Android Studio 数据库连接

Question

This is a model paper I got. I need to make sure that, my codes are 100% correct. a. Create an Activity called Home and design the given layout Create an Activity called ProfileManagement and design the given layout. Create an Activity called EditProfile and design the given layout. (I did all these layout parts)

Final class called 'UserProfile'. Make the default constructor private. Create an inner class called 'Users' by implementing 'BaseColumn' interface. Inside the inner class, define the columns you need along with the table. b.Implement a method named addInfo() to store user details details . c. Implement a method named updateInfor() to modify stored user details based on the user ID. Method must return a Boolean value based on the success or failure. d. Implement a method named readAllInfor() to retrieve all the user details stored in the database table. e. Overload the method readAllInfor() to retrieve the user details based on the primary key. f. Implement a method named deleteInfo() to delete a specific user

import android.provider.BaseColumns;

public final class UserProfile {

    private UserProfile() { }

    public class User implements BaseColumns {
        public static final String TABLE_NAME = "UserInfo";
        public static final String COLUMN_USERNAME = "username";
        public static final String COLUMN_DOB = "dob";
        public static final String COLUMN_PASSWORD = "password";
        public static final String COLUMN_GENDER = "gender";
    }
}

Create another class called DBHelper inside the database folder by extending the class SQLiteOpenHelper as its superclass. Implement the relevant methods and constructors.

package com.bla.androidsqlitebasics.database;

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

import static com.bla.androidsqlitebasics.database.UserProfile.User.*;

public class DBHelper extends SQLiteOpenHelper {

    public static final String DATABASE_NAME = "User.db";
    public static final int DATABASE_VERSION = 3;

    public static final String CREATE_TABLE_QUERY = "CREATE TABLE IF NOT EXISTS "+ TABLE_NAME +"( "+
            _ID + " INTEGER PRIMARY KEY, " +
            COLUMN_USERNAME +" TEXT, "+
            COLUMN_PASSWORD +" TEXT, "+
            COLUMN_DOB +" DATE, " +
            COLUMN_GENDER + ")";

    public static final String SQL_DELETE_ENTRIES = "DROP TABLE IF EXISTS "+ TABLE_NAME;

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE_QUERY);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }

    //Supposed if question asked to implement add, update, read methods in this class
    //to check user when login
    public long checkUser(String username, String password) {
        SQLiteDatabase db = getReadableDatabase();

        //check if entered username and password exists in the users table
        String[] selectionArgs = {username, password};
        String query = "SELECT * FROM " + TABLE_NAME + " WHERE "+ COLUMN_USERNAME + " = ? AND " +
                COLUMN_PASSWORD + " = ?";

        Cursor cursor = db.rawQuery(query, selectionArgs);

        //if username and password match and row count is greater than 1 get that userId or else assign -1 to @useerId
        long userId = -1;
        if (cursor.moveToFirst()) {
            userId = (cursor.getCount() >= 1) ? cursor.getLong(0) : -1;
        }
        //if the user count greater than(shoul be equal to if properly check) 1 user exists and return true
        //return cursor.getCount() >= 1;

        //to login user from primary key
        return userId;
    }

    //register/add user to db table
    public long addInfo(String username, String password) {
        SQLiteDatabase db = getWritableDatabase();

        ContentValues cv = new ContentValues();
        cv.put(COLUMN_USERNAME, username);
        cv.put(COLUMN_PASSWORD, password);

        return db.insert(TABLE_NAME, null, cv);
    }

    public boolean updateInfo(long userId, String username, String password, String dob, String gender) {
        SQLiteDatabase db = getWritableDatabase();

        //to check for the user to update
        String[] selectionArgs = {userId+""};
        String whereClause = _ID + " = ?";

        ContentValues cv = new ContentValues();
        cv.put(COLUMN_USERNAME, username);
        cv.put(COLUMN_PASSWORD, password);
        cv.put(COLUMN_DOB, dob);
        cv.put(COLUMN_GENDER, gender);

        return db.update(TABLE_NAME, cv, whereClause, selectionArgs) > 0;
    }

    public Cursor readAllInfor() {
        SQLiteDatabase db = getReadableDatabase();

