如何在Android Studio中将数据库中的列显示为文本视图？

Question

Hey guys I have been trying this for 2 days now and I cant seem to get it to work. I have tried every tutorial! I am new to android studio and have been trying to make a simple app where I can register and login. I was able to create the database and insert a new row(user) to the database.[Register user]. And also I was able to log the user in.

What I am trying to do now, is retrieve a column or column from the row and display it in a text view.

For example, once I login with a user, I want to display their information from the columns, such as phone number, address, etc.

When the app is first launched, there is a registration activity. you can either register or proceed to the login activity. Once you are logged in from the login activity, there is a new activity where I want to display the information of that logged in user.

databasehelper.java

package easy.eightfivehundred.easy;

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

public class DatabaseHelper extends SQLiteOpenHelper{
    public static final String DATABASE_NAME="register.db";
    public  static final String TABLE_NAME="register";
    public  static final String COL_1="ID";
    public  static final String COL_2="FirstName";
    public  static final String COL_3="LastName";
    public  static final String COL_4="HomeAddress";
    public  static final String COL_5="Phone";
    public  static final String COL_6="Email";
    public  static final String COL_7="Password";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, FirstName TEXT, LastName TEXT, HomeAddress TEXT, Phone TEXT, Email TEXT, Password TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }

}

mainactivity

package easy.eightfivehundred.easy;

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

public class MainActivity extends AppCompatActivity {

    SQLiteOpenHelper openHelper;
    SQLiteDatabase db;
    Button Registerbutton, Loginbutton;
    EditText Firstnametxt, Lastnametxt, Homeaddresstxt, Phonenumbertxt, Emailtext, Passwordtext;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        openHelper = new DatabaseHelper(this);
        Registerbutton =(Button)findViewById(R.id.RegisterButton);
        Loginbutton = (Button)findViewById(R.id.LogInButton);
        Firstnametxt =(EditText)findViewById(R.id.FirstNameText);
        Lastnametxt =(EditText)findViewById(R.id.LastNameText);
        Homeaddresstxt =(EditText)findViewById(R.id.HomeAddressText);
        Phonenumbertxt =(EditText)findViewById(R.id.PhoneText);
        Emailtext =(EditText)findViewById(R.id.EmailText);
        Passwordtext =(EditText)findViewById(R.id.PasswordText);
        Registerbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                db = openHelper.getWritableDatabase();
                String first = Firstnametxt.getText().toString();
                String last = Lastnametxt.getText().toString();
                String address = Homeaddresstxt.getText().toString();
                String phone = Phonenumbertxt.getText().toString();
                String email = Emailtext.getText().toString();
                String password = Passwordtext.getText().toString();

                insertData(first, last, address, phone, email, password);
                Toast.makeText(getApplicationContext(), "You Registered Successfully!", Toast.LENGTH_LONG).show();
            }
        });

        Loginbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, login.class);
                startActivity(intent);
            }
        });

    }

    public void insertData(String first, String last, String address, String phone, String email, String password) {
        ContentValues contentValues = new ContentValues();
        contentValues.put(DatabaseHelper.COL_2, first);
        contentValues.put(DatabaseHelper.COL_3, last);
        contentValues.put(DatabaseHelper.COL_4, address);
        contentValues.put(DatabaseHelper.COL_5, phone);
        contentValues.put(DatabaseHelper.COL_6, email);
        contentValues.put(DatabaseHelper.COL_7, password);
        long id = db.insert(DatabaseHelper.TABLE_NAME, null, contentValues);
    }

}

login

package easy.eightfivehundred.easy;

import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
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;

public class login extends AppCompatActivity {

    SQLiteDatabase db;
    SQLiteOpenHelper openHelper;
    Button Loginbutton;
    EditText Emailtext, Passwordtext;
    Cursor cursor;

    public static final String EXTRA_MESSAGE = " ";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);
        openHelper = new DatabaseHelper(this);
        db = openHelper.getReadableDatabase();
        Loginbutton = (Button)findViewById(R.id.loginbutton);
        Emailtext = (EditText)findViewById(R.id.emaillogintext);
        Passwordtext = (EditText)findViewById(R.id.passwordlogintext);
        Loginbutton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String email = Emailtext.getText().toString();
                String password = Passwordtext.getText().toString();
                cursor = db.rawQuery("SELECT * FROM " + DatabaseHelper.TABLE_NAME + " WHERE " + DatabaseHelper.COL_6 + "=? AND " + DatabaseHelper.COL_7 + "=? ", new String[]{email, password});
                if(cursor != null){
                    if(cursor.getCount() > 0){
                        cursor.moveToNext();
                        Toast.makeText(getApplicationContext(), "Login Successful", Toast.LENGTH_LONG).show();

                        Intent intent = new Intent(login.this, UserHome.class);
                        intent.putExtra(EXTRA_MESSAGE, email);
                        startActivity(intent);
                    }
                    else{
                        Toast.makeText(getApplicationContext(), "Error!", Toast.LENGTH_LONG).show();
                    }
                }
            }
        });

    }
}

userhome

package easy.eightfivehundred.easy;

import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import static easy.eightfivehundred.easy.DatabaseHelper.TABLE_NAME;

public class UserHome extends AppCompatActivity {

    SQLiteDatabase db;
    SQLiteOpenHelper openHelper;
    Cursor cursor;

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

        Intent intent = getIntent();
        String email = intent.getStringExtra(login.EXTRA_MESSAGE);
    }
}

In the userhome.java file is where I'm having trouble at. I simply want to display the columns from the logged in user on this page.

