数据库无法检索图像或为空，导致数组错误。 怎么解决？
我的问题是java.lang.IndexOutOfBoundsException：索引0无效，大小为0 。 我不知道修复此错误，我没有发现我的arrays有任何问题。 我是android的新手。 我希望你们都明白。 也许这会导致我的错误值出错。 输入（KEY_IMG，Utility.getBytes（quest.getBitmap（）））; 。 抱歉，我的英文。
UPDATE
数据库问题导致java.lang.IndexOutOfBoundsException：索引0无效，大小为0
MainActivity.java
package com.example.quizjavatest; import java.util.ArrayList; import android.os.Bundle; import android.app.Activity; import java.util.List; import android.content.Intent; import android.util.Log; import android.view.View; import android.widget.Button; import android.widget.ImageView; import android.widget.RadioButton; import android.widget.RadioGroup; import android.widget.TextView; public class MainActivity extends Activity { List quesList; int score=0; int qid=0; ImageView quizimg; Question currentQ; TextView txtQuestion; RadioButton rda, rdb, rdc; Button butNext; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); DbHelper db=new DbHelper(this); quesList=db.getAllQuestions(); currentQ=quesList.get(qid); quizimg=(ImageView) findViewById(R.id.ImgQuiz); //img quiz txtQuestion=(TextView)findViewById(R.id.textView1); //question rda=(RadioButton)findViewById(R.id.radio0); //option A rdb=(RadioButton)findViewById(R.id.radio1); //option B rdc=(RadioButton)findViewById(R.id.radio2); //option C butNext=(Button)findViewById(R.id.button1); //button next setQuestionView(); butNext.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { RadioGroup grp=(RadioGroup)findViewById(R.id.radioGroup1); RadioButton answer=(RadioButton)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(MainActivity.this, 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(); } } }); } private void setQuestionView() { quizimg.setImageBitmap(currentQ.getBitmap()); txtQuestion.setText(currentQ.getQUESTION()); rda.setText(currentQ.getOPTA()); rdb.setText(currentQ.getOPTB()); rdc.setText(currentQ.getOPTC()); qid++ ; } } DbHelper.java
package com.example.quizjavatest; import java.util.ArrayList; import java.util.List; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.graphics.BitmapFactory; public class DbHelper extends SQLiteOpenHelper{ private Context mContext; private static final int DATABASE_VERSION = 1; // Database Name private static final String DATABASE_NAME = "PediaKids"; // tasks table name private static final String TABLE_QUEST = "planet"; // tasks Table Columns names private static final String KEY_ID = "id"; private static final String KEY_IMG = "img"; 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 SQLiteDatabase dbase; public DbHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); mContext = context; } @Override public void onCreate(SQLiteDatabase db) { dbase=db; String Sql = "CREATE TABLE IF NOT EXISTS " + TABLE_QUEST + " ( " + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "+ KEY_IMG + "BLOB," + KEY_QUES + " TEXT, " + KEY_OPTA +" TEXT, " + KEY_OPTB +" TEXT, "+KEY_OPTC+" TEXT," + KEY_ANSWER + " TEXT)"; db.execSQL(Sql); addQuestion(); //db.close(); } private void addQuestion() { Question q1=new Question(BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_launcher),"an operating system?", "SuSe", "BIOS", "DOS", "BIOS"); this.addQuestion(q1); Question q2=new Question(BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_launcher),"Which of the following is NOT "," SuSe", "BIOS", "DOS", "BIOS"); this.addQuestion(q2); Question q3=new Question(BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_launcher),"Which of the following is the fastest","RAM", "FLASH","Register","Register"); this.addQuestion(q3); Question q4=new Question(BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_launcher),"Which of the following device", "Router", "Bridge", "Hub","Router"); this.addQuestion(q4); Question q5=new Question(BitmapFactory.decodeResource(mContext.getResources(), R.drawable.ic_launcher),"Which of the following is NOT an" ,"Ruby","Python","BASIC","BASIC"); 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_ID, quest.getID()); values.put(KEY_IMG, Utility.getBytes(quest.getBitmap())); 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()); // Inserting Row dbase.insert(TABLE_QUEST, null, values); } public List getAllQuestions(){ List quesList = new ArrayList(); String selectQuery = "SELECT * FROM " + TABLE_QUEST + " ORDER BY RANDOM() LIMIT 5"; 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.setImage(Utility.getPhoto(cursor.getBlob(1))); quest.setQUESTION(cursor.getString(2)); quest.setANSWER(cursor.getString(3)); quest.setOPTA(cursor.getString(4)); quest.setOPTB(cursor.getString(5)); quest.setOPTC(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; } }
