單擊按鈕時如何從sqlite數據庫中檢索數據

Question

我想從數據庫中檢索數據。 那么我應該在代碼中進行哪些更改？ 我的課是

public class Assessment extends Activity 
{
    private static String DB_PATH = "/data/data/+com.comply.assessment()+/Database/"; 
    private static final String DATABASE_NAME = "LMS_MST";
     SQLiteDatabase db;
    TextView mod_code,qst_code,question_id,question,qst_opt1,qst_opt2,qst_opt3,qst_opt4,correct_ans,user_ans;
    Cursor cursor;
    private Button start_test; 
      @SuppressWarnings("unused") 

     ListView li;
     ArrayList<String> it_info;
     ArrayAdapter<String> aa;

     @Override
     public void onCreate(Bundle savedInstanceState) 
     {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        db= openOrCreateDatabase(AppConstants.DATABASE_NAME, Context.MODE_PRIVATE, null);

        db.close();

        initControls(); 
    }

    protected void initControls() {
        // TODO Auto-generated method stub
         start_test=(Button)findViewById(R.id.start_test);
         start_test.setOnClickListener(new OnClickListener()
            {
                public void onClick(View v)
                {
                    Intent intent1= new Intent(Assessment.this,Get_Assessment.class);
                    startActivity(intent1);
                }
            });
    }
    protected void DoWork()
    {
        SQLiteDatabase db= null;
        String TableName = "lms_mst"; 

        try {
            db = this.openOrCreateDatabase("LMS_MST", MODE_PRIVATE,
                null); 
            db.execSQL("DROP TABLE IF EXISTS lms_mst" );

            db.execSQL("create table IF NOT EXISTS  "
                    +AppConstants.TABLE_NAME
                    +"(id INTEGER primary key AUTOINCREMENT,qst_mod_code TEXT,qst_prg_code TEXT,qst_question TEXT,qst_code TEXT,qst_opt1 TEXT,qst_opt2 TEXT,qst_opt3 TEXT,qst_opt4 TEXT,qst_opt01 TEXT,qst_opt02 TEXT,qst_opt03 TEXT,qst_opt04 TEXT,qst_corctopt TEXT,user_code TEXT,qst_company_code TEXT,qst_Marks TEXT);");
        }
        catch(Exception e) {
            Log.e("Error", "Error", e);
           } finally {
             if (db != null)
             db.close();
           } 
        }
    }

而我的dbhelper類是

public class MyOpenHelper extends SQLiteOpenHelper
{
    private static String DB_PATH = "/data/data/+com.comply.assessment()+/databases/"; 
    private static final String DATABASE_NAME = "LMS_MST";
    private static final int DATABASE_VERSION = 1;
    private SQLiteDatabase db;
    private final Context myContext;
    public static final String TABLE_NAME = "LMS_MST";
    private static final String COLUMN_ID = "_id";
    private static final String QST_CODE="QST_CODE";
    private static final String QST_PRG_CODE="QST_PRG_CODE";
    private static final String QST_MOD_CODE="QST_MOD_CODE";
    private static final String QST_QUESTION="QST_QUESTION";
    private static final String QST_OPT1="QST_OPT1";
    private static final String QST_OPT2="QST_OPT2";
    private static final String QST_OPT3="QST_OPT3";
    private static final String QST_OPT4="QST_OPT4";
    private static final String QST_OPT01="QST_OPT01";
    private static final String QST_OPT02="QST_OPT02";
    private static final String QST_OPT03="QST_OPT03";
    private static final String QST_OPT04="QST_OPT04";
    private static final String QST_CORCTOPT="QST_CORCTOPT";
    private static final String USER_CODE="USER_CODE";

    public MyOpenHelper(Context context) 
    {
        super(context,DATABASE_NAME,null,1);
         this.myContext = context;

    }
    /* @Override        
     public void onCreate(SQLiteDatabase db) 
     {                
         db.execSQL("CREATE TABLE " + TABLE_NAME                               
                 + "(_id INTEGER PRIMARY KEY AUTOINCREMENT, "                              
                 + QST_CODE+ " TEXT, "      
                 + QST_PRG_CODE+ " TEXT" + QST_MOD_CODE+ " TEXT" + QST_QUESTION+ " TEXT" +
                 QST_OPT1+ " TEXT" + QST_OPT2+ " TEXT" + QST_OPT3+ " TEXT" + QST_OPT4+ " TEXT" +    
                 QST_OPT01+ " TEXT" + QST_OPT02+ " TEXT" + QST_OPT03+ " TEXT" + QST_OPT04+ " TEXT" + QST_CORCTOPT+ " TEXT" + USER_CODE+ " TEXT" + ");");              
     }*/
      public void createDataBase() throws IOException{

            boolean dbExist = checkDataBase();

            if(dbExist){
                //do nothing - database already exist
            }else{

                //By calling this method and empty database will be created into the default system path
                   //of your application so we are gonna be able to overwrite that database with our database.
                this.getReadableDatabase();

                try {

                    copyDataBase();

                } catch (IOException e) {

                    throw new Error("Error copying database");

                }
            }

        }

      /**
         * Check if the database already exist to avoid re-copying the file each time you open the application.
         * @return true if it exists, false if it doesn't
         */
        private boolean checkDataBase(){

            SQLiteDatabase checkDB = null;

            try{
                String myPath = DB_PATH + DATABASE_NAME;
                checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);

            }catch(SQLiteException e){

                //database does't exist yet.

            }

            if(checkDB != null){

                checkDB.close();

            }

            return checkDB != null ? true : false;
        }
              private void copyDataBase() throws IOException
              {          
                  //Open your local db as the input stream       
                  InputStream myInput = myContext.getAssets().open(DATABASE_NAME);        
                  // Path to the just created empty db         
                  String outFileName = DB_PATH + DATABASE_NAME;         
                  //Open the empty db as the output stream         
                  OutputStream myOutput = new FileOutputStream(outFileName);        
                  //transfer bytes from the inputfile to the 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 + DATABASE_NAME;  
                  db = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);  
                  }   
              @Override    
              public synchronized void close() 
              {           
                  if(db != null)              
                      db.close();           
                  super.close();   
              }

              @Override
            public void onCreate(SQLiteDatabase db) 
              {
                // TODO Auto-generated method stub

            }

    @Override  
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)    
    {
         String sql = myContext.getString(R.string.app_name);       
         db.beginTransaction();       
         try        
         {           
             db.execSQL(sql);     
             db.setTransactionSuccessful(); 
             }catch(SQLException e)      
             {                      
                 System.out.println("Error Upgrading tables...");     
                 }      
             finally       
             {            
                 db.endTransaction();     
                 }       
             onCreate(db);  

    }
     public Cursor getData()    
     {       int qst_code=1;

     //Creates the query String. Query is static in DataCursor inner class       
     String sql = "SELECT * FROM lms_mst_questionbank ";       
     //Create an array of String to specify values for ?'s in the sql Query        
     String sqlArgs[] = new String[]{Integer.toString(qst_code) };      
     //Creates a cursor using the SQLiteDatabase object's rawQuery method      
     Cursor c = db.rawQuery(sql,sqlArgs);     
     //The cursor is returned      
     return c;
        /*Cursor cursor = getReadableDatabase().
        rawQuery("select * from lms_mst_questionbank where _id = ?", new String[] { COLUMN_ID });
        return cursor;*/
     }


}

任何形式的鏈接都是很有意義的。

Answer 1

公共類ListActivity擴展了Activity {

List<Question> quesList;
DataBaseHandler db = new DataBaseHandler(this);
ArrayAdapter<String>adapter;
ArrayList<HashMap<String,String>>alist;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_list);
    ListView lv = (ListView)findViewById(R.id.secondlist);
    alist = new ArrayList<HashMap<String,String>>();
    quesList = db.getAllQuestions();
    for(int i=0;i<db.rowcount();i++){
        HashMap<String,String>hm = new HashMap<String,String>();
        hm.put("question", quesList.get(i).getQuestion());
        hm.put("rightans", quesList.get(i).getCorrectoption());
        alist.add(hm);
    }
    String[]from = {"question","rightans"};
    int[]to = {R.id.listtext,R.id.listtextans};
    SimpleAdapter adapter = new SimpleAdapter(getApplicationContext(), alist, R.layout.listitemoflist, from, to);
    lv.setAdapter(adapter);

    /*List<String> listTitle = new ArrayList<String>();

    for (int i = 0; i < quesList.size(); i++) {
        listTitle.add(i, quesList.get(i).getQuestion());
        listTitle.add(quesList.get(i).getCorrectoption());
    }

    adapter = new ArrayAdapter<String>(this, R.layout.listitemoflist,R.id.listtext,  listTitle);

    lv.setAdapter(adapter);*/
}

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

}

Answer 2

請參閱此GIST的數據庫。我認為這對您有好處：) https://gist.github.com/pookie13/952086a7b78989246c01

Answer 3

            String uname = username.getText().toString();
            String pword = password.getText().toString();
            String cpword = cpassword.getText().toString();
            if(uname.equals("") && pword.equals("") && cpword.equals("") ){
                Toast.makeText(getApplicationContext(), "failed updation", Toast.LENGTH_SHORT).show();
            }
            if(!pword.equals(cpword)){
                Toast.makeText(getApplicationContext(), "Password does not match"
                        , Toast.LENGTH_SHORT).show();   
            }
            else{
                loginDataBaseAdapter.updateEntry(uname, pword);
                Toast.makeText(getApplicationContext(), "Account Successfully Updated"
                        , Toast.LENGTH_SHORT).show();

                Intent i = new Intent(UpdatePassword.this,
                        LoginActivity.class);
                startActivity(i);
                finish();
            }

Answer 4

當我向應用程序添加數據庫支持時，我總是參考這篇文章 。 希望它也對您有幫助！