        String[] projection = {
                _ID,
                COLUMN_USERNAME,
                COLUMN_PASSWORD,
                COLUMN_DOB,
                COLUMN_GENDER
        };

        Cursor cursor = db.query(
                TABLE_NAME,
                projection,
                null,
                null,
                null,
                null,
                null);

        //if the user count greater than(shoul be equal to if properly check) 1 user exists and return true
        return cursor;
    }

    public Cursor readAllInfor(long userId) {
        SQLiteDatabase db = getReadableDatabase();

        //retrieve the user using primary key
        String[] selectionArgs = {userId+""};
        String query = "SELECT * FROM " + TABLE_NAME + " WHERE "+ _ID + " = ? ";

        Cursor cursor = db.rawQuery(query, selectionArgs);

        //if the user count greater than(shoul be equal to if properly check) 1 user exists and return true
        return cursor;
    }

    public boolean deleteInfo(long userId) {
        SQLiteDatabase db = getWritableDatabase();

        //delete user from db table
        String[] selectionArgs = {userId+""};
        String whereClause = _ID + " = ?";

        return db.delete(TABLE_NAME, whereClause, selectionArgs) > 0;
    }
}

Create intent objects to start a. ProfileManagement activity from 'Register' button b. EditProfile activity from 'Update Profile' button a.Call addInfor() method implemented in DbHandler class from the onClick event of Register button. Display a Toast Message indicating success or failure

Home Activity

package com.bla.androidsqlitebasics.activity;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.bla.androidsqlitebasics.database.DBHelper;
import com.live.sinhalacoder.androidsqlitebasics.R;

public class HomeActivity extends AppCompatActivity {

    EditText usernameEt, passwordEt;
    Button loginBt, registerBt;

    //to get access to database table
    DBHelper mHelper;

    //newly added user primary key
    long userId = -1;

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

        usernameEt = findViewById(R.id.idUsernameEt);
        passwordEt = findViewById(R.id.idPasswordEt);

        loginBt = findViewById(R.id.idLoginBt);
        registerBt = findViewById(R.id.idRegisterBt);

        //initialize db helper when app create
        mHelper = new DBHelper(this);

        //if user clicked login button
        loginBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //login existing user
                login();
            }
        });

        //if user clicked register button
        registerBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //add new user to the database
                registerUser();
            }
        });
    }

    private void login() {
        String username = usernameEt.getText().toString();
        String password = passwordEt.getText().toString();

        //if username and pass does not match -1 will return from checkUser function and if not -1 logged in
        userId = mHelper.checkUser(username, password);
        if (userId != -1) {
            Intent intent = new Intent(HomeActivity.this, ProfileManagementActivity.class);
            intent.putExtra("userId", userId);
            startActivity(intent);
        } else {
            Toast.makeText(this, "Err.. Try again!", Toast.LENGTH_SHORT).show();
        }
    }

    public void registerUser() {
        String username = usernameEt.getText().toString();
        String password = passwordEt.getText().toString();

        userId = mHelper.addInfo(username, password);
        if (userId == -1) {
            Toast.makeText(this, "Err.. Try again!", Toast.LENGTH_SHORT).show();
        } else {
            //Toast.makeText(this, "Successfully registed!", Toast.LENGTH_SHORT).show();
            login();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mHelper.close();
    }
}

EditProfile Activty

a. Call readAllInfor() method implemented in DbHandler class from the onClick event of the Search button to retrieve profile of a specific user. b.Call updateInfor() method implemented in DbHandler class from the onClick event of the Edit button to update user details c. Call deleteinfor() method implemented in DbHandler class from the onClick event of the Delete button to delete a user

package com.bla.androidsqlitebasics.activity;

import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Toast;

import com.bla.androidsqlitebasics.database.DBHelper;
import com.live.sinhalacoder.androidsqlitebasics.R;

public class EditProfileActivity extends AppCompatActivity {

    EditText usernameEt, passwordEt, dobEt;
    RadioGroup genderRadio;
    Button editBt, searchBt, deleteBt;

