Realm数据库使用教程（五）

最新推荐文章于 2024-05-08 11:06:50 发布

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最新推荐文章于 2024-05-08 11:06:50 发布

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本文详细介绍了如何在Android中使用Realm数据库进行异步删除操作，包括同步删除和异步删除的各种方法，如deleteFromRealm、deleteFirstFromRealm、deleteLastFromRealm、deleteAllFromRealm等，并推荐使用异步查询配合异步删除，以提高应用性能。

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}

}, 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> callback = new OrderedRealmCollectionChangeListener<RealmResults>() {

@Override

public void onChange(RealmResults 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 titles = new ArrayList<>();

private Realm mRealm;

private RealmAsyncTask realmAsyncTask;

private RealmResults students8;

private RealmResults 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 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 students1 = mRealm.where(Student.class).findAll();

mRealm.executeTransaction(new Realm.Transaction() {

@Override

public vo 《Android学习笔记总结+最新移动架构视频+大厂安卓面试真题+项目实战源码讲义》开源 id execute(Realm realm) {

students1.deleteFirstFromRealm();

}

});

break;

case 2://同步删除（一）:先查找到数据:deleteLastFromRealm()

final RealmResults 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 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 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 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 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 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 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 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 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 students = realm.where(Student.class).findAll();

students.deleteAllFromRealm();

}
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}, new Realm.Transaction.OnSuccess() {

@Override

public void onSuccess() {

UIUtils.showToast(“删除成功”);

}

学习交流

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mRealm()

realmAsyncTask = mRealm.executeTransactionAsync(new Realm.Transaction() {

@Override

public void execute(Realm realm) {

RealmResults students = realm.where(Student.class).findAll();

students.deleteAllFromRealm();

}
Android开源项目《ali1024.coding.net/public/P7/Android/git》
}, new Realm.Transaction.OnSuccess() {

@Override

public void onSuccess() {

UIUtils.showToast(“删除成功”);

}

学习交流

[外链图片转存中…(img-DfLH996G-1650016339845)]

[外链图片转存中…(img-HhTQNLrb-1650016339846)]

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