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

转载自：https://blog.youkuaiyun.com/dsc114/article/details/44857685

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：

[java]  view plain  copy

1. import java.util.ArrayList;  
2.   
3. import android.annotation.SuppressLint;  
4. import android.app.Activity;  
5. import android.app.AlertDialog;  
6. import android.app.Dialog;  
7. import android.content.BroadcastReceiver;  
8. import android.content.Context;  
9. import android.content.DialogInterface;  
10. import android.content.Intent;  
11. import android.content.IntentFilter;  
12. import android.graphics.Color;  
13. import android.graphics.drawable.Drawable;  
14. import android.os.Bundle;  
15. import android.support.v4.app.FragmentManager;  
16. import android.support.v4.app.FragmentTransaction;  
17. import android.view.MotionEvent;  
18. import android.view.View;  
19. import android.view.View.OnClickListener;  
20. import android.widget.ImageButton;  
21. import android.widget.TextView;  
22.   
23. import com.nostra13.universalimageloader.cache.disc.naming.Md5FileNameGenerator;  
24. import com.nostra13.universalimageloader.core.ImageLoader;  
25. import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;  
26. import com.nostra13.universalimageloader.core.assist.QueueProcessingType;  
27.   
28. public class MainActivity extends BaseActivity {  
29.     private static final String LOG_TAG = MainActivity.class.getSimpleName();  
30.       
31.     private FragmentManager fragmentManager;  
32.     private TextView txt_home;  
33.     private TextView txt_find;  
34.     private TextView txt_collection;  
35.     private TextView txt_setting;  
36.       
37.     private FragmentTransaction transaction;  
38.     private HomeFragment homeFragment;  
39.     private FindFragment findFragment;  
40.     private CollectionFragment collectionFragment;  
41.     private SettingFragment settingFragment;  
42.     private ImageButton imgbtn_voice;  
43.     private final static int SCANNIN_GREQUEST_CODE = 65537;  
44.   
45.     private BackBroadcast backBroadcast;  
46.       
47.     @Override  
48.     protected void onCreate(Bundle savedInstanceState) {  
49.         super.onCreate(savedInstanceState);  
50.         ResourceHelper.activityContext = this;  
51.   
52.         setContentView(R.layout.activity_main);  
53.   
54.         initImageLoaderConfi();  
55.   
56.         initView();  
57.           
58.               
59.     }  
60.   
61.     /** 
62.      * 底部菜单切换 
63.      */  
64.     private void initView() {  
65.         fragmentManager = getSupportFragmentManager();  
66.           
67.         txt_home       = (TextView) findViewById(R.id.home_text);  
68.         txt_find       = (TextView) findViewById(R.id.find_text);  
69.         txt_collection = (TextView) findViewById(R.id.collection_text);  
70.         txt_setting    = (TextView) findViewById(R.id.setting_text);  
71.           
72.         txt_home.setOnClickListener(new OnClickListener() {  
73.   
74.             @Override  
75.             public void onClick(View v) {  
76.                 setTabSelection(0);  
77.             }  
78.         });  
79.         txt_find.setOnClickListener(new OnClickListener() {  
80.   
81.             @Override  
82.             public void onClick(View v) {  
83.                 setTabSelection(1);  
84.             }  
85.         });  
86.         txt_collection.setOnClickListener(new OnClickListener() {  
87.   
88.             @Override  
89.             public void onClick(View v) {  
90.                 setTabSelection(2);  
91.             }  
92.         });  
93.         txt_setting.setOnClickListener(new OnClickListener() {  
94.   
95.             @Override  
96.             public void onClick(View v) {  
97.                 setTabSelection(3);  
98.             }  
99.         });  
100.         setTabSelection(0);  
101.     }  
102.   
103.     @SuppressLint("NewApi")  
104.     public void setTabSelection(int index) {  
105.         clearSelection();  
106.         transaction = fragmentManager.beginTransaction();  
107.         hideFragments(transaction);  
108.         switch (index) {  
109.         case 0:  
110.             // 当点击了tab时，改变控件的图片和文字颜色  
111.             Drawable drawable01 = this.getResources().getDrawable(R.drawable.home_home_pressed);  
112.             txt_home.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable01, null, null);  
113.             txt_home.setTextColor(Color.parseColor("#2786c8"));  
114.             if (homeFragment == null) {  
115.                 homeFragment = new HomeFragment();  
116.                 transaction.add(R.id.content, homeFragment);  
117.             } else {  
118.                 transaction.show(homeFragment);  
119.             }  
120.             break;  
121.         case 1:  
