Sqlite的使用增删改查

App.java(初始化数据库)

package com.example.testsqlite;

import com.example.db.DbHelper;

import android.app.Application;
import android.content.Context;

public class App extends Application {
    static Context mContext;
    @Override
    public void onCreate() {
        super.onCreate();
        mContext = this;
        DbHelper dbHelper = DbHelper.getInstance(this);
        dbHelper.getWritableDatabase();//启动程序的时候会检测有没有这个数据库,如果没有就会执行onCreate();

    }


    public static Context getContext() {
        return mContext;
    }

}

dbHelper.java(创建表,更新版本)

package com.example.db;

import com.example.testsqlite.App;

import android.content.Context;
import android.database.sqlite.sqliteDatabase;
import android.database.sqlite.sqliteOpenHelper;
import android.util.Log;
import android.widget.Toast;

public class DbHelper extends sqliteOpenHelper{

    private String TAG = "DbHelper";
    public static DbHelper instance;
    private final static String DB_NAME = "Test.db";
    private final static  int VERSION = 2;//版本

    private String CREATE_TEST = "CREATE TABLE TEST (Id text Not NULL,Name text,Age int,PRIMARY KEY(\"Id\") )";
    private String CREATE_TEST2 = "CREATE TABLE TEST2 (Id text,PRIMARY KEY(\"Id\") )";

    public DbHelper(Context context) {
        super(context,DB_NAME,null,VERSION);
    }

    @Override
    public void onCreate(sqliteDatabase db) {
        db.execsql(CREATE_TEST);
        db.execsql(CREATE_TEST2);
        Toast.makeText(App.getContext(),"create",Toast.LENGTH_LONG).show();

    }

    @Override
    public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
        switch (oldVersion) {
        case 1:
            db.execsql(CREATE_TEST2);
            Toast.makeText(App.getContext(),"v2",Toast.LENGTH_LONG).show();
// break; //不需要break,为了能一直往上升级数据库版本

        default:
        }

    }


    public static DbHelper getInstance(Context context) {
        if (instance == null) {
            instance = new DbHelper(context);
        }
        return instance;

    }

}

TestDao.java(增删改查)

package com.example.db;

import java.util.ArrayList;
import java.util.List;

import com.examole.bean.TestVm;
import com.example.testsqlite.App;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.sqliteDatabase;
import android.provider.Telephony.Sms.Conversations;
import android.util.Log;

public class TestDao {

    private String TAG = "TestDao";
    private DbHelper dbHelper;
    private sqliteDatabase db;
    private String TABLE_NAME = "TEST";

    public TestDao() {
        dbHelper = DbHelper.getInstance(App.getContext());
        db = dbHelper.getWritableDatabase();
    }


    private TestVm readTest(Cursor cr) {
        TestVm testVm = new TestVm();
        testVm.setId(cr.getString(cr.getColumnIndex("Id")));
        testVm.setName(cr.getString(cr.getColumnIndex("Name")));
        testVm.setAge(cr.getInt(cr.getColumnIndex("Age")));
        return testVm;

    }

    /** * 增,改 * @param testVm * @return */
    public boolean updateOrSave(TestVm testVm) {
        ContentValues cv = new ContentValues();
        cv.put("Id",testVm.getId());
        cv.put("Name",testVm.getName());
        cv.put("Age",testVm.getAge());

        boolean flag = db.update(TABLE_NAME,cv,"Id = ?",new String[]{ testVm.getId() }) > 0;//update失败的话 返回值是 0
        if (flag) {
            return true;
        } else {
            return db.insert(TABLE_NAME,cv) != -1; 
        }
    }

    /** * 查 * @return */
    public List<TestVm> getAll() {
        List<TestVm> list = new ArrayList<TestVm>();
        Cursor cr = db.rawQuery("select * from "+TABLE_NAME,null);
        while (cr.movetoNext()) {
            list.add(readTest(cr));
        }
        return list;
    }


    /** * 删 * @param testVm */
    public void delete(TestVm testVm) {
        db.delete(TABLE_NAME,"id = ?",new String[]{ testVm.getId() });
    }


    /** * 清空 */
    public void clear() {
        db.execsql("delete from "+TABLE_NAME);
    }

}

TestVm.java(Bean文件)

package com.examole.bean;

public class TestVm {
    private String Id;
    private String Name;
    private int Age;


    public String getId() {
        return Id;
    }
    public void setId(String id) {
        Id = id;
    }

    public String getName() {
        return Name;
    }
    public void setName(String name) {
        Name = name;
    }
    public int getAge() {
        return Age;
    }
    public void setAge(int age) {
        Age = age;
    }





}

MainActivity.java

package com.example.testsqlite;

import java.util.List;

import com.examole.bean.TestVm;
import com.example.db.TestDao;

import android.support.v7.app.ActionBaractivity;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity implements OnClickListener{

    EditText ed1;

    Button bt1;
    Button bt2;
    Button bt3;
    Button bt4;
    TestDao dao;
    String TAG = "MainActivity";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        dao = new TestDao();

        ed1 = (EditText) findViewById(R.id.ed_id);

        bt1 = (Button) findViewById(R.id.bt_updateorsave);
        bt1.setonClickListener(this);
        bt2 = (Button) findViewById(R.id.bt_getall);
        bt2.setonClickListener(this);
        bt3 = (Button) findViewById(R.id.bt_delete);
        bt3.setonClickListener(this);
        bt4 = (Button) findViewById(R.id.bt_clear);
        bt4.setonClickListener(this);
    }
    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        case R.id.bt_updateorsave:
            TestVm testVm = new TestVm();
            testVm.setId("222301");
            testVm.setName("tom");
            testVm.setAge(21);
            dao.updateOrSave(testVm);
            break;

        case R.id.bt_getall :
            List<TestVm> list = dao.getAll();
            String all = "";
            for (TestVm testVm2 : list) {
                all += testVm2.getId()+",";
                all += testVm2.getName()+",";
                all += testVm2.getAge()+" \n";
            }
            Log.v(TAG,all);
            break;

        case R.id.bt_delete :
            String id = ed1.getText().toString();
            TestVm testVm3 = new TestVm();
            testVm3.setId(id);
            dao.delete(testVm3);
            break;

        case R.id.bt_clear :
            dao.clear();
            break;

        }

    }


}

界面