一.declare-styleable 中的 format 枚举
| 属性名 | 属性说明 | 使用示例 |
|---|---|---|
| reference | 引用某一个资源Id | app:custParams="@drawable/id" |
| color | 颜色 | app:custParams="@color/id" |
| boolean | 布尔值 | app:custParams="true" |
| dimension | 尺寸 | app:custParams="20dp" |
| float | 浮点值 | app:custParams="0.7" |
| integer | 整型 | app:custParams="10" |
| string | 字符串 | app:custParams="自定义属性" |
| fraction | 百分比 | app:custParams="50%" |
| enum | 枚举值 | app:custParams="Vertical" |
| flag | 位或运算 | app:custParams="LEFT/TOP" |
一般来说，属性声明方式为:
enum、flag的声明比较特殊
二 自定义View的四个构造函数
在自定义View时，分别有不同参数的4个构造函数，它们分别被谁调用的?
/**
* 最简单的构造函数
* Simple constructor to use when creating a view from code.
* @param context The Context the view is running in,
* through which it can access the current theme, resources, etc.
*/
public View(Context context)
参数只有上下文的构造函数，一般使用系统默认主题及属性，该方法通常由java代码生成一个控件实例时调用该构造方法,例如以下的使用方式:
ImageView image = new ImageView(MainActivity.this)
/**
* Constructor that is called when inflating a view from XML. This is called
* when a view is being constructed from an XML file, supplying attributes
* that were specified in the XML file. This version uses a default style of
* 0, so the only attribute values applied are those in the Context's Theme
* and the given AttributeSet.
*
*
* The method onFinishInflate() will be called after all children have been
* added.
*
* @param context The Context the view is running in, through which it can
* access the current theme, resources, etc.
* @param attrs The attributes of the XML tag that is inflating the view.
* @see #View(Context, AttributeSet, int)
*/
public View(Context context, @Nullable AttributeSet attrs)
当从XML文件构造视图时该构造方法被调用，提供在XML文件中指定的属性。 此版本使用默认样式为0，因此所应用的属性值是Context's Theme和给定AttributeSet中的属性值。
/**
* Perform inflation from XML and apply a class-specific base style from a
* theme attribute. This constructor of View allows subclasses to use their
* own base style when they are inflating. For example, a Button class's
* constructor would call this version of the super class constructor and
* supply R.attr.buttonStyle for defStyleAttr; this
* allows the theme's button style to modify all of the base view attributes
* (in particular its background) as well as the Button class's attributes.
*
* @param context The Context the view is running in, through which it can
* access the current theme, resources, etc.
* @param attrs The attributes of the XML tag that is inflating the view.
* @param defStyleAttr An attribute in the current theme that contains a
* reference to a style resource that supplies default values for
* the view. Can be 0 to not look for defaults.
* @see #View(Context, AttributeSet)
*/
public View(Context context, @Nullable AttributeSet attrs, int defStyleAttr)
View(Context context, @Nullable AttributeSet attrs) 使用的是系统自带的主题,也就是当我们在xml中添加View控件,如果不设置View的相关属性值,那么这个View控件会中系统的默认主题中获取对应的属性值.如果你需要为该view自定主题,那么这个构造函数就是你想要的.
/**
* Perform inflation from XML and apply a class-specific base style from a
* theme attribute or style resource. This constructor of View allows
* subclasses to use their own base style when they are inflating.
*
* When determining the final value of a particular attribute, there are
* four inputs that come into play:
*
* - Any attribute values in the given AttributeSet.
*
- The style resource specified in the AttributeSet (named "style").
*
- The default style specified by defStyleAttr.
*
- The default style specified by defStyleRes.
*
- The base values in this theme.
*
*
* Each of these inputs is considered in-order, with the first listed taking
* precedence over the following ones. In other words, if in the
* AttributeSet you have supplied <Button * textColor="#ff000000">
*
* , then the button's text will always be black, regardless of
* what is specified in any of the styles.
*
* @param context The Context the view is running in, through which it can
* access the current theme, resources, etc.
* @param attrs The attributes of the XML tag that is inflating the view.
* @param defStyleAttr An attribute in the current theme that contains a
* reference to a style resource that supplies default values for
* the view. Can be 0 to not look for defaults.
* @param defStyleRes A resource identifier of a style resource that
* supplies default values for the view, used only if
* defStyleAttr is 0 or can not be found in the theme. Can be 0
* to not look for defaults.
* @see #View(Context, AttributeSet, int)
*/
public View(Context context, @Nullable AttributeSet attrs,
int defStyleAttr, int defStyleRes)
参考链接:
Android View 四个构造函数详解
Android中自定义样式与View的构造函数中的第三个参数defStyle的意义