Realm 数据库使用教程（五）：删除数据
@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();
}
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(Real
m 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");
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