【SQLite】Android Studio SQLite Database小例

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android studio SQLite Database小例

Android中SQLite应用详解

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

TODO
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

表结构
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：

student表.jpg

id是主键，允许自增

页面布局
创建两个页面布局，第一个页面展示所有学生名字，如下图：

学生列表.jpg

第二个页面是学生的详细信息的页面，用户点击listview的每个item时，将会进入这个页面，如下图：

详细信息或增加数据页面

布局实现
1.新建一个SQLiteDemo的project;
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"><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:text="Add"android:id="@+id/btnAdd"android:layout_alignParentBottom="true"android:layout_alignParentLeft="true"/><ListViewandroid:id="@android:id/list"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_above="@+id/btnAdd"/><Buttonandroid: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"><TextViewandroid: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" /><TextViewandroid: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" /><TextViewandroid: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" /><EditTextandroid: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" /><EditTextandroid: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" /><EditTextandroid: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"/><Buttonandroid:layout_width="wrap_content"android:layout_height="wrap_content"android:id="@+id/btnClose"android:text="Close"android:layout_alignParentBottom="true"android:layout_alignParentRight="true"/><Buttonandroid: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"/><Buttonandroid: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"><TextViewandroid:layout_width="match_parent"android:layout_height="wrap_content"android:id="@+id/student_Id"android:visibility="gone"/><TextViewandroid:layout_width="match_parent"android:layout_height="wrap_content"android:paddingLeft="6dip"android:paddingTop="6dip"android:textSize="22sp"android:textStyle="bold"/>
</LinearLayout>

编码
1.创建Student类

package cn.cfanr.sqlitedemo;/*** Created by ifanr on 2015/3/29.*/
public class Student {//表名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";//属性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);}@Overridepublic 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);}@Overridepublic 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()){do{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()){do{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;@Overrideprotected 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);}@Overridepublic 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;}@Overridepublic 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 SimplifiableIfStatementif (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}@Overridepublic 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;@Overrideprotected 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);}@Overridepublic 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() {@Overridepublic 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();}}}@Overridepublic 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;}@Overridepublic 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 SimplifiableIfStatementif (id == R.id.action_settings) {return true;}return super.onOptionsItemSelected(item);}
}