Dialog的isShowing()方法一直返回为true

常见的Dialog，常用的isShowing方法，用此方法常判断dialog是否正在显示，但是有时发现dialog没有显示，此方法也是返回true，这就尴尬了。

取消显示dialog的方法

一、点击返回按钮或者点击dialog之外的屏幕

/**
     * Called when the dialog has detected the user's press of the back
     * key.  The default implementation simply cancels the dialog (only if
     * it is cancelable), but you can override this to do whatever you want.
     */
    public void onBackPressed() {
        if (mCancelable) {
            cancel();
        }
    }

点击返回按钮，最后调用了cancel的方法；

/**
     * Called when a touch screen event was not handled by any of the views
     * under it. This is most useful to process touch events that happen outside
     * of your window bounds, where there is no view to receive it.
     * 
     * @param event The touch screen event being processed.
     * @return Return true if you have consumed the event, false if you haven't.
     *         The default implementation will cancel the dialog when a touch
     *         happens outside of the window bounds.
     */
    public boolean onTouchEvent(@NonNull MotionEvent event) {
        if (mCancelable && mShowing && mWindow.shouldCloseOnTouch(mContext, event)) {
            cancel();
            return true;
        }

        return false;
    }

点击屏幕之外最后也是调用cancel方法

二、看看cancel()方法

/**
     * Cancel the dialog.  This is essentially the same as calling {@link #dismiss()}, but it will
     * also call your {@link DialogInterface.OnCancelListener} (if registered).
     */
    @Override
    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();
    }

看到源码，cancel方法最后还是调用了dismiss方法

三、看看dimiss()方法

/**
     * 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);
        }
    }

看到源码，dismiss()会调用dismissDialog()方法

四、看看dismissDialog()方法

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();
        }
    }

看到源码，最后将mShowing = false;

五、再看看hide()方法

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

可以看到并没有将mShowing赋值。所以调用hide方法，隐藏dialog但是isShowing方法还是会返回true。

总结：
1.点击返回按键或者点击dialog之外的屏幕->cancel()->dismiss()->dismissDialog->mShowing = false;
此时dialog没有显示， isShowing方法返回false；

2.调用hide()->dialog隐藏，mShowing依然是true；
此时dialog没有显示，isShowing方法返回true；