Android JNI从Java类中获取Two Fields

Question

在我发布任何代码或任何内容之前,让我解释一下我要完成的任务:我要做的是从资源文件夹中获取加载着色器,并将PongDroidShader对象数组传递给C++,以便它可以编译并加载它们.

在我的Java类中,我有一个函数,它遍历着色器文件夹中的每个着色器文件并解析它将它加载到一个String对象中,同时还通过其文件扩展名检查它是什么类型的着色器类型(.eg,一个顶点会有一个.vert扩展).一旦我完成了,我就把它发送到我的本机compileShaders函数,它接受PongDroidShader对象数组和数组的大小.

之后,我解析并链接JNI代码中的着色器.

到目前为止,我无法让JNI识别Java代码并将其加载到变量中.我到目前为止的内容如下:

Java代码

public final class PongDroidShader {
    public String mShaderSrc;
    public ShaderType mType;
}

private class ShaderHandler {


        ...

        private native void compileShaders(PongDroidShader[] shaders, int shaderCount);

        ...

JNI/C++代码

JNIEXPORT void JNICALL Java_com_grepwise_pongdroid_PongDroid_00024ShaderHandler_compileShaders
  (JNIEnv * env, jobject obj, jobjectArray shaders, jint sizeOfShaders) {

    for( int i = 0; i < sizeOfShaders; ++i )
    {
        jclass clazz = env->FindClass( "com/grepwise/pongdroid/PongDroidShader" );
        jclass shaderTypeEnum = env->FindClass( "com/grepwise/pongdroid/ShaderType" );

        jfieldID field = env->GetFieldID( clazz, "mType", "ShaderType" );

        jobject shader = env->GetObjectArrayElement( shaders, i );

        const jchar jShaderChr = env->GetCharField( shader, env->GetFieldID( clazz, "mShaderSrc", "java/lang/String" ) );

        jstring jShaderStr = env->NewString( &jShaderChr, sizeof( jShaderChr ) );

        const char* shaderStr = env->GetStringUTFChars( jShaderStr, 0 );

        //TODO implement GL Shader Manipulation and Allocation here

        optim::Config::Log::info( "Testing shader: %s", shaderStr );

        delete shaderStr;
    }

}

为简单起见,我省略了代码库中存在的很多内容.请注意,即使compileShaders未显示被调用,它也会被activity类调用,它将其父类包装为内部私有类.

到目前为止,我的日志输出如下:

04-25 22:20:56.267 11985 11985 D dalvikvm: Trying to load lib /data/data/com.grepwise.pongdroid/lib/libnativepd.so 0x4051c800
04-25 22:20:56.275 11985 11985 D dalvikvm: Added shared lib /data/data/com.grepwise.pongdroid/lib/libnativepd.so 0x4051c800
04-25 22:20:56.322 11985 11985 D dalvikvm: GetFieldID: unable to find field Lcom/grepwise/pongdroid/PongDroidShader;.mType:ShaderType
04-25 22:20:56.322 11985 11985 D dalvikvm: GetFieldID: unable to find field Lcom/grepwise/pongdroid/PongDroidShader;.mShaderSrc:java/lang/String
04-25 22:20:56.330 11985 11985 I dalvikvm:   at com.grepwise.pongdroid.PongDroid$ShaderHandler.compileShaders(Native Method)
04-25 22:20:56.330 11985 11985 I dalvikvm:   at com.grepwise.pongdroid.PongDroid$ShaderHandler.access$1(PongDroid.java:128)
04-25 22:20:56.330 11985 11985 I dalvikvm:   at com.grepwise.pongdroid.PongDroid.onCreate(PongDroid.java:72)

Answer 1

我相信你应该用这个来获得你的领域:

env->GetFieldID( clazz, "mType", "Lcom/grepwise/pongdroid/ShaderType;" );
env->GetFieldID( clazz, "mShaderSrc", "Ljava/lang/String;" )

并将类和字段移出循环.

编辑:也是这样的:

const jchar jShaderChr = env->GetCharField(...)

从mShaderSrc获取String值是错误的.

你应该使用:

jstring jShaderStr = (jstring)env->GetObjectField(...);
const char* shaderSrc = env->GetStringUTFChars(jShaderStr, 0);
// ... here use shaderSrc
env->ReleaseStringUTFChars(hShaderStr, shaderSrc);