如何在Android中将数据更新到SQLite数据库？

我们已经看到了如何在Android中创建数据并将其添加到SQLite数据库，以及如何在Android中从SQLite数据库读取数据。我们执行了不同的SQL查询，以将数据读取和写入SQLite数据库。在本文中，我们将研究如何在Android中将数据更新到SQLite数据库。

我们将在本文中构建什么?

我们将构建一个简单的应用程序，已在其中添加和读取数据。现在，我们将简单地在新活动中更新数据，然后我们就可以查看更新后的数据。下面提供了一个示例视频，以使您对本文中的工作有个大概的了解。注意，我们将使用Java语言实现该项目。

分步实施

第1步：创建新活动以更新我们的课程

由于我们要更新课程，因此在此过程中，我们将创建一个新活动，在该活动中我们将能够在SQLite数据库中更新我们的课程。要创建一个新的活动，我们必须导航到应用程序> Java >您的应用程序的包名称>右键单击包名称>新建>空活动，并将您的活动命名为UpdateCourseActivity并创建新的活动。确保选择空活动。

步骤2：使用activity_update_course.xml文件

导航到应用程序> res>布局> activity_update_course.xml，然后将以下代码添加到其中。

步骤3：更新我们的DBHandler类

导航到应用程序> Java >应用程序的程序包名称> DBHandler，然后将以下代码添加到其中。在这种情况下，我们只需要创建一个新方法来更新我们的课程即可。

Java

// below is the method for updating our courses
public void updateCourse(String originalCourseName, String courseName, String courseDescription,
                             String courseTracks, String courseDuration) {
          
        // calling a method to get writable database.
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
          
        // on below line we are passing all values
        // along with its key and value pair.
        values.put(NAME_COL, courseName);
        values.put(DURATION_COL, courseDuration);
        values.put(DESCRIPTION_COL, courseDescription);
        values.put(TRACKS_COL, courseTracks);
          
        // on below line we are calling a update method to update our database and passing our values.
        // and we are comparing it with name of our course which is stored in original name variable.
        db.update(TABLE_NAME, values, "name=?", new String[]{originalCourseName});
        db.close();
}

下面是DBHandler的更新代码。 Java文件 添加以上代码段后。

Java

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;
  
public class DBHandler extends SQLiteOpenHelper {
  
    // creating a constant variables for our database.
    // below variable is for our database name.
    private static final String DB_NAME = "coursedb";
  
    // below int is our database version
    private static final int DB_VERSION = 1;
  
    // below variable is for our table name.
    private static final String TABLE_NAME = "mycourses";
  
    // below variable is for our id column.
    private static final String ID_COL = "id";
  
    // below variable is for our course name column
    private static final String NAME_COL = "name";
  
    // below variable id for our course duration column.
    private static final String DURATION_COL = "duration";
  
    // below variable for our course description column.
    private static final String DESCRIPTION_COL = "description";
  
    // below variable is for our course tracks column.
    private static final String TRACKS_COL = "tracks";
  
    // creating a constructor for our database handler.
    public DBHandler(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }
  
    // below method is for creating a database by running a sqlite query
    @Override
    public void onCreate(SQLiteDatabase db) {
        // on below line we are creating
        // an sqlite query and we are
        // setting our column names
        // along with their data types.
        String query = "CREATE TABLE " + TABLE_NAME + " ("
                + ID_COL + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                + NAME_COL + " TEXT,"
                + DURATION_COL + " TEXT,"
                + DESCRIPTION_COL + " TEXT,"
                + TRACKS_COL + " TEXT)";
  
        // at last we are calling a exec sql
        // method to execute above sql query
        db.execSQL(query);
    }
  
    // this method is use to add new course to our sqlite database.
    public void addNewCourse(String courseName, String courseDuration, String courseDescription, String courseTracks) {
  
        // on below line we are creating a variable for
        // our sqlite database and calling writable method
        // as we are writing data in our database.
        SQLiteDatabase db = this.getWritableDatabase();
  
