爲什麼我的應用程序在遊標試圖從數據庫中獲取數據時崩潰？

-1

我試圖從數據庫中獲取一個簡單的圖像和文本，並在列表視圖中顯示它們，但它調試器達到那一點時崩潰，我想知道爲什麼會發生這種情況？爲什麼我的應用程序在遊標試圖從數據庫中獲取數據時崩潰？

突襲表：

import android.provider.BaseColumns; 

public class Schema { 
    public Schema() { 

    } 

    public static abstract class Raiding implements BaseColumns { 



     public static final String TABLE_NAME = "raiding"; 
     public static final String _ID = "_ID"; 
     public static final String ATTACK_NAME = "attack_name"; 
     public static final String ATTACK_TH = "attack_th"; 
     public static final String ATTACK_Type = "attack_type"; 
     public static final String ATTACK_ElixirUsage = "elixir_usage"; 
     public static final String ATTACK_Image = "attack_image"; 
    } 

}

dbHelper：包括兩種方法： 1：添加一個新行分貝 2：讀取行從DB：問題就在這裏，我想，我使用調試器，當它要調用這個方法，它突然死機

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; 

    } 

}

RaidingClass

public class RaidingClass { 

    public int id; 
    public String name; 
    public String th; 
    public String type; 
    public String usage; 
    public byte[] image; 

    public RaidingClass() { 

    } 

    public RaidingClass(int id, String name, String th, String type, String usage, 
      byte[] image) { 
     this.id = id; 
     this.name = name; 
     this.th = th; 
     this.type = type; 
     this.usage = usage; 
     this.image = image; 

    } 

    public RaidingClass(String name, String th, String type, String usage, 
      byte[] image) { 

     this.name = name; 
     this.th = th; 
     this.type = type; 
     this.usage = usage; 
     this.image = image; 
    } 

    public void setID(int id) { 
     this.id = id; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public void setTh(String th) { 
     this.th = th; 
    } 

    public void setType(String type) { 
     this.type = type; 
    } 

    public void setUsage(String usage) { 
     this.usage = usage; 
    } 

    public void setImage(byte[] image) { 
     this.image = image; 
    } 

}

mainActivity.java：

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); 
      } 
     }); 

    } 
}

RaidingAttack：這是我嘗試調用getAllRaidingAttacks（）方法以提取相應的行值的類。

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); 
    } 

}

這也正是調試器停止和應用程序崩潰：

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

，我檢查了數據庫，圖像和文本插入，但我不知道爲什麼光標爲null ！

，這是錯誤日誌：

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

來源

2015-10-20 Masoud

初始化，什麼是崩潰日誌？ – dex

添加您的logcat –

它現在被添加 – Masoud

dbHelper不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();

來源

2015-10-20 21:45:27 petey

哦，是的，沒錯！ tnx一堆！ – Masoud

爲什麼我的應用程序在遊標試圖從數據庫中獲取數據時崩潰？

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