android studio SQLite Database小例

SQLiteDatabase 是一个可以进行增(Create)、查(Retrieve)、改(Update)、删(Delete)数据,即 CRUD 操作的类。
下面教程将向你展示如何使用SQLiteDatabase在Android中实现CRUD操作。

工具使用:
Android studio 1.1.0

在这个教程中,我们将创建一个app,允许对一个student表进行增查改删的数据操作。
很容易吗?是的,如果你知道怎样做的话 :)

android Studio SQLite Database Example

这个student表将用于存储学生的详细数据,为了简单,只创建3个域,如下图:

2.实现第一个页面布局activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Add" android:id="@+id/btnAdd" android:layout_alignParentBottom="true" android:layout_alignParentLeft="true" <ListView android:id="@android:id/list" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_above="@+id/btnAdd" <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="List All" android:id="@+id/btnGetAll" android:layout_alignParentBottom="true" android:layout_toRightOf="@+id/btnAdd"/> </RelativeLayout>

你需要修改ListView的id为 android:id="@+id/listView" 如果你选择继承ListActivity在你的Activity类,否则将会出错;content必须有一个ListView,它的id的属性是‘ android.R.id.list

3.创建另一个activity,StudentDetail.java,其布局为第二个页面activity_student_detail.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="cn.cfanr.sqlitedemo.StudentDetail">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Name"
        android:id="@+id/tvName"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="30dp" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Email"
        android:id="@+id/tvEmail"
        android:layout_below="@id/tvName"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="30dp" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Age"
        android:id="@+id/tvAge"
        android:layout_below="@id/tvEmail"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="30dp" />
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/etName"
        android:inputType="textPersonName"
        android:ems="10"
        android:layout_above="@id/tvEmail"
        android:layout_toRightOf="@id/tvName"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/etEmail"
        android:layout_toRightOf="@id/tvEmail"
        android:inputType="textEmailAddress"
        android:ems="10"
        android:layout_above="@id/tvAge"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/etAge"
        android:inputType="number"
        android:ems="10"
        android:layout_alignBottom="@id/tvAge"
        android:layout_alignLeft="@id/etEmail"
        android:layout_alignStart="@id/etEmail"
        android:layout_alignRight="@id/etEmail"
        android:layout_alignEnd="@id/etEmail"
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btnClose"
        android:text="Close"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btnSave"
        android:text="Save"
        android:layout_alignParentBottom="true"
        android:layout_toLeftOf="@id/btnClose"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btnDelete"
        android:text="Delete"
        android:layout_alignParentBottom="true"
        android:layout_toLeftOf="@id/btnSave"/>
</RelativeLayout>

4.当用户点击ListView的item时展示学生的详细信息的activity,所以我们需要一个特殊的id来检索学生的详细信息,并且这个id必须来自ListView,可以通过两个方法实现:

  • 最简单的方法,可以放id和name进listview的item中,展示给用户(不好的UI设计),当用户点击选中item时,将检索的记录传递到StudentDetail.java的activity。
  • 创建一个layout作为listview的item,通过item中包含学生的id(不过设置成隐藏)来检索学生的详细信息;
  • 采用第二种方法,创建一个新的layout,view_student_entry.xml,代码如下:

    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical" android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/student_Id"
            android:visibility="gone"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:paddingLeft="6dip"
            android:paddingTop="6dip"
            android:textSize="22sp"
            android:textStyle="bold"/>
    </LinearLayout>
    1.创建Student类

    package cn.cfanr.sqlitedemo;
     * Created by ifanr on 2015/3/29.
    public class Student {
        public static final String TABLE="Student";
        //表的各域名
        public static final String KEY_ID="id";
        public static final String KEY_name="name";
        public static final String KEY_email="email";
        public static final String KEY_age="age";
        public int student_ID;
        public String name;
        public String email;
        public int age;
    

