之前已经介绍了android的数据存储的操作,接下来就来介绍android数据库操作,对于数据库的基本增删查改,在这里就不多说了,直接开始介绍android的sqlite数据库运用方式。
1.首先需要定义sqlite的数据库对象
private SQLiteDatabase mydatabase=null;
2.获取数据库操作指针,通过context直接获取,这种方式创建的数据库位于/data/data/{包名}/databases/,openOrCreateDatabase函数,第一个参数为需要打开或创建的数据库名称,第二个参数为模式,即存储模式,和上一篇数据存储的模式大同小异,第三个参数为cursorFactory,用于查询时实例化一个光标,可以填为null
try{
mydatabase=this.openOrCreateDatabase("mydata.db",MODE_PRIVATE, null);
}catch(Exception e){
Toast.makeText(this,e.getMessage(),Toast.LENGTH_LONG).show();
}
3.打开数据库之后就是基本的数据库的操作了,因为sql语句和其他数据库区别不大,就不详细说了,直接开始查询的介绍,对于查询数据库操作首先需要获得一个实例化光标,一种方式是在创建或打开数据库时载入工厂类,另一个就是通过rawQuery来获得实例化光标,这里主要介绍后者,示例代码如下:
public void updataview(){
Cursor cur=null;
List<String> slist=new ArrayList<String>();
String sql="select * from newtable";
try{
cur=mydatabase.rawQuery(sql,new String[]{});
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
//movenext为向下移动,到没有返回false
while(cur.moveToNext())
{
slist.add(cur.getString(0));
slist.add(cur.getString(1));
}
//记住在用完后关闭光标
cur.close();
listshow adapter=new listshow(SqlDemo.this,slist);
adapter.show();
}
在取得cur以后,可以按照自己的习惯将数据存入相应的list或者String数组中,在之后将其显示在界面上,这里一般采用动态生成的代码,定义一个布局,将动态定义的组件通过addView的方式加进去即可
public void show(){
table=(TableLayout)SqlDemo.this.findViewById(R.id.table);
table.removeAllViews();
for(int i=0;i<list.size();i=i+2){
try{
TableRow row=new TableRow(context);
TextView text=new TextView(context);
text.setText(list.get(i).toString());
text.setId(i);
TextView text1=new TextView(context);
text1.setText(list.get(i+1).toString());
text1.setId(i+1);
row.addView(text);
row.addView(text1);
table.addView(row);
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}
示例代码
.java
package com.example.ui_demo;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.SimpleCursorAdapter;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
import android.widget.Toast;
public class SqlDemo extends Activity {
private String []mysql={"读取表","删除表","创建表","插入表"};
//数据库操作
private SQLiteDatabase mydatabase=null;
private TableLayout table=null;
private ListView list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sql_demo);
//创建或打开数据库
try{
mydatabase=this.openOrCreateDatabase("mydata.db",MODE_PRIVATE, null);
}catch(Exception e){
Toast.makeText(this,e.getMessage(),Toast.LENGTH_LONG).show();
}
//table=(TableLayout)this.findViewById(R.id.table);
list=(ListView)this.findViewById(R.id.sqllist);
myadapter m=new myadapter(this);
list.setAdapter(m);
}
public void setupView(){
}
public class myadapter extends BaseAdapter{
private Context context;
public myadapter(Context context){
this.context=context;
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return mysql.length;
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View vi, ViewGroup vg) {
// TODO Auto-generated method stub
Button button=new Button(SqlDemo.this);
button.setText(mysql[position]);
button.setId(position);
buttonclick m=new buttonclick();
button.setOnClickListener(m);
return button;
}
}
public class listshow{
private List<String> list;
private Context context;
public listshow(Context context,List<String> list){
this.context=context;
this.list=list;
}
public void show(){
table=(TableLayout)SqlDemo.this.findViewById(R.id.table);
table.removeAllViews();
for(int i=0;i<list.size();i=i+2){
try{
TableRow row=new TableRow(context);
TextView text=new TextView(context);
text.setText(list.get(i).toString());
text.setId(i);
TextView text1=new TextView(context);
text1.setText(list.get(i+1).toString());
text1.setId(i+1);
row.addView(text);
row.addView(text1);
table.addView(row);
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}
}
/* public class listshow extends BaseAdapter{
private Context context;
private List<String> list;
public listshow(Context context,List<String> list){
this.list=list;
this.context=context;
//this.context.setTheme(android.R.layout.simple_expandable_list_item_2);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return list.size();
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
@Override
public View getView(int position, View vi, ViewGroup vg) {
// TODO Auto-generated method stub
TableLayout table=(TableLayout)vi.findViewById(R.id.table);
TextView text=new TextView(context);
text.setId(position);
text.setText(list.get(position).toString());
table.addView(text);
return table;
}
}*/
public class mydata {
private String id;
private String name;
public void setmydata(String id,String name){
this.id=id;
this.name=name;
}
}
public void updataview(){
Cursor cur=null;
List<String> slist=new ArrayList<String>();
String sql="select * from newtable";
try{
cur=mydatabase.rawQuery(sql,new String[]{});
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
while(cur.moveToNext())
{
slist.add(cur.getString(0));
slist.add(cur.getString(1));
}
cur.close();
listshow adapter=new listshow(SqlDemo.this,slist);
adapter.show();
}
public class buttonclick implements OnClickListener{
private int i=0;
@Override
public void onClick(View vi) {
// TODO Auto-generated method stub
if(vi.getId()==0){
//查询表
updataview();
}else if(vi.getId()==1){
//删除表
String sql="DROP TABLE"+" newtable";
try{
mydatabase.execSQL(sql);
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
updataview();
}else if(vi.getId()==2){
//不存在创建表
String create="CREATE TABLE"+" IF NOT EXISTS"+" newtable"+" (ID INTEGER,NAME TEXT)";
try{
mydatabase.execSQL(create);
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
updataview();
}else if(vi.getId()==3){
//插入表
String insert="insert into "+"newtable"+" values('"+"2"+"','"+"pengchen01"+"');";
try{
mydatabase.execSQL(insert);
}catch(Exception e){
Toast.makeText(SqlDemo.this,e.getMessage(), Toast.LENGTH_LONG).show();
}
updataview();
}
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.sql_demo, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
.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: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="com.example.ui_demo.SqlDemo" >
<TableLayout
android:id="@+id/table"
android:layout_width="wrap_content"
android:layout_height="wrap_content" >
<TableRow>
<TextView
android:id="@+id/textid"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="id" />
<TextView
android:id="@+id/textname"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="name" />
</TableRow>
</TableLayout>
<ListView
android:id="@+id/sqllist"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_marginBottom="14dp" >
</ListView>
</RelativeLayout>