (I want them to be highlighted). Why did it work before extending ListFragment? I tried to create a custom selector in my .xml-files, that didn't seem to work either. I would prefer using the custom one, if there's any.
Here's another method in my ListFragment class:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_listview, container, false);
}
fragment_listview.xml isn't doing anything special apart from changing the background color and the color of the divider.
What should I do?
I tried this, but it didn't work:
In my list_item.xml:
android:background="#drawable/selector"
selector.xml:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="true"
android:drawable="#drawable/item_checked" />
</selector>
item_checked.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http//schemas.android.com/apk/res/android" >
<solid android:color="#000000" />
</shape>

I was having the exact same issue.
I found a solution in this post: Highlight custom listview item when long click
The trick:
Set in the layout file of your list's row (in the top level component, usually a LinearLayout or RelativeLayout):
android:background="?android:attr/activatedBackgroundIndicator"

I cannot find the details right now, but you have to provide a statelist drawable for the listview-items that provides a separate drawable for the checked state.

How to get Background Color of currently selected item from ListView in Android

Can anyone tell me how to get background color of selected item from ListView in android?
Here I an using ListView with multiple item select mode and I just want to set background color of selected items. If user unchecked the option I want to restore it's background color to black.
I can set the background color of selected items but I am not getting the current background color of selected item.
Please help me.
I am using Android 4.0.3 and editor Eclipse

for this you should maintain a boolean variable for each item initially with false and when you click on any item you should make the variable to true.
and in getView() of your custom adapter you check whether it is true or false and do the needfull.
before trying this have a xml file in drawable folder and set it as background if this doesn't work then do the above must work..
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<!-- touch down -->
<item
android:drawable="#drawable/list_selector_pressed"
android:state_pressed="true"/>
<!-- selected -->
<item
android:drawable="#drawable/list_selector_selected"
android:state_selected="true"
android:state_focused="false"
android:state_pressed="false"/>
</selector>
Refer this LINK LINK