Realm数据库使用教程（五）：删除数据

Realm数据库使用教程（四）：更新数据

删除数据

同步删除（一）:先查找到数据:deleteFromRealm(int index)

删除指定数据

final RealmResults<Student> students = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students.deleteFromRealm(0);
}
});

同步删除（一）:先查找到数据:deleteFirstFromRealm()

删除第一条数据

final RealmResults<Student> students1 = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students1.deleteFirstFromRealm();
}
});

同步删除（一）:先查找到数据:deleteLastFromRealm()

删除最后一条数据

final RealmResults<Student> students2 = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students2.deleteLastFromRealm();
}
});

同步删除（一）:先查找到数据:deleteAllFromRealm()

删除全部数据

final RealmResults<Student> students3 = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students3.deleteAllFromRealm();
}
});

同步删除（二）:后查找到数据:deleteFromRealm(int index)

mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFromRealm(0);
}
});

同步删除（二）:后查找到数据:deleteFirstFromRealm()

mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFirstFromRealm();
}
});

同步删除（二）:后查找到数据:deleteLastFromRealm()

mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteLastFromRealm();
}
});

同步删除（二）:后查找到数据:deleteAllFromRealm()

mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteAllFromRealm();
}
});

同步删除：deleteAll()

//所有的数据库都会清除
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.deleteAll();
}
});

同步删除：delete(xxx.class)

//只会删除指定的数据库
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
});

异步删除:后查找到数据:deleteFromRealm(int index)

realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFromRealm(0);
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});

异步操作都需要取消任务

if (realmAsyncTask != null && !realmAsyncTask.isCancelled()) {
realmAsyncTask.cancel();
}

异步删除:后查找到数据:deleteFirstFromRealm()

realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFirstFromRealm();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});

异步删除:后查找到数据:deleteLastFromRealm()

realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteLastFromRealm();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});

异步删除:后查找到数据:deleteAllFromRealm()

realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteAllFromRealm();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});

异步删除：deleteAll()

//删除所有数据库
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.deleteAll();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});

异步删除（推荐使用）：delete(xxx.class)

//删除指定的数据库
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});

推荐使用：异步查询，同步删除

students8 = mRealm.where(Student.class).findAllAsync();
students8.addChangeListener(callback);

/**
* 异步操作的监听
*/
private OrderedRealmCollectionChangeListener<RealmResults<Student>> callback = new OrderedRealmCollectionChangeListener<RealmResults<Student>>() {
@Override
public void onChange(RealmResults<Student> collection, OrderedCollectionChangeSet changeSet) {
if (changeSet == null) {
//第一次异步返回一个空的变更集。
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
});
} else {
//每次RealmResults被更新时都会被调用
}
}
};

if (students8 != null) {
students8.removeChangeListener(callback);
students8.removeAllChangeListeners();
}

推荐使用：异步查询，异步删除

students9 = mRealm.where(Student.class).findAllAsync();
students9.addChangeListener(callback1);

/**

* 异步操作的监听

*/

private OrderedRealmCollectionChangeListener

if (students9 != null) {
students9.removeChangeListener(callback);
students9.removeAllChangeListeners();
}

Realm数据库使用教程（六）：数据迁移

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

avticity全部代码如下：

package tsou.com.simple.realmtest;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
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.RealmAsyncTask;
import io.realm.RealmResults;
import tsou.com.simple.realmtest.adapter.MyAdapter;
import tsou.com.simple.realmtest.bean.Student;
import tsou.com.simple.realmtest.utils.UIUtils;

public class DeleteActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {

private ListView mListview;
private List<String> titles = new ArrayList<>();
private Realm mRealm;
private RealmAsyncTask realmAsyncTask;
private RealmResults<Student> students8;
private RealmResults<Student> students9;

@Override
protected void onDestroy() {
super.onDestroy();
if (students8 != null) {
students8.removeChangeListener(callback);
students8.removeAllChangeListeners();
}
if (students9 != null) {
students9.removeChangeListener(callback);
students9.removeAllChangeListeners();
}
if (realmAsyncTask != null && !realmAsyncTask.isCancelled()) {
realmAsyncTask.cancel();
}
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("同步删除（一）:先查找到数据:deleteFromRealm(int index)");
titles.add("同步删除（一）:先查找到数据:deleteFirstFromRealm()");
titles.add("同步删除（一）:先查找到数据:deleteLastFromRealm()");
titles.add("同步删除（一）:先查找到数据:deleteAllFromRealm()");
titles.add("同步删除（二）:后查找到数据:deleteFromRealm(int index)");
titles.add("同步删除（二）:后查找到数据:deleteFirstFromRealm()");
titles.add("同步删除（二）:后查找到数据:deleteLastFromRealm()");
titles.add("同步删除（二）:后查找到数据:deleteAllFromRealm()");
titles.add("同步删除：deleteAll()");
titles.add("同步删除：delete(xxx.class)");

