android - MutableLiveData 中 setValue() 和 postValue() 的区别

Question

MutableLiveData 的改变值有两种方式。但是 MutableLiveData 中的 setValue() 和 postValue() 有什么区别。

我找不到相同的文档。

这里是Android的MutableLiveData类。

package android.arch.lifecycle;

/**
 * {@link LiveData} which publicly exposes {@link #setValue(T)} and {@link #postValue(T)} method.
 *
 * @param <T> The type of data hold by this instance
 */
@SuppressWarnings("WeakerAccess")
public class MutableLiveData<T> extends LiveData<T> {
    @Override
    public void postValue(T value) {
        super.postValue(value);
    }

    @Override
    public void setValue(T value) {
        super.setValue(value);
    }
}

Answer 1

根据文档:

setValue() :

Sets the value. If there are active observers, the value will be dispatched to them. This method must be called from the main thread.

postValue() :

Posts a task to a main thread to set the given value. If you called this method multiple times before a main thread executed a posted task, only the last value would be dispatched.

总而言之，主要区别在于:

setValue() 方法必须从主线程调用。但是如果你需要从后台线程设置一个值，应该使用 postValue()。