Room 讓資料庫變得無比高效簡潔
阿新 • • 發佈:2021-10-07
def room_version = "2.2.0"
implementation "androidx.room:room-runtime:$room_version"
annotationProcessor "androidx.room:room-compiler:$room_version"
// optional - Test helpers
testImplementation "androidx.room:room-testing:$room_version"
寫實體類 WordEntity
package com.example.roombasic; import androidx.room.ColumnInfo;import androidx.room.Entity; import androidx.room.PrimaryKey; @Entity public class WordEntity { //(autoGenerate = true) 自動生成資料 @PrimaryKey(autoGenerate = true) private int id; //ColumnInfo註釋 @ColumnInfo(name = "english_word") private String word; @ColumnInfo(name = "chinese_meaning")private String chineseMeaning; public WordEntity(String word, String chineseMeaning) { this.word = word; this.chineseMeaning = chineseMeaning; } public int getId() { return id; } public void setId(int id) { this.id = 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; } @Override public String toString() { return "WordEntity{" + "id=" + id + ", word='" + word + '\'' + ", chineseMeaning='" + chineseMeaning + '\'' + '}'; } }
寫dao層介面 WordDao
package com.example.roombasic; import android.service.voice.VoiceInteractionService; import androidx.room.Dao; import androidx.room.Delete; import androidx.room.Insert; import androidx.room.Query; import androidx.room.Update; import java.util.List; @Dao public interface WordDao { //有可能插入多個WordEntity,所以中間寫三個句號,正常插一個的話就寫一個就行 @Insert void insertWords(WordEntity...WordEntity); @Update void updateWordEntity(WordEntity...WordEntity); @Delete void deleteWords(WordEntity...WordEntity); //刪除全部 @Query("delete from wordentity") void deleteAllWords(); @Query("select * from WordEntity order by id desc") List<WordEntity> getAllWords(); }
寫資料庫建立類,並獲取dao層介面 WordDataBase
package com.example.roombasic; import androidx.room.Database; import androidx.room.RoomDatabase; //現在資料庫就一個實體所以寫一個就行了,這玩意能寫多個,現在版本自定義為1 @Database(entities = {WordEntity.class},version = 1,exportSchema = false) public abstract class WordDataBase extends RoomDatabase { public abstract WordDao getWordDao(); }
main
package com.example.roombasic; import androidx.appcompat.app.AppCompatActivity; import androidx.room.Room; import android.os.Bundle; import android.view.View; import android.widget.Button; import android.widget.TextView; import java.util.List; public class MainActivity extends AppCompatActivity { WordDataBase wordDataBase; WordDao wordDao; TextView textView66; String text; Button buttonInsert,buttonDelete,buttonClear,buttonUpdate; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //建立資料庫 fuck是資料庫名 wordDataBase = Room.databaseBuilder(this,WordDataBase.class,"fuck") .allowMainThreadQueries() .build(); wordDao = wordDataBase.getWordDao(); updateView(); buttonInsert = findViewById(R.id.buttonInsert); buttonInsert.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { WordEntity wordEntity = new WordEntity("hello", "你好"); WordEntity wordEntity1 = new WordEntity("world", "世界"); wordDao.insertWords(wordEntity,wordEntity1); updateView(); } }); } void updateView(){ List<WordEntity> allWords = wordDao.getAllWords(); for (int i = 0; i < allWords.size(); i++) { WordEntity word = allWords.get(i); text += word.toString()+" "; } textView66 = findViewById(R.id.text66); textView66.setText(text); } }
寫一個ScrollView 把text放到這裡,如果text過長的話還能滾動
<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout 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" tools:context=".MainActivity"> <Button android:id="@+id/buttonDelete" android:layout_width="219dp" android:layout_height="59dp" android:layout_marginBottom="36dp" android:text="delete" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.181" app:layout_constraintStart_toStartOf="parent" /> <Button android:id="@+id/buttonClear" android:layout_width="219dp" android:layout_height="59dp" android:layout_marginBottom="144dp" android:text="clear" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.118" app:layout_constraintStart_toStartOf="parent" /> <androidx.constraintlayout.widget.Guideline android:id="@+id/guideline2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:orientation="horizontal" app:layout_constraintGuide_begin="754dp" /> <ScrollView android:id="@+id/scrollView2" android:layout_width="546dp" android:layout_height="748dp" app:layout_constraintBottom_toTopOf="@+id/guideline2" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.0" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" app:layout_constraintVertical_bias="0.0"> <TextView android:id="@+id/text66" android:layout_width="match_parent" android:layout_height="wrap_content"/> </ScrollView> <Button android:id="@+id/buttonInsert" android:layout_width="198dp" android:layout_height="47dp" android:layout_marginBottom="244dp" android:text="insert" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.17" app:layout_constraintStart_toStartOf="parent" /> <Button android:id="@+id/buttonUpdate" android:layout_width="145dp" android:layout_height="89dp" android:layout_marginBottom="200dp" android:text="update" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.923" app:layout_constraintStart_toStartOf="parent" /> </androidx.constraintlayout.widget.ConstraintLayout>