Question.java
package com.example.quizjavatest; import android.graphics.Bitmap; public class Question { private int ID; private Bitmap bmp; //byte[] _image; private String QUESTION; private String OPTA; private String OPTB; private String OPTC; private String ANSWER; public Question() { /*ID=0; QUESTION=""; OPTA=""; OPTB=""; OPTC=""; ANSWER="";*/ } public Question(Bitmap img, String qUESTION, String oPTA, String oPTB, String oPTC, String aNSWER ) { bmp = img; QUESTION = qUESTION; OPTA = oPTA; OPTB = oPTB; OPTC = oPTC; ANSWER = aNSWER; } public int getID() { return ID; } public Bitmap getBitmap(){ return bmp; } public void setImage(Bitmap img){ bmp = img; } /*public byte[] getImage(){ return _image; }*/ public String getQUESTION() { return QUESTION; } public String getOPTA() { return OPTA; } public String getOPTB() { return OPTB; } public String getOPTC() { return OPTC; } public String getANSWER() { return ANSWER; } public void setID(int id) { ID=id; } public void setQUESTION(String qUESTION) { QUESTION = qUESTION; } public void setOPTA(String oPTA) { OPTA = oPTA; } public void setOPTB(String oPTB) { OPTB = oPTB; } public void setOPTC(String oPTC) { OPTC = oPTC; } public void setANSWER(String aNSWER) { ANSWER = aNSWER; } }
Utility.java
package com.example.quizjavatest; import java.io.ByteArrayOutputStream; import android.graphics.Bitmap; import android.graphics.Bitmap.CompressFormat; import android.graphics.BitmapFactory; public class Utility { // convert from bitmap to byte array public static byte[] getBytes(Bitmap bitmap) { ByteArrayOutputStream stream = new ByteArrayOutputStream(); bitmap.compress(CompressFormat.PNG, 0, stream); return stream.toByteArray(); } // convert from byte array to bitmap public static Bitmap getPhoto(byte[] image) { return BitmapFactory.decodeByteArray(image, 0, image.length); } }
logcat的
05-03 10:46:26.520: W/dalvikvm(9053): threadid=1: thread exiting with uncaught exception (group=0x41cff700) 05-03 10:46:26.585: E/AndroidRuntime(9053): FATAL EXCEPTION: main 05-03 10:46:26.585: E/AndroidRuntime(9053): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.quizjavatest/com.example.quizjavatest.MainActivity}: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.ActivityThread.access$700(ActivityThread.java:159) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.os.Handler.dispatchMessage(Handler.java:99) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.os.Looper.loop(Looper.java:176) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.ActivityThread.main(ActivityThread.java:5419) 05-03 10:46:26.585: E/AndroidRuntime(9053): at java.lang.reflect.Method.invokeNative(Native Method) 05-03 10:46:26.585: E/AndroidRuntime(9053): at java.lang.reflect.Method.invoke(Method.java:525) 05-03 10:46:26.585: E/AndroidRuntime(9053): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046) 05-03 10:46:26.585: E/AndroidRuntime(9053): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862) 05-03 10:46:26.585: E/AndroidRuntime(9053): at dalvik.system.NativeStart.main(Native Method) 05-03 10:46:26.585: E/AndroidRuntime(9053): Caused by: java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0 05-03 10:46:26.585: E/AndroidRuntime(9053): at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255) 05-03 10:46:26.585: E/AndroidRuntime(9053): at java.util.ArrayList.get(ArrayList.java:308) 05-03 10:46:26.585: E/AndroidRuntime(9053): at com.example.quizjavatest.MainActivity.onCreate(MainActivity.java:36) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.Activity.performCreate(Activity.java:5372) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104) 05-03 10:46:26.585: E/AndroidRuntime(9053): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257) 05-03 10:46:26.585: E/AndroidRuntime(9053): ... 11 more
问题是这两行代码：
quesList=db.getAllQuestions(); currentQ=quesList.get(qid);
第一行实际上只返回一个空数组，因此第二行抛出无法获取位置0的项目。
在这种情况下，我认为最好在访问之前检查quesList的长度：
if(quesList.size()>0){ currentQ=quesList.get(qid); }else{ //maybe put some default question or show no question found message }