android - 为什么从后台线程关闭 ProgressDialog 时没有抛出异常？

Question

我知道当我尝试在后台线程上显示 ProgressDialog 时抛出异常 Can't create handler inside thread that has not called Looper.prepare(),

因为我们试图从后台线程修改 UI。但是当我们在后台线程中关闭该对话框时，不会抛出异常。为什么当我们关闭后台线程中的对话框时不会抛出异常，因为关闭我们也是从后台线程修改 UI。

谢谢

Answer 1

这是 Dialog 的 dismiss() 方法的代码，显示了为什么没有抛出异常并且 dismiss 有效:

/**
 * Dismiss this dialog, removing it from the screen. This method can be
 * invoked safely from any thread.  Note that you should not override this
 * method to do cleanup when the dialog is dismissed, instead implement
 * that in {@link #onStop}.
 */
public void dismiss() {
    if (Thread.currentThread() != mUiThread) {
        mHandler.post(mDismissAction);
    } else {
        mDismissAction.run();
    }
}