錯誤在android studio中的Stackoverflow？

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我想打，顯示從數據庫文件文本的ListView一個應用程序，但它顯示錯誤錯誤在android studio中的Stackoverflow？

這些課程我的應用程序

package com.example.dell.externalfilestoragedatabasedemo.database; 

    import android.content.Context; 
    import android.database.Cursor; 
    import android.database.SQLException; 
    import android.database.sqlite.SQLiteDatabase; 
    import android.database.sqlite.SQLiteOpenHelper; 
    import android.util.Log; 

    import java.io.FileOutputStream; 
    import java.io.IOException; 
    import java.io.InputStream; 
    import java.io.OutputStream; 

    /** 
    * Created by dell on 4/2/2017. 
    */ 

    public class DatabaseHelper extends SQLiteOpenHelper { 

     String DB_PATH = null; 
     private static String DB_NAME = "lib.db"; 
     private SQLiteDatabase myDatabase; 
     private final Context myContext; 

     public DatabaseHelper(Context context) { 
      super(context, DB_NAME, null, 1); 
      myContext = context; 
      this.DB_PATH = "/data/data/" + context.getPackageName() + "/" + "databases/"; 
      Log.e("Path 1", DB_PATH); 
     } 

     public void createDatabase() throws IOException { 

      boolean dbExist = checkDataBase(); 
      if (dbExist) { 

      } else { 
       this.getReadableDatabase(); 
       try { 
        copyDatabase(); 
       } catch (IOException e) { 
        throw new Error("Error Copying Database"); 
       } 
      } 

     } 


     private void copyDatabase() throws IOException { 
      InputStream is; 
      is = myContext.getAssets().open(DB_NAME); 
      String outFileName = DB_PATH + DB_NAME; 
      OutputStream myOutput = new FileOutputStream(outFileName); 
      byte buffer[] = new byte[10]; 
      int length; 
      while ((length = is.read(buffer)) > 0) { 

       myOutput.write(buffer, 0, length); 
    } 
      myOutput.flush(); 
      myOutput.close(); 
      is.close(); 
} 
private boolean checkDataBase() { 
      SQLiteDatabase checkDb = null; 
      try { 
       String myPath = DB_PATH + DB_NAME; 
       checkDb = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); 
      } catch (SQLException e) { 

      } 
      if (checkDb != null) { 
       checkDb.close(); 
      } 
      return checkDb != null ? true : false; 
     } 
public void openDatabase() throws SQLException { 
String myPath = DB_PATH + DB_NAME; 
      myDatabase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); 
     } 

     @Override 
     public synchronized void close() { 
      if (myDatabase != null) { 
       myDatabase.close(); 
      } 
      super.close(); 
     } 

     @Override 
     public void onCreate(SQLiteDatabase sqLiteDatabase) { 

     } 

     @Override 
     public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) { 

      if (newVersion > oldVersion) { 
       try { 
        copyDatabase(); 
       } catch (IOException e) { 
        e.printStackTrace(); 
       } 
      } 
     } 

     public Cursor query(String table, String []columns, String selections, String []selectionArgs, String groupBy, String having, String orderBy){ 

      return query(table,columns,selections,selectionArgs,groupBy,having,orderBy); 
     } 

     public Cursor query(String sql){ 
      return query(sql); 
     } 


    }

MainActivity的是在這裏：

package com.example.dell.externalfilestoragedatabasedemo; 

import android.database.Cursor; 
import android.database.SQLException; 
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.ListView; 
import android.widget.Toast; 

import com.example.dell.externalfilestoragedatabasedemo.constantsToUse.UsefulConstants; 
import com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper; 

import java.io.IOException; 
import java.util.List; 

public class MainActivity extends AppCompatActivity { 

    private ListView listView; 
    private Cursor cousor; 
    String SQl="SELECT Topic FROM TopicTable"; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     this.listView = (ListView) findViewById(R.id.listView); 
     copyDatabase(); 

     listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 

      @Override 
      public void onItemClick(AdapterView<?> parent, View view, 
            int position, long id) { 

       // ListView Clicked item index 
       int itemPosition  = position; 

       // ListView Clicked item value 
       String itemValue = (String) listView.getItemAtPosition(position); 

       switch (itemValue){ 

        case "Education": 
         UsefulConstants.tableConstant=01; 
         SQl="SELECT Educational_Field FROM Education"; 
         break; 

        case "Story": 
         UsefulConstants.tableConstant=02; 
         break; 


        case "Health": 
         UsefulConstants.tableConstant=03; 
         break; 

        case "Competitive": 
         UsefulConstants.tableConstant=11; 
         break; 

        case "Commerce": 
         UsefulConstants.tableConstant=12; 
         break; 

        case "Biology": 
         UsefulConstants.tableConstant=13; 
         break; 

        case "Art": 
         UsefulConstants.tableConstant=14; 
         break; 

        case "Technical ": 
         UsefulConstants.tableConstant=15; 
         SQl="SELECT Technologies FROM Technical"; 
         break; 



       } 




       // Show Alert 
       Toast.makeText(getApplicationContext(), 
         "Position :"+itemPosition+" ListItem : " +itemValue , Toast.LENGTH_LONG) 
         .show(); 

      } 

     }); 

    } 

    private void copyDatabase(){ 
    DatabaseHelper myDb= new DatabaseHelper(this); 
    try { 
     myDb.createDatabase(); 
     UsefulConstants.databaseHelper=myDb; 
    } catch (IOException e) { 
     throw new Error("Unable to Create Database"); 
    } 
    try { 
     myDb.openDatabase(); 
    } 
    catch (SQLException e){ 
     throw e; 
    } 
    Toast.makeText(this,"Success",Toast.LENGTH_LONG).show(); 
    showListView(); 

} 

    private void showListView() { 

     Cursor cursor=UsefulConstants.databaseHelper.query(SQl); 
     if (cursor != null) { 
      Toast.makeText(this, "Done", Toast.LENGTH_LONG).show(); 
      cursor.moveToFirst(); 
      String[] data = new String[cursor.getCount()]; 
      int i = 0; 
      for (; i < cursor.getCount(); i++) { 
       data[i] = cursor.getString(0); 
      } 


      ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, 
        android.R.layout.simple_list_item_1, android.R.id.text1, data); 


      // Assign adapter to ListView 
      listView.setAdapter(adapter); 
     } else if (cursor == null) 
      Toast.makeText(this, Boolean.toString(cursor != null), Toast.LENGTH_LONG).show(); 

    } 


}

這表明錯誤：

com.example.dell.externalfilestoragedatabasedemo E/AndroidRuntime: FATAL EXCEPTION: main 
                            Process: com.example.dell.externalfilestoragedatabasedemo, PID: 12227 
                            java.lang.StackOverflowError: stack size 8MB 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                             at com.example.dell.externalfilestoragedatabasedemo.database.DatabaseHelper.query(DatabaseHelper.java:120) 
                            at com.examp

個le.dell.externalfiles

請幫我出這個

來源

2017-04-02 Vikki Asati

問題的這部分代碼：

public Cursor query(String table, String []columns, String selections, String []selectionArgs, String groupBy, String having, String orderBy){ 
    return query(table,columns,selections,selectionArgs,groupBy,having,orderBy); 
}

您從query方法同樣的方法返回，你有無限遞歸。你應該還回別的東西

來源

2017-04-02 13:33:26 shmakova

錯誤在android studio中的Stackoverflow？

回答

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