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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);
}
});
}http://www.cnblogs.com/cnwutianhao/p/6719380.html
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