Xamarin.Android: Set Style in Codebehind

Question

How do I set the Style attribute of a View or Layout in codebehind? In xaml, it is simply set using the style attribute, but I cannot seem to find anything to set it in codebehind. In my specific case, I am trying to set the style of a GridLayout. Any ideas? Thanks.

Answer 1

Hello,

Welcome to our Microsoft Q&A platform!

For this, you can apply styles programmatically with custom view.

1.You can define the attr of your control in file attrs.xml:

 <?xml version="1.0" encoding="utf-8" ?>  
<resources>  
 <declare-styleable name="test">  
 <attr name="text" format="string" />  
 <attr name="testAttr" format="integer" />  
 <attr name = "fontScale" format = "float" />  
 <attr name="testColor" format="color|reference"/>  
 </declare-styleable>  
</resources>  

2.And create a Custom view MyTextView as follows,and in function Initialize, you can set your style as you want.:

   public class MyTextView : TextView  
{  
    protected MyTextView(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)  
    {  
    }  
    public MyTextView(Context context) : base(context)  
    {  
        Initialize(context);  
    }  

    public MyTextView(Context context, IAttributeSet attrs) : base(context, attrs)  
    {  
        Initialize(context, attrs);  
    }  
    public MyTextView(Context context, IAttributeSet attrs, int defStyleAttr) : base(context, attrs, defStyleAttr)  
    {  
        Initialize(context, attrs);  
    }  
    public MyTextView(Context context, IAttributeSet attrs, int defStyleAttr, int defStyleRes) : base(context, attrs, defStyleAttr, defStyleRes)  
    {  
        Initialize(context, attrs);  
    }  
    float ontScale;  
    private void Initialize(Context context, IAttributeSet attrs = null)  
    {  
        if (attrs != null)  
        {  
            TypedArray ta = context.ObtainStyledAttributes(attrs, Resource.Styleable.test);  
            string text = ta.GetString(Resource.Styleable.test_text);  
            int textAttr = ta.GetInt(Resource.Styleable.test_testAttr, 0);  
            float ontScale = ta.GetFloat(Resource.Styleable.test_fontScale, 0);  

            var myColor = ContextCompat.GetColor(context, Resource.Color.yellow);  

            var testColor = ta.GetColor(Resource.Styleable.test_testColor, myColor);  


            this.TextSize = ontScale;  

            SetTextColor(testColor);  
            ta.Recycle();  
        }  
    }   
}  

3.Usage:

   <?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"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="match_parent"  
    android:orientation="vertical"  
    android:layout_height="match_parent">  

    <CustomTextViewDemo.MyTextView  
        android:layout_width="100dp"  
       android:layout_height="100dp"  
       app:testAttr="600"  
       app:text="welcome"   
       app:fontScale="15"  
       android:text="test" >  
    </CustomTextViewDemo.MyTextView>  
</LinearLayout>  

Update:

Take TextView for example, if you want to set style for it you can do like this:

public void setTextAppearance(Context context, int resId)  
{  
    if (Build.VERSION.SdkInt < BuildVersionCodes.M)  
    {  
        textView1.SetTextAppearance(context, resId);  
    }  
    else  
    {  
        textView1.SetTextAppearance(resId);  
    }  
}  

Note:the resId is the style id you define in file styles.xml

Best Regards,

Jessie Zhang

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