Dialog是任何系统都必须有的一个控件，作为辅助窗口，用于显示一些消息，或请求用户采取一引起操作等。

在Android中也不例外，基本使用可能参看文档。

使用时的注意事项

1. BACK键能取消掉对话框(dismiss)，但是却不会触发其onOkey和onCancel回调接口，所以如果你的对话框会改某些状态，一定要注意还有第三种方式取消对话框。

2. 尽量少用模态对话框(Model dialog)，如果Dialog.setCancellable(false)，就变成了一个模态对话框，除了程序内部把其Dismiss，否则按什么键都无法将其取消。这是极差的用户体验，对话框本身就是一种干扰，再无法取消会把用户搞疯的。所以除非特别有必要，也即当执行某个操作时不希望被打破，才可以使用模态对话框。

3. 尽量少用对话框，它对用户是一种干扰，除非需要用户做操作，或者做出选择。通常的一般性的通知用Toast或者Notification就足够了。

4. 不要使用对话框风格的Activity，也即把Activity变成一个对话框。因为这样是自已定义的布局，与系统Dialog的风格可能会不一致。最严重的是当系统风格发生变化，Dialog的子类会变化，但Activity式的对话框就不会变化。可以在ICS中找一找Activity对话框，你会发现其OK是在左边，而ICS中系统Dialog的OK都是在右边的。

5. 尽量保证Dialog对象活在Activity的生命周期之内，也即至多是在onCreate()和onDestroy()之间。

6. 要想到和测试到Activity在其Dialog.dismiss()之前死掉的情况。因为Activity必须依附于某个正在显示的Activity实例，当显示和取消的时候其Activity实例必须存在，否则就会有"IllegalArgumentException: View not attached to window manager"。

05-15 02:45:26.320: E/AndroidRuntime(1161): java.lang.IllegalArgumentException: View not attached to window manager 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.view.WindowManagerImpl.findViewLocked(WindowManagerImpl.java:355) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.view.WindowManagerImpl.removeView(WindowManagerImpl.java:200) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.view.Window$LocalWindowManager.removeView(Window.java:432) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.app.Dialog.dismissDialog(Dialog.java:278) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.app.Dialog.access$000(Dialog.java:71) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.app.Dialog$1.run(Dialog.java:111) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.app.Dialog.dismiss(Dialog.java:268) 05-15 02:45:26.320: E/AndroidRuntime(1161): at com.hilton.effectiveandroid.app.DialogDemo$1.handleMessage(DialogDemo.java:26) 05-15 02:45:26.320: E/AndroidRuntime(1161): at android.os.Handler.dispatchMessage(Handler.java:99)

7. Dialog.show()必须在主线程里调用，但Dialog.dismiss()却可以在任何线程中调用。

三种使用方式比较

1. 直接创建一个局部的Dialog对象

优点是变量是局部的容易理解和维护。缺点是Dialog对象难以控制，容易引发RuntimeException。

2. 把Dialog对象变成Activity的域

优点是Dialog对象可以重复利用，且Activity可以控制以保证Dialog不会在Activity生命周期外显示。是推荐的使用方式。

3. 用Activity的方法onCreateDialog(), showDialog()和dismissDialog()

优点是Frameworks会帮忙照看Dialog，在大多数情况下这是推荐的做法。但是对于Activity提前死掉的情况，此方法必有RuntimeException，且无法回避。