        // on below line we are creating a
        // variable for content values.
        ContentValues values = new ContentValues();
  
        // on below line we are passing all values
        // along with its key and value pair.
        values.put(NAME_COL, courseName);
        values.put(DURATION_COL, courseDuration);
        values.put(DESCRIPTION_COL, courseDescription);
        values.put(TRACKS_COL, courseTracks);
  
        // after adding all values we are passing
        // content values to our table.
        db.insert(TABLE_NAME, null, values);
  
        // at last we are closing our
        // database after adding database.
        db.close();
    }
  
    // we have created a new method for reading all the courses.
    public ArrayList readCourses() {
        // on below line we are creating a
        // database for reading our database.
        SQLiteDatabase db = this.getReadableDatabase();
  
        // on below line we are creating a cursor with query to read data from database.
        Cursor cursorCourses = db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
  
        // on below line we are creating a new array list.
        ArrayList courseModalArrayList = new ArrayList<>();
  
        // moving our cursor to first position.
        if (cursorCourses.moveToFirst()) {
            do {
                // on below line we are adding the data from cursor to our array list.
                courseModalArrayList.add(new CourseModal(cursorCourses.getString(1),
                        cursorCourses.getString(4),
                        cursorCourses.getString(2),
                        cursorCourses.getString(3)));
            } while (cursorCourses.moveToNext());
            // moving our cursor to next.
        }
        // at last closing our cursor
        // and returning our array list.
        cursorCourses.close();
        return courseModalArrayList;
    }
  
    // below is the method for updating our courses
    public void updateCourse(String originalCourseName, String courseName, String courseDescription,
                             String courseTracks, String courseDuration) {
  
        // calling a method to get writable database.
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
  
        // on below line we are passing all values
        // along with its key and value pair.
        values.put(NAME_COL, courseName);
        values.put(DURATION_COL, courseDuration);
        values.put(DESCRIPTION_COL, courseDescription);
        values.put(TRACKS_COL, courseTracks);
  
        // on below line we are calling a update method to update our database and passing our values.
        // and we are comparing it with name of our course which is stored in original name variable.
        db.update(TABLE_NAME, values, "name=?", new String[]{originalCourseName});
        db.close();
    }
  
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // this method is called to check if the table exists already.
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }
}

步骤4：更新我们的CourseRVAdapter。 Java类

我们将开始一项新的活动，以更新我们的课程。我们必须在单击侦听器上添加RecycleView的项目。要将onClickListener()添加到我们的回收站视图项目，请导航至应用程序> Java >您的应用程序的程序包名称> CourseRVAdapter类，并只需为我们的RecyclerView项目添加一个onClickListener () 。将以下代码添加到您的适配器类。

Java

// below line is to add on click listener for our recycler view item.
holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                
                // on below line we are calling an intent.
                Intent i = new Intent(context, UpdateCourseActivity.class);
  
                // below we are passing all our values.
                i.putExtra("name", modal.getCourseName());
                i.putExtra("description", modal.getCourseDescription());
                i.putExtra("duration", modal.getCourseDuration());
                i.putExtra("tracks", modal.getCourseTracks());
  
                // starting our activity.
                context.startActivity(i);
        }
});

下面是CourseRVAdapter的更新代码。 Java文件 添加以上代码段后。

Java

import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
  
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
  
import java.util.ArrayList;
  
public class CourseRVAdapter extends RecyclerView.Adapter {
  
    // variable for our array list and context
    private ArrayList courseModalArrayList;
    private Context context;
  
    // constructor
    public CourseRVAdapter(ArrayList courseModalArrayList, Context context) {
        this.courseModalArrayList = courseModalArrayList;
        this.context = context;
    }
  
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // on below line we are inflating our layout
        // file for our recycler view items.
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.course_rv_item, parent, false);
        return new ViewHolder(view);
    }
  
    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        // on below line we are setting data
        // to our views of recycler view item.
        CourseModal modal = courseModalArrayList.get(position);
        holder.courseNameTV.setText(modal.getCourseName());
        holder.courseDescTV.setText(modal.getCourseDescription());
        holder.courseDurationTV.setText(modal.getCourseDuration());
        holder.courseTracksTV.setText(modal.getCourseTracks());
  
