这些帮助了我:

1.启用ADB集成 2. 进入Android设备监视器 检查您的设备是否在线，并创建所需的过滤器

尝试点击“Android”视图最右边的图标，你应该在Android视图上看到Logcat选项卡(你可以通过按Alt+6打开Android视图)

我刚把它修好了。在DDMS显示的最右边寻找恢复Devices Logcat视图和ADB视图的小图标。

When the DDMS first came up with both the "ADB Logs" and the "Devices | logcat" tab showing. The "Devices | logcat" is the one that should be showing the device output, but was blank. Somehow I managed to hide one or the other of those tabs, I forget exactly how. But, off to the right there was a tiny icon that said "Restore ADB" view, and I clicked it and it came up. Then there was another tiny icon that said "Restore Devices logcat view". I clicked that, and all of a sudden it appeared and was showing the device output again.

对我来说，问题在于设备是在“仅充电”模式下连接的。

将模式更改为媒体设备(MTP)(或在某些设备中传输文件)解决了问题。

重新启动Android Studio帮助了我。

确保您导入了正确的类

import android.util.Log;