Java 为什么我的应用程序在游标试图从数据库获取数据时崩溃？

我试图从db中获取一个简单的图像和文本，并将它们显示在listview中，但当调试器达到该点时，它会崩溃，我想知道为什么会发生这种情况

搜查表：

dbHelper：包括两种方法： 1：向数据库添加新行 2：从db中读取行：问题在这里，我想，我使用了调试器，当它要调用这个方法时，它突然崩溃了

import java.util.ArrayList;
import java.util.List;

import sqlitemodel.Schema.Raiding;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

public class MyDataBaseHelper extends SQLiteOpenHelper {

    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "strategies.db";
    private static final String TEXT_TYPE = " TEXT";
    private static final String COMMA_SEP = ",";
    public String CREATE_QUERY = "CREATE TABLE " + Raiding.TABLE_NAME + "("
            + Raiding._ID + " INTEGER PRIMARY KEY," + Raiding.ATTACK_NAME
            + TEXT_TYPE + COMMA_SEP + Raiding.ATTACK_TH + TEXT_TYPE + COMMA_SEP
            + Raiding.ATTACK_Type + TEXT_TYPE + COMMA_SEP
            + Raiding.ATTACK_ElixirUsage + TEXT_TYPE + COMMA_SEP
            + Raiding.ATTACK_Image + " Blob" + ")";

    public MyDataBaseHelper(Context context) {

        super(context, DATABASE_NAME, null, DATABASE_VERSION);
        Log.d("db", "created");
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_QUERY);
        Log.d("table!", "Created!");
    }

    @Override
    public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
        arg0.execSQL("DROP TABLE IF EXISTS " + Raiding.TABLE_NAME);
        onCreate(arg0);
    }

    public void addRaiding(RaidingClass raidingClass) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(Raiding.ATTACK_NAME, raidingClass.name);
        values.put(Raiding.ATTACK_TH, raidingClass.th);
        values.put(Raiding.ATTACK_Type, raidingClass.type);
        values.put(Raiding.ATTACK_ElixirUsage, raidingClass.usage);
        values.put(Raiding.ATTACK_Image, raidingClass.image);

        db.insert(Raiding.TABLE_NAME, null, values);
        db.close();
    }

    public List<RaidingClass> getAllRaidingAttacks() {

        List<RaidingClass> raidingAttackList = new ArrayList<RaidingClass>();
        String selectQuery = "SELECT * FROM " + Raiding.TABLE_NAME;
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        Log.d("count", String.valueOf(cursor.getCount()));

        if (cursor.moveToFirst()) {

            do {
                RaidingClass raidingClass = new RaidingClass();
                raidingClass.setID(cursor.getInt(0));
                raidingClass.setName(cursor.getString(1));
                raidingClass.setTh(cursor.getString(2));
                raidingClass.setType(cursor.getString(3));
                raidingClass.setUsage(cursor.getString(4));
                raidingClass.setImage(cursor.getBlob(5));
                raidingAttackList.add(raidingClass);
            } while (cursor.moveToNext());

        }
        db.close();
        return raidingAttackList;

    }

}

mainActivity.java：

RaidingAttack：这是我试图调用getAllRaidingAttacks（）方法获取相应行值的类

public class RaidingAttack extends Activity {
    ArrayList<RaidingClass> raidingDetails = new ArrayList<RaidingClass>();
    RaidingAdapter raidingAdapter;

    MyDataBaseHelper dbHelper;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_raiding);

        dbHelper.getReadableDatabase();

        List<RaidingClass> raiding = dbHelper.getAllRaidingAttacks();

        for (RaidingClass rd : raiding) {
            raidingDetails.add(rd);
        }

        raidingAdapter = new RaidingAdapter(this,
                R.layout.activity_list_singlerow, raidingDetails);
        ListView dataList = (ListView) findViewById(R.id.list);
        dataList.setAdapter(raidingAdapter);
    }

}

---

未在

RaidingAttack

public class RaidingAttack extends Activity {
    ArrayList<RaidingClass> raidingDetails = new ArrayList<RaidingClass>();
    RaidingAdapter raidingAdapter;

