greendao使用总结(一)基础篇-优快云博客

本文介绍如何利用GreenDAO库在Android应用中实现高效的数据管理，包括配置Gradle依赖、创建实体类、初始化数据库及操作数据等关键步骤。

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1.配置

root build.gradle

buildscript {
    repositories {
        jcenter()
        mavenCentral() // add repository
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.1'
        classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2' // add plugin
    }
}
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app/build.gradle

apply plugin: 'com.android.application'
apply plugin: 'org.greenrobot.greendao' // apply plugin
 
dependencies {
    implementation 'org.greenrobot:greendao:3.2.2' // add library
}
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app/build.gradle内与dependencies{}同级别位置添加

greendao {
    schemaVersion 1
    daoPackage 'com.smilemolj.greendaodemotest.db'
    targetGenDir 'src/main/java'
}
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2.bean类

@Entity(indexes = {
        @Index(value = "text, date DESC", unique = true)
})
public class Note {
    @Id
    private Long id;

    @NotNull
    private String text;
    private String comment;
    private java.util.Date date;

    @Convert(converter = NoteTypeConverter.class, columnType = String.class)
    private NoteType type;
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NoteTypeConverter

public class NoteTypeConverter implements PropertyConverter<NoteType, String> {
    @Override
    public NoteType convertToEntityProperty(String databaseValue) {
        return NoteType.valueOf(databaseValue);
    }

    @Override
    public String convertToDatabaseValue(NoteType entityProperty) {
        return entityProperty.name();
    }
}
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NoteType

public enum NoteType {
    TEXT, LIST, PICTURE
}
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3.make project

编译一下工程。如果配置正确，会在配置的包目录下自动会生成 DaoMaster，DaoSession 和 NoteDao 类。

4.继承Application类

public class App extends Application {
    private DaoMaster.DevOpenHelper mHelper;
    private SQLiteDatabase db;
    private DaoMaster daoMaster;
    private DaoSession daoSession;
    public static App instance = null;

    @Override
    public void onCreate() {
        super.onCreate();
        instance = this;
        // 通过 DaoMaster 的内部类 DevOpenHelper，你可以得到一个便利的 SQLiteOpenHelper 对象。
        // 注意：默认的 DaoMaster.DevOpenHelper 会在数据库升级时，删除所有的表，意味着这将导致数据的丢失。
        // 所以，在正式的项目中，你还应该做一层封装，来实现数据库的安全升级。
        mHelper = new DaoMaster.DevOpenHelper(this, "notes-db", null);
        db = mHelper.getWritableDatabase();
        // 注意：该数据库连接属于 DaoMaster，所以多个 Session 指的是相同的数据库连接。
        daoMaster = new DaoMaster(db);
        daoSession = daoMaster.newSession();
    }

    public SQLiteDatabase getDb() {
        return db;
    }

    public DaoSession getDaoSession() {
        return daoSession;
    }

    public static App getInstance() {
        if (instance == null) {
            synchronized (App.class) {
                //同步
                if (instance == null) {
                    instance = new App();
                }
            }
        }
        return instance;
    }

}
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5.修改AndroidManifest.xml文件

application节点内添加

android:name=".App"
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6.activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/sp_16"
    android:paddingLeft="@dimen/sp_16"
    android:paddingRight="@dimen/sp_16"
    android:paddingTop="@dimen/sp_16"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/buttonAdd"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:onClick="onAddButtonClick"
        android:text="添加"/>

    <EditText
        android:id="@+id/editTextNote"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/buttonAdd"
        android:hint="输入新笔记"
        android:imeOptions="actionDone"
        android:inputType="text"/>

    <TextView
        android:id="@+id/textViewNoteInstructions"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/editTextNote"
        android:gravity="center_horizontal"
        android:paddingBottom="8dp"
        android:paddingLeft="8dp"
        android:paddingRight="8dp"
        android:text="点击删除对应笔记"
        android:textSize="12sp"/>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerViewNotes"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/textViewNoteInstructions"
        android:scrollbars="vertical"/>

</RelativeLayout>
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7.item_note.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?android:attr/selectableItemBackground"
    android:orientation="vertical"
    android:padding="16dp">

    <TextView
        android:id="@+id/textViewNoteText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="14sp"
        tools:text="Note Text" />

    <TextView
        android:id="@+id/textViewNoteComment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="12sp"
        tools:text="Note Comment" />

