Question

我在SQLiteBrowser中创建了SQLite数据库。我想在Android应用程序中引用它，所以我把DB文件放在资源文件夹n中使用以下代码将DB复制到App内存。 M使用eclipse进行Android应用程序开发。

但SQLiteOpenHelper构造函数给出了错误。构造函数DB_Import（DB_test1）未定义

package com.example.DB_test1;

public class DB_test1 extends Activity{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        DB_Import my_Import;
        //SQLiteDatabase myDb = null;
        my_Import=new DB_Import(this);
        try {                
            my_Import.createDatabase();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

以下是另一个类文件。

package com.example.DB_test1;

public class DB_Import extends SQLiteOpenHelper{

    private final Context myContext;
     String DB_PATH = "data/data/com.example.DB_test/databases/";
     String DB_NAME = "Dict_temp";
    private SQLiteDatabase myDatabase;

    public DB_Import(Context context) {
            super(context, "data/data/com.example.DB_test/databases/", null, 1);
            this.myContext = context;
        }
    public void createDatabase()throws IOException{
            // TODO Auto-generated method stub
            boolean dbExist = checkDatabase(); ////////////////Check if database Exist
            if (dbExist) {
                //openDatabase();
            }else {
            this.getReadableDatabase();

            try {
            copyDatabase(); ///////////////Copies the database from assets to android
            } catch (IOException e) {
            // TODO Auto-generated catch block
            throw new Error("Error copying database");
            }
            }
        }

Answer 1

试试这段代码：

public class DataBaseHelper extends SQLiteOpenHelper{
private Context mycontext;

private String DB_PATH = "/data/data/gr.peos/databases/";
//private String DB_PATH = mycontext.getApplicationContext().getPackageName()+"/databases/";
private static String DB_NAME = "BLib.sqlite";//the extension may be .sqlite or .db
public SQLiteDatabase myDataBase;
/*private String DB_PATH = "/data/data/"
                        + mycontext.getApplicationContext().getPackageName()
                        + "/databases/";*/

public DataBaseHelper(Context context) throws IOException  {
super(context,DB_NAME,null,1);
this.mycontext=context;
boolean dbexist = checkdatabase();
if(dbexist)
{
    //System.out.println("Database exists");
    opendatabase(); 
}
else
{
    System.out.println("Database doesn't exist");
createdatabase();
}

}

public void createdatabase() throws IOException{
boolean dbexist = checkdatabase();
if(dbexist)
{
    //System.out.println(" Database exists.");
}
else{
    this.getReadableDatabase();
try{
        copydatabase();
    }
    catch(IOException e){
        throw new Error("Error copying database");
    }
}
}
private boolean checkdatabase() {
//SQLiteDatabase checkdb = null;
boolean checkdb = false;
try{
    String myPath = DB_PATH + DB_NAME;
    File dbfile = new File(myPath);
    //checkdb = SQLiteDatabase.openDatabase(myPath,null,SQLiteDatabase.OPEN_READWRITE);
    checkdb = dbfile.exists();
}
catch(SQLiteException e){
    System.out.println("Database doesn't exist");
}

return checkdb;
}
private void copydatabase() throws IOException {

//Open your local db as the input stream
InputStream myinput = mycontext.getAssets().open(DB_NAME);

// Path to the just created empty db
String outfilename = DB_PATH + DB_NAME;

//Open the empty db as the output stream
OutputStream myoutput = new FileOutputStream("/data/data/gr.peos/databases/BLib.sqlite");

// transfer byte to inputfile to outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myinput.read(buffer))>0)
{
    myoutput.write(buffer,0,length);
}

//Close the streams
myoutput.flush();
myoutput.close();
myinput.close();

}

public void opendatabase() throws SQLException
{
//Open the database
String mypath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(mypath, null, SQLiteDatabase.OPEN_READWRITE);

}



public synchronized void close(){
if(myDataBase != null){
    myDataBase.close();
}
super.close();
}

SQLiteOpenHelper构造函数问题

1 个答案: