浅谈Android Content Provider的使用

public class PersonProvider extends ContentProvider {// Content Provider需要继承自ContentProvider类
 // 删改查中，都有两种情况:
 // person 对整个表进行操作
 // person/id 对表中的与id对应记录进行操作
 private DBOpenHelper dbOpenHelper;
 private static final UriMatcher MATCHER = new UriMatcher(UriMatcher.NO_MATCH);// new UriMatcher(code);code即为匹配不成功时返回的值；
 private static final int PERSONS = 1;
 private static final int PERSON = 2;
 // 设置匹配项
 static {
  MATCHER.addURI("cn.wordtech.providers.personprovider", "person",PERSONS);
  MATCHER.addURI("cn.wordtech.providers.personprovider", "person/#",PERSON);// #号表示数字
 }
 // content://cn.wordtech.providers.personprovider/person
 @Override
 public boolean onCreate() {
  // 由系统调用，当ContentProvider的实例被创建出来的时候被调用，Android开机后，当第一次有应用访问ContentProvider时才创建ContentProvider；
  dbOpenHelper = new DBOpenHelper(getContext(), 1);
  return false;
 }

 // 可以供外部的应用查询数据，返回查询得到的游标对象
 @Override
 public Cursor query(Uri uri, String[] projection, String selection,
   String[] selectionArgs, String sortOrder) {
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  switch (MATCHER.match(uri)) {
  case 1:
   return db.query("person", projection, selection, selectionArgs,
     null, null, sortOrder);
  case 2:
   long rowid = ContentUris.parseId(uri);// 返回要操作的id
   String where = "personid=" + rowid;
   if (selection != null && !"".equals(selection.trim())) {
    where += "and" + selection;
   }
   return db.query("person", projection, where, selectionArgs, null,
     null, sortOrder);

  default:
   throw new IllegalArgumentException("");
  }
 }

 // 此方法用于返回目前Uri所代表的数据的MIME类型，
 // 如果操作的数据属于集合类型，则MIME字符串就以"vnd.android.cursor.dir"开头
 // 如果操作的数据属于非集合类型，则MIME字符串就以"vnd.android.cursor.item"开头
 @Override
 public String getType(Uri uri) {
  switch (MATCHER.match(uri)) {
  case 1:
   return "vnd.android.cursor.dir/person";
  case 2:
   return "vnd.android.cursor.item/person";
  default:
   throw new IllegalArgumentException("");
  }
 }

 // 此方法需要返回操作记录对应的Uri
 @Override
 public Uri insert(Uri uri, ContentValues values) {
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  switch (MATCHER.match(uri)) {
  case 1:
   long rowid = db.insert("person", "", values);// 返回行号?主键值
   // Uri insertUri = Uri
   // .parse("content://com.sqlite.PersonProvider/person/"
   // + rowid);
   Uri insertUri = ContentUris.withAppendedId(uri, rowid);
   return insertUri;
  default:
   throw new IllegalArgumentException("this is Unknow Uri:" + uri);
  }

 }

 // 返回受影响的行数
 @Override
 public int delete(Uri uri, String selection, String[] selectionArgs) {
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  int num = 0;
  switch (MATCHER.match(uri)) {
  case 1:
   num = db.delete("person", selection, selectionArgs);// 清空整个表
   break;
  case 2:
   long rowid = ContentUris.parseId(uri);// 返回要操作的id
   String where = "personid=" + rowid;
   if (selection != null && !"".equals(selection.trim())) {
    where += "and" + selection;
   }
   num = db.delete("person", where, selectionArgs);
   break;
  default:
   throw new IllegalArgumentException("");
  }
  return num;
 }

 @Override // 返回受影响的行数
 public int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {
  SQLiteDatabase db = dbOpenHelper.getWritableDatabase();
  int num = 0;
  switch (MATCHER.match(uri)) {
  case 1:
   num = db.update("person", values, selection, selectionArgs);
   break;
  case 2:
   long rowid = ContentUris.parseId(uri);// 返回要操作的id
   String where = "personid=" + rowid;
   if (selection != null && !"".equals(selection.trim())) {
    where += "and" + selection;
   }
   num = db.update("person", values, where, selectionArgs);
   break;
  default:
   throw new IllegalArgumentException("");
  }
  return num;
 }
} 

public class AccessContentProviderTest extends AndroidTestCase {
 public void testinsert() {
  Uri uri = Uri.parse("content://cn.wordtech.providers.personprovider/person");// 根据标识名得到内容提供者
  ContentResolver cr = this.getContext().getContentResolver(); // This class provides applications access to the content model
  ContentValues values = new ContentValues();
  values.put("name", "Livingstone");
  values.put("phone", "110");
  values.put("amount", "1111111111");
  cr.insert(uri, values);// 在cr的内部会调用内容提供者的值；
 }

 public void testdelete() {
  Uri uri = Uri.parse("content://cn.wordtech.providers.personprovider/person/1");// 根据标识名得到内容提供者
  ContentResolver cr = this.getContext().getContentResolver();
  cr.delete(uri, null, null);
 }

 public void testupdate() {
  Uri uri = Uri.parse("content://cn.wordtech.providers.personprovider/person/2");// 根据标识名得到内容提供者
  ContentResolver cr = this.getContext().getContentResolver();
  ContentValues values = new ContentValues();
  values.put("name", "Livingstone11");
  cr.update(uri, values, null, null);
 }

 public void testquery() {
  Uri uri = Uri.parse("content://cn.wordtech.providers.personprovider/person");// 根据标识名得到内容提供者
  ContentResolver cr = this.getContext().getContentResolver();
  Cursor cursor = cr.query(uri, null, null, null, "personid asc");
  while (cursor.moveToNext()) {
   String name = cursor.getString(cursor.getColumnIndex("name"));
   Log.i("Name", name);
  }
 }
}