122.             Drawable drawable02 = this.getResources().getDrawable(R.drawable.home_find_pressed);  
123.             txt_find.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable02, null, null);  
124.             txt_find.setTextColor(Color.parseColor("#2786c8"));  
125.             if (findFragment == null) {  
126.                 findFragment = new FindFragment();  
127.                 transaction.add(R.id.content, findFragment);  
128.             } else {  
129.                 transaction.show(findFragment);  
130.             }  
131.             break;  
132.         case 2:  
133.             Drawable drawable03 = this.getResources().getDrawable(R.drawable.home_collection_pressed);  
134.             txt_collection.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable03, null, null);  
135.             txt_collection.setTextColor(Color.parseColor("#2786c8"));  
136.             if (collectionFragment == null) {  
137.                 collectionFragment = new CollectionFragment();  
138.                 transaction.add(R.id.content, collectionFragment);  
139.             } else {  
140.                 transaction.show(collectionFragment);  
141.             }  
142.             break;  
143.         case 3:  
144.             Drawable drawable04 = this.getResources().getDrawable(R.drawable.home_setting_pressed);  
145.             txt_setting.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawable04, null, null);  
146.             txt_setting.setTextColor(Color.parseColor("#2786c8"));  
147.             if (settingFragment == null) {  
148.                 settingFragment = new SettingFragment();  
149.                 transaction.add(R.id.content, settingFragment);  
150.             } else {  
151.                 transaction.show(settingFragment);  
152.             }  
153.             break;  
154.         }  
155.         transaction.commitAllowingStateLoss();   //该处是重点，如果使用transaction.commit()会一直崩溃报错。  
156.     }  
157.   
158.     // 每次选中之前先清楚掉上次的选中状态  
159.     @SuppressLint("NewApi")  
160.     private void clearSelection() {  
161.         txt_home.setTextColor(Color.parseColor("#82858b"));  
162.         Drawable drawableHome = this.getResources().getDrawable(R.drawable.home_home_normal);  
163.         txt_home.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableHome, null, null);  
164.           
165.         txt_find.setTextColor(Color.parseColor("#82858b"));  
166.         Drawable drawableFind = this.getResources().getDrawable(R.drawable.home_find_normal);  
167.         txt_find.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableFind, null, null);  
168.           
169.         txt_collection.setTextColor(Color.parseColor("#82858b"));  
170.         Drawable drawableMy = this.getResources().getDrawable(R.drawable.home_collection_normal);  
171.         txt_collection.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableMy, null, null);  
172.           
173.         txt_setting.setTextColor(Color.parseColor("#82858b"));  
174.         Drawable drawableMore = this.getResources().getDrawable(R.drawable.home_setting_normal);  
175.         txt_setting.setCompoundDrawablesRelativeWithIntrinsicBounds(null, drawableMore, null, null);  
176.     }  
177.     // 先隐藏掉所有的Fragment，以防止有多个Fragment显示在界面上的情况  
178.     private void hideFragments(FragmentTransaction transaction) {  
179.         if (homeFragment != null) {  
180.             transaction.hide(homeFragment);  
181.         }  
182.         if (findFragment != null) {  
183.             transaction.hide(findFragment);  
184.         }  
185.         if (collectionFragment != null) {  
186.             transaction.hide(collectionFragment);  
187.         }  
188.         if (settingFragment != null) {  
189.             transaction.hide(settingFragment);  
190.         }  
191.     }  
192.       
193.     @Override  
194.     protected void onResume() {  
195.         super.onResume();  
196. //      setTabSelection(0);  
197.           
198.         backBroadcast = new BackBroadcast();  
199.         registerReceiver(backBroadcast, new IntentFilter(Constant.HOME_BACK_ACTION));  
200.     }  
201.       
202.     @Override  
203.     protected void onDestroy() {  
204.         super.onDestroy();  
205.         unregisterReceiver(backBroadcast);  
206.     }  
207.     private class BackBroadcast extends BroadcastReceiver{  
208.   
209.         @Override  
210.         public void onReceive(Context context, Intent intent) {  
211.             String temp = intent.getAction();  
212.             if (temp.equals(Constant.HOME_BACK_ACTION)) {  
213.                 setTabSelection(0);  
214.             }  
215.         }  
216.     }  
217.       
218.     @Override  
219.     protected void onSaveInstanceState(Bundle outState) {  
220.         super.onSaveInstanceState(outState);  
221.     }  
222. }  

