编写“Hello World”程序


编写“Hello World”程序

下方将展示如何在单板上运行第一个应用程序,其中包括新建应用程序、编译、烧写、运行等步骤,最终输出“Hello World!”。

示例目录

示例完整目录如下:

applications/sample/hello
│── BUILD.gn
└── src
    └── helloworld.c
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开发步骤

请在源码目录中通过以下步骤创建“Hello World”应用程序:

  1. 新建目录及源码。

    新建applications/sample/hello/src/helloworld.c目录及文件,代码如下所示,用户可以自定义修改打印内容(例如:修改OHOS为World)。当前应用程序可支持标准C及C++的代码开发。

    #include <stdio.h>
    
    int main(int argc, char **argv)
    {
        printf("\n\n");
        printf("\n\t\tHello OHOS!\n");
        printf("\n\n\n");
    
        return 0;
    }
    
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  2. 新建编译组织文件。

    新建applications/sample/hello/BUILD.gn文件,内容如下所示:

    import("//build/lite/config/component/lite_component.gni")
    lite_component("hello-OHOS") {
      features = [ ":helloworld" ]
    }
    executable("helloworld") {
      output_name = "helloworld"
      sources = [ "src/helloworld.c" ]
    }
    
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  3. 添加新组件。

    修改文件build/lite/components/applications.json,添加组件hello_world_app的配置,如下所示为applications.json文件片段,"##start##"和"##end##"之间为新增配置("##start##"和"##end##"仅用来标识位置,添加完配置后删除这两行):

    {
      "components": [
        {
          "component": "camera_sample_communication",
          "description": "Communication related samples.",
          "optional": "true",
          "dirs": [
            "applications/sample/camera/communication"
          ],
          "targets": [
            "//applications/sample/camera/communication:sample"
          ],
          "rom": "",
          "ram": "",
          "output": [],
          "adapted_kernel": [ "liteos_a" ],
          "features": [],
          "deps": {
            "components": [],
            "third_party": []
          }
        },
    ##start##
        {
          "component": "hello_world_app",
          "description": "hello world samples.",
          "optional": "true",
          "dirs": [
            "applications/sample/hello"
          ],
          "targets": [
            "//applications/sample/hello:hello-OHOS"
          ],
          "rom": "",
          "ram": "",
          "output": [],
          "adapted_kernel": [ "liteos_a" ],
          "features": [],
          "deps": {
            "components": [],
            "third_party": []
          }
        },
    ##end##
        {
          "component": "camera_sample_app",
          "description": "Camera related samples.",
          "optional": "true",
          "dirs": [
            "applications/sample/camera/launcher",
            "applications/sample/camera/cameraApp",
            "applications/sample/camera/setting",
            "applications/sample/camera/gallery",
            "applications/sample/camera/media"
          ],
    
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  4. 修改单板配置文件。

    修改文件vendor/hisilicon/hispark_taurus/config.json,新增hello_world_app组件的条目,如下所示代码片段为applications子系统配置,"##start##"和"##end##"之间为新增条目("##start##"和"##end##"仅用来标识位置,添加完配置后删除这两行):

          {
            "subsystem": "applications",
            "components": [
              { "component": "camera_sample_app", "features":[] },
              { "component": "camera_sample_ai", "features":[] },
    ##start##
              { "component": "hello_world_app", "features":[] },
    ##end##
              { "component": "camera_screensaver_app", "features":[] }
            ]
          },
    
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