Question

当我在下面的代码中调用FPlatformNetworkState := TPlatformNetworkState.Create;时，我收到了段错误。

我对segfault 11的了解是，当我尝试访问我不允许的内存（类似于Windows中的AccessViolation）时会发生这种情况。但是，由于我正在创建一个新实例，不应该分配新的内存吗？

我应该如何创建它以便它不会访问不应该存在的内存？

完整单位：

unit UNetworkState;

{From http://delphi.radsoft.com.au/2013/11/checking-for-an-internet-connection-on-mobile-devices-with-delphi-xe5/ (16-2-2015)}

interface

type
  TCustomNetworkState = class(TObject)
    function CurrentSSID: string; virtual; abstract;
    function IsConnected: Boolean; virtual; abstract;
    function IsWifiConnected: Boolean; virtual; abstract;
    function IsMobileConnected: Boolean; virtual; abstract;
  end;

  TNetworkState = class(TCustomNetworkState)
  private
    FPlatformNetworkState: TCustomNetworkState;
  public
    constructor Create;
    destructor Destroy; override;
    function CurrentSSID: string;
    function IsConnected: Boolean; override;
    function IsWifiConnected: Boolean; override;
    function IsMobileConnected: Boolean; override;
  end;

implementation

uses
{$IFDEF IOS}
  //NetworkState.iOS;
{$ENDIF}
{$IFDEF ANDROID}
  UNetworkStateAndroid;
{$ENDIF}

{ TNetworkState }

constructor TNetworkState.Create;
begin
  inherited;
  FPlatformNetworkState := TPlatformNetworkState.Create;
end;

destructor TNetworkState.Destroy;
begin
  FPlatformNetworkState.Free;
  inherited;
end;

function TNetworkState.CurrentSSID: string;
begin
  Result := FPlatformNetworkState.CurrentSSID;
end;

function TNetworkState.IsConnected: Boolean;
begin
  Result := FPlatformNetworkState.IsConnected;
end;

function TNetworkState.IsMobileConnected: Boolean;
begin
  Result := FPlatformNetworkState.IsMobileConnected;
end;

function TNetworkState.IsWifiConnected: Boolean;
begin
  Result := FPlatformNetworkState.IsWifiConnected;
end;

end.

调用create的表单：

unit UMainForm;

interface

uses
  System.SysUtils,
  System.Types,
  System.UITypes,
  System.Classes,
  System.Variants,
  FMX.Types,
  FMX.Graphics,
  FMX.Controls,
  FMX.Forms,
  FMX.Dialogs,
  FMX.TabControl,
  FMX.StdCtrls,
  FMX.Gestures;

type
  TappMainForm = class(TForm)
    HeaderToolBar: TToolBar;
    ToolBarLabel: TLabel;
    TabControl1: TTabControl;
    TabItem1: TTabItem;
    TabItem2: TTabItem;
    TabItem3: TTabItem;
    TabItem4: TTabItem;
    GestureManager1: TGestureManager;
    NotificationsPanel: TPanel;
    procedure FormCreate(Sender: TObject);
    procedure FormGesture(Sender: TObject; const EventInfo: TGestureEventInfo;
      var Handled: Boolean);
    procedure EmbedForm(ArgParent : TControl; ArgForm : TCustomForm);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  appMainForm: TappMainForm;

implementation

{$R *.fmx}
uses
  UNetworkState;

procedure TappMainForm.FormCreate(Sender: TObject);
var
  NS : TNetworkState;
begin
  { This defines the default active tab at runtime }
  TabControl1.ActiveTab := TabItem1;

  NS.Create;
  try
    if not NS.IsConnected then begin
      ShowMessage('No network connection detected.'#13#10'Please connect to the internet in your device''s settings.');
    end else if NS.IsWifiConnected then begin
      ShowMessage('WiFi connection detected.');
    end else if NS.IsMobileConnected then begin
      ShowMessage('Mobile connection detected.');
    end;
  finally
    NS.Free;
  end;
end;

procedure TappMainForm.FormGesture(Sender: TObject;
  const EventInfo: TGestureEventInfo; var Handled: Boolean);
begin
{$IFDEF ANDROID}
  case EventInfo.GestureID of
    sgiLeft:
    begin
      if TabControl1.ActiveTab <> TabControl1.Tabs[TabControl1.TabCount-1] then
        TabControl1.ActiveTab := TabControl1.Tabs[TabControl1.TabIndex+1];
      Handled := True;
    end;

    sgiRight:
    begin
      if TabControl1.ActiveTab <> TabControl1.Tabs[0] then
        TabControl1.ActiveTab := TabControl1.Tabs[TabControl1.TabIndex-1];
      Handled := True;
    end;
  end;
{$ENDIF}
end;
end.

Answer 1

在您的表单代码中，调用NS.Create是错误的。它需要NS := TNetworkState.Create代替。

分段错误（11）在android中创建新对象

1 个答案: