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在使用内部类 BroadcastReceiver 中使用Intent调用startActivity时报异常解决方案。 核心代码

public void onReceive(Context context, Intent intent) {
	Intent mainIntent = new Intent();
	mainIntent.setClass(context, MainActivity.class);
	context.startActivity(mainIntent);	
}

异常信息：E/AndroidRuntime(5189): java.lang.RuntimeException: Error receiving broadcast Intent { act=xxx (has extras) } in xxxxxx 可以在 E/AndroidRuntime(5189): FATAL EXCEPTION: main 上面看到一行 Warning : W/dalvikvm(5189): threadid=1: thread exiting with uncaught exception 既然是异常 exception 于是尝试在调用activity的时候添加 try 核心代码

public void onReceive(Context context, Intent intent) {
	try{
		Intent mainIntent = new Intent();
		mainIntent.setClass(context, MainActivity.class);
		context.startActivity(mainIntent);
	}catch(Exception e){
		e.printStackTrace();
	}	
}

在用LogCat看捕获到的异常 发现 System.err 错误 信息是 W/System.err(4555): android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want? 发现这个Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. 这个错误于是在startActivity之前添加了一行代码 mainIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 现在代码如下：

public void onReceive(Context context, Intent intent) {
	try{
		Intent mainIntent = new Intent();
		mainIntent.setClass(context, MainActivity.class);
		mainIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
		context.startActivity(mainIntent);
	}catch(Exception e){
		e.printStackTrace();
	}	
}

OK，上面的问题“Error receiving broadcast Intent” 和 “Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag.”都解决了。 下面解释了为什么使用Context的startActivity方法（比如在Service中或者BroadcastReceiver中启动Activity）为什么需要添加flag：FLAG_ACTIVITY_NEW_TASK。

/**
     * Launch a new activity.  You will not receive any information about when
     * the activity exits.
     *
     * Note that if this method is being called from outside of an 
     * {@link android.app.Activity} Context, then the Intent must include 
     * the {@link Intent#FLAG_ACTIVITY_NEW_TASK} launch flag. This is because, 
     * without being started from an existing Activity, there is no existing 
     * task in which to place the new activity and thus it needs to be placed 
     * in its own separate task. 
     * 
     * This method throws {@link ActivityNotFoundException} 
     * if there was no Activity found to run the given Intent. 
     * 
     * @param intent The description of the activity to start. 
     * 
     * @throws ActivityNotFoundException 
     * 
     * @see PackageManager#resolveActivity 
     **/

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