以下是一个简单的示例,展示了如何使用MVVM架构,LiveData,Room和SearchView来实现一个带有删除功能的Android应用。
首先,我们需要添加所需的依赖项到项目的build.gradle文件中:
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.3.1'
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.3.1'
implementation 'androidx.room:room-runtime:2.3.0'
implementation 'androidx.room:room-ktx:2.3.0'
implementation 'androidx.recyclerview:recyclerview:1.2.1'
接下来,我们需要创建一个数据实体类,表示我们要在应用中存储和显示的单词:
@Entity(tableName = "word_table")
data class Word(
@PrimaryKey(autoGenerate = true)
val id: Long = 0,
val word: String
)
然后,我们需要创建一个用于访问数据库的数据访问对象(DAO):
@Dao
interface WordDao {
@Query("SELECT * FROM word_table WHERE word LIKE :searchQuery")
fun searchWords(searchQuery: String): LiveData>
@Insert
suspend fun insertWord(word: Word)
@Delete
suspend fun deleteWord(word: Word)
}
接下来,我们需要创建一个用于管理数据的Repository类:
class WordRepository(private val wordDao: WordDao) {
val allWords: LiveData> = wordDao.getAllWords()
suspend fun insert(word: Word) {
wordDao.insertWord(word)
}
suspend fun delete(word: Word) {
wordDao.deleteWord(word)
}
fun searchWords(searchQuery: String): LiveData> {
return wordDao.searchWords("%$searchQuery%")
}
}
然后,我们需要创建一个ViewModel类,负责从Repository获取数据并在需要时更新UI:
class WordViewModel(private val repository: WordRepository) : ViewModel() {
private val _searchQuery = MutableLiveData()
val searchQuery: LiveData
get() = _searchQuery
val searchResults: LiveData> = Transformations.switchMap(_searchQuery) {
repository.searchWords(it)
}
fun setSearchQuery(query: String) {
_searchQuery.value = query
}
fun deleteWord(word: Word) {
viewModelScope.launch {
repository.delete(word)
}
}
}
接下来,我们需要创建一个适配器类来显示单词列表:
class WordAdapter(private val onWordDelete: (Word) -> Unit) :
RecyclerView.Adapter() {
private var words: List = emptyList()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): WordViewHolder {
val itemView = LayoutInflater.from(parent.context)
.inflate(R.layout.item_word, parent, false)
return WordViewHolder(itemView)
}
override fun onBindViewHolder(holder: WordViewHolder, position: Int) {
val currentWord = words[position]
holder.bind(currentWord)
}
override fun getItemCount(): Int {
return words.size
}
fun setWords(words: List) {
this.words = words
notifyDataSetChanged()
}
inner class WordViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val wordTextView: TextView = itemView.findViewById(R.id.wordTextView)
private val deleteButton: ImageButton = itemView.findViewById(R.id.deleteButton)
fun bind(word: Word) {
wordTextView.text = word.word
deleteButton.setOnClickListener {
onWordDelete(word)
}
}
}
}
接下来,我们需要在Activity或Fragment中使用这些组件来构建应用程序。在这个示例中,我们将在Fragment中实现:
class WordFragment : Fragment() {
private lateinit var wordViewModel: WordViewModel
private lateinit var wordAdapter: WordAdapter
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
val view = inflater.inflate(R.layout.fragment_word, container, false)
val searchView: SearchView = view.findViewById(R.id.searchView)
val recyclerView: RecyclerView = view.findViewById(R.id.recyclerView)
wordAdapter = WordAdapter { word ->
wordViewModel.deleteWord(word)
}
recyclerView.adapter