Android 使用Room操作SQLite数据库让其变得无比高效和简洁(教程一)

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前言：首先添加依赖和创建布局页面实现添加，更新，删除，清空这四个按钮，之后再去实现相应的功能。

一、首先在build.gradle里面添加相关的依赖

	def room_version = "2.3.0"implementation "androidx.room:room-runtime:$room_version"annotationProcessor "androidx.room:room-compiler:$room_version"// optional - Test helperstestImplementation "androidx.room:room-testing:$room_version"// optional - Paging 3 Integrationimplementation "androidx.room:room-paging:2.4.0-beta01"

二、布局页面activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".MainActivity"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"><TextViewandroid:id="@+id/tv_text"android:layout_width="match_parent"android:layout_height="wrap_content" /></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"android:orientation="vertical"><LinearLayoutandroid:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"android:gravity="center"android:orientation="horizontal"><Buttonandroid:id="@+id/btn_insert"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="添加" /><Buttonandroid:id="@+id/btn_update"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginLeft="50dp"android:text="更新" /></LinearLayout><LinearLayoutandroid:layout_width="match_parent"android:layout_height="0dp"android:layout_weight="1"android:gravity="center"android:orientation="horizontal"><Buttonandroid:id="@+id/btn_clear"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="清空" /><Buttonandroid:id="@+id/btn_delete"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_marginLeft="50dp"android:text="删除" /></LinearLayout></LinearLayout></LinearLayout>

三、创建实体类Word,具体注释都已给出

@Entity
public class Word {//标注为主键 并且自动生成@PrimaryKey(autoGenerate = true)public int id;//ColumnInfo标注列的名称 如果不标注则以变量名 为列名@ColumnInfo(name="english_word")public String word;@ColumnInfo(name = "chinese_meaning")public String chineseMeaning;public Word(String word, String chineseMeaning) {this.word = word;this.chineseMeaning = chineseMeaning;}public void setId(int id) {this.id = id;}public int getId() {return id;}public String getWord() {return word;}public void setWord(String word) {this.word = word;}public String getChineseMeaning() {return chineseMeaning;}public void setChineseMeaning(String chineseMeaning) {this.chineseMeaning = chineseMeaning;}
}

四、创建一个访问数据库操作的接口WordDao，具体的增删改查功能，都要在这个接口里面声明

//访问数据库操作的接口
@Dao  //Database access Object
public interface WordDao {//添加数据@Insertvoid insertWords(Word...words);@Delete//根据条件删除数据void deleteWords(Word...words);//删除所有数据@Query("DELETE FROM WORD")void deleteAllWords();//更新数据@Updatevoid updateWords(Word...words);//查询返回所有数据@Query("SELECT * FROM WORD ORDER BY ID DESC")List<Word> getAllWords();
}

五、创建一个抽象类WordDataBase，如果有多个entities，则应该写多个Dao

// 参数1：实体类  参数2：数据库版本号 参数3：禁止将数据库架构导入到给定的文件夹中
@Database(entities = {Word.class},version = 1,exportSchema = false)
public abstract class WordDataBase extends RoomDatabase {public abstract WordDao getWordDao();
}

六、所有准备工作完成后，在Activity文件中，进行相应功能的实现：

public class MainActivity extends AppCompatActivity {private WordDataBase wordDataBase;private WordDao wordDao;private Button btn_insert, btn_clear, btn_update, btn_delete;private TextView tv_text;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);wordDataBase = Room.databaseBuilder(this, WordDataBase.class, "word_database").allowMainThreadQueries().build();wordDao = wordDataBase.getWordDao();btn_insert = findViewById(R.id.btn_insert);btn_clear = findViewById(R.id.btn_clear);btn_update = findViewById(R.id.btn_update);btn_delete = findViewById(R.id.btn_delete);tv_text = findViewById(R.id.tv_text);updateView();btn_insert.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Word word1 = new Word("Hello", "你好！");Word word2 = new Word("World", "世界！");wordDao.insertWords(word1, word2);updateView();}});btn_clear.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {wordDao.deleteAllWords();updateView();}});btn_update.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {Word word = new Word("Hi", "你好啊");word.setId(10);wordDao.updateWords(word);updateView();}});btn_delete.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View view) {Word word = new Word("Hi", "你好啊");word.setId(10);wordDao.deleteWords(word);updateView();}});}private void updateView() {List<Word> list = wordDao.getAllWords();String text = "";for (int i = 0; i < list.size(); i++) {Word word = list.get(i);text += word.getId() + ":" + word.getWord() + "=" + word.getChineseMeaning() + "\n";}tv_text.setText(text);}}

效果图：

这只是一个简单的实现效果，后续会陆续完善~
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