Android自定義View系列之可伸縮的TextView

經常訪問我博客的同學應該注意到了我的博客大部分是關于分析Android系統原理的，很少涉及應用層的知識，但是想要開發一個用戶歡迎的App，沒有一個炫酷的UI肯定是不行的，就好比一個人想成為武林高手僅僅修煉內功是不行的，必須內功和外功同時修煉才能成為真正的武林高手。很多人在開發Android的App過程中有這樣的感覺，我不用學習Android系統原理照樣可以進行Android開發，而且可以做出非常炫酷的效果，確實是這樣的 ，因為對于一款App，它的大部分需求無非就是請求數據然后展示數據，至于一些炫酷的UI控件網上有很多開源的，所以我們不用懂Android系統的原理同樣可以進行App開發，相信你自己也發現了，長期做這樣的工作，你的技術是永遠得不到提升的，當你使用別人開源的炫酷的控件時，你并不知道別人是怎么實現的，即使你有興趣看別人的實現方法，如果你不懂Android系統原理，估計你也看不懂別人為什么要這么做。所以從今天起的半年時間，我會將學習重點放在應用層的開發，主要是自定義View和炫酷的動畫的學習上。

該自定義View具備如下特性：

1. 當顯示的內容沒有2行(可以通過屬性配置)時，和普通的TextView一樣

2. 當顯示的內容大于2行時，僅僅顯示兩行，并且沒有顯示完的內容使用省略號代替，并顯示向下箭頭表示還有內容沒有顯示全

3. 當用戶點擊TextView時，內容全部展開，當用戶再次點擊時，TextView又變為壓縮模式

下面我們開始代碼實現，正如上面所說，此View支持自定義屬性，所以我們先要定義attrs.xml文件，如何編寫attrs.xml文件網上有很多教程，我這里就不在說了。

<?xml version="1.0" encoding="utf-8"?><resources>
    <declare-styleable name="ExpandTextView">
        <attr name="textcolor" format="color"></attr>
        <attr name="textsize" format="dimension"></attr>
        <attr name="icon" format="reference"></attr>
        <attr name="lines" format="integer"></attr>
        <attr name="text" format="string"></attr>
    </declare-styleable></resources>12345678910

這幾個屬性的意義如下：

• textcolor : 字體顏色

http://www.gexing.com/tupian/t/%E5%8D%97%E9%95%BF%E5%8C%BA%E5%A4%A7%E5%9C%A3%E5%A8%B1%E4%B9%90QQ82933700

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