Android数据持久化之ContentProvider机制详解

<!-- 设置类名和授权 multiprocess属性是数据的同步性（同一时间可能有多个程序访问该内容提供器）-->
<provider
  android:name="ContentProviderClass"
  android:multiprocess="true"
  android:authorities="com.example.data_contentprovider.ContentProviderClass" >
</provider>

//acquire the Uri of ContentProvider
getIntent().setData(Uri.parse("content://com.example.data_contentprovider.ContentProviderClass"));
Uri uri = getIntent().getData();

package com.example.data_contentprovider;
import com.example.data_contentprovider.DB.DBHelper;
import android.net.Uri;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
public class ContentProviderClass extends ContentProvider {
  DBHelper dataBaseHelper; // 定义DataBaseHelper类变量dataBaseHelper
  // 实现ContentProvider的onCreate方法
  @Override
  public boolean onCreate() {
    // TODO Auto-generated method stub
    dataBaseHelper = new DBHelper(getContext());
    return true;
  }
  @Override
  public Uri insert(Uri uri, ContentValues values) {
    // TODO Auto-generated method stub
    SQLiteDatabase db = dataBaseHelper.getWritableDatabase();
    db.insert("test", null, values);
    return null;
  }
  @Override
  public Cursor query(Uri uri, String[] projection, String selection,
      String[] selectionArgs, String sortOrder) {
    // TODO Auto-generated method stub
    SQLiteDatabase db = dataBaseHelper.getReadableDatabase();
    SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
    queryBuilder.setTables("test");
    Cursor cursor = queryBuilder.query(db, projection, selection,
        selectionArgs, null, null, null);
    return cursor;
  }
  @Override
  public int delete(Uri uri, String selection, String[] selectionArgs) {
    // TODO Auto-generated method stub
    return 0;
  }
  @Override
  public String getType(Uri uri) {
    // TODO Auto-generated method stub
    return null;
  }
  @Override
  public int update(Uri uri, ContentValues values, String selection,
      String[] selectionArgs) {
    // TODO Auto-generated method stub
    return 0;
  }
}

<!-- 设置类名和授权 multiprocess属性是数据的同步性（同一时间可能有多个程序访问该内容提供器）-->
<provider
  android:name="ContentProviderClass"
  android:multiprocess="true"
  android:authorities="com.example.data_contentprovider.ContentProviderClass" >
</provider>

package com.example.data_contentprovider.DB;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.provider.BaseColumns;
public class DBHelper extends SQLiteOpenHelper {
  // 建立test.db数据库
  public DBHelper(Context context) {
    super(context, "test.db", null, 1);
  }
  // 建立test表
  @Override
  public void onCreate(SQLiteDatabase db) {
    db.execSQL("create table test (" + BaseColumns._ID
        + "integer primary key," + "name text," + "description text"
        + ");");
  }
  // 更新新版本
  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS test");
    onCreate(db);
  }
}

package com.example.data_contentprovider;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class ContentProviderActivity extends Activity {
  String [] from = {"column00","column01","column02"};
  @SuppressWarnings("deprecation")
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    //acquire the Uri of ContentProvider
    getIntent().setData(Uri.parse("content://com.example.data_contentprovider.ContentProviderClass"));
    Uri uri = getIntent().getData();
    //create some data to test
    ContentValues values = new ContentValues();
    values.put("name", "marry");
    values.put("description", "123456");
    getContentResolver().insert(uri, values); //获取ContentResolver对象(在应用程序B中，通过ContentResolver获取程序A的ContentProvider中的数据。)
    values.put("name", "hello");
    values.put("description", "654321");
    getContentResolver().insert(uri, values);
    //search db all colum,cursor point to first colum of result
    Cursor cursor = managedQuery(uri, null, null, null, null);
    cursor.moveToFirst();
    //set ArrayList,view more field table
    ArrayList<Map<String,Object>> data = new ArrayList<Map<String,Object>>();
    Map<String, Object> item;
    //from db read data and save to ArrayList data container
    for (int i = 0; i < cursor.getCount(); i++) {
      item = new HashMap<String, Object>();
      item.put("column00", cursor.getString(0));
      item.put("column01", cursor.getString(1));
      item.put("column02", cursor.getString(2));
      data.add(item);
      cursor.moveToNext();
    }
    cursor.close();
    //ArrayList container data save to listView
    ListView listView = new ListView(this);
    SimpleAdapter adapter = new SimpleAdapter(this, data, R.layout.activity_content_provider, from, new int[]{R.id.text1,R.id.text2,R.id.text3});
    listView.setAdapter(adapter);
    setContentView(listView);
  }
}