[WPF 学习] 14.PlaceHolder的简单实现

为了能实现placeholder的效果，用[]([wpf 学习] 12.动态绑定visualbrush)的方式，实在是十分麻烦，要为每个文本框都折腾一把，实在不爽。现在介绍个简单的方法，借用tag属性传递placeholder的内容，代码如下：

    <window.resources>
        <system:string x:key="placeholderen">english</system:string>
        <system:string x:key="placeholdercn">中文</system:string>
        <controltemplate x:key="textboxtemplateplaceholder" targettype="textbox">
            <border x:name="border" background="{templatebinding background}" borderthickness="{templatebinding borderthickness}" borderbrush="{templatebinding borderbrush}" snapstodevicepixels="true" cornerradius="15" padding="5,0">
                <grid>
                    <scrollviewer x:name="part_contenthost" focusable="false" horizontalscrollbarvisibility="hidden" verticalscrollbarvisibility="hidden"/>
                    <textblock x:name="placeholder" text="{templatebinding tag}" horizontalalignment="center" verticalalignment="center" opacity="0" background="transparent"></textblock>
                </grid>
            </border>
            <controltemplate.triggers>
                <trigger  property="text" value="">
                    <setter targetname="placeholder" property="opacity" value="0.3"></setter>
                </trigger>
            </controltemplate.triggers>
        </controltemplate>
    </window.resources>
    <stackpanel name="abc">
        <textbox fontsize="40" text="" tag="{dynamicresource placeholderen}"  name="aaa" template="{staticresource textboxtemplateplaceholder}"/>
        <textbox fontsize="40" text="" tag="{dynamicresource placeholdercn}"   template="{staticresource textboxtemplateplaceholder}"/>
    </stackpanel>
</window>

哦，顺便弄了个圆角，那叫一个方便，爽！