Question

我正在制作这个示例应用程序，它将插入，更新，删除和检索数据库中的数据。现在我面临的问题是如何更新记录。我知道我必须通过Id，但是如何。

MainActivity.java：

public class MainActivity extends Activity {

Button btnSubmit, btnUpdate, btnDelete;
EditText UserName, FirstName, LastName, txtPassword;
RunDatabase db;

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

    db = new RunDatabase(this);

    UserName = (EditText) findViewById(R.id.User_Name);
    FirstName = (EditText) findViewById(R.id.First_Name);
    LastName = (EditText) findViewById(R.id.Last_Name);
    txtPassword = (EditText) findViewById(R.id.Password);

    btnSubmit = (Button) findViewById(R.id.btn_Submit);
    btnSubmit.setOnClickListener  (new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            addRow();
        }
    });

    btnUpdate = (Button) findViewById(R.id.btn_Update);
    btnUpdate.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            updateRow();
        }
    });

}   

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

private void addRow()
{
    try
    {
        db.addRow
        (
                UserName.getText().toString(),
                FirstName.getText().toString(),
                LastName.getText().toString(),
                txtPassword.getText().toString()
        );

        // remove all user input from the Activity
        emptyFormFields();
    }
    catch (Exception e)
    {
        Log.e("Add Error", e.toString());
        e.printStackTrace();
    }
 }


private void updateRow()
{
    try
    {

        db.updateRow
        (
            UserName.getText().toString(),
            FirstName.getText().toString(),
            LastName.getText().toString(),
            txtPassword.getText().toString()
        );

        emptyFormFields();
    }
    catch (Exception e)
    {
        Log.e("Update Error", e.toString());
        e.printStackTrace();
    }
}

private void emptyFormFields()
{
    User_Id.setText("");
    FirstName.setText("");
    LastName.setText("");
    UserName.setText("");
    txtPassword.setText("");
}
}

RunDatabase.java：

 public class RunDatabase {

Context context;

private SQLiteDatabase db; // a reference to the database manager class.
private final String DB_NAME = "Records"; // the name of our database
private final int DB_VERSION = 1; // the version of the database

// the names for our database columns
private final String TABLE_NAME = "tblRecords";
private final String TABLE_ROW_ID = "id";
private final String TABLE_ROW_ONE = "UserName";
private final String TABLE_ROW_TWO = "FirstName";
private final String TABLE_ROW_THREE = "LastName";
private final String TABLE_ROW_FOUR = "Password";

// the beginnings our SQLiteOpenHelper class

    public void onCreate(SQLiteDatabase db)
    {
        String newTableQueryString =    
            "create table " +
            TABLE_NAME +
            " (" +
        TABLE_ROW_ID + " integer primary key autoincrement not null, " +
            TABLE_ROW_ONE + " text, " +
            TABLE_ROW_TWO + " text, " +
            TABLE_ROW_THREE + " text, " +
            TABLE_ROW_FOUR + " text" +
            ");";
     System.out.println(newTableQueryString);
        // execute the query string to the database.
        db.execSQL(newTableQueryString);
    }

    public RunDatabase(Context context)
    {
        this.context = context;

        // create or open the database
    CustomSQLiteOpenHelper helper = new CustomSQLiteOpenHelper(context);
        this.db = helper.getWritableDatabase();
    }


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

}

public void addRow(String rowStringOne, String rowStringTwo, String rowStringThree, String rowStringFour)
{
    // this is a key value pair holder used by android's SQLite functions
    ContentValues values = new ContentValues();

    values.put(TABLE_ROW_ONE, rowStringOne);
    values.put(TABLE_ROW_TWO, rowStringTwo);
    values.put(TABLE_ROW_THREE, rowStringThree);
    values.put(TABLE_ROW_FOUR, rowStringFour);

    try
    {
        db.insert(TABLE_NAME, null, values);
    }
    catch(Exception e)
    {
        Log.e("DB ERROR", e.toString()); 
        e.printStackTrace(); // prints the stack trace to the log
    }
}

public void updateRow(long rowID, String rowStringOne, String rowStringTwo, String rowStringThree, String rowStringFour)
{

    ContentValues values = new ContentValues();
    values.put(TABLE_ROW_ONE, rowStringOne);
    values.put(TABLE_ROW_TWO, rowStringTwo);
    values.put(TABLE_ROW_THREE, rowStringThree);
    values.put(TABLE_ROW_FOUR, rowStringFour);

    try {db.update(TABLE_NAME, values, TABLE_ROW_ID + "=" + rowID, null);}
    catch (Exception e)
    {
        Log.e("DB Error", e.toString());
        e.printStackTrace();
    }
}
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
    {
        // NOTHING TO DO HERE. THIS IS THE ORIGINAL DATABASE VERSION.
        // OTHERWISE, YOU WOULD SPECIFIY HOW TO UPGRADE THE DATABASE.
    }
}
}

Answer 1

你可以尝试这样 -

db.update(TABLE_NAME, values, TABLE_ROW_ID + "=?", String[]{rowID});

Answer 2

1。在您的创建表字符串

中

String newTableQueryString =    
            "create table " +
            TABLE_NAME +
            " (" +
        TABLE_ROW_ID + " integer primary key autoincrement not null, " +
            TABLE_ROW_ONE + " text, " +
            TABLE_ROW_TWO + " text, " +
            TABLE_ROW_THREE + " text, " +
            TABLE_ROW_FOUR + " text" +
            ");";

ROW_ID是一个整数，所以在函数updateRow()中，rowID参数的数据类型应该是整数，它在“where”子句中传递。所以应该改变 - ＆GT; public void updateRow(long rowID, String rowStringOne,...

2。要识别您添加的行，您需要拥有一个主键，您可以根据该条目识别该主键。

自动增量整数有助于确保数据库每次都有一个新行，
但您需要的主键应该是您将要知道的区分条目的东西。

可以尝试一个派生密钥，它将是你的数据库中的另一个列，插入相同的添加行将是：

String customPrimaryKey="UserName.getText().toString()+FirstName.getText().toString()+txtPassword.getText().toString()";
db.updateRow
        (
            UserName.getText().toString(),
            FirstName.getText().toString(),
            LastName.getText().toString(),
            txtPassword.getText().toString(),
// add one more value for a particular entry-a primary key for You to identify that row
            customPrimaryKey
        );

因此，您可以确定要更新的行，并在where子句的updateRow()参数中传递相同的内容

无法更新sqlite数据库中的记录

2 个答案: