Can android PopupWindow show another PopupWindow?
How many PopupWindow can be opened in the same time? Only one?

The first PopupWindow is displayed normally. But on button click (which is in the first PopupWindow contentview) i am having an exception:

```
08-13 16:28:38.682: ERROR/AndroidRuntime(11760): FATAL EXCEPTION: main
        android.view.WindowManager$BadTokenException: Unable to add window -- token android.view.ViewRootImpl$W@41286250 is not valid; is your activity running?
        at android.view.ViewRootImpl.setView(ViewRootImpl.java:600)
        at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:313)
        at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:215)
        at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:140)
        at android.view.Window$LocalWindowManager.addView(Window.java:537)
        at android.widget.PopupWindow.invokePopup(PopupWindow.java:992)
        at android.widget.PopupWindow.showAsDropDown(PopupWindow.java:901)
        at org.example.qberticus.quickactions.BetterPopupWindow.showLikePopDownMenu(BetterPopupWindow.java:159)
        at org.example.qberticus.quickactions.BetterPopupWindow.showLikePopDownMenu(BetterPopupWindow.java:129)
        at name.antonsmirnov.android.popup.ui.MainActivity$1$1.run(MainActivity.java:44)
        at android.app.Activity.runOnUiThread(Activity.java:4170)
        at name.antonsmirnov.android.popup.ui.MainActivity$1.onClick(MainActivity.java:42)
        at android.view.View.performClick(View.java:3558)
        at android.view.View$PerformClick.run(View.java:14157)
        at android.os.Handler.handleCallback(Handler.java:605)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4514)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
        at dalvik.system.NativeStart.main(Native Method)

```

the code is:

```
    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);
    bindControls();
    initControls();
}

private Button button;

private void bindControls() {
    button = (Button) findViewById(R.id.button);
}

private void initControls() {
    initButton(button);
}

private void initButton(final Button button) {
    button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            final BetterPopupWindow window = new BetterPopupWindow(button);

            View popupview = createPopupView();
            window.setContentView(popupview);
            runOnUiThread(new Runnable() {
                public void run() {
                    window.showLikePopDownMenu();
                }
            });
        }
    });
}

private View createPopupView() {
    View v = LayoutInflater.from(MainActivity.this).inflate(R.layout.window, null);
    Button popupButton = (Button) v.findViewById(R.id.popupbutton);
    initButton(popupButton);
    return v;
}

```