【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"> <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>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); } @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()){ 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; @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：
学生列表(添加数据后，原来为空)
学生详细信息页面.png
参考http://instinctcoder.com/android-studio-sqlite-database-example/
另外，SQLite的详细资料，Android中SQLite应用详解
文／cfanr（简书作者）
原文链接：http://www.jianshu.com/p/ee08f75b407c
著作权归作者所有，转载请联系作者获得授权，并标注“简书作者”。
原文链接：http://www.jianshu.com/p/ee08f75b407c
著作权归作者所有，转载请联系作者获得授权，并标注“简书作者”。
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