这是小项目的样子，主界面是一个recyclerView从room取出的所有数据并使用livedata观察，左边floatiingButton点击清除room数据库，右边floatingButton点击进入存储数据界面insert表。
db
room数据库所有操作
WordRoomDatabase
1、创建abstract WordRoomDatabase继承RoomDatabase，create abstract fun wordDao()
2、dcl单例wordRoomDatabase instance by fun getDatabase
3、addCallback()，wordDatabaseCallback override fun onCreate use coroutine function launch()对room init。deleteAll() insert() insert()
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| @Database(entities = arrayOf(Word::class), version = 1, exportSchema = false)
abstract class WordRoomDatabase : RoomDatabase() {
abstract fun wordDao(): WordDao
companion object {
@Volatile
private var INSTANCE: WordRoomDatabase? = null
fun getDatabase(context: Context, scope: CoroutineScope): WordRoomDatabase {
return INSTANCE ?: synchronized(this) {
val instance = Room.databaseBuilder(
context.applicationContext,
WordRoomDatabase::class.java,
"word_database"
).addCallback(WordDatabaseCallback(scope)).build()
INSTANCE = instance
instance
}
}
}
private class WordDatabaseCallback(private val scope: CoroutineScope) :
RoomDatabase.Callback() {
override fun onCreate(db: SupportSQLiteDatabase) {
super.onCreate(db)
INSTANCE?.let { wordRoomDatabase ->
scope.launch {
populateDatabase(wordRoomDatabase.wordDao())
}
}
}
suspend fun populateDatabase(wordDao: WordDao) {
wordDao.deleteAll()
wordDao.insert(Word("BE BRAVE DI"))
wordDao.insert(Word("DO NOT GIVEUP"))
}
}
}
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Word
word表。tableName 设置表名称，ColumnInfo设置每一列名称，在这里只有word和autoGenerate id
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| @Entity(tableName = "work_table")
data class Word(
@ColumnInfo(name = "word")
var word: String = ""
) {
@PrimaryKey(autoGenerate = true)
var id: Int = 0
}
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WordDao
对word表进行的sql操作。
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| @Dao
interface WordDao {
@Query("SELECT * FROM work_table ORDER BY word ASC")
fun getAlphabetizedWords() :Flow<List<Word>>
@Insert(onConflict = OnConflictStrategy.IGNORE)
suspend fun insert(word: Word)
@Query("DELETE FROM work_table")
suspend fun deleteAll()
}
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repo
WordRepository是对db和net进行的统一管理，调用wordDao.function
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| class WordRepository(private val wordDao: WordDao) {
val allWords: Flow<List<Word>> = wordDao.getAlphabetizedWords()
@Suppress("RedundantSuspendModifier")
@WorkerThread
suspend fun insert(word: Word){
wordDao.insert(word)
}
@WorkerThread
suspend fun deleteAll(){
wordDao.deleteAll()
}
}
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viewmodel
viewmodel对activity界面数据保存
WordViewModelFactory
Return WordViewModel(repository) as T
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| class WordViewModelFactory(private val repository: WordRepository) : ViewModelProvider.Factory {
override fun <T : ViewModel?> create(modelClass: Class<T>): T {
if (modelClass.isAssignableFrom(WordViewModel::class.java)){
@Suppress("UNCHECK_CAST")
return WordViewModel(repository) as T
}
throw IllegalArgumentException("Unknown ViewModel class")
}
}
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WordViewModel
allWords()使用Flow.asLiveData
Insert()使用协程viewmodelscope.launch()
deleteAdd()同上
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| class WordViewModel(private var repository: WordRepository) : ViewModel() {
val allWords:LiveData<List<Word>> = repository.allWords.asLiveData()
fun insert(word: Word) = viewModelScope.launch {
repository.insert(word)
}
fun deleteAdd() = viewModelScope.launch {
repository.deleteAll()
}
}
|
adapter
WordListAdapter
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| class WordListAdapter : ListAdapter<Word, WordListAdapter.WordViewHolder>(WordsComparator()) {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WordViewHolder {
return WordViewHolder.create(parent)
}
override fun onBindViewHolder(holder: WordViewHolder, position: Int) {
val current = getItem(position)
holder.bind(current.word)
}
class WordViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val wordItemView: TextView = itemView.findViewById(R.id.textView)
private val wordItemContent: ConstraintLayout = itemView.findViewById(R.id.recyclerviewcontent)
fun bind(text: String?) {
wordItemView.text = text
val colorArr = arrayOf(Color.WHITE, Color.YELLOW, Color.GREEN, Color.RED)
wordItemContent.setBackgroundColor(colorArr[Random.nextInt(colorArr.size)])
}
companion object {
fun create(parent: ViewGroup): WordViewHolder {
val view: View = LayoutInflater.from(parent.context)
.inflate(R.layout.recyclerview_item, parent, false)
return WordViewHolder(view)
}
}
}
class WordsComparator : DiffUtil.ItemCallback<Word>() {
override fun areItemsTheSame(oldItem: Word, newItem: Word): Boolean {
return oldItem === newItem
}
override fun areContentsTheSame(oldItem: Word, newItem: Word): Boolean {
return oldItem.word == newItem.word
}
}
}
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Activity and application
WordsApplication
By lazy调用到在初始化
Init function: WordRoomDatabase.getDatabase(this,scope), WordRepository(database.wordDao)
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| class WordsApplication : Application() {
val applicationScope = CoroutineScope(SupervisorJob())
val database by lazy { WordRoomDatabase.getDatabase(this, scope = applicationScope) }
val repository by lazy { WordRepository(database.wordDao()) }
}
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NewWordActivity
存储word表
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| class NewWordActivity : AppCompatActivity() {
private lateinit var binding:ActivityNewWordBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityNewWordBinding.inflate(layoutInflater)
setContentView(binding.root)
binding.buttonSave.setOnClickListener {
val replyIntent = Intent()
if (TextUtils.isEmpty(binding.editWord.text)){
setResult(Activity.RESULT_CANCELED, replyIntent)
} else {
Log.d("DI", binding.editWord.text.toString())
replyIntent.putExtra(EXTRA_REPLY, binding.editWord.text.toString())
setResult(Activity.RESULT_OK, replyIntent)
}
finish()
}
}
companion object{
const val EXTRA_REPLY = "com.example.android.wordlistsqp.REPLY"
}
}
|
MainActivity
first —> viewModel. ‘’Viewmodel include liveData scope’’
Second —> livedata.observe() 数据变化则adapter跟着变化.
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| class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private val newWOrdActivityRequestCode = 1
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
var adapter = WordListAdapter()
binding.recyclerview.adapter = adapter
binding.recyclerview.layoutManager = LinearLayoutManager(this)
wordViewModel.allWords.observe(this, Observer { wordViewModel ->
wordViewModel?.let {
adapter.submitList(it)
}
})
binding.floatingActionButton.setOnClickListener{
val intent = Intent(this, NewWordActivity::class.java)
startActivityForResult(intent, newWOrdActivityRequestCode)
}
binding.clear.setOnClickListener{
wordViewModel.deleteAdd()
}
}
private val wordViewModel: WordViewModel by viewModels {
WordViewModelFactory((application as WordsApplication).repository)
}
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (requestCode == newWOrdActivityRequestCode && resultCode == Activity.RESULT_OK) {
data?.getStringExtra(NewWordActivity.EXTRA_REPLY)?.let {
wordViewModel.insert(Word(it))
}
} else {
Snackbar.make(binding.content, "没有数据返回哦", Snackbar.LENGTH_LONG).show()
}
}
}
|