Android Studio 拖入控件報錯或不顯示的解決辦法

當拖放控件到屏幕時，會報2個錯誤：less       錯誤信息1：Failed to load AppCompat ActionBar with unknown error.工具       錯誤信息2：This view is not constrained. It only has designtime positions, so it will jump to (0,0) at runti

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