java - Android 代码在后端出现错误。但我不知道代码哪里出了问题

Question

我不知道我的代码出了什么问题。它不会显示该页面，并且我确定错误出现在 Java 代码中的某个位置。因为我检查布局及其工作是否完美，直到我放置后端。但我就是不知道错误在哪里。所以请有人帮助我。

package calculator.apk;

import android.support.v7.app.ActionBarActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;

public class signMeup extends ActionBarActivity {

    Button sign;
    EditText name,birthD,birthM,birthY,pass;
    String fname,passWord,bdate,bmonth,byear,gender;
    CheckBox checkgen;
    RadioButton female, male;
    RadioGroup group;

    int inputField;


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

        name = (EditText) findViewById (R.id.editText1);
        birthD = (EditText) findViewById (R.id.editText2);
        birthM = (EditText) findViewById (R.id.editText3);
        birthY = (EditText) findViewById (R.id.editText4);
        pass = (EditText) findViewById (R.id.editText5);
        male =(RadioButton) findViewById (R.id.radioButton1);
        female =(RadioButton) findViewById (R.id.radioButton2);
        group = (RadioGroup)findViewById(R.id.radioGroup);

        sign.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                try{
                fname = name.getText().toString();
                checkInput (fname);
                bdate = birthD.getText().toString();
                checkInput(bdate);
                bmonth = birthM.getText().toString();
                checkInput(bmonth);
                byear = birthY.getText().toString();
                checkInput(byear);
                passWord = pass.getText().toString();
                checkInput(passWord);
                checkRadioButton();


                Intent intent = new Intent(getBaseContext(), profile.class);
                intent.putExtra("fName", fname);
                intent.putExtra("bDate", bdate);
                intent.putExtra("bMonth", bmonth);
                intent.putExtra("bYear", byear);
                intent.putExtra("pWord", passWord);
                intent.putExtra("genDer", gender);

                startActivity(intent);
                }
                 catch (Exception e) { 
                     // do nothing
                 }

            }
        });     
    }

    public void checkRadioButton()
    {

        int index = group.getCheckedRadioButtonId();
        if(index==-1){
            inputField++;
        }
        else{
            //Checking for Male
            if(male.isChecked()){
                gender="Male";
                Toast.makeText(getApplicationContext(), "You selected Male.", Toast.LENGTH_SHORT).show(); 
            }
            //Checking for Female
            else if(female.isChecked()){
                gender="Female";
                Toast.makeText(getApplicationContext(), "You selected Female.", Toast.LENGTH_SHORT).show(); 
            }
        }
    }

    public void checkInput(String input)
    {
        if(input.matches("")){
            inputField++;
        }
    }


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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Answer 1

在下面的行中，您将得到 NULL POINTER EXCEPTION

sign.setOnClickListener(new View.OnClickListener() {

因为您从未像其他属性一样初始化您的按钮标志。

sign = (Button)findViewById(R.id.yourButtonId);