相关疑难解决方法(0)

我真的开始学习Java了.当我运行此代码时,一切正常,直到我将EditText框保留为空并点击运行按钮.然后我得到:

ERROR/AndroidRuntime(866): FATAL EXCEPTION: main
ERROR/AndroidRuntime(866): java.lang.NumberFormatException: 
ERROR/AndroidRuntime(866):     at org.apache.harmony.luni.util.FloatingPointParser.parseDouble(FloatingPointParser.java:267)

我想当我尝试从字符串解析Double时,它不会获得任何值并产生错误.我想知道如何避免这个错误,并给变量赋予某种值,所以它永远不会是空的？感谢您的帮助!

import android.app.Activity;
import android.os.Bundle;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Button;
import android.view.View;
import android.view.View.OnClickListener;

public class Main extends Activity {

    private EditText noKids;
    private EditText noGumballs;
    private TextView noSum;
    private Button b;
    private Button br;
    double etKids = 0;
    double etGumballs = 0;
    private double tvSumIn = 0.00;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        initControls();
    }


    private void …