Android:可以在可绘制选择器中使用字符串/枚举吗? [英] Android: Is it possible to use string/enum in drawable selector?
问题描述
第1季度:有没有人设法让自定义字符串/枚举属性在xml选择器中工作?我通过遵循[1]得到了一个布尔属性，但没有一个字符串属性.
Q1: Has anyone managed to get custom string/enum attribute working in xml selectors? I got a boolean attribute working by following [1], but not a string attribute.
感谢您的回答.目前，Android仅支持布尔选择器.查看原因的可接受答案.
Thanks for answers. Currently android supports only boolean selectors. See accepted answer for the reason.
我打算实现一个复杂的自定义按钮，其外观取决于两个变量.其他将是布尔属性(是或否)，而另一个将是类类别的属性(具有许多不同的可能值).我的计划是使用布尔值和字符串(或可能是枚举?)属性.我希望可以使用boolean和string属性在xml选择器中定义UI.
I'm planning to implement a little complex custom button, whose appearance depends on two variables. Other will be a boolean attribute (true or false) and another category-like attribute (has many different possible values). My plan is to use boolean and string (or maybe enum?) attributes. I was hoping I could define the UI in xml selector using boolean and string attribute.
第二季度:为什么在[1]中的onCreateDrawableState()中，布尔属性仅在它们为true时才被合并?
Q2: Why in [1] the onCreateDrawableState(), boolean attributes are merged only if they are true?
注意:这只是一个测试应用程序，用于确定xml选择器中是否可以使用string/enum属性.我知道我可以在没有自定义属性的情况下设置按钮的文本颜色.
NOTE: This is just a test app to figure out if string/enum attribute is possible in xml selector. I know that I could set button's textcolor without a custom attribute.
在演示应用程序中，我使用boolean属性将按钮背景设置为深色/明亮，并使用string属性设置文本颜色，例如{"red"，"green"，"blue"}中的一种.属性在/res/values/attrs.xml
In my demo application, I use a boolean attribute to set button background to dark/bright and string attribute to set text color, one of {"red", "green", "blue"}. Attributes are defined in /res/values/attrs.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="MyCustomButton">
<attr name="make_dark_background" format="boolean" />
<attr name="str_attr" format="string" />
</declare-styleable>
</resources>
这是我要实现的选择器:
Here are the selectors I want to achieve:
@ drawable/custom_button_background(有效)
@drawable/custom_button_background (which works)
<?xml version="1.0" encoding="utf-8"?>
<selector
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res/com.example.customstringattribute">
<item app:make_dark_background="true" android:drawable="@color/dark" />
<item android:drawable="@color/bright" />
</selector>
@ color/custom_button_text_color(无效)
@color/custom_button_text_color (which does not work)
<selector
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res/com.example.customstringattribute">
<item app:str_attr="red" android:color="@color/red" />
<item app:str_attr="green" android:color="@color/green" />
<item app:str_attr="blue" android:color="@color/blue" />
<item android:color="@color/grey" />
</selector>
这是将自定义按钮背景连接到布尔选择器，以及将文本颜色连接到字符串选择器的方式.
Here is how custom button background is connected to boolean selector, and text color is connected to string selector.
<com.example.customstringattribute.MyCustomButton
...
android:background="@drawable/custom_button_background"
android:textColor="@color/custom_button_text_color"
...
/>
这是在init()方法中加载属性的方式:
Here is how attributes are loaded in the init() method:
private void init(AttributeSet attrs) {
TypedArray a = getContext().obtainStyledAttributes(attrs,
R.styleable.MyCustomButton);
final int N = a.getIndexCount();
for (int i = 0; i < N; ++i)
{
int attr = a.getIndex(i);
switch (attr)
{
case R.styleable.MyCustomButton_str_attr:
mStrAttr = a.getString(attr);
break;
case R.styleable.MyCustomButton_make_dark_background:
mMakeDarkBg = a.getBoolean(attr, false);
break;
}
}
a.recycle();
}
我有用于属性的int []数组
I have the int[] arrays for the attributes
private static final int[] MAKE_DARK_BG_SET = { R.attr.make_dark_background };
private static final int[] STR_ATTR_ID = { R.attr.str_attr };
然后将这些int []数组合并为可绘制状态
And those int[] arrays are merged to drawable state
@Override
protected int[] onCreateDrawableState(int extraSpace) {
Log.i(TAG, "onCreateDrawableState()");
final int[] drawableState = super.onCreateDrawableState(extraSpace + 2);
if(mMakeDarkBg){
mergeDrawableStates(drawableState, MAKE_DARK_BG_SET);
}
mergeDrawableStates(drawableState, STR_ATTR_ID);
return drawableState;
}
我的属性设置器方法中也有refreshDrawableState():
I also have refreshDrawableState() in my attribute setter methods:
public void setMakeDarkBg(boolean makeDarkBg) {
if(mMakeDarkBg != makeDarkBg){
mMakeDarkBg = makeDarkBg;
refreshDrawableState();
}
}
public void setStrAttr(String str) {
if(mStrAttr != str){
mStrAttr = str;
refreshDrawableState();
}
}
[1]:如何添加自定义按钮状态
推荐答案
第一季度:
打开StateListDrawable.java的源代码时，您可以在读取可绘制xml选择器的inflate方法中看到以下代码:
https://android. googlesource.com/platform/frameworks/base/+/refs/heads/master/graphics/java/android/graphics/drawable/StateListDrawable.java
When you open the source-code of StateListDrawable.java, you can see this piece of code in the inflate method that reads the drawable xml selector:
https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/graphics/java/android/graphics/drawable/StateListDrawable.java
...
for (i = 0; i < numAttrs; i++) {
final int stateResId = attrs.getAttributeNameResource(i);
if (stateResId == 0) break;
if (stateResId == com.android.internal.R.attr.drawable) {
drawableRes = attrs.getAttributeResourceValue(i, 0);
} else {
states[j++] = attrs.getAttributeBooleanValue(i, false)
? stateResId
: -stateResId;
}
}
...
attrs是<selector>中每个<item>元素的属性.
attrs are the attributes of each <item> element in the <selector>.
在此for循环中，它获取android:drawable，各种android:state_xxxx和自定义app:xxxx属性.除了android:drawable属性之外的所有属性似乎都只解释为布尔值:调用了attrs.getAttributeBooleanValue(....).
In this for-loop it gets the android:drawable, the various android:state_xxxx and custom app:xxxx attributes. All but the android:drawable attributes seem to be interpreted as booleans only: attrs.getAttributeBooleanValue(....) is called.
我认为这是答案，基于源代码:
I think this is the answer, based on the source code:
您只能向XML添加自定义布尔属性，而不能添加任何其他类型(包括枚举).
You can only add custom boolean attributes to your xml, not any other type (including enums).
第二季度:
我不确定为什么仅将状态专门设置为true才合并状态.我怀疑代码应该看起来像这样:
I'm not sure why the state is merged only if it is specifically set to true. I would suspect the code should have looked like this instead:
private static final int[] MAKE_DARK_BG_SET = { R.attr.make_dark_background };
private static final int[] NOT_MAKE_DARK_BG_SET = { -R.attr.make_dark_background };
....
....
@Override
protected int[] onCreateDrawableState(int extraSpace) {
Log.i(TAG, "onCreateDrawableState()");
final int[] drawableState = super.onCreateDrawableState(extraSpace + 2);
mergeDrawableStates(drawableState, mMakeDarkBg? MAKE_DARK_BG_SET : NOT_MAKE_DARK_BG_SET);
//mergeDrawableStates(drawableState, STR_ATTR_ID);
return drawableState;
}
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