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作为Android开发者，一定不会对 GreenDao 和 ReactiveX 陌生。
GreenDao 号称Android最快的关系型数据库
ReactiveX Rx是一个编程模型,目标是提供一致的编程接口,帮助开发者更方便的处理异步数据流。
下面我们就通过一个实例，来讲解有无Rx支持的时候GreenDao应该怎么用，实现增删操作。
首先导入需要的库(本文针对的 GreenDao 是 3.x 版本， Rx 是 1.x 版本)
GreenDao导入需求库的说明: https://github.com/greenrobot/greenDAO/
在 build.gradle(Project:Xxx) 下，添加：
buildscript {
repositories {
...
mavenCentral()
...
}
dependencies {
...
classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2'
...
}
}
在 build.gradle(Module:Xxx) 下，添加：
...
apply plugin: 'org.greenrobot.greendao'
...
dependencies {
...
compile 'org.greenrobot:greendao:3.2.2'
...
}
Rx导入需求库的说明: https://github.com/ReactiveX/RxJava/tree/1.x
在 build.gradle(Module:Xxx) 下，添加：
dependencies {
...
compile 'io.reactivex:rxjava:1.2.9'
compile 'io.reactivex:rxandroid:1.2.1'
...
}
需求库添加完之后就可以进入正题了
1.参考GreenDao官方文档，添加必要的类 Note 、 NotesAdapter 、 NoteType 、 NoteTypeConverter
Note :
/**
* Entity mapped to table "NOTE".
*/
@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; @Generated(hash = 1272611929)
public Note() {
} public Note(Long id) {
this.id = id;
} @Generated(hash = 1686394253)
public Note(Long id, @NotNull String text, String comment, java.util.Date date, NoteType type) {
this.id = id;
this.text = text;
this.comment = comment;
this.date = date;
this.type = type;
} public Long getId() {
return id;
} public void setId(Long id) {
this.id = id;
} @NotNull
public String getText() {
return text;
} /**
* Not-null value; ensure this value is available before it is saved to the database.
*/
public void setText(@NotNull String text) {
this.text = text;
} public String getComment() {
return comment;
} public void setComment(String comment) {
this.comment = comment;
} public java.util.Date getDate() {
return date;
} public void setDate(java.util.Date date) {
this.date = date;
} public NoteType getType() {
return type;
} public void setType(NoteType type) {
this.type = type;
} }
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();
}
}
NoteType :
public enum NoteType {
TEXT, LIST, PICTURE
}
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();
}
}
必要的类添加之后，接下来就是重头戏：
用代码说话，横向比较 GreenDao 在有无 Rx 的支持下应该如何书写
1.初始化类
无 Rx 写法
private NoteDao noteDao;
private Query<Note> notesQuery;
有 Rx 写法
private RxDao<Note, Long> noteDao;
private RxQuery<Note> notesQuery;
2.将记录保存到DAO里
无 Rx 写法
DaoSession daoSession = ((BaseApplication) getApplication()).getDaoSession();
noteDao = daoSession.getNoteDao();
有 Rx 写法
DaoSession daoSession = ((BaseApplication) getApplication()).getDaoSession();
noteDao = daoSession.getNoteDao().rx();
3.查询所有记录，按A-Z分类
无 Rx 写法
notesQuery = noteDao.queryBuilder().orderAsc(NoteDao.Properties.Text).build();
有 Rx 写法
notesQuery = daoSession.getNoteDao().queryBuilder().orderAsc(NoteDao.Properties.Text).rx();
4.初始化View
无 Rx 写法
protected void setUpViews() {
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerViewNotes);
//noinspection ConstantConditions
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
notesAdapter = new NotesAdapter(noteClickListener);
recyclerView.setAdapter(notesAdapter);
addNoteButton = findViewById(R.id.buttonAdd);
//noinspection ConstantConditions
addNoteButton.setEnabled(false);
editText = (EditText) findViewById(R.id.editTextNote);
editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
@Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
if (actionId == EditorInfo.IME_ACTION_DONE) {
addNote();
return true;
}
return false;
}
});
editText.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
boolean enable = s.length() != 0;
addNoteButton.setEnabled(enable);
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void afterTextChanged(Editable s) {
}
});
}
有 Rx 写法
protected void setUpViews() {
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerViewNotes);
//noinspection ConstantConditions
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
notesAdapter = new NotesAdapter(noteClickListener);
recyclerView.setAdapter(notesAdapter);
addNoteButton = findViewById(R.id.buttonAdd);
editText = (EditText) findViewById(R.id.editTextNote);
//noinspection ConstantConditions
RxTextView.editorActions(editText).observeOn(AndroidSchedulers.mainThread())
.subscribe(new Action1<Integer>() {
@Override
public void call(Integer actionId) {
if (actionId == EditorInfo.IME_ACTION_DONE) {
addNote();
}
}
});
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);
}
});
}
5.更新记录
无 Rx 写法
private void updateNotes() {
List<Note> notes = notesQuery.list();
notesAdapter.setNotes(notes);
}
有 Rx 写法
private void updateNotes() {
notesQuery.list()
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Action1<List<Note>>() {
@Override
public void call(List<Note> notes) {
notesAdapter.setNotes(notes);
}
});
}
6.添加记录
无 Rx 写法
private void addNote() {
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();
note.setText(noteText);
note.setComment(comment);
note.setDate(new Date());
note.setType(NoteType.TEXT);
noteDao.insert(note);
Log.d("DaoExample", "Inserted new note, ID: " + note.getId());
updateNotes();
}
有 Rx 写法
private void addNote() {
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) {
Log.d("DaoExample", "Inserted new note, ID: " + note.getId());
updateNotes();
}
});
}
7.删除记录
无 Rx 写法
NotesAdapter.NoteClickListener noteClickListener = new NotesAdapter.NoteClickListener() {
@Override
public void onNoteClick(int position) {
Note note = notesAdapter.getNote(position);
Long noteId = note.getId();
noteDao.deleteByKey(noteId);
Log.d("DaoExample", "Deleted note, ID: " + noteId);
updateNotes();
}
};
有 Rx 写法
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) {
Log.d("DaoExample", "Deleted note, ID: " + noteId);
updateNotes();
}
});
}
};
最后别忘了新建一个Application类，并添加到Manifest中
public class BaseApplication extends Application {
/**
* A flag to show how easily you can switch from standard SQLite to the encrypted SQLCipher.
*/
public static final boolean ENCRYPTED = true;
private DaoSession daoSession;
@Override
public void onCreate() {
super.onCreate();
DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(
this, ENCRYPTED ? "notes-db-encrypted" : "notes-db");
Database db = ENCRYPTED ? helper.getEncryptedWritableDb("super-secret") : helper.getWritableDb();
daoSession = new DaoMaster(db).newSession();
}
public DaoSession getDaoSession() {
return daoSession;
}
}
文中额外可能会用到的库
compile 'com.jakewharton.rxbinding:rxbinding:1.0.1'
compile 'net.zetetic:android-database-sqlcipher:3.5.6'