Unable to instantiate activity ComponentInfo：class xxx is not accessible from class

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.lzw.reading/com.lzw.reading.ReaderActivity}: java.lang.IllegalAccessException: class com.lzw.reading.ReaderActivity is not accessible from class android.app.Instrumentation

错误原因：

使用 alt+enter 自动创建类后，默认没有public，导致该类不能访问

class ReaderActivity extends AppCompatActivity

 改为：

public class ReaderActivity extends AppCompatActivity {

 即可