Android学习（十） SQLite 基于SQLiteOpenHelper的操作方式

main.xml

<LinearLayout 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:orientation="vertical"    tools:context=".MainActivity" >    <Button        android:id="@+id/button1"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="插入数据" />    <Button        android:id="@+id/button2"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="读取数据" />    <Button        android:id="@+id/button3"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="修改数据" />    <Button        android:id="@+id/button4"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="删除数据" /></LinearLayout>

DBOpenHelper.java

package com.example.sqlitedemo3;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBOpenHelper extends SQLiteOpenHelper{    //实例化时，指定创建数据库的名称    public DBOpenHelper(Context context, String name) {        super(context, name, null, 1);    }    @Override  //当第一次创建数据库时调用，系统自动调用，只执行一次    public void onCreate(SQLiteDatabase db) {        //第一次执行时，创建tb_user表        db.execSQL("create table if not exists tb_user(id integer primary key autoincrement,name text not null,age integer not null,sex text not null)");    }    @Override  //当数据库版本发生改变时调用，系统自动调用    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {            }}

main.java

package com.example.sqlitedemo3;import android.os.Bundle;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.Toast;public class MainActivity extends Activity {    Button btnAdd;    Button btnQuery;    Button btnUpdate;    Button btnDelete;    SQLiteDatabase db;    DBOpenHelper helper;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //创建DBOpenHelper对象，第一个参数为调用的activity，第二个参数为数据库的名称        helper = new DBOpenHelper(MainActivity.this, "user.db");                btnAdd = (Button) findViewById(R.id.button1);        btnQuery = (Button) findViewById(R.id.button2);        btnUpdate = (Button) findViewById(R.id.button3);        btnDelete = (Button) findViewById(R.id.button4);        btnAdd.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                                //只是可写的数据库对象                db = helper.getWritableDatabase();                                ContentValues values = new ContentValues();                values.put("name", "李四");                values.put("age", 20);                values.put("sex", "女");                                db.insert("tb_user", null, values);                values.clear();                                values.put("name", "王五");                values.put("age", 22);                values.put("sex", "男");                                db.insert("tb_user", null, values);                Toast.makeText(MainActivity.this, "添加成功", 1).show();                                db.close();            }        });        btnQuery.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                //只是可写的数据库对象                db = helper.getReadableDatabase();                //其他方法和前面没有区别                Cursor cur = db.query("tb_user", new String[]{"id","name","age","sex"}, null, null, null, null, null);                while(cur.moveToNext()){                    int id = cur.getInt(0);                    String name = cur.getString(cur.getColumnIndex("name"));                    int age = cur.getInt(cur.getColumnIndex("age"));                    String sex = cur.getString(cur.getColumnIndex("sex"));                                        Log.i("stuinfo",id + ","+ name + "," + age + "," + sex);                }                cur.close();                db.close();            }        });        btnUpdate.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                //修改数据                db = helper.getWritableDatabase();                ContentValues values = new ContentValues();                values.put("name", "张三丰");                int result = db.update("tb_user", values, "id=?", new String[]{"1"});                if(result > 0)                    Toast.makeText(MainActivity.this, "修改成功", 1).show();                else                    Toast.makeText(MainActivity.this, "修改失败", 1).show();                db.close();            }        });        btnDelete.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View v) {                db = helper.getWritableDatabase();                //删除数据                int result = db.delete("tb_user", "id=?", new String[]{"1"});                if(result > 0)                    Toast.makeText(MainActivity.this, "删除成功", 1).show();                else                    Toast.makeText(MainActivity.this, "删除失败", 1).show();                db.close();            }        });    }}

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