連接到SQLite數據庫

Question

我已經在新項目中爲我的BMI應用程序創建了SQLite數據庫。
現在問題是我不知道如何連接到數據庫。

private string file = "mydata";是否改爲別的或它是正確的？

CalculatorActivity。 java

public class CalculatorActivity extends AppCompatActivity { 
    private EditText etWeight, etHeight; 
    private TextView tvDisplayResult, tvResultStatus; 
    Button bSave, bRead; 
    TextView tvStored; 
    String data; 
    private String file = "mydata"; 


    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_calculator); 
     etWeight = (EditText) findViewById(R.id.weight); 
     etHeight = (EditText) findViewById(R.id.height); 
     tvDisplayResult = (TextView) findViewById(R.id.display_result); 
     tvResultStatus = (TextView) findViewById(R.id.result_status); 
     tvResultStatus = (TextView) findViewById(R.id.result_status); 
     bSave = (Button) findViewById(R.id.savebutton); 
     bRead = (Button) findViewById(R.id.readbutton); 
     tvStored = (TextView) findViewById(R.id.displaysaveditem); 
     bSave.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       data = tvDisplayResult.getText().toString() + "\n"; 

       try { 
        FileOutputStream fOut = openFileOutput(file, Context.MODE_APPEND); 
        fOut.write(data.getBytes()); 
        fOut.close(); 
        Toast.makeText(getBaseContext(), "file saved", Toast.LENGTH_SHORT).show(); 
       } catch (Exception e) { 
        // TODO Auto-generated catch block 
        e.printStackTrace(); 
       } 
      } 
     }); 

     //Read 
     bRead.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       startActivity(new Intent(CalculatorActivity.this, RecordActivity.class)); 
       finish(); 

      } 
     }); 


    } 

    public void onClick(View v) { 
     switch (v.getId()) { 
      case R.id.button_calculate: 
       Log.d("check", "Button Clicked!"); 
       calculate(); 
       break; 
      case R.id.button_reset: 
       reset(); 
       break; 
     } 
    } 

    private void calculate() { 
     String weight = etWeight.getText().toString(); 
     String height = etHeight.getText().toString(); 

     double bmiResult = Double.parseDouble(weight)/(Double.parseDouble(height) * Double.parseDouble(height)); 

     tvDisplayResult.setText(String.valueOf(bmiResult)); 


     if (bmiResult < 18.5) { 
      tvResultStatus.setText(R.string.under); 
      tvResultStatus.setBackgroundColor(Color.parseColor("#F1C40F")); 
      tvResultStatus.setTextColor(Color.parseColor("#FFFFFF")); 
     } else if (bmiResult >= 18.5 && bmiResult <= 24.9) { 
      tvResultStatus.setText(R.string.normal); 
      tvResultStatus.setBackgroundColor(Color.parseColor("#2ECC71")); 
      tvResultStatus.setTextColor(Color.parseColor("#FFFFFF")); 
     } else if (bmiResult >= 24.9 && bmiResult <= 29.9) { 
      tvResultStatus.setText(R.string.over); 
      tvResultStatus.setBackgroundColor(Color.parseColor("#E57E22")); 
      tvResultStatus.setTextColor(Color.parseColor("#FFFFFF")); 
     } else if (bmiResult >= 30) { 
      tvResultStatus.setText(R.string.obes); 
      tvResultStatus.setBackgroundColor(Color.parseColor("#C0392B")); 
      tvResultStatus.setTextColor(Color.parseColor("#FFFFFF")); 
     } 


    } 

    private void reset() { 
     etWeight.setText(""); 
     etHeight.setText(""); 
     tvDisplayResult.setText(R.string.default_result); 
     tvResultStatus.setText(R.string.na); 
     tvResultStatus.setBackgroundColor(0); 
     tvResultStatus.setTextColor(0); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     MenuInflater inflater = getMenuInflater(); 
     inflater.inflate(R.menu.menu_options, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle item selection 
     switch (item.getItemId()) { 
      case R.id.menu_home: 
       startActivity(new Intent(CalculatorActivity.this, CalculatorActivity.class)); 
       finish(); 
       break; 
      case R.id.menu_info: 
       startActivity(new Intent(CalculatorActivity.this, InformationActivity.class)); 
       finish(); 
       break; 

     } 
     return true; 
    } 

} 

DBHandler。 java的

import android.content.ContentValues; 
import android.content.Context; 
import android.database.Cursor; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteOpenHelper; 

import java.util.ArrayList; 
import java.util.List; 



public class DBHandler extends SQLiteOpenHelper { 

    // Database Version 
    public static final int DATABASE_VERSION = 1; 
    // Database Name 
    public static final String DATABASE_NAME = "RecordDB"; 
    // Record table name 
    public static final String TABLE_RECORD = "recordtable"; 
    // Record Table Columns names 
    public static final String KEY_ID = "id"; 
    public static final String KEY_BMI = "bmi"; 


    public DBHandler(Context context) { 
     super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     String CREATE_RECORD_TABLE = "CREATE TABLE " + TABLE_RECORD + "(" + KEY_ID + " INTEGER PRIMARY KEY," + KEY_BMI + " TEXT " + ")"; 
     db.execSQL(CREATE_RECORD_TABLE); 
    } 


    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
     // Drop older table if existed 
     db.execSQL("DROP TABLE IF EXISTS " + TABLE_RECORD); 
     // Creating tables again 
     onCreate(db); 

    } 


    public void addBmi(Record record) { 

     SQLiteDatabase db = this.getWritableDatabase(); 
     ContentValues values = new ContentValues(); 
     values.put(KEY_BMI, record.getBmi()); // BMI value 

     // Inserting Row 
     db.insert(TABLE_RECORD, null, values); 
     db.close(); // Closing database connection 
    } 

    public List<Record> getAllRecords() { 
     List<Record> recordList = new ArrayList<Record>(); 
     // Select All Query 
     String selectQuery = "SELECT * FROM " + TABLE_RECORD; 

     SQLiteDatabase db = this.getWritableDatabase(); 
     Cursor cursor = db.rawQuery(selectQuery, null); 

     // looping through all rows and adding to list 
     if (cursor.moveToFirst()) { 
      do { 
       Record record = new Record(); 
       record.setId(Integer.parseInt(cursor.getString(0))); 
       record.setBmi(cursor.getString(1)); 
       // Adding record to list 
       recordList.add(record); 
      } while (cursor.moveToNext()); 
     } 

     // return record list 
     return recordList; 
    } 
} 

Answer 1

我不知道如何將數據庫在我的BMI應用

好連接，你需要聲明它並對其進行初始化。

public class CalculatorActivity extends AppCompatActivity { 

    private DBHandler dbHandler; 

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

     dbHandler = new DBHandler(this); 

     // Use it... 

是在private string file = "mydata";需要被改變東西或者其正確的？

你能夠保持它，它是正確的，但它是不相關的數據庫。