    MyDataBaseHelper dbHelper;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_raiding);
        //init dbHelper
        dbHelper = new MyDataBaseHelper(this);
        dbHelper.getReadableDatabase();

public class RaidingAttack扩展活动{
ArrayList raidingDetails=新建ArrayList（）；
RaidingAdapter RaidingAdapter；
MyDataBaseHelper-dbHelper；
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.layout_raiding）；
//init dbHelper
dbHelper=新的MyDataBaseHelper（此）；
dbHelper.getReadableDatabase（）；

什么是崩溃日志？现在就添加了它。您是否找到了该行上发生null异常的位置？您找到了什么。您调试dbhelper类的过程有多深？代码转储是这样的，希望我们告诉您…@t0mm13b好吧，我复制了该行中关于代码的所有其他信息？

public class MainActivity extends Activity {

    Button btnattack;
    MyDataBaseHelper dbHelper;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        dbHelper = new MyDataBaseHelper(this);
        dbHelper.getWritableDatabase();
        Bitmap image = BitmapFactory.decodeResource(getResources(),
                R.drawable.barcher);
        //
        // // convert bitmap to byte
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        image.compress(Bitmap.CompressFormat.PNG, 100, stream);
        byte imageInByte[] = stream.toByteArray();
        dbHelper.addRaiding(new RaidingClass("barcher", "8", "R", "many",
                imageInByte));

        btnattack = (Button) findViewById(R.id.btnattack);
        btnattack.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                Intent myIntent = new Intent(MainActivity.this,
                        RaidingAttack.class);
                startActivity(myIntent);
            }
        });

    }
}

public class RaidingAttack extends Activity {
    ArrayList<RaidingClass> raidingDetails = new ArrayList<RaidingClass>();
    RaidingAdapter raidingAdapter;

    MyDataBaseHelper dbHelper;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_raiding);

        dbHelper.getReadableDatabase();

        List<RaidingClass> raiding = dbHelper.getAllRaidingAttacks();

        for (RaidingClass rd : raiding) {
            raidingDetails.add(rd);
        }

        raidingAdapter = new RaidingAdapter(this,
                R.layout.activity_list_singlerow, raidingDetails);
        ListView dataList = (ListView) findViewById(R.id.list);
        dataList.setAdapter(raidingAdapter);
    }

}

List<RaidingClass> raiding = dbHelper.getAllRaidingAttacks();

10-20 05:11:29.102: E/AndroidRuntime(14511): FATAL EXCEPTION: main
10-20 05:11:29.102: E/AndroidRuntime(14511): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.masoudseraj.clashofclansstrategies/com.masoudseraj.clashofclansstrategies.RaidingAttack}: java.lang.NullPointerException
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.ActivityThread.access$600(ActivityThread.java:123)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.os.Handler.dispatchMessage(Handler.java:99)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.os.Looper.loop(Looper.java:137)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.ActivityThread.main(ActivityThread.java:4424)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at java.lang.reflect.Method.invokeNative(Native Method)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at java.lang.reflect.Method.invoke(Method.java:511)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at dalvik.system.NativeStart.main(Native Method)
10-20 05:11:29.102: E/AndroidRuntime(14511): Caused by: java.lang.NullPointerException
10-20 05:11:29.102: E/AndroidRuntime(14511):    at com.masoudseraj.clashofclansstrategies.RaidingAttack.onCreate(RaidingAttack.java:24)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.Activity.performCreate(Activity.java:4465)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-20 05:11:29.102: E/AndroidRuntime(14511):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
10-20 05:11:29.102: E/AndroidRuntime(14511):    ... 11 more

public class RaidingAttack extends Activity {
    ArrayList<RaidingClass> raidingDetails = new ArrayList<RaidingClass>();
    RaidingAdapter raidingAdapter;

    MyDataBaseHelper dbHelper;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_raiding);
        //init dbHelper
        dbHelper = new MyDataBaseHelper(this);
        dbHelper.getReadableDatabase();