Android项目使用SCPSolver求解线性规划时触发空指针异常

我在Android项目中使用SCPSolver求解线性规划问题，已下载Jar包并添加至lib目录，调用solve方法前一切看似正常，但调用该方法时出现了空指针异常。

问题代码 #

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.Toast;

import scpsolver.constraints.LinearBiggerThanEqualsConstraint;
import scpsolver.constraints.LinearSmallerThanEqualsConstraint;
import scpsolver.lpsolver.LinearProgramSolver;
import scpsolver.lpsolver.SolverFactory;
import scpsolver.problems.LinearProgram;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        LinearProgram lp = new LinearProgram(new double[]{5.0,10.0});
        lp.addConstraint(new LinearBiggerThanEqualsConstraint(new double[]{3.0,1.0}, 8.0, "c1"));
        lp.addConstraint(new LinearBiggerThanEqualsConstraint(new double[]{0.0,4.0}, 4.0, "c2"));
        lp.addConstraint(new LinearSmallerThanEqualsConstraint(new double[]{2.0,0.0}, 2.0, "c3"));
        lp.setMinProblem(true);
        LinearProgramSolver solver  = SolverFactory.newDefault();
        double[] sol = solver.solve(lp);
    }
}

报错信息 #

java.lang.RuntimeException: 无法启动Activity
Attempt to invoke interface method 'double[] scpsolver.lpsolver.LinearProgramSolver.solve(scpsolver.problems.LinearProgram)' on a null object reference
....
Caused by: java.lang.NullPointerException: 在空对象引用上调用接口方法'double[] scpsolver.lpsolver.LinearProgramSolver.solve(scpsolver.problems.LinearProgram)'

解决办法 #

空指针的核心原因是SolverFactory.newDefault()返回了null，SCPSolver的默认求解器依赖在Android环境下无法被正确加载或缺失。可以按以下步骤处理：

• 检查SCPSolver Jar包是否完整，确认其依赖的第三方库（如Apache Commons Math）已一同添加到项目的lib目录中
• 避免使用SolverFactory.newDefault()，直接实例化具体的求解器实现类，例如ApacheCommonsSolver（需确保对应依赖已引入）
• 确认Android项目的依赖配置正确，在Module的build.gradle文件中添加Jar包的依赖声明，比如：

  implementation files('libs/scpsolver.jar')
  implementation files('libs/commons-math3-x.x.jar')
  

内容的提问来源于stack exchange，提问作者Abdalnassir Ghzawi