一、开发环境

系统版本：OpenHarmony 4.0.10.13
设备平台：rk3588
SDK版本：fullSDK 4.0.10.13

二、背景

使用自研应用作为默认Launcher，或者说使特定应用默认开机自启作为Home应用。

三、分析过程

通过分析原生Launcher启动流程可知：
AMS启动根据应用优先级启动应用，通常是OOBE或Launcher
foundation/ability/ability_runtime/services/abilitymgr/src/ability_manager_service.cpp

void AbilityManagerService::StartUserApps(int32_t userId, bool isBoot)
{
HILOG_INFO("StartUserApps, userId:%{public}d, currentUserId:%{public}d", userId, GetUserId());
if (currentMissionListManager_ && currentMissionListManager_->IsStarted()) {
HILOG_INFO("missionListManager ResumeManager");
currentMissionListManager_->ResumeManager();
}
//启动优先级最高的应用
StartHighestPriorityAbility(userId, isBoot);
}

...

void AbilityManagerService::StartHighestPriorityAbility(int32_t userId, bool isBoot)
{
    ...
    /* Query the highest priority ability or extension ability, and start it. usually, it is OOBE or launcher */
    Want want;
    want.AddEntity(HIGHEST_PRIORITY_ABILITY_ENTITY);
    AppExecFwk::AbilityInfo abilityInfo;
    AppExecFwk::ExtensionAbilityInfo extensionAbilityInfo;
    int attemptNums = 0;
    //ImplicitQueryInfoByPriority查询应用ability和extensionAbility配置中的优先级
    while (!IN_PROCESS_CALL(bms->ImplicitQueryInfoByPriority(want,
        AppExecFwk::AbilityInfoFlag::GET_ABILITY_INFO_DEFAULT, userId,
        abilityInfo, extensionAbilityInfo))) {
        HILOG_INFO("Waiting query highest priority ability info completed.");
        ++attemptNums;
        if (!isBoot && attemptNums > SWITCH_ACCOUNT_TRY) {
            HILOG_ERROR("Query highest priority ability failed.");
            return;
        }
        AbilityRequest abilityRequest;
        ComponentRequest componentRequest = initComponentRequest();
        if (!IsComponentInterceptionStart(want, componentRequest, abilityRequest)) {
            return;
        }
        usleep(REPOLL_TIME_MICRO_SECONDS);
    }
	...
	//启动查询到的最高优先级应用
    /* note: OOBE APP need disable itself, otherwise, it will be started when restart system everytime */
    (void)StartAbility(abilityWant, userId, DEFAULT_INVAL_VALUE);
}

至此我们了解到应用优先级取决于应用ability和extensionAbility 优先级配置
查看官方资料
module.json5配置文件

查看launcher module.json5配置文件

"extensionAbilities": [
      {
        "priority": 2,  //优先级设定为2
        "skills": [  //接受home Want的特征标签
          {
            "entities": [
              "entity.system.home",
              "flag.home.intent.from.system"
            ],
            "actions": [
              "action.system.home",
              "com.ohos.action.main",
              "action.form.publish"
            ]
          }
        ],
        "exported": false,  //本组件不可被其他应用调研
        "name": "com.ohos.launcher.MainAbility&#