实例

public class DialogDemo extends Activity { private static final int DISMISS_DIALOG = 1; private ProgressDialog mBetterDialog; private Handler mMainHandler = new Handler() { @Override public void handleMessage(Message msg) { switch (msg.what) { case DISMISS_DIALOG: Dialog dialog = (Dialog) msg.obj; dialog.dismiss(); break; default: break; } } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.dialog_demo); final Button sucking = (Button) findViewById(R.id.sucking); sucking.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { final Activity activity = DialogDemo.this; final ProgressDialog dialog = new ProgressDialog(activity); dialog.setTitle("Worst dialogging"); dialog.setMessage("This is the worst dialogging scheme, NEVER use it. This dialog is easy to " + "run out of its attached activity, yielding WindowManager#BadTokenException if the activity is gone when dismissing"); dialog.setIndeterminate(true); dialog.setCancelable(true); // You MUST do the show in main thread anyway dialog.show(); new Thread(new Runnable() { public void run() { SystemClock.sleep(10000); /* * IllegalArgumentException: View not attached to window manager * If the activity showing the dialog was killed before dismiss() out of rotation or locale changed, * the dialog will gone with activity, but when dismiss() yields "IllegalArgumentException: View not attached to * window manager". * Checking isShowing() won't help. * Checking activity.isFinishing() won't help, either. * Dismiss it in main thread also won't give any help. */ // THIS WON't WORK // if (dialog.isShowing()) { // dialog.dismiss(); // } // if (!activity.isFinishing()) { // dialog.dismiss(); // } Message msg = Message.obtain(); msg.what = DISMISS_DIALOG; msg.obj = dialog; mMainHandler.sendMessage(msg); } }).start(); } }); final Button better = (Button) findViewById(R.id.better); better.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { mBetterDialog = new ProgressDialog(DialogDemo.this); mBetterDialog.setTitle("Better dialogging"); mBetterDialog.setMessage("This dialogging can be used. The dialog object is a field of its activity, so activity can" + " control it to make sure dialog only lives within activity lifecircle"); mBetterDialog.setIndeterminate(true); mBetterDialog.setCancelable(true); // You MUST do the show in main thread anyway mBetterDialog.show(); new Thread(new Runnable() { public void run() { SystemClock.sleep(10000); /* * This is much better, mBetterDialog is a field of its activity, so activity can take care of it in order * to make sure dialog only live within activity's life circle, to avoid any unexpected exceptions. */ // THIS really works if (mBetterDialog != null && mBetterDialog.isShowing()) { mBetterDialog.dismiss(); } } }).start(); } }); final Button optional = (Button) findViewById(R.id.optional); optional.setOnClickListener(new View.OnClickListener() { @SuppressWarnings("deprecation") public void onClick(View v) { showDialog(0); new Thread(new Runnable() { public void run() { SystemClock.sleep(10000); /* * This way works best for most of time, except if activity died before dismissing, exception must be * thrown: "IllegalArgumentException: View not attached to window manager". * Although activity takes care of its belonging dialog, there is no way to operate it manually any more. * First you do not have reference to dialog object and second, any manual operation only interferences * and breaks state maintained by frameworks. */ dismissDialog(0); } }).start(); } }); } @Override protected Dialog onCreateDialog(int id) { ProgressDialog d = new ProgressDialog(this); d.setTitle("Optional dialogging"); d.setMessage("This dialogging scheme works best for most times, the dialogs are all taken care of by activitys and frameworks" + ". Except for activity being killed during dialog showing"); d.setIndeterminate(true); d.setCancelable(true); return d; } @Override protected void onDestroy() { super.onDestroy(); // Activity is dying, all its belonging dialogs should be dismissed, of course. if (mBetterDialog != null && mBetterDialog.isShowing()) { mBetterDialog.dismiss(); mBetterDialog = null; } // For dialogs showed via showDialog(int), no way to stop it in onDestroy() // dismissDialog(0); // cause "IllegalArgumentException: no dialog with id 0 was ever shown via Activity#showDialog" // This is because Activity has to manage its dialog during onPause() and onResume() to restore // dialogs' state. So if you manually dismiss it in onDestroy(), it will cause JE. // removeDialog(0);// cause "IllegalArgumentException: no dialog with id 0 was ever shown via Activity#showDialog", when // dismissing in thread. // This is because Activity has to manage its dialog during onPause() and onResume() to restore // dialogs' state. So if you manually dismiss it in onDestroy(), it will cause JE. } }