如何保存List< Object>并使用Hive检索？ [英] How to save a List<Object> and retrieve using Hive?

问题描述

我有一个墙纸应用程序，它使用Firestore存储墙纸。

I have a Wallpaper App and it uses Firestore to store the wallpapers.

我想使用Hive存储云Firestore中的墙纸列表，但如何保存墙纸列表并在以后检索？

I want to use Hive to store a list of wallpapers from cloud firestore but how to save the List of Wallpapers and retrieve it later?

当我尝试保存列表时出现此错误：

When I try to save the list I get this error:

E / flutter（9995）：[错误：flutter / shell / common / shell.cc（199）] Dart错误：未处理的异常：
E / flutter（9995）：HiveError：无法写入，未知类型：墙纸。您忘记注册适配器了吗？

E/flutter ( 9995): [ERROR:flutter/shell/common/shell.cc(199)] Dart Error: Unhandled exception: E/flutter ( 9995): HiveError: Cannot write, unknown type: Wallpaper. Did you forget to register an adapter?

代码：

class Wallpaper extends HiveObject {


  String date;
  String url;

  Wallpaper();

}

static Future<void> addWallpapers({@required String boxName, @required List<Wallpaper> wallpapers}) async {

    var box = await Hive.openBox(boxName);
    box.put(boxName, wallpapers);

    print("WALLPAPER ADICIONADO NO HIVE!");

  }

  static Future<List<Wallpaper>> getWallpapers({@required String boxName}) async {

    var box = await Hive.openBox(boxName);

    List<Wallpaper> wallpapers = box.get("latest");

    return wallpapers;

  }

推荐答案

您有使用@HiveType（）注释对象。并且必须注册您的对象Hive.registerAdapter（WallpaperAdapter（），0）;。

You have to anotate your object with @HiveType(). And have to register your object Hive.registerAdapter(WallpaperAdapter(), 0);.

但是，您是否有 part'wallpaper.g .dart'; 生成所需的代码？

And yet, do you have part 'wallpaper.g.dart'; to generate the needed code?

编辑：
首先导入对pubspec的依赖项：

EDITED: First of all import the dependencies on your pubspec:

dependencies:
  hive: ^[version]
  hive_flutter: ^[version]

dev_dependencies:
  hive_generator: ^[version]
  build_runner: ^[version]

Hive.registerAdapter（MyObjectAdapter（），0）; 您应该放入 main.dart 函数。在runApp之前

The Hive.registerAdapter(MyObjectAdapter(), 0); you should put inside your main.dart function. Right before runApp

您的HiveObject应该具有这样的注释：

Your HiveObject should have annotations like that:

@HiveType()
class Person extends HiveObject {
  @HiveField(0);
  String name;

  @HiveField(1);
  int age;
}

将此命令放在您的进口 part'person附近。 g.dart'; 并在您的终端上运行代码生成。 flutter包pub run build_runner build 。

Put this command near your imports part 'person.g.dart'; and run the code generation on your terminal. flutter packages pub run build_runner build.

具有代码生成功能的Hive函数，因此此命令将生成您需要的文件

Hive function with code generation, so this command will generate the file you need

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