Android中ContentProvider详解

在 Android中，对于数据的存贮，有几种方式，有文件方式，有文件式数据库方式,网络数据,Android自带了一个SQLite数据库，做嵌入开发的人对这个跨平台的本地文件数据库一定不会陌生，在Android对于数据的访问，提出了新的方式，ContentProvider方式，我们首先来看看SQLite在 Android中的使用，在Android中有最简单的使用方式，就是利Context对象的openorCreateDatabase
我们来看看一段代码：
Java代码
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

public class DBActivity extends Activity {
private SQLiteDatabase mdb = null;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initDatabase();
        setContentView(R.layout.main);
    }
    @Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated method stub
super.onCreateOptionsMenu(menu);
menu.add(1, Menu.FIRST +1, 1, "GetName");
menu.add(1, Menu.FIRST +2, 2, "Test");
return true;
}

    public boolean onOptionsItemSelected(MenuItem item) {
// TODO Auto-generated method stub
super.onOptionsItemSelected(item);
switch (item.getItemId())
{
   case Menu.FIRST+ 1:
   {
    TextView tv = (TextView)this.findViewById(R.id.view_main);
    tv.setText(this.getName());
    break;
   }
   case Menu.FIRST + 2:
   {
    this.setTitle("Del Item...");
    break;
   }
}
return true;
}

    private void initDatabase()
    {
     mdb = this.openOrCreateDatabase("dbfile", 0, null);
     String sql_create = "create table test (id int, name TEXT)";
     mdb.execSQL(sql_create);
     String sql_insert = "insert into test(id, name) values(3, 'name3')";
     mdb.execSQL(sql_insert);
    }
    private String getName()
    {
     String name = null;

     Cursor cur = mdb.rawQuery("select * from test", null);
     cur.moveToFirst();
     while (!cur.isLast())
     {
      name = name + cur.getString(1)+ "\r\n";
      cur.moveToNext();
     }
     return name;
    }
}
我们再来看看单独使用SQLiteOpenHelper方式：
先由SQLiteOpenHelper继承一个数据库操作类，其中onCreate, onUpgrade必须重载并实现，
Java代码
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
public DatabaseHelper(Context ct,String dbName)
{
super(ct,dbName,null,1);
}
public boolean insert(String insert)
{
this.getWritableDatabase().execSQL(insert);
return true;
}
public boolean update(String update)
{
this.getWritableDatabase().execSQL(update);
return true;
}
public boolean delete(String del)
{
this.getWritableDatabase().execSQL(del);
return true;
}
public Cursor query(String query)
{
Cursor cur = this.getReadableDatabase().rawQuery(query, null);
return cur;
}
}

再创建一个使用者（消费者）
Java代码
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

public class DBActivity extends Activity {
private SQLiteDatabase mdb = null;
private DatabaseHelper helper = null;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initDatabase();
        setContentView(R.layout.main);
    }
    @Override
public boolean onCreateOptionsMenu(Menu menu) {
// TODO Auto-generated meth

补充：移动开发 , Android ,