Android java.lang.NullPointer。 Eclipse Juno-JDK7错误的路径？

Question

Can't run my little Android code in Eclipse, I get this error message:

E/AndroidRuntime(275): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mytest.threedee/com.mytest.threedee.MainActivity}: java.lang.NullPointerException

What more info could be helpful? I guess my code is irrelevent because Eclipse fails to even start executing it. I do import java.lang.math.* Why does it say it's a "nullpointer"? The editor doesn't mark my math functions with any error. I suppose this is some obscure path problem with Eclipse.

Project/properties/Order and Export only lists: - 2Dto3D/src (2Dto3D is my project name) - 2Dto3D/gen - Android 4.2 - Android Dependencies

Should there maybe be something more there?

Under source tab, it says "Native library location: (None)". Sounds bad, doesn't it?

I have: Windows 7, 64 bit Have downloaded java JDK 7, 64 bit Eclipse for Mobile Developers Juno release 1 Try to run my code on a virtual device API 8

And my code (beginnings of a test calculation): (Sorry that the import block won't get into the code formatting here)

package com.mytest.threedee;

import com.mytest.threedee.R; import android.app.Activity; import android.os.Bundle; import android.view.Menu; import android.widget.TextView; import static java.lang.Math.*;

public class MainActivity extends Activity {

static final double pixPerRad = 4850;
static final double center2Dhor = 276.6;
static final double center2Dver = 293.7;
static final double short2D = 426.3;
static final double long2D = 2719.3;
static final double tilt2D = -0.2557;

double minor, major, MSC, CSL; // angles
double CM, MS, ML, CL; // distances
double gQJ, gVQ, gQL, gHL, gVL, gMLV, gCLQ; // temporary guessing variables
double[] gCQ, gmajor; // guessing variables whose guess values will be stored

String[] gmajor_Text;
String[] gCQ_Text;

TextView text1 = null;
TextView text2 = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    text1 = (TextView)findViewById(R.id.textView1);
    text2 = (TextView)findViewById(R.id.textView2);

    minor = short2D/pixPerRad;
    major = long2D/pixPerRad;

    MS = 1/asin(minor); 
    ML = MS; 
    CM = sqrt(MS*MS - 1);
    CL = MS - ML;

    // Guessing triangle VQJ:

    for (int i=0; i<2; i++)
    {       
    gCQ[i] = i/3; // First two guesses

    // Side QJ:

    gQJ = sqrt(1 - gCQ[i]*gCQ[i]);

    // Side VQ:

    gQL = sqrt(CL*CL + gCQ[i]*gCQ[i]);
    gCLQ = asin(gCQ[i]/gQL);
    gMLV = gCLQ;
    gHL = ML*cos(gMLV); 
    gVL = 2*gHL;
    gVQ = gVL - gQL;

    // major angle resulting from guess:

    gmajor[i] = 2 * atan(gQJ/gVQ);

    gmajor_Text[i] = String.valueOf(gmajor);
    gCQ_Text[i] = String.valueOf(gCQ);


    }//END for i
    text1.setText(gmajor_Text[0]);
    text2.setText(gCQ_Text[1]);



}//END onCreate

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}//END MainActivity

Answer 1

You still haven't initialized your arrays

double[] gCQ;
// later, you use it as is
gCQ[i] = i/3; 

You should initialize either in the onCreate() or outside

gCQ = new double[size];

Same goes for both your double[] and String[]

Answer 2

Not sure if your crash is due to that you have 1.7 but I thought that the Android SDK only supported Jdk 1.6.

Not sure if this works but here is a link to something similar: Can the Android SDK work with JDK 1.7?