How to create a custom theme and use it in an Android application?

Create Custome Views:

public class CustomTextView extends AppCompatTextView {

public CustomTextView(Context context) {
    super(context);
    setCommonChanges(DefaultTheme.getInstance().textColor, true, context);
}

public CustomTextView(Context context, AttributeSet attrs) {
    super(context, attrs);
    setDefaultValues(context, attrs);
}

public CustomTextView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    setDefaultValues(context, attrs);
}

private void setDefaultValues(Context context, AttributeSet attrs) {

    TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomTextView);
    final int N = a.getIndexCount();
    int color = DefaultTheme.getInstance().textColor;
    boolean isCustomFont = a.getBoolean(R.styleable.CustomTextView_isCustomFont, true);
    for (int i = 0; i < N; ++i) {

        int colorIndex = a.getInteger(R.styleable.CustomTextView_tvBackground, 2);
        switch (colorIndex) {
            case 1:
                color = DefaultTheme.getInstance().headingTextColor;
                break;

            case 2:
                color = DefaultTheme.getInstance().textColor;
                break;

            case 3:
                color = DefaultTheme.getInstance().textHintColor;
                break;

            case 4:
                color = DesignUtils.getColorIdFromHexCode("#FFFFFF");
                break;

            case 5:
                color = DefaultTheme.getInstance().iconColor;
                break;
            case 6:
                color = DefaultTheme.getInstance().menuHeaderTextColor;
                break;
            case 7:
                color = DefaultTheme.getInstance().menuTextColor;
                break;
            case 8:
                color = DefaultTheme.getInstance().keyboardtextcolor;
                break;
            case 9:
                color = DesignUtils.getColorIdFromHexCode("#BEBEBE");
                break;
        }


    }
    a.recycle();

    setCommonChanges(color, isCustomFont, context);
}

private void setCommonChanges(int color, boolean isCustomFont, Context context) {
    if (isCustomFont) {
        Typeface typeface = DefaultTheme.getInstance().getTVFont(context);
        setTypeface(typeface, getTypeface().getStyle());
    }
    setTextColor(color);
}

public void updateTypeFace(int style){
    Typeface typeface = DefaultTheme.getInstance().getTVFont(getContext());
    setTypeface(typeface, style);
}