    2.为了创建表,需要使用到SQLiteDatabase类(实现CRUD操作)和SQLiteOpenHelper(用于数据库的创建和版本管理),下面先创建一个DBHelper类

    package cn.cfanr.sqlitedemo;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.content.Context;
     * Created by ifanr on 2015/3/29.
    public class DBHelper extends SQLiteOpenHelper {
        //数据库版本号
        private static final int DATABASE_VERSION=4;
        //数据库名称
        private static final String DATABASE_NAME="crud.db";
        public DBHelper(Context context){
            super(context,DATABASE_NAME,null,DATABASE_VERSION);
        @Override
        public void onCreate(SQLiteDatabase db) {
            //创建数据表
            String CREATE_TABLE_STUDENT="CREATE TABLE "+ Student.TABLE+"("
                    +Student.KEY_ID+" INTEGER PRIMARY KEY AUTOINCREMENT ,"
                    +Student.KEY_name+" TEXT, "
                    +Student.KEY_age+" INTEGER, "
                    +Student.KEY_email+" TEXT)";
            db.execSQL(CREATE_TABLE_STUDENT);
        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            //如果旧表存在,删除,所以数据将会消失
            db.execSQL("DROP TABLE IF EXISTS "+ Student.TABLE);
            //再次创建表
            onCreate(db);
    

    3.新建StudentRepo类,编写CRUD函数。

    package cn.cfanr.sqlitedemo;
    import android.content.ContentValues;
    import android.content.Context;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import java.util.ArrayList;
    import java.util.HashMap;
     * Created by ifanr on 2015/3/29.
    public class StudentRepo {
        private DBHelper dbHelper;
        public StudentRepo(Context context){
            dbHelper=new DBHelper(context);
        public int insert(Student student){
            //打开连接,写入数据
            SQLiteDatabase db=dbHelper.getWritableDatabase();
            ContentValues values=new ContentValues();
            values.put(Student.KEY_age,student.age);
            values.put(Student.KEY_email,student.email);
            values.put(Student.KEY_name,student.name);
            long student_Id=db.insert(Student.TABLE,null,values);
            db.close();
            return (int)student_Id;
        public void delete(int student_Id){
            SQLiteDatabase db=dbHelper.getWritableDatabase();
            db.delete(Student.TABLE,Student.KEY_ID+"=?", new String[]{String.valueOf(student_Id)});
            db.close();
        public void update(Student student){
            SQLiteDatabase db=dbHelper.getWritableDatabase();
            ContentValues values=new ContentValues();
            values.put(Student.KEY_age,student.age);
            values.put(Student.KEY_email,student.email);
            values.put(Student.KEY_name,student.name);
            db.update(Student.TABLE,values,Student.KEY_ID+"=?",new String[] { String.valueOf(student.student_ID) });
            db.close();
        public ArrayList<HashMap<String, String>> getStudentList(){
            SQLiteDatabase db=dbHelper.getReadableDatabase();
            String selectQuery="SELECT "+
                    Student.KEY_ID+","+
                    Student.KEY_name+","+
                    Student.KEY_email+","+
                    Student.KEY_age+" FROM "+Student.TABLE;
            ArrayList<HashMap<String,String>> studentList=new ArrayList<HashMap<String, String>>();
            Cursor cursor=db.rawQuery(selectQuery,null);
            if(cursor.moveToFirst()){
                    HashMap<String,String> student=new HashMap<String,String>();
                    student.put("id",cursor.getString(cursor.getColumnIndex(Student.KEY_ID)));
                    student.put("name",cursor.getString(cursor.getColumnIndex(Student.KEY_name)));
                    studentList.add(student);
                }while(cursor.moveToNext());
            cursor.close();
            db.close();
            return studentList;
        public Student getStudentById(int Id){
            SQLiteDatabase db=dbHelper.getReadableDatabase();
            String selectQuery="SELECT "+
                    Student.KEY_ID + "," +
                    Student.KEY_name + "," +
                    Student.KEY_email + "," +
                    Student.KEY_age +
                    " FROM " + Student.TABLE
                    + " WHERE " +
                    Student.KEY_ID + "=?";
            int iCount=0;
            Student student=new Student();
            Cursor cursor=db.rawQuery(selectQuery,new String[]{String.valueOf(Id)});
            if(cursor.moveToFirst()){
                    student.student_ID =cursor.getInt(cursor.getColumnIndex(Student.KEY_ID));
                    student.name =cursor.getString(cursor.getColumnIndex(Student.KEY_name));
                    student.email  =cursor.getString(cursor.getColumnIndex(Student.KEY_email));
                    student.age =cursor.getInt(cursor.getColumnIndex(Student.KEY_age));
                }while(cursor.moveToNext());
            cursor.close();
            db.close();
            return student;
    

