Android中的小技巧

• Android中ListView等滚动到某个位置失效

//第一种
lv.setSelection(position)
//第二种
lv.smoothScrollToPosition(position)

第一种直接就是选中位置，第二种有滚动动画，但是有时候，滚动效果看不到，解决方式新建一个runnable，如下：

 lv.post(new Runnable() {
                    @Override
                    public void run() {
                        lv.smoothScrollToPosition(position);
                    }
                });

• 类似的问题，就是使用SwipeRefreshLayout的时候，希望打开页面的时候，SwipeRefreshLayout正在刷新，可是调用SwipeRefreshLayout的setRefreshing(true)无效，主要原因是页面未渲染完成，解决方式就是延迟执行刷新。

srl.post(new Runnable() {
            @Override
            public void run() {
                    srl.setRefreshing(true);
            }
        });

• EditText限制输入的小数位数
  Android中提供了一个输入过滤器InputFilter,用于过滤用户输入的内容。
  
  • 定义一个类实现InputFilter 接口

public class DoubleInputFilter implements InputFilter {
    /**
     * 输入框小数的位数  示例保留一位小数
     */
    private static final int DECIMAL_DIGITS = 2;

    /**
     * This method is called when the buffer is going to replace the
     * range dstart … dend of dest
     * with the new text from the range start … end
     * of source.  Return the CharSequence that you would
     * like to have placed there instead, including an empty string
     * if appropriate, or null to accept the original
     * replacement.  Be careful to not to reject 0-length replacements,
     * as this is what happens when you delete text.  Also beware that
     * you should not attempt to make any changes to dest
     * from this method; you may only examine it for context.
     * 

     * Note: If source is an instance of {@link Spanned} or
     * {@link Spannable}, the span objects in the source should be
     * copied into the filtered result (i.e. the non-null return value).
     * {@link TextUtils#copySpansFrom} can be used for convenience.
     *
     * @param source
     * @param start
     * @param end
     * @param dest
     * @param dstart
     * @param dend
     */
    @Override
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
        if ("".equals(source.toString())) {
            return null;
        }
        String value = dest.toString();
        String[] split = value.split("\\.");
        if (split.length > 1) {
            String s = split[1];
            int i = s.length() + 1 - DECIMAL_DIGITS;
            if (i > 0) {
                return source.subSequence(start, end - i);
            }
        }
        return null;
    }
}

• 使用

et.setFilters(new InputFilter[]{new DoubleInputFilter()});

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