可以通过JNI and NDK从Delphi调用Android C函数。要实现此功能需要进行大量工作,建议直接调用NDK函数。为此,我创建了一个小示例文件,按照我在Delphi源代码中找到的方式声明了一个外部C函数。在<path to delphi>\source\rtl\android中更具体。

我创建了一个非常小的测试程序来测试直接从Delphi调用C函数的功能。您将在下面找到所有源代码,这是我目前正在测试的代码。

  unit DLL_external;

  interface

  const
     MIDI_Lib = '/usr/lib/libmiditest.so';
     test_fun = 'test_1';

  function test_1 (n: Integer): Integer; cdecl;
    external MIDI_Lib name test_fun;

  implementation

  initialization

  finalization

  end.

初始化和完成是必要的,因为否则会发生链接错误,这些错误指的是缺少一些初始化和完成代码。调用类:
  unit DLL_Test_Main;

  interface

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

  //{$I Androidapi.inc}

  type
     TForm1 = class(TForm)
      Button_Load: TButton;
      Label1: TLabel;

      procedure Button_LoadClick (Sender: TObject);
      procedure FormCreate(Sender: TObject);

     public
        procedure call_external_function (value: Integer);
     end; // Class: TForm1 //

  var
     Form1: TForm1;

  implementation

  {$R *.fmx}

  procedure TForm1.FormCreate (Sender: TObject);
  begin
     Label1.Text := 'External function not called yet';
  end; // FormCreate //

  procedure TForm1.Button_LoadClick (Sender: TObject);
  begin
     call_external_function (3);
  end; // Button_LoadClick //

  procedure TForm1.call_external_function (value: integer);
  var n: Int32;
  begin
     n := test_1 (value);
     Label1.Text := Format ('%d = test_1 (%d)', [n, value]);
  end; // call_external_function //

  end.

连同本地库miditest。这是使用ndk-build构建的。生成的库libmiditest.so已复制到C:\Users\Public\Documents\RAD Studio\12.0\PlatformSDKs\android-ndk-r8e\platforms\android-14\arch-arm\usr\lib,因为这是Delphi放置自己的库的地方。
  #include <jni.h>

  int test_1 (int n) // little test for callability
  {
     return n * n;
  }

当我执行ndk-build时,在子目录libmiditest.so中会生成一个文件libs\armeabi-v7a。我将此文件复制到<path to your ndk directory>\platforms\android-14\arch-arm\usr\lib。由于开始时出现一些链接错误(错误的名称和那种愚蠢的错误),所以我使用readelf -AWs libmiditest.so生成了符号列表和所需的库体系结构。符号test_1和arm v7架构一样都在符号列表中(我使用Nexus 7进行测试)。当我运行Delphi程序时,它立即在Android上崩溃:“不幸的是,DLL_Test_Propject已停止”。检查adb输出(请参见下文),看来文件libDLL_Test_Project.so是预期的。我将DLL_external单元中的libmiditest.so替换为libDLL_Test_Project.so,并将/usr/lib/libmiditest.so复制到/usr/lib/libDLL_Test_Project.so。那没有帮助。

