小编use*_*641的帖子

当我尝试构建我的iOS应用程序时,我收到链接器错误.将C++标准库设置为"libstdc ++"可能会修复它,但我不确定如何在QT创建器中执行此操作.

Undefined symbols for architecture armv7:
  "tesseract::TessBaseAPI::End()", referenced from:
      Ocr::~Ocr() in ocr.o
  "tesseract::TessBaseAPI::SetImage(Pix const*)", referenced from:
      Ocr::recognize(char const*) in ocr.o
  "tesseract::TessBaseAPI::GetUTF8Text()", referenced from:
      Ocr::recognize(char const*) in ocr.o
  "_pixRead", referenced from:
      Ocr::recognize(char const*) in ocr.o
  "_pixDestroy", referenced from:
      Ocr::recognize(char const*) in ocr.o
  "tesseract::TessBaseAPI::TessBaseAPI()", referenced from:
      Ocr::Ocr(char const*) in ocr.o
  "tesseract::TessBaseAPI::Init(char const*, char const*, tesseract::OcrEngineMode, char**, int, GenericVector<STRING> const*, GenericVector<STRING> const*, bool)", referenced from:
      Ocr::Ocr(char const*) in ocr.o
ld: symbol(s) not found for architecture armv7
clang: error: linker command failed with …

AnimatedRotation 用于动画罗盘

我正在尝试向我的应用程序添加指南针。将旋转动画从 359 设置为 0 或从 0 设置为 359 的最佳方法是什么？是否有更适合这种类型旋转的小部件？

AnimatedRotation(
      duration: const Duration(milliseconds: 250),
      turns: -heading / 360.0,
      curve: Curves.linear,

尝试通过添加差异而不是分配角度来做到这一点，但如果它沿同一方向旋转，它可能会溢出。

if(previousHeading - heading > 180) {
  turns += ((360.0 - previousHeading) + heading) / 360.0;
}
else if(previousHeading - heading < -180) {
  turns -= ((360.0 - heading + previousHeading)) / 360.0;
}
else {
  turns += ((previousHeading - heading) / 360.0);
}

previousHeading = heading;