Fragment java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

首先描述下所要实现的功能点：

MainActivity使用Fragment实现底部菜单，底部共有四个菜单按钮，分别对应：AFragment，BFragment，CFragment，DFragment。其中AFragment是默认显示。

点击CFragment中的一个button后跳转到第二个Activity界面：SecondActivity。

SecondActivity返回键有两个：button01、button02.其中button01返回的是CFragment；button02返回的是AFragment。

问题出现了：

button01可以返回到MainActivity中的CFragment,但是button02却没实现返回到MainActivity中的AFragment,无论是在SecondActivity中使用finish()，还是使用Intent跳转，都不能实现返回到MainActivity中的AFragment。

最后想到了广播机制来实现（我总感觉应该有更简单更好的方法，却始终没找到，迫不得已使用广播机制）。

去出现了另外一个问题：

Fragment java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState。

最后fragmentTransaction.commitAllowingStateLoss()替换掉fragmentTransaction.commit()解决问题。

最后再浏览下代码：

import java.util.ArrayList;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageButton;
import android.widget.TextView;

import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.QueueProcessingType;

public class MainActivity extends BaseActivity {
private static final String LOG_TAG = MainActivity.class.getSimpleName();

private FragmentManager fragmentManager;
private TextView txt_home;
private TextView txt_find;
private TextView txt_collection;
private TextView txt_setting;

private FragmentTransaction transaction;
private HomeFragment homeFragment;
private FindFragment findFragment;
private CollectionFragment collectionFragment;
private SettingFragment settingFragment;
private ImageButton imgbtn_voice;
private final static int SCANNIN_GREQUEST_CODE = 65537;

private BackBroadcast backBroadcast;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ResourceHelper.activityContext = this;

setContentView(R.layout.activity_main);

initImageLoaderConfi();

initView();

}

/**
* 底部菜单切换
*/
private void initView() {
fragmentManager = getSupportFragmentManager();

txt_home       = (TextView) findViewById(R.id.home_text);
txt_find       = (TextView) findViewById(R.id.find_text);
txt_collection = (TextView) findViewById(R.id.collection_text);
txt_setting    = (TextView) findViewById(R.id.setting_text);

txt_home.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
setTabSelection(0);
}
});
txt_find.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
setTabSelection(1);
}
});
txt_collection.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
setTabSelection(2);
}
});
txt_setting.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
setTabSelection(3);
}
});
setTabSelection(0);
}

@SuppressLint("NewApi")
public void setTabSelection(int index) {
clearSelection();
transaction = fragmentManager.beginTransaction();
hideFragments(transaction);
switch (index) {
case 0:
// 当点击了tab时，改变控件的图片和文字颜色
Drawable drawable01 = this.getResources().getDrawable(R.drawable.home_home_pressed);
txt_home.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable01, null, null);
txt_home.setTextColor(Color.parseColor("#2786c8"));
if (homeFragment == null) {
homeFragment = new HomeFragment();
transaction.add(R.id.content, homeFragment);
} else {
transaction.show(homeFragment);
}
break;
case 1:
Drawable drawable02 = this.getResources().getDrawable(R.drawable.home_find_pressed);
txt_find.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable02, null, null);
txt_find.setTextColor(Color.parseColor("#2786c8"));
if (findFragment == null) {
findFragment = new FindFragment();
transaction.add(R.id.content, findFragment);
} else {
transaction.show(findFragment);
}
break;
case 2:
Drawable drawable03 = this.getResources().getDrawable(R.drawable.home_collection_pressed);
txt_collection.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable03, null, null);
txt_collection.setTextColor(Color.parseColor("#2786c8"));
if (collectionFragment == null) {
collectionFragment = new CollectionFragment();
transaction.add(R.id.content, collectionFragment);
} else {
transaction.show(collectionFragment);
}
break;
case 3:
Drawable drawable04 = this.getResources().getDrawable(R.drawable.home_setting_pressed);
txt_setting.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable04, null, null);
txt_setting.setTextColor(Color.parseColor("#2786c8"));
if (settingFragment == null) {
settingFragment = new SettingFragment();
transaction.add(R.id.content, settingFragment);
} else {
transaction.show(settingFragment);
}
break;
}
transaction.commitAllowingStateLoss();   //该处是重点，如果使用transaction.commit()会一直崩溃报错。
}

// 每次选中之前先清楚掉上次的选中状态
@SuppressLint("NewApi")
private void clearSelection() {
txt_home.setTextColor(Color.parseColor("#82858b"));
Drawable drawableHome = this.getResources().getDrawable(R.drawable.home_home_normal);
txt_home.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableHome, null, null);

txt_find.setTextColor(Color.parseColor("#82858b"));
Drawable drawableFind = this.getResources().getDrawable(R.drawable.home_find_normal);
txt_find.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableFind, null, null);

txt_collection.setTextColor(Color.parseColor("#82858b"));
Drawable drawableMy = this.getResources().getDrawable(R.drawable.home_collection_normal);
txt_collection.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableMy, null, null);

txt_setting.setTextColor(Color.parseColor("#82858b"));
Drawable drawableMore = this.getResources().getDrawable(R.drawable.home_setting_normal);
txt_setting.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableMore, null, null);
}
// 先隐藏掉所有的Fragment，以防止有多个Fragment显示在界面上的情况
private void hideFragments(FragmentTransaction transaction) {
if (homeFragment != null) {
transaction.hide(homeFragment);
}
if (findFragment != null) {
transaction.hide(findFragment);
}
if (collectionFragment != null) {
transaction.hide(collectionFragment);
}
if (settingFragment != null) {
transaction.hide(settingFragment);
}
}

@Override
protected void onResume() {
super.onResume();
//		setTabSelection(0);

backBroadcast = new BackBroadcast();
registerReceiver(backBroadcast, new IntentFilter(Constant.HOME_BACK_ACTION));
}

@Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(backBroadcast);
}
private class BackBroadcast extends BroadcastReceiver{

@Override
public void onReceive(Context context, Intent intent) {
String temp = intent.getAction();
if (temp.equals(Constant.HOME_BACK_ACTION)) {
setTabSelection(0);
}
}
}

@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
}
}

顺便把布局也贴出来吧：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<FrameLayout
android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1" >
</FrameLayout>

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/home_bottom"
android:baselineAligned="true" >

<TextView
android:id="@+id/home_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="10dip"
android:layout_weight="1"
android:drawableTop="@drawable/home_home"
android:gravity="center"
android:text="首页"
android:textColor="#82858b" />

<TextView
android:id="@+id/find_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="10dip"
android:layout_weight="1"
android:drawableTop="@drawable/home_find"
android:gravity="center"
android:text="发现"
android:textColor="#82858b" />

<TextView
android:id="@+id/collection_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="10dip"
android:layout_weight="1"
android:drawableTop="@drawable/home_collection"
android:gravity="center"
android:text="收藏"
android:textColor="#82858b" />

<TextView
android:id="@+id/setting_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="10dip"
android:layout_weight="1"
android:drawableTop="@drawable/home_setting"
android:gravity="center"
android:text="设置"
android:textColor="#82858b" />
</LinearLayout>

</LinearLayout>