Entities and Pojos must have a usable public constructor. You can have an empty constructor or a co-优快云博客

本文详细解析了在Kotlin中定义实体类时构造函数的重要性，特别是在使用Room数据库时，实体和POJO必须具备可用的公共构造函数。文章通过实例展示了如何修正构造函数以避免错误，包括提供空构造方法和为忽略的属性设置默认值。

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Kotlin：实体和pojo必须有一个可用的公共构造函数。您可以有一个空的构造函数或一个其参数与字段(按名称和类型)匹配的构造函数。

1、修改前的写法（报错了）：

@Entity(tableName = "inspectItem")
data class InspectItemInfo(
        @PrimaryKey
        @ColumnInfo(name = "id")
        @NonNull
        var carInspectRecordId: Int,
        var cubeName: String,
        @Ignore
        var imageType: String,
        var plateColor: String,
        var plateNo: String,
        var shotTime: String,
        var storagePath: String,
        var bottomImageUrl: String
)

报错信息：Entities and Pojos must have a usable public constructor. You can have an empty constructor or a constructor whose parameters match the fields (by name and type).

2、修改后的（写法一）：

说明：提供空构造方法。

@Entity(tableName = "inspectItem")
data class InspectItemInfo(
        @PrimaryKey
        @ColumnInfo(name = "id")
        @NonNull
        var carInspectRecordId: Int,
        var cubeName: String,
        @Ignore
        var imageType: String,
        var plateColor: String,
        var plateNo: String,
        var shotTime: String,
        var storagePath: String,
        var bottomImageUrl: String
) {
    constructor() : this(0, "", "", "", "", "", "", "")
}

3、修改后的（写法二）：

说明：ignore的属性需要给默认值。

@Entity(tableName = "inspectItem")
data class InspectItemInfo(
        @PrimaryKey
        @ColumnInfo(name = "id")
        @NonNull
        var carInspectRecordId: Int,
        var cubeName: String,
        var plateColor: String,
        var plateNo: String,
        var shotTime: String,
        var storagePath: String,
        var bottomImageUrl: String
) {
    @Ignore
    var imageType: String = ""
}