Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK

今天在项目中碰到的一个错误：

项目中涉及到很多Activity之间相互跳转的代码，如下所示的代码，感觉很繁琐，因此想到了封装一下：

Intent intent = new Intent(SplashActivity.this , MainFragmentActivity.class);
startActivity(intent);

封装在了另一个类：UIHelper.java中

Intent intent = new Intent();
intent.setClass(context, cls);
context.startActivity(intent);

运行后，就报错了，错误log:

04-09 15:55:08.165: E/AndroidRuntime(3403): android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity  context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.app.ContextImpl.startActivity(ContextImpl.java:964)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.app.ContextImpl.startActivity(ContextImpl.java:951)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.content.ContextWrapper.startActivity(ContextWrapper.java:290)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at com.nfschina.sign.cover.UIHelper.startUserActivity(UIHelper.java:76)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at com.nfschina.sign.cover.activity.SettingActivity.onPreferenceClick(SettingActivity.java:125)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.preference.Preference.performClick(Preference.java:952)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.preference.PreferenceScreen.onItemClick(PreferenceScreen.java:215)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.widget.AdapterView.performItemClick(AdapterView.java:315)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.widget.AbsListView.performItemClick(AbsListView.java:1107)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.widget.AbsListView$PerformClick.run(AbsListView.java:2795)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.widget.AbsListView$1.run(AbsListView.java:3470)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.os.Handler.handleCallback(Handler.java:730)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.os.Handler.dispatchMessage(Handler.java:92)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.os.Looper.loop(Looper.java:137)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at android.app.ActivityThread.main(ActivityThread.java:5136)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at java.lang.reflect.Method.invokeNative(Native Method)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at java.lang.reflect.Method.invoke(Method.java:525)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-09 15:55:08.165: E/AndroidRuntime(3403): 	at dalvik.system.NativeStart.main(Native Method)

第一行提示：
Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?

错误分析：

Context中有一个startActivity方法，Activity继承自Context，重载了startActivity方法。如果使用Activity的startActivity方法，不会有任何限制，而如果使用Context的startActivity方法的話，就需要开启一个新的的task，遇到这个异常，是因为使用了Context的startActivity方法。解决办法是，加一个flag。
代码：
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK );
这样就可以在新的task里面启动这个Activity了。

/**
	 * 启动新的Activity
	 * @param context 当前Activity
	 * @param cls     要启动的Activity的类
	 */
	public static void startUserActivity(Context context , Class cls){
		Intent intent = new Intent();
		intent.setClass(context, cls);
		intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK );
		context.startActivity(intent);
		
	}

在这里插入图片描述

Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK

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