    //to get access to database table
    DBHelper mHelper;

    long userId;

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

        usernameEt = findViewById(R.id.idUsernameEt);
        passwordEt = findViewById(R.id.idPasswordEt);
        dobEt = findViewById(R.id.idBirthdayEt);

        genderRadio = findViewById(R.id.radioGroup);

        editBt = findViewById(R.id.idEditBt);
        searchBt = findViewById(R.id.idSearchBt);
        deleteBt = findViewById(R.id.idDeleteBt);

        //initialize db helper when app create
        mHelper = new DBHelper(this);

        //TODO: get userId that is coming from the home activity to search using user Id(not sure this way or using search username)
        //If press update or delete without searching user id coming from the home activity will be deleted
        Intent intent = getIntent();
        if (intent != null) {
            userId = intent.getLongExtra("userId", -1);
        }

        //if user clicked edit button
        editBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String uname = usernameEt.getText().toString();
                String pass = passwordEt.getText().toString();
                String dob = dobEt.getText().toString();
                String gender = "";
                if (genderRadio.getCheckedRadioButtonId() == R.id.idMaleRadio) {
                    gender = "Male";
                } else if (genderRadio.getCheckedRadioButtonId() == R.id.idFemaleRadio) {
                    gender = "Female";
                }

                //edit logged in user
                if (mHelper.updateInfo(userId, uname, pass, dob, gender)) {
                    Toast.makeText(EditProfileActivity.this, "Updated!", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(EditProfileActivity.this, "Cannot update!", Toast.LENGTH_SHORT).show();
                }
            }
        });

        //if user clicked search button
        searchBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //get typed username to search
                String username = usernameEt.getText().toString();

                //get current user values to textFields from readInfo
                Cursor cursor = mHelper.readAllInfor();

                //TODO: I think this way is not the perfect since, we can directly search using the query
                while (cursor.moveToNext()) {
                    //if typed username equals with table value
                    if (username.equals(cursor.getString(1))) {
                        //get the user id to update and delete
                        userId = cursor.getLong(0);
                        //if there is any matching username with db user table get those values and place into textfields
                        passwordEt.setText(cursor.getString(2));
                        dobEt.setText(cursor.getString(3));

                        if (cursor.getString(4) != null) {
                            if (cursor.getString(4).equals("Male")) {
                                genderRadio.check(R.id.idMaleRadio);
                            } else if (cursor.getString(4).equals("Female"))
                                genderRadio.check(R.id.idFemaleRadio);
                        }
                    }
                }
                cursor.close();

                //dumb trick to display if user not exists
                if (passwordEt.getText().toString().equals("")) {
                    //if searched user not exists
                    Toast.makeText(EditProfileActivity.this, "No user found!", Toast.LENGTH_SHORT).show();
                }
            }
        });

        //if user clicked delete button
        deleteBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //delete user from table and if deleted count is greater than 0 display delete message
                if (mHelper.deleteInfo(userId)) {
                    Toast.makeText(EditProfileActivity.this, "Deleted!", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(EditProfileActivity.this, "User not in the table!", Toast.LENGTH_SHORT).show();
                }

                //clear out editText after deleted
                usernameEt.setText("");
                passwordEt.setText("");
                dobEt.setText("");
                genderRadio.clearCheck();
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mHelper.close();
    }
}

Profile Management Activity

package com.bla.androidsqlitebasics.activity;

import android.content.Intent;
import android.database.Cursor;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Toast;

import com.bla.androidsqlitebasics.database.DBHelper;
import com.live.sinhalacoder.androidsqlitebasics.R;

public class ProfileManagementActivity extends AppCompatActivity {

    EditText usernameEt, passwordEt, dobEt;
    RadioGroup genderRadio;
    Button updateProfileBt;

