Android:无法调用没有args的私有android.net.Uri()

Question

我使用Gson将自定义模型的arraylist保存到共享首选项中

存储代码:

ArrayList<DownloadProgressDataModel> arrayList = getArrayListFromPref(downloadProgressDataModel);
        SharedPreferences.Editor prefsEditor = getSharedPreferences("APPLICATION_PREF", MODE_PRIVATE).edit();

        Gson gson = new Gson();
        String json = gson.toJson(arrayList);
        prefsEditor.putString("DownloadManagerList", json);
        prefsEditor.apply();
    }

检索

ArrayList<DownloadProgressDataModel> arrayList;
        Gson gson = new Gson();

        SharedPreferences  mPrefs = getSharedPreferences("APPLICATION_PREF", MODE_PRIVATE);
        String json = mPrefs.getString("DownloadManagerList", "");

        if (json.isEmpty()) {
            arrayList = new ArrayList<DownloadProgressDataModel>();
        } else {
            Type uriPath = new TypeToken<ArrayList<DownloadProgressDataModel>>() {
            }.getType();
            arrayList = gson.fromJson(json, uriPath);  <------ Error line
        }

但是我得到的错误行:无法实例化类android.net.Uri

模型

public class DownloadProgressDataModel {
    private Uri uriPath;
    private long referenceId;

    public Uri getUriPath() {
        return uriPath;
    }

    public void setUriPath(Uri uriPath) {
        this.uriPath = uriPath;
    }

    public long getReferenceId() {
        return referenceId;
    }

    public void setReferenceId(long referenceId) {
        this.referenceId = referenceId;
    }
}

Answer 1

Uri类构造函数是私有的,它是一个抽象类.Gson尝试Uri使用Reflection API 为类创建一个新对象(我们不能为抽象类创建一个对象).这么简单的解决方案就是uriPath改成String而不是Uri.

 private String uriPath;