android中提前获取TextView行数

Java基础

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2019-8-22

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  一般情况下,TextView的行数要等到其布局完成后才能获取到,否则如果直接调用textView.getLineCount()函数获取到的结果只会为0,那能不能提前获取到TextView的行数呢,当然是肯定的。TextView内部的换行是通过一个StaticLayout的类来处理的,而且我们调用的getLineCount()方法最后也是调用的StaticLayout类中的getLineCount()方法,所以我们只需要创建一个和TextView内部一样的StaticLayout就可以了,然后调用staticLayout.getLineCount()方法就可以获取到和当前TextView行数一样的值了,但要注意一个前提条件就是保证TextView的width是已知的,否则也无法获取到正确的行数。

/**
 * 提前获取textview行数
 */
public class TextViewLinesUtil {
    public static int getTextViewLines(TextView textView, int textViewWidth) {
        int width = textViewWidth - textView.getCompoundPaddingLeft() - textView.getCompoundPaddingRight();
        StaticLayout staticLayout;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            staticLayout = getStaticLayout23(textView, width);
        } else {
            staticLayout = getStaticLayout(textView, width);
        }
        int lines = staticLayout.getLineCount();
        int maxLines = textView.getMaxLines();
        if (maxLines > lines) {
            return lines;
        }
        return maxLines;
    }

    /**
     * sdk>=23
     */
    @RequiresApi(api = Build.VERSION_CODES.M)
    private static StaticLayout getStaticLayout23(TextView textView, int width) {
        StaticLayout.Builder builder = StaticLayout.Builder.obtain(textView.getText(),
                0, textView.getText().length(), textView.getPaint(), width)
                .setAlignment(Layout.Alignment.ALIGN_NORMAL)
                .setTextDirection(TextDirectionHeuristics.FIRSTSTRONG_LTR)
                .setLineSpacing(textView.getLineSpacingExtra(), textView.getLineSpacingMultiplier())
                .setIncludePad(textView.getIncludeFontPadding())
                .setBreakStrategy(textView.getBreakStrategy())
                .setHyphenationFrequency(textView.getHyphenationFrequency())
                .setMaxLines(textView.getMaxLines() == -1 ? Integer.MAX_VALUE : textView.getMaxLines());
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            builder.setJustificationMode(textView.getJustificationMode());
        }
        if (textView.getEllipsize() != null && textView.getKeyListener() == null) {
            builder.setEllipsize(textView.getEllipsize())
                    .setEllipsizedWidth(width);
        }
        return builder.build();
    }

    /**
     * sdk<23
     */
    private static StaticLayout getStaticLayout(TextView textView, int width) {
        return new StaticLayout(textView.getText(),
                0, textView.getText().length(),
                textView.getPaint(), width, Layout.Alignment.ALIGN_NORMAL,
                textView.getLineSpacingMultiplier(),
                textView.getLineSpacingExtra(), textView.getIncludeFontPadding(), textView.getEllipsize(),
                width);
    }
}

作者:caochengzhi