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我试图实现一个类似于在FMX.Advertising.Android. 

type
  // Forward declaration
  JAttentiveListener = interface;   //com.pack.AttentiveListener
  //...
  JAttentiveListenerClass = interface(IJavaClass)
  ['{28A2CA13-A965-4EAB-A4F0-481E20C9AF2A}']
  end;

  [JavaSignature('com/pack/AttentiveListener')]
  JAttentiveListener = interface(IJavaInstance)
  ['{45D40262-E5C2-4650-B64A-4C5D56EA6107}']
    {Methods}
    procedure onClicked; cdecl;
    procedure onNotReceived(message1: JString); cdecl;
    procedure onReceived; cdecl;
  end;
  TJAttentiveListener = class(TJavaGenericImport<JAttentiveListenerClass, JAttentiveListener>) end;

  TMyListener = class(TJavaLocal, JAttentiveListener)     // JAttentiveListener is Android interface imported above using JNI
  private
    FObj: TCallbackObj;
  public
    constructor Create(Obj: TCallbackObj);
    destructor Destroy; override;
    procedure onClicked; cdecl;
    procedure onNotReceived(message1: JString); cdecl;
    procedure onReceived; cdecl;
  end;

{TMyListener}

constructor TMyListener.Create(Obj: TCallbackObj);
begin
  inherited Create;   // exception here.
  FObj := Obj;
end;

构造函数在 UI 线程中调用，并NullPointerException在调用父构造函数期间抛出。日志中有以下消息： [dvmFindClassByName 拒绝，java.lang.NullPointerException

我尝试一步一步调试，并步入TJavaLocal's c-tor. 此 c-tor 的以下语句中出现异常：

FLocalRefObjectID := AJNIEnv^.CallObjectMethodA(AJNIEnv, AJNIObject, CreateProxyClass, PJNIValue(ArgsToJNIValues([ClsID, Self])));
HandleJNIException(AJNIEnv);    // NullPointerException is here

为什么同样的事情FMX.Advertising.Android在我的代码中起作用而在我的代码中不起作用？（我正在尝试创建一个侦听器来实现一个接口并执行类似AdsListenerfrom 的所有操作FMX.Advertising.Android。）

4

1 回答 1

2

多注意日志输出。NullPointerException前面有'dvmFindClassByName拒绝X'，这意味着dalvik找不到listener的类。也许它在 classes.dex 文件中不存在，也许你在 .dex 文件中指定了错误的签名[JavaSignature('com/pack/AttentiveListener')]。

于 2014-05-20T13:29:50.240 回答