Realm数据库使用教程（三）：查询数据

Realm数据库使用教程（二）：增加数据

查询数据

• 同步操作：findAll查询

 /**                 * 注意：RealmResults虽然实现了List接口，不过有很多方法是不能用的。                 * 比如add、addAll、remove、clear等，                 * 调用后会直接抛异常。                 * 因为它们都被标记为@Deprecated了。                 */                RealmResults<Men> menList = mRealm.where(Men.class)                        .findAll();                for (int i = 0; i < menList.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            menList.get(i).getName() + "----" + menList.get(i).getAge());                }

• 异步操作：findAllAsync查询(isLoaded)

  RealmResults<Men> menList1 = mRealm.where(Men.class)                        .findAllAsync();                menList1.load();//等到查询完成。这将阻塞该线程，使查询再次同步                if (menList1 != null && menList1.isLoaded()) {                    for (int i = 0; i < menList1.size(); i++) {                        Log.d("huangxiaoguo", "huangixoaguo==>" +                                menList1.get(i).getName() + "----" + menList1.get(i).getAge());                    }                }

• 异步操作：findAllAsync查询(RealmChangeListener)

menList2 = mRealm.where(Men.class)                        .findAllAsync();                menList2.addChangeListener(callback);

    /**     * 异步操作的监听     */    private OrderedRealmCollectionChangeListener<RealmResults<Men>> callback = new OrderedRealmCollectionChangeListener<RealmResults<Men>>() {        @Override        public void onChange(RealmResults<Men> collection, OrderedCollectionChangeSet changeSet) {            if (changeSet == null) {                //第一次异步返回一个空的变更集。                for (int i = 0; i < collection.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            collection.get(i).getName() + "----" + collection.get(i).getAge());                }            } else {                //每次RealmResults被更新时都会被调用            }        }    };

  @Override    protected void onDestroy() {        super.onDestroy();        if (menList2 != null) {            menList2.removeChangeListener(callback);            menList2.removeAllChangeListeners();        }        if (mRealm != null && !mRealm.isClosed()) {            mRealm.close();        }    }

• findFirst :查询第一条数据

 Men men = mRealm.where(Men.class).findFirst();                Log.d("huangxiaoguo", "huangixoaguo==>" +                        men.getName() + "----" + men.getAge());

• equalTo :根据条件单级查询

   RealmResults<Men> menRealmResults = mRealm.where(Men.class)                        .equalTo("name", "huangxiaoguo1").findAll();                for (int i = 0; i < menRealmResults.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            menRealmResults.get(i).getName() + "----" + menRealmResults.get(i).getAge());                }

• equalTo :根据条件多级查询

 //只能是一对一的表，一对多时，子表查询条件无效                RealmResults<Person> people = mRealm.where(Person.class)                        .equalTo("city", "杭州")                        .equalTo("men.age", 20)//这是他的子类Men的属性                        .findAll();                for (int i = 0; i < people.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            people.get(i).getMen().getName() + "----" +                            people.get(i).getMen().getAge());                }

• 聚合

    /**                 * sum()：对指定字段求和。                 average()：对指定字段求平均值。                 min(): 对指定字段求最小值。                 max() : 对指定字段求最大值。count : 求结果集的记录数量。                 findAll(): 返回结果集所有字段，返回值为RealmResults队列                 findAllSorted() : 排序返回结果集所有字段，返回值为RealmResults队列                 between(), greaterThan(),lessThan(), greaterThanOrEqualTo() & lessThanOrEqualTo()                 equalTo() & notEqualTo()                 contains(), beginsWith() & endsWith()                 isNull() & isNotNull()                 isEmpty()& isNotEmpty()                 */                RealmResults<Men> results = mRealm.where(Men.class).findAll();                long sum = results.sum("age").longValue();                long min = results.min("age").longValue();                long max = results.max("age").longValue();                double average = results.average("age");                long matches = results.size();                Log.d("huangxiaoguo", "sum=" + sum + ",min=" + min + ",max=" + max +                        ",average=" + average + ",matches=" + matches);

