Android以编程方式创建选择器

Question

如何以编程方式创建选择器？
我有一个分配给TabWidgetas 的xml选择器Tab indicator color

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <!-- Non focused states -->
    <item android:state_focused="false" android:state_selected="false" android:state_pressed="false" android:drawable="@drawable/bg_tab_unselected" />
    <item android:state_focused="false" android:state_selected="true"  android:state_pressed="false" android:drawable="@drawable/bg_tab_selected" />

    <!-- Focused states -->
    <item android:state_focused="true" android:state_selected="false" android:state_pressed="false" android:drawable="@drawable/bg_tab_unselected_focused" />
    <item android:state_focused="true" android:state_selected="true"  android:state_pressed="false" android:drawable="@drawable/bg_tab_selected_focused" />

    <!-- Pressed -->
    <!--    Non focused states -->
    <item android:state_focused="false" android:state_selected="false" android:state_pressed="true" android:drawable="@drawable/bg_tab_unselected_pressed" />
    <item android:state_focused="false" android:state_selected="true"  android:state_pressed="true" android:drawable="@drawable/bg_tab_selected_pressed" />

    <!--    Focused states -->
    <item android:state_focused="true" android:state_selected="false" android:state_pressed="true" android:drawable="@drawable/bg_tab_unselected_pressed" />
    <item android:state_focused="true" android:state_selected="true"  android:state_pressed="true" android:drawable="@drawable/bg_tab_selected_pressed" />
</selector>

有没有办法动态创建上面的xml代码？

Answer 1

你可以像这样使用它:

public static StateListDrawable makeSelector(int color) {
    StateListDrawable res = new StateListDrawable();
    res.setExitFadeDuration(400);
    res.setAlpha(45);
    res.addState(new int[]{android.R.attr.state_pressed}, new ColorDrawable(color));
    res.addState(new int[]{}, new ColorDrawable(Color.TRANSPARENT));
    return res;
}

然后:

view.setBackground(makeSelector(Color.RED));

Answer 2

您可以直接创建StateListDrawable并用于addState添加您在 XML 中定义的状态：

StateListDrawable d = new StateListDrawable();

[...]

int[] sFocusedSelected = { android.R.attr.state_focused, android.R.attr.state_selected };
Drawable dFocusedSelected = getDrawable(R.drawable.bg_tab_selected_focused);
d.addState(sFocusedSelected, dFocusedSelected);

[...]

相同的规则适用于XML：

选择不是基于“最佳匹配”，而是基于满足该州最低标准的第一个项目。