DialogFragment使用中show()方法遇到的IllegalStateException

  最近在首页做了一个弹窗，用dialogFragment 实现的，线上报了一个crash:

ava.lang.IllegalStateException: Can not perform this action after onSaveInstanceStateat android.support.v4.app.FragmentManagerImpl.checkStateLoss(FragmentManager.java:1493)

特此记录一下。

此问题的原因是：mainActivity 调用了onSaveInstanceState（）以后有触发了dialog的显示，dialog.show（）方法里边用的是commit（）而不是commitAllowingStateLoss（）

追踪一下代码：

DialogFragment中：

public void show(FragmentManager manager, String tag) {        mDismissed = false;        mShownByMe = true;        FragmentTransaction ft = manager.beginTransaction();        ft.add(this, tag);        ft.commit();    }

从调用下手：

dialog.show(getActivity().getSupportFragmentManager(), "");

可以追踪下去，第一个参数manager是：

final FragmentManagerImpl mFragmentManager = new FragmentManagerImpl();

FragmentTransaction ft = manager.beginTransaction();

 @Override    public FragmentTransaction beginTransaction() {        return new BackStackRecord(this);    }

BackStackRecord中：

public int commit() {        return commitInternal(false);    }public int commitAllowingStateLoss() {        return commitInternal(true);    }

可以看到这俩函数的区别就是commitInternal()方法中参数一个为true，一个为false，看一下这个函数：

int commitInternal(boolean allowStateLoss) {        if (mCommitted) throw new IllegalStateException("commit already called");        if (FragmentManagerImpl.DEBUG) {            Log.v(TAG, "Commit: " + this);            LogWriter logw = new LogWriter(TAG);            PrintWriter pw = new PrintWriter(logw);            dump("  ", null, pw, null);        }        mCommitted = true;        if (mAddToBackStack) {            mIndex = mManager.allocBackStackIndex(this);        } else {            mIndex = -1;        }        mManager.enqueueAction(this, allowStateLoss);        return mIndex;    }

再追踪到enqueueAction(this,allowStateLoss)：

public void enqueueAction(Runnable action, boolean allowStateLoss) {        if (!allowStateLoss) {            checkStateLoss();        }        synchronized (this) {            if (mDestroyed || mHost == null) {                throw new IllegalStateException("Activity has been destroyed");            }            if (mPendingActions == null) {                mPendingActions = new ArrayList<Runnable>();            }            mPendingActions.add(action);            if (mPendingActions.size() == 1) {                mHost.getHandler().removeCallbacks(mExecCommit);                mHost.getHandler().post(mExecCommit);            }        }    }

可以看到函数第一行根据allowStateLoss做了一个判断，看一下checkStateLoss():

private void checkStateLoss() {        if (mStateSaved) {            throw new IllegalStateException(                    "Can not perform this action after onSaveInstanceState");        }        if (mNoTransactionsBecause != null) {            throw new IllegalStateException(                    "Can not perform this action inside of " + mNoTransactionsBecause);        }    }

怎么样，终于把这个异常信息给抓出来了吧，特么的，

知道了bug原因那我们来说一下解决吧，有人说用反射的方法拿到commitAllowingStateLoss（）方法，调用他，但是这也太麻烦了，所简单点的办法就是：

重写show方法catch住异常即可，做好容错处理：

 /**     * 为了解决:mainActivity调用onSaveInstanceState以后又调用了show方法,     * 出现的Can not perform this action after onSaveInstanceState     * 这个异常(不应该用commit ,而是用commitAllowingStateLoss)     * 得罪了,不会反射 ,先把你catch住吧.乖     * @param manager     * @param tag     */    @Override    public void show(FragmentManager manager, String tag) {        try {            super.show(manager, tag);        } catch (IllegalStateException ignore) {            //  容错处理,不做操作        }    }

另外别忘记dissmiss也要做处理：

/**     * 注意,不要用super.dismiss(),bug 同上show()     * super.onDismiss就没问题     */    public void dismissDialog() {        if ( getActivity() != null && !getActivity().isFinishing()) {            super.dismissAllowingStateLoss();        }    }

而这个方法是没问题的：

@Override    public void onDismiss(DialogInterface dialog) {        super.onDismiss(dialog);    }

因为他调用的就是：

public void onDismiss(DialogInterface dialog) {        if (!mViewDestroyed) {            // Note: we need to use allowStateLoss, because the dialog            // dispatches this asynchronously so we can receive the call            // after the activity is paused.  Worst case, when the user comes            // back to the activity they see the dialog again.            dismissInternal(true);        }    }

好了，特此纪念一下，再犯此错误，