Здравствуйте!У меня приложение в Android studio.При подключении к базе данных вылетает приложение не могу понять
причину.Вот код.
DatabaseAccess class
package com.example.myapplication;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseAccess {
private SQLiteOpenHelper openHelper;
private SQLiteDatabase db;
private static DatabaseAccess instance;
Cursor c=null;
private DatabaseAccess(Context context){
this.openHelper=new DatabaseOpenHelper(context);
}
public static DatabaseAccess getInstance(Context context)
{
if(instance==null)
{
instance=new DatabaseAccess(context);
}
return instance;
}
public void open()
{
this.db=openHelper.getWritableDatabase();
}
public void close() {
if (db != null) {
this.db.close();
}
}
public String getAddress(String name)
{
c=db.rawQuery("select Address from Table1 where Name='"+name+"'",new String[]{});
StringBuffer buffer =new StringBuffer();
while(c.moveToNext())
{
String address = c.getString(0);
buffer.append(""+address);
}
return buffer.toString();
}
}
main activity class
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
public EditText name;
public Button guery_button;
public TextView result;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
name=findViewById(R.id.name);
guery_button=findViewById(R.id.guery_button);
result=findViewById(R.id.result);
guery_button.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
DatabaseAccess databaseAccess = DatabaseAccess.getInstance(getApplicationContext());
databaseAccess.open();
String n=name.getText().toString();
String address=databaseAccess.getAddress(n);
result.setText(address);
databaseAccess.close();
}
});
}
}
}
}
DatabaseOpenHelper
package com.example.myapplication;
import android.content.Context;
import com.readystatesoftware.sqliteasset.SQLiteAssetHelper;
public class DatabaseOpenHelper extends SQLiteAssetHelper {
private static final String DATABASE_NAME="Database.db";
private static final int DATABASE_VERSION=1;
public DatabaseOpenHelper(Context context)
{
super(context,DATABASE_NAME,null,DATABASE_VERSION);
}
}
Простой
Средний
