android - 切换 fragment 错误

Question

try {
        FragmentManager manager = getSupportFragmentManager();

        FragmentTransaction transaction = manager.beginTransaction();
        transaction.setCustomAnimations(android.R.anim.fade_in,
                android.R.anim.fade_out);
        transaction.replace(R.id.record_container, fragment, mark);
        transaction.commit();
        //manager.executePendingTransactions();
    } catch (Exception e) {
        Log.e("my", "replaceFrag error");
    }

当我在我的三个 Fragment 之间切换时，有时会抛出这个错误:

java.lang.IllegalStateException: No host
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1184)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1179)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1991)
at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1976)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1041)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1197)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1562)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:483)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5047)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:609)
at dalvik.system.NativeStart.main(Native Method)

日志显示 No host，但我不知道主机是什么？

fragment 是这样创建的:

if (intent.getAction().equals(Constants.P2P.RET_GET_PLAYBACK_FILES)) {
            Log.e("waitload", "waitload=" + waitload);
            if (null == rlFrag) {
                rlFrag = new RecordListFragment();
                rlFrag.setUser(contact);
            }
            String[] names = (String[]) intent
                    .getCharSequenceArrayExtra("recordList");
            list = new ArrayList<String>();
            for (String str : names) {
                list.add(str);
            }
            if (waitload > 0) {
                rlFrag.setList(list);
                isLoadingChange = false;
                madapter.setList(list);
                madapter.notifyDataSetChanged();
                replaceFrag(rlFrag, fragments[0]);
                waitload--;
                Log.e("waitload", "loaded" + waitload);
            } else {
                madapter.upLoadData(list);
                Intent it = new Intent();
                it.setAction(Constants.Action.REPEAT_LOADING_DATA);
                // it.putStringArrayListExtra("adddata", (ArrayList<String>)
                // list);
                sendBroadcast(it);
            }
        } else if (intent.getAction().equals(
                Constants.P2P.ACK_RET_GET_PLAYBACK_FILES)) {
            if (null == faultFrag) {
                faultFrag = new FaultFragment();
            }
            int result = intent.getIntExtra("result", -1);
            if (result == Constants.P2P_SET.ACK_RESULT.ACK_PWD_ERROR) {
                finish();
                T.showShort(mContext, R.string.password_error);
            } else if (result == Constants.P2P_SET.ACK_RESULT.ACK_NET_ERROR) {
                Log.e("my", "net error resend:set npc time");
                faultFrag.setErrorText(getResources().getString(
                        R.string.net_error));
                waitload = 0;
                replaceFrag(faultFrag, fragments[2]);
            } else if (result == Constants.P2P_SET.ACK_RESULT.ACK_INSUFFICIENT_PERMISSIONS) {
                finish();
                T.showShort(mContext, R.string.insufficient_permissions);
            }
        } 

Answer 1

看一下FragmentManagerImpl的源码SourceCodeLink , int 方法 moveToState, 你会看到

if (mActivity == null && newState != Fragment.INITIALIZING) {
        throw new IllegalStateException("No activity");
}

所以，“No Host”意味着“No activity”，我猜想当你在三个 Fragment 之间切换时，会抛出一个异常导致你的 App 崩溃并使宿主 Activity 为空。