app报错2

1、Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference

(1)网上的解答:  在全局变量定义了TextView，然后在控件初始化时，又定义了

(2)我的问题

2、android.content.ActivityNotFoundException: Unable to find explicit activity class {com.myplayer.activity/com.myplayer.activity.MainActivity};

have you declared this activity in your AndroidManifest.xml?

清单文件配置错误