Question

我收到空指针错误我怎么能解决这个问题？

我该如何解决这个问题？请帮忙感谢

simple_ques.java

package com.mimoh.kulkarni.mimoh;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
public class simple_ques extends AppCompatActivity implements View.OnClickListener{

private allstrings ostring = new allstrings();

TextView qcurr,qtotal,scoreno,question;
Button bchoice1,bchoice2,bchoice3,bchoice4,bback,bans,bforward;
private String mans;
int qno=0,score=0;

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

    qcurr = (TextView)findViewById(R.id.curr);
    qtotal = (TextView)findViewById(R.id.total);
    scoreno = (TextView)findViewById(R.id.score);
    question = (TextView)findViewById(R.id.question);

    bchoice1 = (Button)findViewById(R.id.bchoice1);
    bchoice2 = (Button)findViewById(R.id.bchoice2);
    bchoice3 = (Button)findViewById(R.id.bchoice3);
    bchoice4 = (Button)findViewById(R.id.bchoice4);
    bback = (Button)findViewById(R.id.bback);
    bans = (Button)findViewById(R.id.banswer);
    bforward = (Button)findViewById(R.id.bforward);

    bback.setOnClickListener(this);
    bans.setOnClickListener(this);
    bforward.setOnClickListener(this);

    bchoice1.setOnClickListener(this);
    bchoice2.setOnClickListener(this);
    bchoice3.setOnClickListener(this);
    bchoice4.setOnClickListener(this);

    updatequestion();


}

@Override
public void onClick(View view) {
    switch (view.getId()){

        case R.id.bchoice1:
            if(bchoice1.getText() == mans){
                score = score + 1;
                scoreno.setText(score);
                updatequestion();
                Toast.makeText(this,"Correct",Toast.LENGTH_LONG).show();
            }
            else{
                Toast.makeText(this,"Wrong",Toast.LENGTH_LONG).show();
            }
            break;

            case R.id.bchoice2:
            if(bchoice2.getText() == mans){
                score = score + 1;
                scoreno.setText(score);
                updatequestion();
                Toast.makeText(this,"Correct",Toast.LENGTH_LONG).show();
            }
            else{
                Toast.makeText(this,"Wrong",Toast.LENGTH_LONG).show();
            }
            break;

            case R.id.bchoice3:
            if(bchoice3.getText() == mans){
                score = score + 1;
                scoreno.setText(score);
                updatequestion();
                Toast.makeText(this,"Correct",Toast.LENGTH_LONG).show();
            }
            else{
                Toast.makeText(this,"Wrong",Toast.LENGTH_LONG).show();
            }
            break;

            case R.id.bchoice4:
            if(bchoice4.getText() == mans){
                score = score + 1;
                scoreno.setText(score);
                updatequestion();
                Toast.makeText(this,"Correct",Toast.LENGTH_LONG).show();
            }
            else{
                Toast.makeText(this,"Wrong",Toast.LENGTH_LONG).show();
            }
            break;

    }
}

private void updatequestion(){
    question.setText(ostring.getquestion(qno));
    bchoice1.setText(ostring.getchoice1(qno));
    bchoice2.setText(ostring.getchoice2(qno));
    bchoice3.setText(ostring.getchoice3(qno));
    bchoice4.setText(ostring.getchoice4(qno));
    mans = ostring.get_corr_answer(qno);
    qno++;
}

}

allstrings.java

package com.mimoh.kulkarni.mimoh;

public class allstrings {

private String simple_questions[] ={
        "What is your name ?",
        "What is your age ?",
        "What is your surname ?"
};

private String simple_answers[][] = {
    {"Mimoh","Kulkarni","Mayur","Mangesh"},
    {"root","trunk","stem","leaves"},
    {"root","trunk","stem","leaves"}
};

private String corr_simple_answers[] ={"Mimoh","stem","leaves"};


public String getquestion(int a){
    String question = simple_questions[a];
    return question;
}

public String getchoice1(int a){
    String choice = simple_answers[a][0];
    return choice;
}

public String getchoice2(int a){
    String choice = simple_answers[a][1];
    return choice;
}

public String getchoice3(int a){
    String choice = simple_answers[a][2];
    return choice;
}

public String getchoice4(int a){
    String choice = simple_answers[a][3];
    return choice;
}

public String get_corr_answer(int a){
    String answer = corr_simple_answers[a];
    return answer;
}

}

logcat错误： -

02-09 22:55:45.719 5026-5026/com.mimoh.kulkarni.mimoh D/AndroidRuntime: Shutting down VM
02-09 22:55:45.719 5026-5026/com.mimoh.kulkarni.mimoh E/AndroidRuntime: FATAL EXCEPTION: main
                                                                    Process: com.mimoh.kulkarni.mimoh, PID: 5026

