dismiss和cancel在我们看来两者效果都是一样的，其实看下源码就知道cancel肯定会去调dismiss的，不过如果我们调用的cancel的话就可以监听DialogInterface.OnCancelListener，不调用cancel的话就只能监听DialogInterface.OnDismissListener。

/**

* Cancel the dialog. This is essentially the same as calling {@link #dismiss()}, but it will

* also call your {@link DialogInterface.OnCancelListener} (if registered).

*/

public void cancel() {

if (!mCanceled && mCancelMessage != null) {

mCanceled = true;

// Obtain a new message so this dialog can be re-used

Message.obtain(mCancelMessage).sendToTarget();

}

dismiss();

}

dismiss可以在任何线程调用，但是最好不要覆写dismiss方法，实在需要就在onStop里去override。

/**

* 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}.

*/

@Override

public void dismiss() {

if (Looper.myLooper() == mHandler.getLooper()) {

dismissDialog();

} else {

mHandler.post(mDismissAction);

}

}

在dismissDialog里调用了onStop。

void dismissDialog() {

if (mDecor == null || !mShowing) {

return;

}

if (mWindow.isDestroyed()) {

Log.e(TAG, "Tried to dismissDialog() but the Dialog's window was already destroyed!");

return;

}

try {

mWindowManager.removeViewImmediate(mDecor);

} finally {

if (mActionMode != null) {

mActionMode.finish();

}

mDecor = null;

mWindow.closeAllPanels();

onStop();

mShowing = false;

sendDismissMessage();

}

}

hide方法，注释上说了hide只是隐藏了对话框并没有销毁，如果打算用这方法来销毁对话框就会出现问题，在Activity销毁的时候就会出现崩溃日志了，因为Activity销毁时是需要把对话框都关闭掉的。不然会报窗口泄露异常。

/**

* Hide the dialog, but do not dismiss it.

*/

public void hide() {

if (mDecor != null) {

mDecor.setVisibility(View.GONE);

}

}