        // below line is to add on click listener for our recycler view item.
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                  
                // on below line we are calling an intent.
                Intent i = new Intent(context, UpdateCourseActivity.class);
  
                // below we are passing all our values.
                i.putExtra("name", modal.getCourseName());
                i.putExtra("description", modal.getCourseDescription());
                i.putExtra("duration", modal.getCourseDuration());
                i.putExtra("tracks", modal.getCourseTracks());
  
                // starting our activity.
                context.startActivity(i);
            }
        });
    }
  
    @Override
    public int getItemCount() {
        // returning the size of our array list
        return courseModalArrayList.size();
    }
  
    public class ViewHolder extends RecyclerView.ViewHolder {
  
        // creating variables for our text views.
        private TextView courseNameTV, courseDescTV, courseDurationTV, courseTracksTV;
  
        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            // initializing our text views
            courseNameTV = itemView.findViewById(R.id.idTVCourseName);
            courseDescTV = itemView.findViewById(R.id.idTVCourseDescription);
            courseDurationTV = itemView.findViewById(R.id.idTVCourseDuration);
            courseTracksTV = itemView.findViewById(R.id.idTVCourseTracks);
        }
    }
}

步骤5：使用UpdateCourseActivity。 Java文件

导航到应用程序> Java >您的应用程序包名称> UpdateCourseActivity。 Java文件，并向其中添加以下代码。在代码内部添加了注释，以更详细地了解代码。

Java

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
  
import androidx.appcompat.app.AppCompatActivity;
  
public class UpdateCourseActivity extends AppCompatActivity {
  
    // variables for our edit text, button, strings and dbhandler class.
    private EditText courseNameEdt, courseTracksEdt, courseDurationEdt, courseDescriptionEdt;
    private Button updateCourseBtn;
    private DBHandler dbHandler;
    String courseName, courseDesc, courseDuration, courseTracks;
  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_update_course);
          
        // initializing all our variables.
        courseNameEdt = findViewById(R.id.idEdtCourseName);
        courseTracksEdt = findViewById(R.id.idEdtCourseTracks);
        courseDurationEdt = findViewById(R.id.idEdtCourseDuration);
        courseDescriptionEdt = findViewById(R.id.idEdtCourseDescription);
        updateCourseBtn = findViewById(R.id.idBtnUpdateCourse);
  
        // on below line we are initialing our dbhandler class.
        dbHandler = new DBHandler(UpdateCourseActivity.this);
          
        // on below lines we are getting data which 
        // we passed in our adapter class.
        courseName = getIntent().getStringExtra("name");
        courseDesc = getIntent().getStringExtra("description");
        courseDuration = getIntent().getStringExtra("duration");
        courseTracks = getIntent().getStringExtra("tracks");
          
        // setting data to edit text 
        // of our update activity.
        courseNameEdt.setText(courseName);
        courseDescriptionEdt.setText(courseDesc);
        courseTracksEdt.setText(courseTracks);
        courseDurationEdt.setText(courseDuration);
  
        // adding on click listener to our update course button.
        updateCourseBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                  
                // inside this method we are calling an update course 
                // method and passing all our edit text values.
                dbHandler.updateCourse(courseName, courseNameEdt.getText().toString(), courseDescriptionEdt.getText().toString(), courseTracksEdt.getText().toString(), courseDurationEdt.getText().toString());
                  
                // displaying a toast message that our course has been updated.
                Toast.makeText(UpdateCourseActivity.this, "Course Updated..", Toast.LENGTH_SHORT).show();
                  
                // launching our main activity.
                Intent i = new Intent(UpdateCourseActivity.this, MainActivity.class);
                startActivity(i);
            }
        });
    }
}

现在运行您的应用程序，并查看该应用程序的输出。确保在更新数据之前将数据添加到SQLite数据库。

输出：

下面是执行更新操作后的完整项目文件结构：