一个关于Dialog内的UI线程的使用问题

在Dialog.java类中，有几行代码是关乎UI线程的操作的，拿出来研究一下，呵呵

 

private final Thread mUiThread ;

private final Handler mHandler = new Handler();// 只在下面用了一次而已

private final Runnable mDismissAction = new Runnable() {
        public void run() {
            dismissDialog();
        }
    };

 

/**
 * 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();
        }
    }

 

/**
     * Create a Dialog window that uses a custom dialog style.
     *
     * @param context The Context in which the Dialog should run. In particular, it
     *                uses the window manager and theme from this context to
     *                present its UI.
     * @param theme A style resource describing the theme to use for the
     * window. See <a href="{@docRoot}guide/topics/resources/available-resources.html#stylesandthemes">Style
     * and Theme Resources</a> for more information about defining and using
     * styles.  This theme is applied on top of the current theme in
     * <var>context</var>.  If 0, the default dialog theme will be used.
     */
    public Dialog(Context context, int theme) {
        mContext = new ContextThemeWrapper(
            context, theme == 0 ? com.android.internal.R.style.Theme_Dialog : theme);
        mWindowManager = (WindowManager)context.getSystemService("window");
        Window w = PolicyManager.makeNewWindow(mContext);
        mWindow = w;
        w.setCallback(this);
        w.setWindowManager(mWindowManager, null, null);
        w.setGravity(Gravity.CENTER);
        mUiThread = Thread.currentThread();
        mListenersHandler = new ListenersHandler(this);
    }

 

我猜想，这个像对话框这种控件是只允许在UI主线程内操作的，也就是说只能由UI主线程来控制显示或消失等等，

那么有些对话框不依赖于Activity也就不容易找到UI主线程，所以就得需要把它的新线程的操作并入UI主线程中去完成，

也就是mHandler.post(mDismissAction);

 

那么主线程从哪来的呢？就在Dialog的构造里找到的，mUiThread = Thread.currentThread();

这依赖于制造这个Dialog的地方的性质。

 

只是我的猜想，如果有人觉得可以再分析一下，欢迎讨论，敬请指教，谢啦