</LinearLayout>
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8.NotesAdapter

public class NotesAdapter extends RecyclerView.Adapter<NotesAdapter.NoteViewHolder> {

    private NoteClickListener clickListener;
    private List<Note> dataset;

    public interface NoteClickListener {
        void onNoteClick(int position);
    }

    static class NoteViewHolder extends RecyclerView.ViewHolder {

        public TextView text;
        public TextView comment;

        public NoteViewHolder(View itemView, final NoteClickListener clickListener) {
            super(itemView);
            text = (TextView) itemView.findViewById(R.id.textViewNoteText);
            comment = (TextView) itemView.findViewById(R.id.textViewNoteComment);
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    if (clickListener != null) {
                        clickListener.onNoteClick(getAdapterPosition());
                    }
                }
            });
        }
    }

    public NotesAdapter(NoteClickListener clickListener) {
        this.clickListener = clickListener;
        this.dataset = new ArrayList<Note>();
    }

    public void setNotes(@NonNull List<Note> notes) {
        dataset = notes;
        notifyDataSetChanged();
    }

    public Note getNote(int position) {
        return dataset.get(position);
    }

    @Override
    public NotesAdapter.NoteViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_note, parent, false);
        return new NoteViewHolder(view, clickListener);
    }

    @Override
    public void onBindViewHolder(NotesAdapter.NoteViewHolder holder, int position) {
        Note note = dataset.get(position);
        holder.text.setText(note.getText());
        holder.comment.setText(note.getComment());
    }

    @Override
    public int getItemCount() {
        return dataset.size();
    }
}
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9.MainActivity

public class MainActivity extends AppCompatActivity {

    private EditText editText;
    private View addNoteButton;

    private RxDao<Note, Long> noteDao;
    private RxQuery<Note> notesQuery;
    private NotesAdapter notesAdapter;

    NotesAdapter.NoteClickListener noteClickListener = new NotesAdapter.NoteClickListener() {
        @Override
        public void onNoteClick(int position) {
            Note note = notesAdapter.getNote(position);
            final Long noteId = note.getId();

            noteDao.deleteByKey(noteId)
                    .observeOn(AndroidSchedulers.mainThread())
                    .subscribe(new Action1<Void>() {
                        @Override
                        public void call(Void aVoid) {
                            Toast.makeText(MainActivity.this, "Deleted note, ID: " + noteId, Toast.LENGTH_SHORT).show();
                            updateNotes();
                        }
                    });
        }
    };

    //    oncreate
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        RecyclerView recyclerView = findViewById(R.id.recyclerViewNotes);
        //noinspection ConstantConditions
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        notesAdapter = new NotesAdapter(noteClickListener);

        recyclerView.setAdapter(notesAdapter);
        addNoteButton = findViewById(R.id.buttonAdd);
        editText = findViewById(R.id.editTextNote);
        RxTextView.editorActions(editText).observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<Integer>() {
                    @Override
                    public void call(Integer actionId) {
                        if (actionId == EditorInfo.IME_ACTION_DONE) {

                            String noteText = editText.getText().toString();
                            editText.setText("");

                            final DateFormat df = DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.MEDIUM);
                            String comment = "Added on " + df.format(new Date());

                            Note note = new Note(null, noteText, comment, new Date(), NoteType.TEXT);
                            noteDao.insert(note)
                                    .observeOn(AndroidSchedulers.mainThread())
                                    .subscribe(new Action1<Note>() {
                                        @Override
                                        public void call(Note note) {
                                            Toast.makeText(MainActivity.this, "Inserted new note, ID: " + note.getId(), Toast.LENGTH_SHORT).show();
                                            updateNotes();
                                        }
                                    });
                        }
                    }
                });
        RxTextView.afterTextChangeEvents(editText).observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<TextViewAfterTextChangeEvent>() {
                    @Override
                    public void call(TextViewAfterTextChangeEvent textViewAfterTextChangeEvent) {
                        boolean enable = textViewAfterTextChangeEvent.editable().length() > 0;
                        addNoteButton.setEnabled(enable);
                    }
                });

        // get the Rx variant of the note DAO
        DaoSession daoSession = App.getInstance().getDaoSession();

        noteDao = daoSession.getNoteDao().rx();

        // query all notes, sorted a-z by their text
        notesQuery = daoSession.getNoteDao().queryBuilder().orderAsc(NoteDao.Properties.Text).rx();
        updateNotes();

    }
    //    oncreate()

    private void updateNotes() {
        notesQuery.list()
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<List<Note>>() {
                    @Override
                    public void call(List<Note> notes) {
                        notesAdapter.setNotes(notes);
                    }
                });
    }

    public void onAddButtonClick(View view) {
        String noteText = editText.getText().toString();
        editText.setText("");

        final DateFormat df = DateFormat.getDateTimeInstance(DateFormat.MEDIUM, DateFormat.MEDIUM);
        String comment = "Added on " + df.format(new Date());

        Note note = new Note(null, noteText, comment, new Date(), NoteType.TEXT);
        noteDao.insert(note)
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Action1<Note>() {
                    @Override
                    public void call(Note note) {
                        Toast.makeText(MainActivity.this, "Inserted new note, ID: " + note.getId(), Toast.LENGTH_SHORT).show();
                        updateNotes();
                    }
                });
    }

}
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