自定义数据库 -- ContentProvider和ContentResolver

在android中自己通过ContentProvider创建一个上述数据表。

1. 首先通过SQLiteOpenHelper执行SQL语句，创建数据表。

	private static final String DATABASE_NAME = "simrecord.db";
private static final int DATABASE_VERSION = 1;
<p>	private static final String SIMCARD_TABLE_CREATE = "CREATE TABLE " + TABLE_NAME + //“CREATE TABLE ”后面需要加一个空格
"(_id INTEGER primary key," +
" card_id VARCHAR," +
"date VARCHAR," +
"sim_state VARCHAR," +
"sim_operator VARCHAR," +
"sim_country VARCHAR," +
"data_state VARCHAR," +
"network_type VARCHAR)";
</p>

<pre class="java" name="code">private class MyDataBaseHelper extends SQLiteOpenHelper{
//by SQLiteOpenHelper to make SQLiteDatabase
public MyDataBaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
Log.d(TAG,"MyDataBaseHelper onCreate()");
db.execSQL(SIMCARD_TABLE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
Log.d(TAG,"MyDataBaseHelper onUpgrade()");
}
}

2.然后通过继承ContentProvider类

其中onCreate()方法，通过SQLiteOpenHelper类的getWritableDatabase()方法获取数据库SQLiteDatabase类mDb，然后通过mDb对数据库进行各项操作。
覆写其中查询/删除/插入/增加方法，通过mDb对数据表进行相应的操作。

public class SimRecordProvider extends ContentProvider {
private static final String TAG ="simrecord: SimRecordProvider";
private static final String PROVIDER_NAME ="com.sec.provider.simrecord";
private static final String TABLE_NAME = "simrecord";
private
MyDataBaseHelper mDataBaseHelper;
private
SQLiteDatabase mDb;
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
Log.d(TAG," onCreate()");
mDataBaseHelper =new MyDataBaseHelper(getContext());
mDb = mDataBaseHelper.getWritableDatabase();
return true;
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
Log.d(TAG," delete()");
//Log.d(TAG," delete() where : " +selection);
mDb.delete(TABLE_NAME, selection, null);
return 0;
}
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
Log.d(TAG," getType()");
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
// TODO Auto-generated method stub
Log.d(TAG," insert()");
//Log.d(TAG," insert() values : " +values);
mDb.insert(TABLE_NAME, null, values);
return null;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] seletionArgs,
String sortOrder) {
// TODO Auto-generated method stub
Log.d(TAG," query()");
//Log.d(TAG," query() where : " +selection);
//String where = "card_id=?";
Cursor mCursor =null;
mCursor = mDb.query(TABLE_NAME, null, selection, seletionArgs, null, null, null);
return mCursor;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] seletionArgs) {
// TODO Auto-generated method stub
Log.d(TAG," update()");
//Log.d(TAG," update() where : " +selection);
mDb.update(TABLE_NAME, values, selection, seletionArgs);
return 0;
}
}

3.在AndroidManifest.xml文件中添加SimRecordProvider.java的authorities, 这样子ContentResolver才可以通过URI查找到该数据库

<provider
android:name=".SimRecordProvider"
android:authorities="com.sec.provider.simrecord"
android:exported="true">
</provider>

4.ContentResolver类其实就是提供给用户进行操作数据库的接口。

通过context.getContentResolver() 获取ContentResolver，ContentResolver类中的方法：query()/delete()/insert()/update()分别对应着ContentProvider类中的相应方法。

CONTENT_URI相当于ContentProvider类中的地址，ContentResolver通过CONTENT_URI查找到对应的ContentProvider。

private static final String CONTENT_URI ="content://com.sec.provider.simrecord";
mContentResolver = context.getContentResolver();

查询数据表中有多少条数据：

	public int queryCount (){
//Log.d(TAG," queryCount()****************Begin");
Cursor mCursor = mContentResolver.query(Uri.parse(CONTENT_URI), null, null, null, null);
if(mCursor==null){
return 0;
}
//Log.d(TAG," queryCount() mCursor = " + mCursor);
Log.d(TAG," queryCount() mCursor.getCount() = " + mCursor.getCount());
int count = mCursor.getCount();
return count;
}

插入新的卡数据：通过ContentValues类封装需要保存的数据。

	public void insertCard(String card_id, ContentValues values){
//Log.d(TAG," insertCard()****************Begin");
//Log.d(TAG," insertCard() card_id = " + card_id);
if(!isNewCard(card_id)){
Toast.makeText(mContext, "the card_id is alread exsit", Toast.LENGTH_SHORT).show();
Log.d(TAG," insertCard()**the card_id is alread exsit");
return ;
}
mContentResolver.insert(Uri.parse(CONTENT_URI), values);
Log.d(TAG," insertCard()** the card
inserted in database");
Toast.makeText(mContext, "insert card_id="+card_id, Toast.LENGTH_SHORT).show();
}

删除指定card_id的卡数据：

	public void deleteCard(String card_id){
if(card_id != null){
String where = "card_id='"+card_id+"'";
// where = '123456'
Log.d(TAG," deleteCard() where= "+where );
mContentResolver.delete(Uri.parse(CONTENT_URI), where, null);
}
}

最后

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