DialogFragment使用中show()方法遇到的IllegalStateException

  最近在首頁做了一個彈窗，用dialogFragment 實現的，線上報了一個crash:

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

特此記錄一下。

此問題的原因是：mainActivity 調用了onSaveInstanceState（）以後有觸發了dialog的顯示，dialog.show（）方法裏邊用的是commit（）而不是commitAllowingStateLoss（）

追蹤一下代碼：

DialogFragment中：

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

從調用下手：

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

可以追蹤下去，第一個參數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);
    }

可以看到這倆函數的區別就是commitInternal()方法中參數一個爲true，一個爲false，看一下這個函數：

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;
    }

再追蹤到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);
            }
        }
    }

可以看到函數第一行根據allowStateLoss做了一個判斷，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);
        }
    }

怎麼樣，終於把這個異常信息給抓出來了吧，特麼的，

知道了bug原因那我們來說一下解決吧，有人說用反射的方法拿到commitAllowingStateLoss（）方法，調用他，但是這也太麻煩了，所簡單點的辦法就是：

重寫show方法catch住異常即可，做好容錯處理：

 /**
     * 爲了解決:mainActivity調用onSaveInstanceState以後又調用了show方法,
     * 出現的Can not perform this action after onSaveInstanceState
     * 這個異常(不應該用commit ,而是用commitAllowingStateLoss)
     * 得罪了,不會反射 ,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) {
            //  容錯處理,不做操作
        }
    }

另外別忘記dissmiss也要做處理：

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

而這個方法是沒問題的：

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

因爲他調用的就是：

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，特此紀念一下，再犯此錯誤，