titles.add("异步删除:后查找到数据:deleteFromRealm(int index)");
titles.add("异步删除:后查找到数据:deleteFirstFromRealm()");
titles.add("异步删除:后查找到数据:deleteLastFromRealm()");
titles.add("异步删除:后查找到数据:deleteAllFromRealm()");
titles.add("异步删除：deleteAll()");
titles.add("异步删除（推荐使用）：delete(xxx.class)");

titles.add("推荐使用：异步查询，同步删除");
titles.add("推荐使用：异步查询，异步删除");
}

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://同步删除（一）:先查找到数据:deleteFromRealm(int index)
final RealmResults<Student> students = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students.deleteFromRealm(0);
}
});
break;
case 1://同步删除（一）:先查找到数据:deleteFirstFromRealm()
final RealmResults<Student> students1 = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students1.deleteFirstFromRealm();
}
});
break;
case 2://同步删除（一）:先查找到数据:deleteLastFromRealm()
final RealmResults<Student> students2 = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students2.deleteLastFromRealm();
}
});
break;
case 3://同步删除（一）:先查找到数据:deleteAllFromRealm()
final RealmResults<Student> students3 = mRealm.where(Student.class).findAll();
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
students3.deleteAllFromRealm();
}
});
break;
case 4://同步删除（二）:后查找到数据:deleteFromRealm(int index)
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFromRealm(0);
}
});
break;
case 5://同步删除（二）:后查找到数据:deleteFirstFromRealm()
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFirstFromRealm();
}
});
break;
case 6://同步删除（二）:后查找到数据:deleteLastFromRealm()
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteLastFromRealm();
}
});
break;
case 7://同步删除（二）:后查找到数据:deleteAllFromRealm()
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteAllFromRealm();
}
});
break;
case 8://同步删除：deleteAll()
//所有的数据库都会清除
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.deleteAll();
}
});
break;
case 9://同步删除：delete(xxx.class)
//只会删除指定的数据库
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
});
break;

case 10://异步删除:后查找到数据:deleteFromRealm(int index)
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFromRealm(0);
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
break;
case 11://异步删除:后查找到数据:deleteFirstFromRealm()
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteFirstFromRealm();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
break;
case 12://异步删除:后查找到数据:deleteLastFromRealm()
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteLastFromRealm();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
break;
case 13://异步删除:后查找到数据:deleteAllFromRealm()
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
RealmResults<Student> students = realm.where(Student.class).findAll();
students.deleteAllFromRealm();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
break;
case 14://异步删除：deleteAll()
//删除所有数据库
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.deleteAll();
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
break;
case 15://异步删除：delete(xxx.class)
//删除指定的数据库
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
break;

case 16://推荐使用：异步查询，同步删除
students8 = mRealm.where(Student.class).findAllAsync();
students8.addChangeListener(callback);
break;
case 17://推荐使用：异步查询，异步删除
students9 = mRealm.where(Student.class).findAllAsync();
students9.addChangeListener(callback1);
break;
}
}
/**
* 异步操作的监听
*/
private OrderedRealmCollectionChangeListener<RealmResults<Student>> callback = new OrderedRealmCollectionChangeListener<RealmResults<Student>>() {
@Override
public void onChange(RealmResults<Student> collection, OrderedCollectionChangeSet changeSet) {
if (changeSet == null) {
//第一次异步返回一个空的变更集。
mRealm.executeTransaction(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
});
} else {
//每次RealmResults被更新时都会被调用
}
}
};
/**
* 异步操作的监听
*/
private OrderedRealmCollectionChangeListener<RealmResults<Student>> callback1 = new OrderedRealmCollectionChangeListener<RealmResults<Student>>() {
@Override
public void onChange(RealmResults<Student> collection, OrderedCollectionChangeSet changeSet) {
if (changeSet == null) {
//第一次异步返回一个空的变更集。
realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm realm) {
realm.delete(Student.class);
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
UIUtils.showToast("删除成功");
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
UIUtils.showToast("删除失败");
}
});
} else {
//每次RealmResults被更新时都会被调用
}
}
};
}

Realm数据库使用教程（六）：数据迁移

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