context中启动activity

Caused by: android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?

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方法的话,就需要开启一个新的task,遇到上面那个异常的,都是因为使用了Context的startActivity方法。解决办法是,加一个flag。

intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 

以上转自:http://www.cnblogs.com/rioder/archive/2011/11/02/2233584.html

以下为Context源码中的startActivity:

    /**
     * Launch a new activity.  You will not receive any information about when
     * the activity exits.
     *
     * <p>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.
     *
     * <p>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
     */
    public abstract void startActivity(Intent intent);

以上解释了为什么使用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

原文地址:https://www.cnblogs.com/shenbin/p/2662317.html