    //to get access to database table
    DBHelper mHelper;

    long userId;

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

        usernameEt = findViewById(R.id.idUsernameEt);
        passwordEt = findViewById(R.id.idPasswordEt);
        dobEt = findViewById(R.id.idBirthdayEt);

        genderRadio = findViewById(R.id.radioGroup);

        updateProfileBt = findViewById(R.id.idUpdateBt);

        //initialize db helper when app create
        mHelper = new DBHelper(this);

        //get userId that is coming from the home activity
        Intent intent = getIntent();
        if (intent != null) {
            userId = intent.getLongExtra("userId", -1);
        }

        //get logged in or registered user data from table and bind to editTexts
        Cursor cursor = mHelper.readAllInfor(userId);
        if (cursor.moveToFirst()) {
            usernameEt.setText(cursor.getString(1));
            passwordEt.setText(cursor.getString(2));
            dobEt.setText(cursor.getString(3));
            if (cursor.getString(4) != null) {
                if (cursor.getString(4).equals("Male")) {
                    genderRadio.check(R.id.idMaleRadio);
                } else {
                    genderRadio.check(R.id.idFemaleRadio);
                }
            }
        }
        //if user clicked edit button
        updateProfileBt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //open update profile
                Intent intent = new Intent(ProfileManagementActivity.this, EditProfileActivity.class);
                intent.putExtra("userId", userId);
                startActivity(intent);
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mHelper.close();
    }
}

These are my layouts files. ActivityHOme

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginHorizontal="@dimen/layout_margin_horizontal"
    tools:context="com.bla.androidsqlitebasics.activity.HomeActivity">

    <TextView
        android:id="@+id/usernameLabelTv"
        android:layout_width="@dimen/label_width"
        android:layout_height="@dimen/label_height"
        android:layout_marginTop="@dimen/username_label_margin_top"
        android:text="@string/username_tv"
        android:textSize="@dimen/labels_size"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/idUsernameEt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/username_et_margin_start"
        android:layout_marginTop="@dimen/username_et_margin_top"
        android:ems="10"
        android:hint="@string/username_tv"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.384"
        app:layout_constraintStart_toEndOf="@id/usernameLabelTv"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/passwordLabelTv"
        android:layout_width="@dimen/label_width"
        android:layout_height="@dimen/label_height"
        android:layout_marginTop="@dimen/password_label_margin_top"
        android:text="@string/password_label_tv"
        android:textSize="@dimen/labels_size"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/usernameLabelTv" />

    <EditText
        android:id="@+id/idPasswordEt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/username_et_margin_start"
        android:layout_marginTop="@dimen/password_et_margin_top"
        android:ems="10"
        android:hint="@string/password_label_tv"
        android:inputType="textPassword"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.384"
        app:layout_constraintStart_toEndOf="@id/passwordLabelTv"
        app:layout_constraintTop_toBottomOf="@id/idUsernameEt" />

    <Button
        android:id="@+id/idLoginBt"
        android:layout_width="@dimen/bt_width"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/log_bt_margin_top"
        android:text="@string/login_bt_label"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/passwordLabelTv"
        app:layout_constraintVertical_bias="0.023" />

    <Button
        android:id="@+id/idRegisterBt"
        android:layout_width="@dimen/bt_width"
        android:layout_height="wrap_content"
        android:layout_marginStart="@dimen/username_et_margin_start"
        android:layout_marginTop="@dimen/reg_bt_margin_top"
        android:text="@string/register_bt_label"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.395"
        app:layout_constraintStart_toEndOf="@id/idLoginBt"
        app:layout_constraintTop_toBottomOf="@id/idPasswordEt"
        app:layout_constraintVertical_bias="0.028" />
    </android.support.constraint.ConstraintLayout>

Answer 1

Your code seems to be working fine. But I think there might be an error in your layouts. please make sure your layouts are correct.

Answer 2

请检查您的 Intent 对象和布局。