1
我遇到了onCLick方法的問題，放置在一個片段中的按鈕。它拋出一個NullPointerException，我無法解決這個問題。NullPointerException onClick Android按鈕中的片段
IqDbHelper.java代碼：
package com.example.scientia;
import java.util.ArrayList;
import java.util.List;
import com.example.scientia.Question;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class IqDbHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "iqQuiz";
// tasks table name
private static final String TABLE_QUEST = "quest";
// tasks Table Columns names
private static final String KEY_ID = "id";
private static final String KEY_QUES = "question";
private static final String KEY_ANSWER = "answer"; //correct option
private static final String KEY_OPTA= "opta"; //option a
private static final String KEY_OPTB= "optb"; //option b
private static final String KEY_OPTC= "optc"; //option c
private static final String KEY_OPTD= "optd"; //option d
private SQLiteDatabase dbase;
public IqDbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
dbase=db;
String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_QUEST + " ("
+ KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_QUES
+ " TEXT, " + KEY_ANSWER+ " TEXT, "+KEY_OPTA +" TEXT, "
+KEY_OPTB +" TEXT, "+KEY_OPTC+" TEXT, "+KEY_OPTD+" TEXT);";
db.execSQL(sql);
addQuestions();
// db.close();
}
private void addQuestions()
{
Question q1=new Question("We need to cut a cake in more than 6 pieces. How many cuts we must make atleast to get this?","2", "3", "4","5", "3");
this.addQuestion(q1);
Question q2=new Question("(896)²-(205)² is divisible by 691", "691", "1101", "Both a and b","None","Both a and b");
this.addQuestion(q2);
Question q3=new Question("Reindeer: Fawn:: Llama:?","Colt", "Foal","Cria"," Anubhav", "Cria");
this.addQuestion(q3);
Question q4=new Question("How many meters will I be away from my home if I travel 5 metres towards north, take a right and travel 4 metres and travel 5 metres towards south?", "5", "4", "10","15","4");
this.addQuestion(q4);
Question q5=new Question("Cake: Bakery:: Beer: X","Distillery","Wine shop","Brewery","XYZ","Brewery");
this.addQuestion(q5);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldV, int newV) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_QUEST);
// Create tables again
onCreate(db);
}
// Adding new question
public void addQuestion(Question quest) {
//SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_QUES, quest.getQUESTION());
values.put(KEY_ANSWER, quest.getANSWER());
values.put(KEY_OPTA, quest.getOPTA());
values.put(KEY_OPTB, quest.getOPTB());
values.put(KEY_OPTC, quest.getOPTC());
values.put(KEY_OPTD, quest.getOPTD());
// Inserting Row
dbase.insert(TABLE_QUEST, null, values);
}
public List<Question> getAllQuestions() {
List<Question> quesList = new ArrayList<Question>();
// Select All Query
String selectQuery = "SELECT * FROM " + TABLE_QUEST;
dbase=this.getReadableDatabase();
Cursor cursor = dbase.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
Question quest = new Question();
quest.setID(cursor.getInt(0));
quest.setQUESTION(cursor.getString(1));
quest.setANSWER(cursor.getString(2));
quest.setOPTA(cursor.getString(3));
quest.setOPTB(cursor.getString(4));
quest.setOPTC(cursor.getString(5));
quest.setOPTD(cursor.getString(6));
quesList.add(quest);
} while (cursor.moveToNext());
}
// return quest list
return quesList;
}
public int rowcount()
{
int row=0;
String selectQuery = "SELECT * FROM " + TABLE_QUEST;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
row=cursor.getCount();
return row;
}
}
含有片段並在它的按鈕，這將引發一個NullPointerException編碼如下所述的IqQuiz.java：
