How can I add gradient effect to background color

问题:

In reference to these questions :

Adding gradient effect to TextView in a ListView generates NPE

and

How to change color and font on ListView

I would like to know how to go about setting the background of a TextView in a ListView with gradient effect?

In one of the questions above, I ended up having the gradient effect added to the text in the TextView. And after skimming through the second question, it seems I can add only fixed background colors.

How do I go about adding gradient to background? Should I make a CustomListAdapter?

回答1:

You just need to create a drawable resource (see an example below), and add it to the layout you created for your ListItem.

The drawable (in your res\drawable folder - name it whatever - listgrad.xml for ex) could look like:

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
      android:startColor="@color/gradient_start"
      android:endColor="@color/gradient_end"
      android:angle="-270" /> 
</shape>

The you would add it to the layout for your list item (the layout.xml file you define for this) like this code snippet:

<TextView
        android:id="@+id/ranking_order"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/list_grad"
        />
...

回答2:

Once you create a gradient you can apply it to pretty much anything let it be textView, layout or button.

To understand how to create and use a gradient refer this link.

To create a gradient you need to add it to the below directory

Code for gradient would be something like this -

<?xml version="1.0" encoding="UTF-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape>
            <gradient
                android:startColor="#ff2d9a59"
                android:centerColor="#ff42959a"
                android:endColor="#ff23729a"
                android:angle="135"/>
        </shape>
    </item>
</selector>

回答3:

Referred from here : How do I create a ListView with rounded corners in Android? (I have found it very useful.)

Add the following into a file (say gradient.xml) and then place it in (res/drawable/gradient.xml) directory.

<?xml version="1.0" encoding="UTF-8"?> 
<shape xmlns:android="http://schemas.android.com/apk/res/android" 
     android:shape="rectangle"> 
     <gradient 
         android:startColor="#SomeGradientBeginColor"
         android:endColor="#SomeGradientEndColor" 
         android:angle="270"/> 

    <corners 
         android:bottomRightRadius="7dp" 
         android:bottomLeftRadius="7dp" 
         android:topLeftRadius="7dp" 
         android:topRightRadius="7dp"/> 
</shape> 

Once you are done with creating this file,just set the background in one of the following ways:

Through Code: listView.setBackgroundResource(R.drawable.customshape);

Through XML,just add the following attribute to the container (ex: LinearLayout or to any fields):

android:background="@drawable/customshape"