NumberPicker中ArrayIndexOutOfBoundsException解决方案

场景

通常使用NumberPicker我们都是只初始化一次数据就好了，但最近项目需要做一个城市选择器，每次选择了一个省份或者城市，都会去更新下城市或者区县。然而使用如下代码去更新NumberPicker数据时，会报数组越界的异常：

private void updateCitySelector() {
cityPicker.setDisplayedValues(mCitys);
cityPicker.setMaxValue(mCitys.length - 1);
}

java.lang.ArrayIndexOutOfBoundsException: length=1; index=3
at android.widget.NumberPicker.ensureCachedScrollSelectorValue(NumberPicker.java:1882)
at android.widget.NumberPicker.incrementSelectorIndices(NumberPicker.java:1848)
at android.widget.NumberPicker.scrollBy(NumberPicker.java:1142)
at android.widget.NumberPicker.computeScroll(NumberPicker.java:1097)
at android.view.View.draw(View.java:15984)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16111)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16204)
at android.view.View.draw(View.java:16113)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16111)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16111)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16204)
at android.view.View.draw(View.java:16113)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16204)
at android.view.View.draw(View.java:16113)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16111)
at android.view.ViewGroup.drawChild(ViewGroup.java:3610)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3400)
at android.view.View.draw(View.java:16204)
at java.lang.ThreadGroup.uncaughtException(ThreadGroup.java:690)

解决方案一

1、当前NumberPicker的最大值大于数组大小时，先setMaxValue再setDisplayedValues。

2、当前NumberPicker的最大值小于数组大小时，先setDisplayedValues再setMaxValue。

private void updateCitySelector() {
int oldMax = cityPicker.getMaxValue();
int newMax = mCitys.length - 1;
if(newMax > oldMax) {
cityPicker.setDisplayedValues(mCitys);
cityPicker.setMaxValue(newMax);
} else {
cityPicker.setMaxValue(newMax);
cityPicker.setDisplayedValues(mCitys);
}
}

解决方案二（推荐）：

在设置最大值和最新数组数据前，先将数据设为null。

private void updateCitySelector() {
cityPicker.setDisplayedValues(null);
cityPicker.setMaxValue(mCitys.length - 1);
cityPicker.setDisplayedValues(mCitys);
}

以上两种方案亲测可以解决越界问题