Android this与Activity.this的区别

写语句的时候有两种情况: Toast.makeText(AlarmActivity.this,闹钟取消, Toast.LENGTH_SHORT); Toast.makeText(this,闹钟5秒后启动, Toast.LENGTH_SHORT); 用英文在google搜what‘s difference between this and Activity.this,终于有了结果(其实自己后面用了Java里ClassName.this和this 之前搜的是Activity.this,所以没有结果,这