Android TextView:有没有办法用短文强制选框动画？

Question

我有一个带有一些文本的TextView,我想让它用滚动的选框动画制作动画.我看到了关于强制选框动画的这个流行问题,但是答案中的代码只有在文本足够长以超出TextView的边界(因此文本被截断)时才起作用,我正在寻找永久性的解决方案无论文本的宽度如何,都要使文本具有此选取框动画; 这可能吗？

Answer 1

制作自己的动画.

动画/ marquee.xml

<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate
        android:fromXDelta="100%"
        android:toXDelta="-100%"
        android:duration="10000"
        android:repeatCount="infinite"
        android:repeatMode="restart"
        android:interpolator="@android:anim/linear_interpolator"/>
</set>

在你的活动中,

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.my_activity);

    TextView myTextView = (TextView) findViewById(R.id.myTextView);
    Animation marquee = AnimationUtils.loadAnimation(this, R.anim.marquee);
    myTextView.startAnimation(marquee);
}

Answer 2

采纳 @JodiMiddleton 关于填充文本的建议，我构建了一些辅助方法，以基于 TextPaint 对象将文本填充到目标宽度（确保测量时字体等的大小正确）：

/**
 * Pad a target string of text with spaces on the right to fill a target
 * width
 * 
 * @param text The target text
 * @param paint The TextPaint used to measure the target text and
 *            whitespaces
 * @param width The target width to fill
 * @return the original text with extra padding to fill the width
 */
public static CharSequence padText(CharSequence text, TextPaint paint, int width) {

    // First measure the width of the text itself
    Rect textbounds = new Rect();
    paint.getTextBounds(text.toString(), 0, text.length(), textbounds);

    /**
     * check to see if it does indeed need padding to reach the target width
     */
    if (textbounds.width() > width) {
        return text;
    }

    /*
     * Measure the text of the space character (there's a bug with the
     * 'getTextBounds() method of Paint that trims the white space, thus
     * making it impossible to measure the width of a space without
     * surrounding it in arbitrary characters)
     */
    String workaroundString = "a a";
    Rect spacebounds = new Rect();
    paint.getTextBounds(workaroundString, 0, workaroundString.length(), spacebounds);

    Rect abounds = new Rect();
    paint.getTextBounds(new char[] {
        'a'
    }, 0, 1, abounds);

    float spaceWidth = spacebounds.width() - (abounds.width() * 2);

    /*
     * measure the amount of spaces needed based on the target width to fill
     * (using Math.ceil to ensure the maximum whole number of spaces)
     */
    int amountOfSpacesNeeded = (int)Math.ceil((width - textbounds.width()) / spaceWidth);

    // pad with spaces til the width is less than the text width
    return amountOfSpacesNeeded > 0 ? padRight(text.toString(), text.toString().length()
            + amountOfSpacesNeeded) : text;
}

/**
 * Pads a string with white space on the right of the original string
 * 
 * @param s The target string
 * @param n The new target length of the string
 * @return The target string padded with whitespace on the right to its new
 *         length
 */
public static String padRight(String s, int n) {
    return String.format("%1$-" + n + "s", s);
}

因此，当您使用基于 TextView 的方法时，您将调用：

textView.setText(padText(myTargetString, textView.getPaint(), textView.getWidth()));

它并不优雅，而且我几乎可以肯定可以进行改进（更不用说更好的方法了），但尽管如此，我在代码中使用了它，而且它似乎起到了作用:)

更新的答案

measureText允许更准确的测量（使用上面的内容我发现空格字符比测量的稍短，足以不选框）。

调整上面的答案将简化为：

public static CharSequence padText(CharSequence text, TextPaint paint, int width) {

        float widthOfText = paint.measureText(text.toString());

        if (widthOfText > width) {
            return text;
        }

        // Calculate how many spaces are required
        float widthOfSpace = paint.measureText(" ");

        int amountOfSpacesNeeded = (int) Math.ceil((width - widthOfText) / widthOfSpace);

        return amountOfSpacesNeeded > 0 ? padRight(text.toString(), text.toString().length()
                + amountOfSpacesNeeded) : text;
    }