如何正确覆盖`toString()`以摆脱哈希码 [英] How to override `toString()` properly to get rid of hash code

问题描述

我正在从 Room 检索测试数据，但我得到的只是哈希码数据，即使我覆盖了 toString() 方法在我的 >@Entity 类.我怎么知道是否使用了覆盖方法?

I'm retrieving test data from Room, but all I get is the hash-code data, even though I override the toString() method in my @Entity class. How do I know if the override method is used at all?

我已经使用 database、repository、viewModel 和 view<正确设置了 Room/code> 使用 Live-data.从 onCreate 我有一个 observer 可以正确触发，并显示数据.正如预期的那样，它是 has-code 数据.通常我通过覆盖 @Entity 类中的 toString() 然后在 onCreate()<中使用它来将其转换为 string 数据/code> 但它不起作用.它仍然给我 hash 数据.

I have properly set up Room with a database, repository, viewModel and view using Live-data. From onCreate I have an observer that triggers correctly, and data is shown. As expected it is has-code data. Usually I turn this into string data by overriding toString() in the @Entity class and then using it in onCreate() but it doesn't work. It still gives me the hash data.

在我的 @Entity 类中，我像这样覆盖了 toString():

In my @Entity class I override toString() like this:

@Override
public String toString() {
    return "MyEntity{" +
            "id=" + id +
            ", title='" + title + '\'' +
            ", description='" + description + '\'' +
            ", priority=" + priority +
            '}';
}

在我的 onCreate() 中，我调用 Interface 使用:

And in my onCreate() I call the Interface using:

myViewModel.getAllData().observe( this, new Observer<List<MyEntity>>() {
        @Override
        public void onChanged(@Nullable List<MyEntity> myEntities) {

            Log.d("TAG: ", "DATA CHANGED! " + myViewModel.getAllData().toString());
        }
} );

但是尽管使用了 .toString() 我仍然只得到哈希数据:

But despite using .toString() I still just get the hash data:

D/TAG:: DATA CHANGED! android.arch.lifecycle.ComputableLiveData$1@a12e85e

我期待一些基本的测试数据:

I expect some basic test data:

"MY FIRST OBJECT", "THIS IS MY OBJECT", 1 

推荐答案

您正在对 ComputableLiveData 调用 toString()，你必须在 myEntities 上调用 toString() ，这又会在 MyEntitytoString()代码>.

You are calling toString() on ComputableLiveData, you have to call toString() on myEntities which will in turn call toString() on the individual elements which are MyEntity.

myViewModel.getAllData().observe( this, new Observer<List<MyEntity>>() {
    @Override
    public void onChanged(@Nullable List<MyEntity> myEntities) {
        Log.d("TAG: ", "DATA CHANGED! " + myEntities.toString());
    }
});

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