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mimoh.kulkarni.mimoh/com.mimoh.kulkarni.mimoh.simple_ques}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
                                                                        at android.app.ActivityThread.-wrap12(ActivityThread.java)
                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
                                                                        at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                        at android.os.Looper.loop(Looper.java:154)
                                                                        at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
                                                                     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
                                                                        at com.mimoh.kulkarni.mimoh.simple_ques.updatequestion(simple_ques.java:122)
                                                                        at com.mimoh.kulkarni.mimoh.simple_ques.onCreate(simple_ques.java:50)
                                                                        at android.app.Activity.performCreate(Activity.java:6679)
                                                                        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
                                                                        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
                                                                        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                                                                        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                                                                        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                                                                        at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                        at android.os.Looper.loop(Looper.java:154) 
                                                                        at android.app.ActivityThread.main(ActivityThread.java:6119) 
                                                                        at java.lang.reflect.Method.invoke(Native Method) 
                                                                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
02-09 22:55:45.730 1732-1744/system_process W/ActivityManager:   Force finishing activity com.mimoh.kulkarni.mimoh/.simple_ques
02-09 22:55:45.829 1732-1744/system_process W/ActivityManager:   Force finishing activity com.mimoh.kulkarni.mimoh/.homepage

simple_ques.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:weightSum="100">


<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="8"
    android:orientation="horizontal"
    android:background="@drawable/topbottom">

    <TextView
        android:id="@+id/curr"
        android:layout_width="100dp"
        android:layout_height="match_parent"
        android:text="@string/currq"
        android:textAlignment="viewEnd"
        android:textSize="25sp"/>

    <TextView
        android:id="@+id/total"
        android:layout_width="100dp"
        android:layout_height="match_parent"
        android:text="@string/totalq"
        android:textAlignment="viewStart"
        android:textSize="25sp"/>

    <TextView
        android:id="@+id/namescore"
        android:layout_width="120dp"
        android:layout_height="match_parent"
        android:text="@string/score"
        android:textAlignment="viewEnd"
        android:textSize="25sp"
        android:textColor="#ff0000"/>

    <TextView
        android:id="@+id/score"
        android:layout_width="80dp"
        android:layout_height="match_parent"
        android:text="@string/score"
        android:textSize="25sp"
        android:textAlignment="viewStart"
        android:textColor="#ff0000"
        />

</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:orientation="vertical"
    android:layout_weight="80"
    android:weightSum="10"
    android:background="@drawable/middle">

    <TextView
        android:id="@+id/textView5"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="4"
        android:text="@string/question"
        android:textSize="30sp"
        android:padding="5dp"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="6"
        android:orientation="vertical">

        <Button
            android:id="@+id/bchoice1"
            android:layout_width="300dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="Button" />

        <android.support.v4.widget.Space
            android:layout_width="match_parent"
            android:layout_height="10dp" />

        <Button
            android:id="@+id/bchoice2"
            android:layout_width="300dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="Button" />

        <android.support.v4.widget.Space
            android:layout_width="match_parent"
            android:layout_height="10dp" />

        <Button
            android:id="@+id/bchoice3"
            android:layout_width="300dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="Button" />

        <android.support.v4.widget.Space
            android:layout_width="match_parent"
            android:layout_height="10dp" />

        <Button
            android:id="@+id/bchoice4"
            android:layout_width="300dp"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="Button" />
    </LinearLayout>

</LinearLayout>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:orientation="horizontal"
    android:layout_weight="12"
    android:weightSum="5"
    android:background="@drawable/topbottom">

    <android.support.v4.widget.Space
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"/>

    <Button
        android:id="@+id/bback"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:background="@drawable/back"/>

    <Button
        android:id="@+id/banswer"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:background="@drawable/ans_button"/>

    <Button
        android:id="@+id/bforward"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:background="@drawable/forward"/>
</LinearLayout>

我收到空指针错误我尝试了太多方法来解决这个错误。我怎么能解决这个问题？请帮忙感谢

这只是为了在帖子中添加扣留请忽略

Answer 1

似乎updatequestion上使用的变量之一由null初始化。怎么样？

我认为其中一个资源ID不正确。检查资源文件（布局文件）（。xml）。

要进行调试，您可以

Log.i("QUESTION", (question == null) ? "NULL" : "NOT NULL")
Log.i("BCHOICE1", (bchoice1 == null) ? "NULL" : "NOT NULL")
Log.i("BCHOICE2", (bchoice2 == null) ? "NULL" : "NOT NULL")
Log.i("BCHOICE3", (bchoice3 == null) ? "NULL" : "NOT NULL")
Log.i("BCHOICE4", (bchoice4 == null) ? "NULL" : "NOT NULL")

这可以放在updatequestion的开头，而 "NULL" 将指示什么获取调用方法的空指针。

android中的错误空指针异常

1 个答案: