Could not start android adv in terminal on Mac

Question

My operating system is MacOS, and I am developing a mobile application for Android. I downloaded android studio and installed android_home environment. I installed the marshmallow6.0 SDK. I tried android avd in terminal and could not open avd.

 java.lang.IllegalArgumentException: Argument cannot be null at org.eclipse.swt.SWT.error(Unknown Source) at org.eclipse.swt.SWT.error(Unknown Source) at org.eclipse.swt.SWT.error(Unknown Source) at org.eclipse.swt.widgets.Widget.error(Unknown Source) at org.eclipse.swt.widgets.Label.setText(Unknown Source) at com.android.sdkuilib.internal.widgets.AvdDetailsDialog.displayValue(AvdDetailsDialog.java:156) at com.android.sdkuilib.internal.widgets.AvdDetailsDialog.createContents(AvdDetailsDialog.java:73) at com.android.sdkuilib.ui.SwtBaseDialog.open(SwtBaseDialog.java:93) at com.android.sdkuilib.internal.widgets.AvdSelector.onDetails(AvdSelector.java:964) at com.android.sdkuilib.internal.widgets.AvdSelector.access$600(AvdSelector.java:86) at com.android.sdkuilib.internal.widgets.AvdSelector$11.widgetDefaultSelected(AvdSelector.java:728) at org.eclipse.swt.widgets.TypedListener.handleEvent(Unknown Source) at org.eclipse.swt.widgets.EventTable.sendEvent(Unknown Source) at org.eclipse.swt.widgets.Display.sendEvent(Unknown Source) at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source) at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source) at org.eclipse.swt.widgets.Widget.sendEvent(Unknown Source) at org.eclipse.swt.widgets.Widget.notifyListeners(Unknown Source) at org.eclipse.swt.widgets.Display.runDeferredEvents(Unknown Source) at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source) at com.android.sdkuilib.internal.repository.ui.AvdManagerWindowImpl1.open(AvdManagerWindowImpl1.java:146) at com.android.sdkuilib.repository.AvdManagerWindow.open(AvdManagerWindow.java:94) at com.android.sdkmanager.Main.showAvdManagerWindow(Main.java:438) at com.android.sdkmanager.Main.doAction(Main.java:380) at com.android.sdkmanager.Main.run(Main.java:151) at com.android.sdkmanager.Main.main(Main.java:117) 

I do not know what unknow source means. Do I need to include some source files?

I am trying to open avd through android studio. But when I open the project, ADV Manager is gray, which does not allow me to open adv. How can I fix this problem? Thank you very much.