记录一个坑——SpannableStringBuilder

PPPeyton

于 2017-10-26 19:45:32 发布

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分类专栏： Android

本文链接：https://blog.youkuaiyun.com/qq1263292336/article/details/78357869

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本文记录在使用SpannableStringBuilder时遇到的问题。当传入的text为null，会导致NullPointerException。为避免此异常，需要对传入的start和end进行有效性检查。

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android.text.SpannableStringBuilder

public SpannableStringBuilder(CharSequence text) {
    this(text, 0, text.length());
}

public SpannableStringBuilder append(CharSequence text) {
    int length = length();
    return replace(length, length, text, 0, text.length());
}

如果text为null会抛出NullPointerException

setSpan(Object what, int start, int end, int flags)中有一个checkRange(final String operation, int start, int end)方法

private void checkRange(final String operation, int start, int end) {
    if (end < start) {
        throw new IndexOutOfBoundsException(operation + " " +
                region(start, end) + " has end before start");
    }

    int len = length();

    if (start > len || end > len) {
        throw new IndexOutOfBoundsException(operation + " " +
                region(start, end) + " ends beyond length " + len);
    }

    if (start < 0 || end < 0) {
        throw new IndexOutOfBoundsException(operation + " " +
                region(start, end) + " starts before 0");
    }
}