• or的使用

 RealmResults<Men> menList2 = mRealm.where(Men.class)                        .equalTo("name", "huangxiaoguo0")                        .or().equalTo("name", "huangxiaoguo2")                        .findAll();                for (int i = 0; i < menList2.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList2.get(i).getName() +                            ",age=" + menList2.get(i).getAge());                }

• 排序

   RealmResults<Men> menList3 = mRealm.where(Men.class).findAll();                menList3 = menList3.sort("age"); //根据age，正序排列                for (int i = 0; i < menList3.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList3.get(i).getName() +                            ",age=" + menList3.get(i).getAge());                }                menList3 = menList3.sort("age", Sort.DESCENDING);//逆序排列                for (int i = 0; i < menList3.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList3.get(i).getName() +                            ",age=" + menList3.get(i).getAge());                }

• 区间查询

  RealmResults<Men> menList4 = mRealm.where(Men.class)                        .between("age", 0, 30)                        .findAll();                for (int i = 0; i < menList4.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList4.get(i).getName() +                            ",age=" + menList4.get(i).getAge());                }

Realm数据库使用教程（四）：更新数据

Demo地址：https://gitee.com/huangxiaoguo/Realm

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activity全部代码如下：

package tsou.com.simple.realmtest;import android.os.Bundle;import android.support.v7.app.AppCompatActivity;import android.util.Log;import android.view.View;import android.widget.AdapterView;import android.widget.ListView;import java.util.ArrayList;import java.util.List;import io.realm.OrderedCollectionChangeSet;import io.realm.OrderedRealmCollectionChangeListener;import io.realm.Realm;import io.realm.RealmResults;import io.realm.Sort;import tsou.com.simple.realmtest.adapter.MyAdapter;import tsou.com.simple.realmtest.bean.Men;import tsou.com.simple.realmtest.bean.Person;import tsou.com.simple.realmtest.utils.UIUtils;public class QueryActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {    private ListView mListview;    private List<String> titles = new ArrayList<>();    private Realm mRealm;    private RealmResults<Men> menList2;    @Override    protected void onDestroy() {        super.onDestroy();        if (menList2 != null) {            menList2.removeChangeListener(callback);            menList2.removeAllChangeListeners();        }        if (mRealm != null && !mRealm.isClosed()) {            mRealm.close();        }    }    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_add);        mRealm = UIUtils.getRealmInstance();        initData();        initView();        initListener();    }    private void initData() {        titles.add("同步操作：findAll查询");        titles.add("异步操作：findAllAsync查询(isLoaded)");        titles.add("异步操作：findAllAsync查询(RealmChangeListener)");        titles.add("findFirst :查询第一条数据");        titles.add("equalTo :根据条件单级查询");        titles.add("equalTo :根据条件多级查询");        titles.add("聚合");        titles.add("or的使用");        titles.add("排序");        titles.add("区间查询");    }    private void initView() {        mListview = (ListView) findViewById(R.id.listview);        mListview.setAdapter(new MyAdapter(this, titles));    }    private void initListener() {        mListview.setOnItemClickListener(this);    }    @Override    public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {        switch (position) {            default:                break;            case 0://同步操作：findAll查询                /**                 * 注意：RealmResults虽然实现了List接口，不过有很多方法是不能用的。                 * 比如add、addAll、remove、clear等，                 * 调用后会直接抛异常。                 * 因为它们都被标记为@Deprecated了。                 */                RealmResults<Men> menList = mRealm.where(Men.class)                        .findAll();                for (int i = 0; i < menList.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            menList.get(i).getName() + "----" + menList.get(i).getAge());                }                break;            case 1://异步操作：findAllAsync查询(isLoaded)                RealmResults<Men> menList1 = mRealm.where(Men.class)                        .findAllAsync();                menList1.load();//等到查询完成。