CODEWITHSUNDEEP
javaandroidandroid-ndkjava-native-interface
nmxprime
nmxprime

Reputation: 1506

android jni reading jobjectArray field fails

I want to read the elements of a java class in native c code.

Java class is as below

static public class GraphViewData implements GraphViewDataInterface {
    public final double valueX;
    public final double valueY;
    public GraphViewData(double valueX, double valueY) {
        super();
        this.valueX = valueX;
        this.valueY = valueY;
    }
    @Override
    public double getX() {
        return valueX;
    }
    @Override
    public double getY() {
        return valueY;
    }
}

I am passing an array of this class to native function, and trying to read the valueX & valueY fields.

int Java_com_example_fftplot_PlotActivity_computeFFT(JNIEnv *env, jobject thiz,jint function,jobjectArray data) {

int i;
jsize inLength = (*env)->GetArrayLength(env,data); //size of input object array
for(i = 0; i < inLength/8 ; i++){
    jobject inData = (*env)->GetObjectArrayElement(env,data,i);
    jclass inDataClass = (*env)->GetObjectClass(env,data);
    jfieldID inXval = (*env)->GetFieldID(env,inDataClass,"valueX","D");
    jfieldID inYval = (*env)->GetFieldID(env,inDataClass,"valueY","D");
    __android_log_print(ANDROID_LOG_ERROR, "inXval =", "%l",inXval);
    __android_log_print(ANDROID_LOG_ERROR, "inYval =", "%l",inYval);
}
}

But i get error , as below

01-25 17:29:15.780: W/dalvikvm(3958): JNI WARNING: JNI method called with exception pending
01-25 17:29:15.780: W/dalvikvm(3958):              in Lcom/example/fftplot/PlotActivity;.computeFFT:(I[Lcom/jjoe64/graphview/GraphView$GraphViewData;)I (GetFieldID)
01-25 17:29:15.780: W/dalvikvm(3958): Pending exception is:
01-25 17:29:15.790: I/dalvikvm(3958): java.lang.NoSuchFieldError: no field with name='valueX' signature='D' in class [Lcom/jjoe64/graphview/GraphView$GraphViewData;
01-25 17:29:15.790: I/dalvikvm(3958):   at com.example.fftplot.PlotActivity.computeFFT(Native Method)

What i am doing wrong, also, what is the meaning of JNI WARNING?. How to solve it?

Upvotes: 0

Views: 1166

Answers (1)

fadden
fadden

Reputation: 52343

no field with name='valueX' signature='D' in class [Lcom/jjoe64/graphview/GraphView$GraphViewData;

Note the '[' in the class name. You're looking for a field called valueX in the array class GraphViewData[] rather than the class GraphViewData.

Perhaps you meant to pass inData rather than data to GetObjectClass?

Upvotes: 2

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