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
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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();
??????? }
??? };
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/**
?* 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);
??? }
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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