顺便把布局也贴出来吧：

[html]  view plain  copy

1. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
2.     xmlns:tools="http://schemas.android.com/tools"  
3.     android:layout_width="match_parent"  
4.     android:layout_height="match_parent"  
5.     android:orientation="vertical"  
6.     tools:context=".MainActivity" >  
7.   
8.     <FrameLayout  
9.         android:id="@+id/content"  
10.         android:layout_width="match_parent"  
11.         android:layout_height="0dp"  
12.         android:layout_weight="1" >  
13.     </FrameLayout>  
14.   
15.     <LinearLayout  
16.         android:layout_width="match_parent"  
17.         android:layout_height="wrap_content"  
18.         android:background="@drawable/home_bottom"  
19.         android:baselineAligned="true" >  
20.   
21.         <TextView  
22.             android:id="@+id/home_text"  
23.             android:layout_width="wrap_content"  
24.             android:layout_height="wrap_content"  
25.             android:layout_gravity="center"  
26.             android:layout_marginTop="10dip"  
27.             android:layout_weight="1"  
28.             android:drawableTop="@drawable/home_home"  
29.             android:gravity="center"  
30.             android:text="首页"  
31.             android:textColor="#82858b" />  
32.   
33.         <TextView  
34.             android:id="@+id/find_text"  
35.             android:layout_width="wrap_content"  
36.             android:layout_height="wrap_content"  
37.             android:layout_gravity="center"  
38.             android:layout_marginTop="10dip"  
39.             android:layout_weight="1"  
40.             android:drawableTop="@drawable/home_find"  
41.             android:gravity="center"  
42.             android:text="发现"  
43.             android:textColor="#82858b" />  
44.   
45.         <TextView  
46.             android:id="@+id/collection_text"  
47.             android:layout_width="wrap_content"  
48.             android:layout_height="wrap_content"  
49.             android:layout_gravity="center"  
50.             android:layout_marginTop="10dip"  
51.             android:layout_weight="1"  
52.             android:drawableTop="@drawable/home_collection"  
53.             android:gravity="center"  
54.             android:text="收藏"  
55.             android:textColor="#82858b" />  
56.   
57.         <TextView  
58.             android:id="@+id/setting_text"  
59.             android:layout_width="wrap_content"  
60.             android:layout_height="wrap_content"  
61.             android:layout_gravity="center"  
62.             android:layout_marginTop="10dip"  
63.             android:layout_weight="1"  
64.             android:drawableTop="@drawable/home_setting"  
65.             android:gravity="center"  
66.             android:text="设置"  
67.             android:textColor="#82858b" />  
68.     </LinearLayout>  
69.   
70. </LinearLayout>