context中启动activity

解决Android中startActivity异常

最新推荐文章于 2024-05-26 22:48:24 发布

转载最新推荐文章于 2024-05-26 22:48:24 发布 · 105 阅读

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原文链接：http://www.cnblogs.com/shenbin/archive/2012/08/29/2662317.html

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#移动开发

本文详细解析了在Android开发中，使用Context的startActivity方法时出现特定异常的原因及解决方案。强调在非Activity环境下启动Activity时，需添加FLAG_ACTIVITY_NEW_TASK标志。此问题常见于Service或BroadcastReceiver中启动Activity场景。

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);