原生andriod开发基础之SQLite数据库使用

layout

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="18dp"
        android:text="Num" />

    <EditText
        android:id="@+id/editText2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/editText1"
        android:layout_alignTop="@+id/textView2"
        android:ems="10" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="49dp"
        android:ems="10"
        android:inputType="textPersonName" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText1"
        android:layout_alignBottom="@+id/editText1"
        android:layout_marginRight="23dp"
        android:layout_toLeftOf="@+id/editText1"
        android:text="Name" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button4"
        android:layout_alignBottom="@+id/button4"
        android:layout_alignLeft="@+id/textView2"
        android:text="查" />

    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/editText2"
        android:layout_below="@+id/button2"
        android:layout_marginRight="35dp"
        android:layout_marginTop="27dp"
        android:text="改" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignRight="@+id/button4"
        android:layout_centerVertical="true"
        android:text="删" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button2"
        android:layout_alignBottom="@+id/button2"
        android:layout_alignLeft="@+id/button3"
        android:text="增" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button3"
        android:layout_marginLeft="20dp"
        android:layout_toRightOf="@+id/button3"
        android:text="TextView" />

</RelativeLayout>

Myhelper.java

package com.example.bd;

import android.content.Context;
import android.database.sqlite.*;

public class Myhelper extends SQLiteOpenHelper{

	public Myhelper(Context context) {
		super(context, "student.db", null, 2);
		// TODO Auto-generated constructor stub
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		// TODO Auto-generated method stub
		//初始化数据库的表结构
		String sql="create table info (name varchar(20),num varchar(20))";
		db.execSQL(sql);
		
	}

	@Override
	public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
		// TODO Auto-generated method stub
		
	}

}

mainactivity.java

package com.example.bd;

import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.*;

public class MainActivity extends Activity implements OnClickListener{
    private EditText etName;
    private EditText etNum;
    private Button badd;
    private Button bquery;
    private Button bdelete;
    private Button bupdate;
    private  TextView tv;
    private Myhelper helper;
    private StringBuffer strb;
    String name;
    String  num;
    public void init()
    {
    	
    	etName = (EditText) findViewById(R.id.editText1);
    	etNum = (EditText) findViewById(R.id.editText2);
    	badd=(Button) findViewById(R.id.button1);
    	bquery=(Button) findViewById(R.id.button3);
    	bdelete=(Button) findViewById(R.id.button2);
    	bupdate=(Button) findViewById(R.id.button4);
    	tv = (TextView) findViewById(R.id.textView3);
    	tv.setText("");
    	badd.setOnClickListener(this);
    	bquery.setOnClickListener(this);
    	bdelete.setOnClickListener(this);
    	bupdate.setOnClickListener(this);
    	helper = new Myhelper(this);
    	strb=new StringBuffer();//查询
    }
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		init();
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
	@Override
	public void onClick(View v) {
		// TODO Auto-generated method stub
       switch(v.getId()){
        case R.id.button1:
    	  name= etName.getText().toString();
    	  num = etNum.getText().toString().trim();
    	   add(name,num);
    	   break;
       case R.id.button3://查
    	   query("zhangsan1");
    	   break;
       case R.id.button2://删
    	   del("lisi");
    	   break;
       case R.id.button4://改
    	   update("zhangsan","789");
    	   break;
       default:
    	   break;
       }
	}
	public void add(String name,String num){
		SQLiteDatabase db =	helper.getWritableDatabase();
		ContentValues values = new ContentValues();
	    values.put("name",name);
	    values.put("num",num);
		db.insert("info", null, values);
		db.close();
	}
	public void query(String name){
		SQLiteDatabase db = helper.getWritableDatabase();
		String sql = "select * from info where name=? ";
		Cursor  cursor = db.rawQuery(sql,new String[]{name});
		while(cursor.moveToNext()){
			name=cursor.getString(0);
			num =cursor.getString(1);
			strb.append(name+":"+num+"\n");
		}
		if(strb.length()==0){//没有找到记录
			tv.setText("not find!");
		}else{
			tv.setText(strb.toString());
		}
		db.close();
	}
	public void update(String name,String newnum){
		SQLiteDatabase db = helper.getWritableDatabase();
		ContentValues values = new ContentValues();
		values.put("num",newnum);
		db.update("info", values,"name=?",new String[]{name});
        db.close();
	}
	public void del(String name){
		SQLiteDatabase db = helper.getWritableDatabase();
		db.delete("info","name=?",new String[]{name});
		db.close();
	}
}