Android对话框之dismiss和cancel和hide区别

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，如果调用的cancel的话就可以监听DialogInterface.OnCancelListener。

/**
* 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();
}
}

补上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灭掉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。

日志如下：

android.view.WindowLeaked: Activity com.example.androidtest_progressdialog.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{434557e8 G.E..... R.....ID 0,0-1026,288} that was originally added here

再看一下hide里是做什么操作：

/**
* Hide the dialog, but do not dismiss it.
*/
public void hide() {
if (mDecor != null) {
mDecor.setVisibility(View.GONE);
}
}

可以看出，hide只是把对话框里的DecorView设置为不可见，并没有从Window移除掉这个DecorView。