Answer 1

This should get you on your way:-

Step 1.

Amend the layout to include the TextViews with id's that will be used to show the extracted data eg :-

<TextView
    android:id="@+id/firstname"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
<TextView
    android:id="@+id/lastname"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
<TextView
    android:id="@+id/homaddress"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
<TextView
    android:id="@+id/phone"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
<TextView
    android:id="@+id/email"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />
<TextView
    android:id="@+id/password"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

Step 2.

Add a method (added to DatabAseHelper.java although could be elsewhere like your InsertData method in MainActivity.java ) to get the data as a Cursor.

eg :-

public Cursor getUserInfo(String email) {
    SQLiteDatabase db = this.getWritableDatabase();
    String whereclause = COL_6 + "=?"; //<<<< select according to email
    String[] whereargs = new String[]{email};
    return db.query(
            TABLE_NAME,
            null,
            whereclause,
            whereargs,
            null,null,null
            );
}

• The above will equate to SELECT * FROM register WHERE Email = '??????'
  • where ?????? will the string as passed to the method.

Step 3.

In Userhome.java declare the class variables for the TextViews , an instance of YOUR DatabaseHelper (not SQLiteOpenHelper) and the Cursor (you already have this).

eg :-

TextView mFirstName, mLastName, mHomeAddress, mPhone, mEmail, mPassword;
DatabaseHelper mDBHlpr;
Cursor cursor; 

Step 4.

Again in UserHome.java as the onCreate method use :-

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main); //<<<< USE YOUR LAYOUT


    Intent intent = getIntent();
    String email = intent.getStringExtra(login.EXTRA_MESSAGE);

    //<<<<<<<<<< NEW CODE >>>>>>>>>>
    mFirstName = (TextView) this.findViewById(R.id.firstname);
    mLastName = (TextView) this.findViewById(R.id.lastname);
    mHomeAddress = (TextView) this.findViewById(R.id.homaddress);
    mPhone = (TextView) this.findViewById(R.id.phone);
    mEmail = (TextView) this.findViewById(R.id.email);
    mPassword = (TextView) this.findViewById(R.id.password);

    mDBHlpr = new DatabaseHelper(this); //<<<< get Instance of DatbaseHelper
    cursor = mDBHlpr.getUserInfo(email); //<<< get the Cursor according to email
    if (cursor.moveToFirst()) {
        mFirstName.setText(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COL_2)));
        mLastName.setText(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COL_3)));
        mHomeAddress.setText(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COL_4)));
        mPhone.setText(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COL_5)));
        mEmail.setText(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COL_6)));
        mPassword.setText(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COL_7)));
    } else {
        // HANDLE NO DATA THAT MATCHES WHERE CLAUSE
        mFirstName.setText("Sorry No User found that has email as :- " + email);
    }
    cursor.close(); //<<<< DONE WITH THE CURSOR SO CLOSE IT
}

• A Cursor when returned will be positioned at a position before the first row (position -1). To get to the data you need to move to a row.
• The move????? methods return true or false. The former if the move could be made (so moveToFirst , if there are no rows will return false, or true if there is at least one row). Hence how you can use if (cursor.moveToFirst()){.....} .
• So if there is data (a row or more, one is assumed as there should probably not be users with the same email) the TextView's are populated (otherwise ie else, the firstname TextView indicates user not found (shouldn't happen though)).
• Data is extracted from the Cursor using get????? ( getString in this case, there are other methods such as getInt , getLong ......).
• The get???? methods take an integer, the column offset (first column ID is offset 0 , the 2nd firstname is offset 1 ......). However, using hard coded offsets can easily result in issues, so it's recommended to use the Cursor getColumnIndex , which returns the column offset according to the column name (more flexible).
• Note how the column names are retrieved from the DatabaseHelper , using this way reduces the chance for typing errors.
  • You could consider changing your onCreate method in the DatabaseHelper to also utilise this single source for column names by using (replaced code commented out).

:-

@Override
public void onCreate(SQLiteDatabase db) {

    String crt_sql = "CREATE TABLE " + TABLE_NAME + "(" +
            // Note AUTOINCREMENT is very likely not needed
            // refer to https://sqlite.org/autoinc.html
            COL_1 + " INTEGER PRIMARY KEY, " +
            COL_2 + " TEXT, " +
            COL_3 + " TEXT, " +
            COL_4 + " TEXT, " +
            COL_5 + " TEXT, " +
            COL_6 + " TEXT, " +
            COL_7 + " TEXT " +
            ")";
    db.execSQL(crt_sql);
    /*
    db.execSQL("CREATE TABLE " + TABLE_NAME + " (ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
            "FirstName TEXT, LastName TEXT, HomeAddress TEXT, Phone TEXT, Email TEXT, Password TEXT)");
            */
}

• You may wish to have a look at SQLite Autoincrement in regads to the exclusion of the AUTOINCREMENT keyword.

• You may also wish to have a look at Cursor for the numerous Cursor methods (eg get???? and move????? )

Testing

the above was tested by adding a user who's first name was Fred, lastname FlitStone ... using this snippet of code :-

        mDBHlpr.insertUser("Fred",
                "Flintsone",
                "1 The Caves, Bedrock",
                "01 2345 6789",
                email_for_testing,
                "fredflintsone"
        );

resulting in :-