这将阻塞该线程，使查询再次同步                if (menList1 != null && menList1.isLoaded()) {                    for (int i = 0; i < menList1.size(); i++) {                        Log.d("huangxiaoguo", "huangixoaguo==>" +                                menList1.get(i).getName() + "----" + menList1.get(i).getAge());                    }                }                break;            case 2://异步操作：findAllAsync查询(RealmChangeListener)                menList2 = mRealm.where(Men.class)                        .findAllAsync();                menList2.addChangeListener(callback);                break;            case 3://findFirst :查询第一条数据                Men men = mRealm.where(Men.class).findFirst();                Log.d("huangxiaoguo", "huangixoaguo==>" +                        men.getName() + "----" + men.getAge());                break;            case 4://equalTo ——根据条件单级查询                RealmResults<Men> menRealmResults = mRealm.where(Men.class)                        .equalTo("name", "huangxiaoguo1").findAll();                for (int i = 0; i < menRealmResults.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            menRealmResults.get(i).getName() + "----" + menRealmResults.get(i).getAge());                }                break;            case 5://equalTo ——根据条件多级查询                //只能是一对一的表，一对多时，子表查询条件无效                RealmResults<Person> people = mRealm.where(Person.class)                        .equalTo("city", "杭州")                        .equalTo("men.age", 20)//这是他的子类Men的属性                        .findAll();                for (int i = 0; i < people.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            people.get(i).getMen().getName() + "----" +                            people.get(i).getMen().getAge());                }                break;            case 6://聚合                /**                 * sum()：对指定字段求和。                 average()：对指定字段求平均值。                 min(): 对指定字段求最小值。                 max() : 对指定字段求最大值。count : 求结果集的记录数量。                 findAll(): 返回结果集所有字段，返回值为RealmResults队列                 findAllSorted() : 排序返回结果集所有字段，返回值为RealmResults队列                 between(), greaterThan(),lessThan(), greaterThanOrEqualTo() & lessThanOrEqualTo()                 equalTo() & notEqualTo()                 contains(), beginsWith() & endsWith()                 isNull() & isNotNull()                 isEmpty()& isNotEmpty()                 */                RealmResults<Men> results = mRealm.where(Men.class).findAll();                long sum = results.sum("age").longValue();                long min = results.min("age").longValue();                long max = results.max("age").longValue();                double average = results.average("age");                long matches = results.size();                Log.d("huangxiaoguo", "sum=" + sum + ",min=" + min + ",max=" + max +                        ",average=" + average + ",matches=" + matches);                break;            case 7://or的使用                RealmResults<Men> menList2 = mRealm.where(Men.class)                        .equalTo("name", "huangxiaoguo0")                        .or().equalTo("name", "huangxiaoguo2")                        .findAll();                for (int i = 0; i < menList2.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList2.get(i).getName() +                            ",age=" + menList2.get(i).getAge());                }                break;            case 8://排序                RealmResults<Men> menList3 = mRealm.where(Men.class).findAll();                menList3 = menList3.sort("age"); //根据age，正序排列                for (int i = 0; i < menList3.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList3.get(i).getName() +                            ",age=" + menList3.get(i).getAge());                }                menList3 = menList3.sort("age", Sort.DESCENDING);//逆序排列                for (int i = 0; i < menList3.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList3.get(i).getName() +                            ",age=" + menList3.get(i).getAge());                }                break;            case 9:                RealmResults<Men> menList4 = mRealm.where(Men.class)                        .between("age", 0, 30)                        .findAll();                for (int i = 0; i < menList4.size(); i++) {                    Log.d("huangxiaoguo", "name=" + menList4.get(i).getName() +                            ",age=" + menList4.get(i).getAge());                }                break;        }    }    /**     * 异步操作的监听     */    private OrderedRealmCollectionChangeListener<RealmResults<Men>> callback = new OrderedRealmCollectionChangeListener<RealmResults<Men>>() {        @Override        public void onChange(RealmResults<Men> collection, OrderedCollectionChangeSet changeSet) {            if (changeSet == null) {                //第一次异步返回一个空的变更集。                for (int i = 0; i < collection.size(); i++) {                    Log.d("huangxiaoguo", "huangixoaguo==>" +                            collection.get(i).getName() + "----" + collection.get(i).getAge());                }            } else {                //每次RealmResults被更新时都会被调用            }        }    };}

Realm数据库使用教程（四）：更新数据

Demo地址：https://gitee.com/huangxiaoguo/Realm