package com.example.scientia;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.util.List;
import android.content.Intent;
import android.util.Log;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import com.example.scientia.IqDbHelper;
public class IqQuiz extends Fragment implements View.OnClickListener{
List<Question> quesList;
int score=0;
int qid=0;
Question currentQ;
TextView txtQuestion;
RadioButton rda, rdb, rdc, rdd;
Button butNext;
@Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// TODO Auto-generated method stub
IqDbHelper db = new IqDbHelper(getActivity());
View v=inflater.inflate(R.layout.iqquiz, container, false);
quesList=db.getAllQuestions();
currentQ=quesList.get(qid);
txtQuestion=(TextView)v.findViewById(R.id.textView1);
rda=(RadioButton)v.findViewById(R.id.radio0);
rdb=(RadioButton)v.findViewById(R.id.radio1);
rdc=(RadioButton)v.findViewById(R.id.radio2);
rdd=(RadioButton)v.findViewById(R.id.radio3);
butNext=(Button)v.findViewById(R.id.button1);
setQuestionView();
butNext.setOnClickListener(this);
return v;
}
private void setQuestionView()
{
txtQuestion.setText(currentQ.getQUESTION());
rda.setText(currentQ.getOPTA());
rdb.setText(currentQ.getOPTB());
rdc.setText(currentQ.getOPTC());
rdd.setText(currentQ.getOPTD());
qid++;
}
@Override
public void onClick(View v) {
if(v==butNext){
RadioGroup grp=(RadioGroup)v.findViewById(R.id.radioGroup1);
RadioButton answer=(RadioButton)v.findViewById(grp.getCheckedRadioButtonId());
Log.d("yourans", currentQ.getANSWER()+" "+answer.getText());
if(currentQ.getANSWER().equals(answer.getText()))
{
score++;
Log.d("score", "Your score"+score);
}
if(qid<5){
currentQ=quesList.get(qid);
setQuestionView();
}else{
Intent intent = new Intent(getActivity(), ResultActivity.class);
Bundle b = new Bundle();
b.putInt("score", score); //Your score
intent.putExtras(b); //Put your score to your next Intent
startActivity(intent);
// finish();
}
}
}
}
沒有編譯錯誤。該應用程序崩潰的按鈕單擊和LogCat顯示一個NullPointerException拋出其點擊。
的logcat：
08-14 23:40:45.486: D/AndroidRuntime(1974): Shutting down VM
08-14 23:40:45.496: W/dalvikvm(1974): threadid=1: thread exiting with uncaught exception (group=0xb0cdeb20)
08-14 23:40:45.496: E/AndroidRuntime(1974): FATAL EXCEPTION: main
08-14 23:40:45.496: E/AndroidRuntime(1974): Process: com.example.scientia, PID: 1974
08-14 23:40:45.496: E/AndroidRuntime(1974): java.lang.NullPointerException
08-14 23:40:45.496: E/AndroidRuntime(1974): at com.example.scientia.IqQuiz.onClick(IqQuiz.java:67)
08-14 23:40:45.496: E/AndroidRuntime(1974): at android.view.View.performClick(View.java:4438)
08-14 23:40:45.496: E/AndroidRuntime(1974): at android.view.View$PerformClick.run(View.java:18422)
08-14 23:40:45.496: E/AndroidRuntime(1974): at android.os.Handler.handleCallback(Handler.java:733)
08-14 23:40:45.496: E/AndroidRuntime(1974): at android.os.Handler.dispatchMessage(Handler.java:95)
08-14 23:40:45.496: E/AndroidRuntime(1974): at android.os.Looper.loop(Looper.java:136)
08-14 23:40:45.496: E/AndroidRuntime(1974): at android.app.ActivityThread.main(ActivityThread.java:5001)
08-14 23:40:45.496: E/AndroidRuntime(1974): at java.lang.reflect.Method.invokeNative(Native Method)
08-14 23:40:45.496: E/AndroidRuntime(1974): at java.lang.reflect.Method.invoke(Method.java:515)
08-14 23:40:45.496: E/AndroidRuntime(1974): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
08-14 23:40:45.496: E/AndroidRuntime(1974): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
08-14 23:40:45.496: E/AndroidRuntime(1974): at dalvik.system.NativeStart.main(Native Method)
我已經試過幾件事情。請幫忙:(
安置自己的logcat –
老兄你說你有一個空的異常和yoi不要複製跟蹤日誌，我們怎麼能夠幫助？我們是程序員而非精神病 – Gatunox