有谁知道为什么Delphi生成的应用程序会尝试加载自身的库?更好的是:关于如何通过Delphi调用Android C函数的任何建议?
  I/InputReader(  608): Reconfiguring input devices.  changes=0x00000010
  D/dalvikvm(  799): GC_FOR_ALLOC freed 2003K, 15% free 14582K/16964K, paused 29ms, total 29ms
  I/PCKeyboard(  799): Loaded dictionary, len=841005
  I/HK/LatinKeyboardBaseView(  799): onMeasure width=1200
  I/HK/LatinKeyboardBaseView(  799): onMeasure width=1200
  D/Documents( 3358): Used cached roots for com.android.providers.downloads.documents
  D/Documents( 3358): Used cached roots for com.android.externalstorage.documents
  D/Documents( 3358): Used cached roots for com.android.providers.media.documents
  D/Documents( 3358): Used cached roots for com.google.android.apps.docs.storage
  D/Documents( 3358): Update found 7 roots in 28ms
  D/BackupManagerService(  608): Received broadcast Intent { act=android.intent.action.PACKAGE_ADDED dat=package:com.embarcadero.DLL_Test_Project flg=0x4000010 (has extras) }
  V/BackupManagerService(  608): addPackageParticipantsLocked: #1
  D/SystemBroadcastService(  987): Received broadcast action=android.intent.action.PACKAGE_ADDED and uri=
  W/ContextImpl(  987): Implicit intents with startService are not safe: Intent { act=com.google.android.gms.games.service.INTENT } android.content.ContextWrapper.startService:494 com.google.android.gms.games.service.GamesIntentService.a:101 com.google.android.gms.games.service.GamesIntentService.b:368
  I/ActivityManager(  608): Delay finish: com.android.vending/com.google.android.finsky.receivers.PackageMonitorReceiver$RegisteredReceiver
  I/ActivityManager(  608): Resuming delayed broadcast
  I/ActivityManager(  608): Delay finish: com.google.android.apps.plus/.service.PackagesMediaMonitor
  I/ActivityManager(  608): Resuming delayed broadcast
  V/GelStubAppWatcher( 3631): onReceive: android.intent.action.PACKAGE_ADDED
  I/Icing.InternalIcingCorporaProvider( 3631): Updating corpora: A: com.embarcadero.DLL_Test_Project, C: MAYBE
  I/ActivityManager(  608): START u0 {flg=0x10800000 cmp=com.estrongs.android.pop/.app.InstallMonitorActivity (has extras)} from pid 3466
  D/dalvikvm(  608): GC_EXPLICIT freed 1385K, 11% free 19671K/22028K, paused 3ms+8ms, total 194ms
  D/dalvikvm(  608): WAIT_FOR_CONCURRENT_GC blocked 24ms
  D/AndroidRuntime( 4437): Shutting down VM
  D/dalvikvm( 4437): GC_CONCURRENT freed 95K, 16% free 560K/660K, paused 0ms+0ms, total 2ms
  W/InputMethodManagerService(  608): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@42c98f48 attribute=null, token = android.os.BinderProxy@42b91f10
  D/dalvikvm( 3631): GC_CONCURRENT freed 560K, 6% free 10268K/10860K, paused 2ms+2ms, total 23ms
  D/AndroidRuntime( 4476):
  D/AndroidRuntime( 4476): >>>>>> AndroidRuntime START com.android.internal.os.RuntimeInit <<<<<<
  D/AndroidRuntime( 4476): CheckJNI is OFF
  D/dalvikvm( 4476): Trying to load lib libjavacore.so 0x0
  D/dalvikvm( 4476): Added shared lib libjavacore.so 0x0
  D/dalvikvm( 4476): Trying to load lib libnativehelper.so 0x0
  D/dalvikvm( 4476): Added shared lib libnativehelper.so 0x0
  D/dalvikvm( 4476): No JNI_OnLoad found in libnativehelper.so 0x0, skipping init
  D/dalvikvm( 4476): Note: class Landroid/app/ActivityManagerNative; has 179 unimplemented (abstract) methods
  D/AndroidRuntime( 4476): Calling main entry com.android.commands.am.Am
  I/ActivityManager(  608): START u0 {flg=0x10000000 cmp=com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNativeActivity (has extras)} from pid 4476
  D/dalvikvm(  608): GC_FOR_ALLOC freed 807K, 12% free 19517K/22028K, paused 63ms, total 63ms
  D/AndroidRuntime( 4476): Shutting down VM
  D/dalvikvm( 4476): GC_CONCURRENT freed 96K, 15% free 586K/684K, paused 0ms+0ms, total 2ms
  D/dalvikvm( 4507): Late-enabling CheckJNI
  I/ActivityManager(  608): Start proc com.embarcadero.DLL_Test_Project for activity com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNativeActivity: pid=4507 uid=10113 gids={50113, 3003, 1028, 1015}
  I/dalvikvm( 4507): Enabling JNI app bug workarounds for target SDK version 9...
  V/PhoneStatusBar(  667): setLightsOn(true)
  D/AndroidRuntime( 4507): Shutting down VM
  W/dalvikvm( 4507): threadid=1: thread exiting with uncaught exception (group=0x41ccbba8)
  E/AndroidRuntime( 4507): FATAL EXCEPTION: main
  E/AndroidRuntime( 4507): Process: com.embarcadero.DLL_Test_Project, PID: 4507
  E/AndroidRuntime( 4507): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNativ
  eActivity}: java.lang.IllegalArgumentException: Unable to load native library: /data/app-lib/com.embarcadero.DLL_Test_Project-1/libDLL_Test_Project.so
  E/AndroidRuntime( 4507):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
  E/AndroidRuntime( 4507):        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
  E/AndroidRuntime( 4507):        at android.app.ActivityThread.access$800(ActivityThread.java:135)
  E/AndroidRuntime( 4507):        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
  E/AndroidRuntime( 4507):        at android.os.Handler.dispatchMessage(Handler.java:102)
  E/AndroidRuntime( 4507):        at android.os.Looper.loop(Looper.java:136)
  E/AndroidRuntime( 4507):        at android.app.ActivityThread.main(ActivityThread.java:5017)
  E/AndroidRuntime( 4507):        at java.lang.reflect.Method.invokeNative(Native Method)
  E/AndroidRuntime( 4507):        at java.lang.reflect.Method.invoke(Method.java:515)
  E/AndroidRuntime( 4507):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
  E/AndroidRuntime( 4507):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
  E/AndroidRuntime( 4507):        at dalvik.system.NativeStart.main(Native Method)
  E/AndroidRuntime( 4507): Caused by: java.lang.IllegalArgumentException: Unable to load native library: /data/app-lib/com.embarcadero.DLL_Test_Project-1/libDLL_Test_Project.so
  E/AndroidRuntime( 4507):        at android.app.NativeActivity.onCreate(NativeActivity.java:183)
  E/AndroidRuntime( 4507):        at com.embarcadero.firemonkey.FMXNativeActivity.onCreate(FMXNativeActivity.java:67)
  E/AndroidRuntime( 4507):        at android.app.Activity.performCreate(Activity.java:5231)
  E/AndroidRuntime( 4507):        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
  E/AndroidRuntime( 4507):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
  E/AndroidRuntime( 4507):        ... 11 more
  W/ActivityManager(  608):   Force finishing activity com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNativeActivity
  I/WindowManager(  608): Screenshot max retries 4 of Token{42a06c48 ActivityRecord{42a42de8 u0 com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNat
  iveActivity t17 f}} appWin=Window{42a1bab8 u0 Starting com.embarcadero.DLL_Test_Project} drawState=4
  W/WindowManager(  608): Screenshot failure taking screenshot for (1200x1920) to layer 21015
  W/ActivityManager(  608): Activity pause timeout for ActivityRecord{42a42de8 u0 com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNativeActivity t17 f}
  E/WindowManager(  608): Starting window AppWindowToken{4308ff58 token=Token{42a06c48 ActivityRecord{42a42de8 u0 com.embarcadero.DLL_Test_Project/com.embarcadero.firemonkey.FMXNativeActivity t17}}} timed out
  I/Process ( 4507): Sending signal. PID: 4507 SIG: 9
  W/InputMethodManagerService(  608): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@42a1abd0 attribute=null, token = android.os.BinderProxy@42b91f10
  I/ActivityManager(  608): Process com.embarcadero.DLL_Test_Project (pid 4507) has died.
  D/Finsky  ( 1567): [1] 5.onFinished: Installation state replication succeeded.

更新1

从评论中,我认为代码可能是更大系统的一部分。此代码是一个小型独立程序。本地代码库确实和您在此处看到的一样小。

更新2

正如Arioch所指出的那样,通过使用静态链接(或Windows术语中的隐式加载),当库未加载时,主程序将不会加载。这就解释了上面提到的adb消息。因此,问题是:为什么libmiditest.so无法加载?

最佳答案

一种解决方案是按照Arioch'The在其评论中的建议动态绑定(bind)库。有关如何执行此操作的机制,请参见他的Wiki链接。要链接到库中,请使用dlopen单元中的Posix.Dlfcn

但是,必须提供一个通往库的路径。在下面的示例代码中,我在Data\d目录中创建了目录sdcard0,并将libmiditest.so复制到其中。在其他系统上,该目录可能不同。实际上,这可以解释静态绑定(bind)不起作用的原因(尚未)。查找库时,该库未复制到系统搜索的路径中。

  unit DLL_Test_Main;

  interface

  uses
     System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
     FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs, FMX.StdCtrls,
     Posix.Dlfcn, FMX.Layouts, FMX.Memo, System.Math;


  const
     lib_path = '/storage/sdcard0/Data/d/libmiditest.so';
     fun_name = 'test_1';

  type
     TForm1 = class(TForm)
        Button_Load: TButton;
        Memo1: TMemo;

        procedure Button_LoadClick (Sender: TObject);
        procedure FormCreate(Sender: TObject);

      protected
         Lib_Handle: THandle;
      public
         procedure call_external_function (value: Integer);
      end; // Class: TForm1 //

  var
     Form1: TForm1;

  implementation

  {$R *.fmx}

  procedure TForm1.FormCreate (Sender: TObject);
  begin
     Lib_Handle := THandle (dlopen (lib_path, RTLD_LAZY));
     if Lib_Handle = 0 then
     begin
        Memo1.Lines.Add ('Cannot open library: ' + lib_path);
     end else
     begin
        Memo1.Lines.Add ('Opened library: ' + lib_path);
     end; // if
  end; // FormCreate //

  procedure TForm1.Button_LoadClick (Sender: TObject);
  begin
     call_external_function (RandomRange (0, 99));
  end; // Button_LoadClick //

  procedure TForm1.call_external_function (value: integer);
  var
     test_1: function (n: integer): integer; cdecl;
     n: Int32;
  begin
     if Lib_Handle <> 0 then
     begin
        test_1 := dlsym (Lib_Handle, fun_name);
        if not assigned (test_1) then
        begin
           Memo1.Lines.Add ('Cannot create function: ' + fun_name);
        end else
        begin
           n := test_1 (value);
           Memo1.Lines.Add (Format ('%d = %s (%d)', [n, fun_name, value]));
        end;
     end;
  end; // call_external_function //

  end.

09-10 07:30
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