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默认的控制器为site，修改文件

vendor\yiisoft\yii2\web\Application.php

public $defaultRoute = 'site';//http://localhost:8080/index.php的默认控制器

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修改默认action

对应文件\vendor\yiisoft\yii2\base\Controller.php

public $defaultAction = 'index';//默认index.php

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修改默认布局文件

vendor\yiisoft\yii2\base\Application.php

public $layout = 'main';//默认main.php

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