    4.用户点击item,进入的详细页面StudentDetail

    package cn.cfanr.sqlitedemo;
    import android.content.Intent;
    import android.support.v7.app.ActionBarActivity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.Toast;
    public class StudentDetail extends ActionBarActivity implements View.OnClickListener {
        private Button btnSave,btnDelete;
        private Button btnClose;
        private EditText etName;
        private EditText etEmail;
        private EditText etAge;
        private int _student_id=0;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_student_detail);
            btnSave = (Button) findViewById(R.id.btnSave);
            btnDelete = (Button) findViewById(R.id.btnDelete);
            btnClose = (Button) findViewById(R.id.btnClose);
            etName = (EditText) findViewById(R.id.etName);
            etEmail = (EditText) findViewById(R.id.etEmail);
            etAge = (EditText) findViewById(R.id.etAge);
            btnSave.setOnClickListener(this);
            btnDelete.setOnClickListener(this);
            btnClose.setOnClickListener(this);
            _student_id =0;
            Intent intent = getIntent();
            _student_id =intent.getIntExtra("student_Id", 0);
            StudentRepo repo = new StudentRepo(this);
            Student student = new Student();
            student = repo.getStudentById(_student_id);
            etAge.setText(String.valueOf(student.age));
            etName.setText(student.name);
            etEmail.setText(student.email);
        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.menu_student_detail, menu);
            return true;
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
            //noinspection SimplifiableIfStatement
            if (id == R.id.action_settings) {
                return true;
            return super.onOptionsItemSelected(item);
        @Override
        public void onClick(View v) {
            if(v==findViewById(R.id.btnSave)){
                StudentRepo repo=new StudentRepo(this);
                Student student=new Student();
                student.age=Integer.parseInt(etAge.getText().toString());
                student.email=etEmail.getText().toString();
                student.name=etName.getText().toString();
                student.student_ID=_student_id;
                if(_student_id==0){
                    _student_id=repo.insert(student);
                    Toast.makeText(this,"New Student Insert",Toast.LENGTH_SHORT).show();
                }else{
                    repo.update(student);
                    Toast.makeText(this,"Student Record updated",Toast.LENGTH_SHORT).show();
            }else if (v== findViewById(R.id.btnDelete)){
                StudentRepo repo = new StudentRepo(this);
                repo.delete(_student_id);
                Toast.makeText(this, "Student Record Deleted", Toast.LENGTH_SHORT);
                finish();
            }else if (v== findViewById(R.id.btnClose)){
                finish();
    

    5.在MainActivity实现获取学生列表和跳转到StudentDetail页面

    package cn.cfanr.sqlitedemo;
    import android.app.ListActivity;
    import android.content.Intent;
    import android.support.v7.app.ActionBarActivity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.AdapterView;
    import android.widget.Button;
    import android.widget.ListAdapter;
    import android.widget.ListView;
    import android.widget.SimpleAdapter;
    import android.widget.TextView;
    import android.widget.Toast;
    import java.util.ArrayList;
    import java.util.HashMap;
    public class MainActivity extends ListActivity implements android.view.View.OnClickListener {
        private Button btnAdd,btnGetAll;
        private TextView student_Id;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            btnAdd = (Button) findViewById(R.id.btnAdd);
            btnAdd.setOnClickListener(this);
            btnGetAll = (Button) findViewById(R.id.btnGetAll);
            btnGetAll.setOnClickListener(this);
        @Override
        public void onClick(View v) {
            if (v== findViewById(R.id.btnAdd)){
                Intent intent = new Intent(this,StudentDetail.class);
                intent.putExtra("student_Id",0);
                startActivity(intent);
            }else {
                StudentRepo repo = new StudentRepo(this);
                ArrayList<HashMap<String, String>> studentList =  repo.getStudentList();
                if(studentList.size()!=0) {
                    ListView lv = getListView();
                    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                        @Override
                        public void onItemClick(AdapterView<?> parent, View view,int position, long id) {
                            student_Id = (TextView) view.findViewById(R.id.student_Id);
                            String studentId = student_Id.getText().toString();
                            Intent objIndent = new Intent(getApplicationContext(),StudentDetail.class);
                            objIndent.putExtra("student_Id", Integer.parseInt( studentId));
                            startActivity(objIndent);
                    ListAdapter adapter = new SimpleAdapter( MainActivity.this,studentList, R.layout.view_student_entry, new String[] { "id","name"}, new int[] {R.id.student_Id, R.id.student_name});
                    setListAdapter(adapter);
                }else{
                    Toast.makeText(this, "No student!", Toast.LENGTH_SHORT).show();
        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.menu_main, menu);
            return true;
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
            //noinspection SimplifiableIfStatement
            if (id == R.id.action_settings) {
                return true;
            return super.onOptionsItemSelected(item);
    

    6.运行结果如下: