Question

我已经尝试了很多关于如何在android项目中显示资产文件夹中的数据的代码，但我无法做到这一点。请帮我解决这个问题。

感谢您的帮助编辑： -
我的适配器类

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

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

    public class DBAdapter extends SQLiteOpenHelper{
        private static String DB_PATH = "/data/data/com.example.mynwedb/databases/wbty";

        private static String DB_NAME = "wbty";

        private SQLiteDatabase myDataBase;

        private final Context myContext;

        public DBAdapter(Context context) 
        {
            super(context, DB_NAME, null, 1);
            this.myContext = context;
        }

        public void createDataBase() throws IOException{
            boolean dbExist = checkDataBase();

            if(dbExist)
            {
                Log.i("DB....", "database available....");
            }
            else
            {
                this.getWritableDatabase();

                try {

                    copyDataBase();

                } catch (IOException e) {

                    throw new Error("Error copying database");

                }

                Log.i("DB..", "database created.....");
            }   

        }


        public boolean checkDataBase(){

            SQLiteDatabase checkDB = null;

            try{

                String myPath = DB_PATH + DB_NAME;

                checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

            }catch(SQLiteException e){

                Log.e("CheckDb","DB not found");
                //database does't exist yet.

                if(checkDB != null){

                    checkDB.close();

                }
            }
            finally
            {
                if(checkDB != null){

                    checkDB.close();

                } 
                this.close();
            }
            return checkDB != null ? true : false;

        }




        private void copyDataBase() throws IOException{

            InputStream myInput = myContext.getAssets().open(DB_NAME);

            String outFileName = DB_PATH + DB_NAME;

            OutputStream myOutput = new FileOutputStream(outFileName);
            byte[] buffer = new byte[1024];

            int length;

            while ((length = myInput.read(buffer))>0){

                myOutput.write(buffer, 0, length);

            }

            myOutput.flush();

            myOutput.close();

            myInput.close();

        }

        public SQLiteDatabase openDataBase() throws SQLException{

            String myPath = DB_PATH + DB_NAME;

            return myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);

        }


        @Override

        public synchronized void close() {

            if(myDataBase != null)

                myDataBase.close();

            super.close();

        }

        @Override

        public void onCreate(SQLiteDatabase db) {

        }

        @Override

        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {


        }  


        public void getData()
        {
            SQLiteDatabase myDB ;
            Cursor cursor ;
            try {

                myDB=this.openDataBase();                   

                cursor=myDB.rawQuery("SELECT * FROM descriptions",null);


                if (cursor != null ) {
                    if  (cursor.moveToFirst()) {
                        do {

                            // put your code to get data from cursor                      

                        }while (cursor.moveToNext());
                    }

                }



                if(cursor != null)
                {
                    myDB.close();
                    cursor.close();
                }                      
            }catch(SQLException sqle){

                throw sqle;

            }


        }
    }

和MyActivity类： -

import java.io.IOException;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

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

        DBAdapter myDbHelper = new DBAdapter(MainActivity.this); 
        try 
        {
            myDbHelper.createDataBase();
        }catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        finally
        {
            myDbHelper.close();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

我已将db文件保存在assets文件夹中。

Answer 1

你得到哪种错误？请告诉我们有关您的问题的更多信息并发布logcat。这不应该是一个答案，但我需要解释你做错了什么：

您为outputFile写道：

       String outFileName = DB_PATH + DB_NAME;

但是这会给你以下路径：

      "/data/data/com.example.mynwedb/databases/wbtywbty";

因为您的DB_PATH是

      "/data/data/com.example.mynwedb/databases/wbty";

并且您的DB_NAME是：

      "wbty";

如果我们获得更多信息，我会尽力帮助你。

修改

checkDatabase()：

相同

     String myPath = DB_PATH + DB_NAME;

在android中访问SQLite数据库时出错

1 个答案:

修改