error: cannot find symbol class CopyDbActivity

Question

我在 youtube 上关注这个教程大约

"How to include SQLite database in android app"

这是link

https://www.youtube.com/watch?v=iE_bsPfB00w&t=2s

这是我的 MainActivity 的代码

 import java.io.IOException;
 import android.database.Cursor;
 import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.database.SQLException;
 import android.widget.Toast;


 public class MainActivity extends AppCompatActivity {

Cursor c = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ((Button) findViewById(R.id.button)).setOnClickListener(new 
     View.OnClickListener(){
        @Override
        public void onClick(View v){
            DatabaseHelper myDbHelper = new 
            DatabaseHelper(CopyDbActivity.this);
            try{
                myDbHelper.createDataBase();
            }catch (IOException ioe){
                throw new Error("Unable to create database");
            }
            try{
                myDbHelper.openDataBase();
            }catch (SQLException sqle){
                throw sqle;
            }

  Toast.makeText(CopyDbActivity.this,"Success",Toast.LENGTH_SHORT).show();
  c= myDbHelper.query("penyakit_TABLE",null,null,null,null,null,null);
            if(c.moveToFirst()){
                do{
 Toast.makeText(CopyDbActivity.this,"simptom"+c.getString(1),Toast.LENGTH_LONG).show();

                }while(c.moveToNext());
            }
        }
    });
}

}

我遇到了这些错误。如何解决？

Error:(25, 64) error: cannot find symbol class CopyDbActivity
Error:(36, 32) error: cannot find symbol class CopyDbActivity
Error:(40, 40) error: cannot find symbol class CopyDbActivity

Answer 1

只需将 CopyDbActivity 替换为 MainActivity，如下所示：

public class MainActivity extends AppCompatActivity {

Cursor c = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ((Button) findViewById(R.id.button)).setOnClickListener(new 
     View.OnClickListener(){
        @Override
        public void onClick(View v){
            DatabaseHelper myDbHelper = new 
            DatabaseHelper(MainActivity.this);
            try{
                myDbHelper.createDataBase();
            }catch (IOException ioe){
                throw new Error("Unable to create database");
            }
            try{
                myDbHelper.openDataBase();
            }catch (SQLException sqle){
                throw sqle;
            }

  Toast.makeText(MainActivity.this,"Success",Toast.LENGTH_SHORT).show();
  c= myDbHelper.query("penyakit_TABLE",null,null,null,null,null,null);
            if(c.moveToFirst()){
                do{
 Toast.makeText(MainActivity.this,"simptom"+c.getString(1),Toast.LENGTH_LONG).show();

                }while(c.moveToNext());
            }
        }
    });
}

error: cannot find symbol class CopyDbActivity

error: cannot find symbol class CopyDbActivity

sqlite

android

android-database