def __check_changes(self, module_name, fpath, module_cache):
        if not fpath:
            return False

        if fpath not in module_cache:
            self.debug('find new file {}'.format(fpath))
            return True

        stat = module_cache[fpath]
        mtime = os.path.getmtime(fpath)
        if mtime > stat['mtime']:
            self.debug('find {} has modification.'.format(fpath))
            stat['mtime'] = mtime
            self._stat_cache[module_name][fpath] = stat

            md5 = get_md5(fpath)
            if md5 != stat['md5']:
                self.debug('find {} has modification.'.format(fpath))
                stat['md5'] = md5
                self._stat_cache[module_name][fpath] = stat
                return True
        return False

# scan src
            src_dirs = self._config['project_source_sets'][module_name]['main_src_directory']
            for src_dir in src_dirs:
                if os.path.exists(src_dir):
                    for dirpath, dirnames, files in os.walk(src_dir):
                        if re.findall(r'[/\\+]androidTest[/\\+]', dirpath) or '/.' in dirpath:
                            continue
                        for fn in files:
                            if fn.endswith('java'):
                                if fn.endswith('package-info.java') or fn.endswith('BuildConfig.java'):
                                    continue
                                fpath = os.path.join(dirpath, fn)
                                if self.__check_changes(module_name, fpath, module_cache):
                                    self._changed_files[module_name]['src'].append(fpath)
                            # 添加kotlin的增量检查
#                            elif fn.endswith('kt'):
#                               fpath = os.path.join(dirpath, fn)
#                              if self.__check_changes(module_name, fpath, module_cache):
#                                 self._changed_files[module_name]['kotlin'].append(fpath)

    # 删减了一些处理兼容性 apt什么的代码 为了方便阅读
    def _generate_java_compile_args(self, extra_javac_args_enabled=False):
        javacargs = [self._javac]
        arguments = ['-encoding', 'UTF-8', '-g']
        if not self._is_retrolambda_enabled:
            arguments.extend(['-target', '1.7', '-source', '1.7'])

        arguments.append('-cp')
        arguments.append(os.pathsep.join(self._classpaths))

        # 睁大眼睛
        for fpath in self._changed_files['src']:
            arguments.append(fpath)
    
        arguments.append('-d')
        arguments.append(self._finder.get_patch_classes_cache_dir())

        javacargs.extend(arguments)
        return javacargs

class GradleIncJavacCommand(IncJavacCommand):
    def __init__(self, module_name, invoker):
        IncJavacCommand.__init__(self, module_name, invoker)

    def execute(self):
        self._invoker.check_r_md5()  # check if R.java has changed
        # self._invoker.check_other_modules_resources()
        should_run_javac_task = self._invoker.check_javac_task()
        if not should_run_javac_task:
            self.debug('no need to execute')
            return

        self.debug('start to execute javac command...')
        self._invoker.append_r_file()
        self._invoker.fill_classpaths()
        self._invoker.fill_extra_javac_args()
        self._invoker.clean_dex_cache()
        self._invoker.run_apt_only()
        self._invoker.run_javac_task() # 在这个方法里面调用了_generate_java_compile_args
        self._invoker.run_retrolambda()

class GradleIncDexCommand(IncDexCommand):
    def __init__(self, module_name, invoker):
        IncDexCommand.__init__(self, module_name, invoker)

    def execute(self):
        should_run_dex_task = self._invoker.check_dex_task() 
        if not should_run_dex_task:
            self.debug('no need to execute')
            return

        self.debug('start to execute dex command...')
        self._invoker.run_dex_task()

  # 根据字节码打包成dex  
  def run_dex_task(self):
        patch_classes_cache_dir = self._finder.get_patch_classes_cache_dir()
        # dex_path = self._finder.get_dst_dex_path()
        dex_path = self._finder.get_patch_dex_dir()
        add_path = None
        if is_windows_system():
            add_path = str(os.path.abspath(os.path.join(self._javac, os.pardir)))
            dex_args = [self._dx, '--dex', '--multi-dex', '--output=' + dex_path, patch_classes_cache_dir]
        else:
            dex_args = [self._dx, '--dex', '--no-optimize', '--force-jumbo', '--multi-dex', '--output=' + dex_path,
                        patch_classes_cache_dir]

        self.debug('dex exec: ' + ' '.join(dex_args))
        output, err, code = cexec(dex_args, add_path=add_path)

        if code != 0:
            raise FreelineException('incremental dex compile failed.', '{}\n{}'.format(output, err))
        else:
            mark_restart_flag(self._cache_dir)