如何在Delphi Android应用程序中调用本机摄像头?

我正在使用Delphi10.3社区版来编写一个简单的Android应用程序,并试图调用本机设备摄像头,但却出现了一个错误。

我在跟踪官方的德尔菲 guide :

在表单设计器上,选择按钮(用于拍照)。 在“对象检查器”中,选择“操作”属性的下拉列表。 从CameraAction中选择新建标准动作|媒体库| TTakPhoto:

在“事件”选项卡上,展开“操作”节点,然后双击OnDidFinishTaking事件。

将以下代码添加到OnDidFinishTaking事件处理程序:

procedure TForm1.TakePhotoFromCameraAction1DidFinishTaking(Image: TBitmap);
begin
  Image1.Bitmap.Assign(Image);
end;

此代码将从移动设备照相机拍摄的照片分配给TImage组件的位图属性。

我已验证项目|选项|使用权限-相机设置设置为 true

然而,有一个问题。单击按钮时,我收到以下错误消息:

java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法“android.content.res.XmlResourceParser android.content.pm.PackageItemInfo.loadXmlMetaData(android.content.pm.PackageManager,java.lang.String)”。

以下是我为最简单的测试应用程序编写的代码:

unit Unit1;
interface
uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, System.Permissions,
  FMX.StdCtrls, FMX.MediaLibrary, FMX.Platform, System.Messaging, FMX.Objects,
  System.Actions, FMX.ActnList, FMX.StdActns, FMX.MediaLibrary.Actions,
  FMX.Controls.Presentation;

type
  TForm1 = class(TForm)
    Button1: TButton;
    ActionList1: TActionList;
    TakePhotoFromCameraAction1: TTakePhotoFromCameraAction;
    procedure FormCreate(Sender: TObject);
  private
    procedure PermissionRequestResult(Sender: TObject; const APermissions: TArray<string>; const AGrantResults: TArray<TPermissionStatus>);
    procedure DisplayRationale(Sender: TObject; const APermissions: TArray<string>; const APostRationaleProc: TProc);
  end;

var
  Form1: TForm1;

implementation
uses
{$IFDEF ANDROID}
  Androidapi.Helpers,
  Androidapi.JNI.JavaTypes,
  Androidapi.JNI.Os,
{$ENDIF}
  FMX.DialogService;

{$R *.fmx}

procedure TForm1.PermissionRequestResult(Sender: TObject; const APermissions: TArray<string>; const AGrantResults: TArray<TPermissionStatus>);
begin
  // 3 permission involved
  if (Length(AGrantResults) = 3)
  and (AGrantResults[0] = TPermissionStatus.Granted)
  and (AGrantResults[1] = TPermissionStatus.Granted)
  and (AGrantResults[2] = TPermissionStatus.Granted) then
  else
    ShowMessage('Required permission has not been granted') ;
end;

procedure TForm1.DisplayRationale(Sender: TObject; const APermissions: TArray<string>; const APostRationaleProc: TProc);
begin
  TDialogService.ShowMessage('Need to access the camera',
    procedure(const AResult: TModalResult)
    begin
      APostRationaleProc;
    end);
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  permCam, permRead, permWrite: string;
begin
  // Request permissions
  permCam := JStringToString(TJManifest_permission.JavaClass.CAMERA);
  permRead := JStringToString(TJManifest_permission.JavaClass.READ_EXTERNAL_STORAGE);
  permWrite := JStringToString(TJManifest_permission.JavaClass.WRITE_EXTERNAL_STORAGE);
  PermissionsService.RequestPermissions([permCam, permRead, permWrite], PermissionRequestResult, DisplayRationale);
end;

end.