我正在使用 Delphi 10.3 Community Edition 编写一个简单的 Android 应用程序并尝试调用本机设备摄像头,但出现错误。
我正在关注 Delphi 官方指南:
在表单设计器上,选择按钮(用于拍照)。在 Object Inspector 中,选择 Action 属性的下拉列表。选择新标准动作 | 媒体库 | TtakePhotoFromCameraAction:
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相机拍摄的图片分配给 TImage 组件的 Bitmap 属性。
我已验证该项目 | 选项 | 使用权限 - 相机设置设置为true
。我也在申请启动应用所需的权限。在 Debug 或 Release 中运行没有区别。
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)'。
这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.
如何使本机相机 TTakePhotoFromCameraAction 工作?