布尔上的nullObjectReference

Question

出于某种原因，我得到了这个布尔值的空对象引用，我不知道为什么。我不明白为什么布尔值返回空对象引用

这是活动代码

package com.spizer.mizer2;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.Toast;

public class ProblemSelector extends AppCompatActivity {

public Boolean AddProb;
public Boolean SubProb;
public Boolean MultiProb;
public Boolean DivisProb;

public int ANum = 0;
public int SNum;
public int MNum;
public int DNum;

//ProblemSelector PS = new ProblemSelector();

CheckBox checkbox1, checkbox2, checkbox3, checkbox4;

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

    checkbox1 = (CheckBox) findViewById(R.id.checkBox1);
    checkbox2 = (CheckBox) findViewById(R.id.checkBox2);
    checkbox3 = (CheckBox) findViewById(R.id.checkBox3);
    checkbox4 = (CheckBox) findViewById(R.id.checkBox4);

    checkbox1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            if (b) {
                AddProb = true;
                Toast.makeText(getBaseContext(), "Add: True", Toast.LENGTH_SHORT).show();
            } else {
                AddProb = false;
                Toast.makeText(getBaseContext(), "Add: False", Toast.LENGTH_SHORT).show();
            }
        }
    });
    checkbox2.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            if (b) {
                SubProb = true;
                if(AddProb == false) {
                    SNum = 0;
                }
                else if(AddProb == true) {
                    SNum = 1;
                }
            } else {
                SubProb = false;
            }
        }
    });
    checkbox3.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            if (b) {
                MultiProb = true;
                if(AddProb == false && SubProb == false) {
                    MNum = 0;
                }
                else if(AddProb == true && SubProb == false || AddProb == false && SubProb == true) {
                    MNum = 1;
                }
                else if(AddProb == true && SubProb == true) {
                    MNum = 2;
                }
            } else {
                MultiProb = false;
            }
        }
    });
    checkbox4.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
            if (b) {
                DivisProb = true;
                if(AddProb == false && SubProb == false && MultiProb == false) {
                    DNum = 0;
                }
                else if(AddProb == true && SubProb == false && MultiProb == false || AddProb == false && SubProb == true && MultiProb == false || AddProb == false && SubProb == false && MultiProb == true) {
                    DNum = 1;
                }
                else if(AddProb == true && SubProb == true && MultiProb == false || AddProb == false && SubProb == true && MultiProb == true || AddProb == true && SubProb == false && MultiProb == true) {
                    DNum = 2;
                }
                else if(AddProb == true && SubProb == true && MultiProb == true) {
                    DNum = 3;
                }
            } else {
                DivisProb = false;
            }
        }
    });
}

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

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

/** this is called when the user hits the continue button **/
public void DifficultyMenu(View view) {
    Intent DifficultyView = new Intent(this, DifficultyMenu.class);
    //DifficultyView.putExtra("addProb", PS.AddProb);
    //DifficultyView.putExtra("subProb", PS.SubProb);
    //DifficultyView.putExtra("multiProb", PS.MultiProb);
    //DifficultyView.putExtra("divisProb", PS.DivisProb);
    startActivity(DifficultyView);
}
}

这是发生在第101行和第75行的完整错误日志

09-21 11:26:24.671    5078-5078/com.spizer.mizer2 E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.spizer.mizer2, PID: 5078
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.Boolean.booleanValue()' on a null object reference
        at com.spizer.mizer2.ProblemSelector$3.onCheckedChanged(ProblemSelector.java:75)
        at android.widget.CompoundButton.setChecked(CompoundButton.java:161)
        at android.widget.CompoundButton.toggle(CompoundButton.java:115)
        at android.widget.CompoundButton.performClick(CompoundButton.java:127)
        at android.view.View$PerformClick.run(View.java:20916)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:145)
        at android.app.ActivityThread.main(ActivityThread.java:5972)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

Answer 1

您应该使用布尔基元数据类型，而不是布尔类对象（注意布尔中的小b），什么时候应该使用布尔的空值？

此外，如果你真的想使用布尔对象，你应该使用equals（）来比较值