这篇文章主要讲解了Android如何实现记事本功能，内容清晰明了，对此有兴趣的小伙伴可以学习一下，相信大家阅读完之后会有帮助。
该记事本包含创建新条目，数据库增删改查，条目可编辑，滑动删除与拖拽排序，简单闹钟实现（还有个简陋背景音乐开关就不提了太简单），接下来逐一介绍一下。
build.gradle导入
apply plugin: 'kotlin-kapt' ''' implementation 'com.google.android.material:material:1.0.0' implementation 'de.hdodenhof:circleimageview:3.0.1' implementation 'com.android.support.constraint:constraint-layout:1.1.3' implementation 'androidx.room:room-runtime:2.1.0' implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0' implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.2.0' implementation 'androidx.recyclerview:recyclerview:1.0.0' kapt "androidx.room:room-compiler:2.1.0"
没什么多说的。
Room数据库
room数据库相比于sqlite来说对新人确实友好很多，在没有SQL基础的前提下，增删改查等实现都很简单，只需创建一个实例，便可在线程中进行。具体代码为
①接口：
@Dao
interface NoteDao {
@Update
fun updateNote(newNote: Note)
@Query("select * from Note")
fun loadAllNotes(): List<Note>
@Query("select * from Note where title > :title")
fun loadNotesLongerThan(title:String) : List<Note>
@Query("select * from Note where id == :id")
fun loadById(id:Long) :Note
@Delete
fun deleteNote(note: Note)
@Query("delete from Note where title == :title")
fun deleteNoteByTitle(title: String): Int
@Insert
fun insertNote(note: Note)
}②Appdatabase类（获取实例
@Database(version = 1, entities = [Note::class])
abstract class AppDatabase: RoomDatabase(){
abstract fun noteDao() : NoteDao
companion object{
//访问实例
private var instance : AppDatabase? = null
@Synchronized//同步化
fun getDatabase(context: Context):AppDatabase{
instance?.let {
return it
}
return Room.databaseBuilder(context.applicationContext,
AppDatabase::class.java, "app_database")
.build().apply {
instance = this
}
}
}
}滑动删除和拖拽排序
class RecycleItemTouchHelper(private val helperCallback: ItemTouchHelperCallback) :
ItemTouchHelper.Callback() {
//设置滑动类型标记
override fun getMovementFlags(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder
): Int {
return makeMovementFlags(ItemTouchHelper.UP or ItemTouchHelper.DOWN,
ItemTouchHelper.END or ItemTouchHelper.START )
}
override fun isLongPressDragEnabled(): Boolean {
return true
}
//滑动
override fun isItemViewSwipeEnabled(): Boolean {
return true
}
//拖拽回调
override fun onMove(
recyclerView: RecyclerView,
viewHolder: RecyclerView.ViewHolder,
target: RecyclerView.ViewHolder
): Boolean {
helperCallback.onMove(viewHolder.adapterPosition, target.adapterPosition)
return true
}
//滑动
override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int): Unit {
helperCallback.onItemDelete(viewHolder.adapterPosition)
}
//状态回调
override fun onSelectedChanged(
viewHolder: RecyclerView.ViewHolder?,
actionState: Int
) {
super.onSelectedChanged(viewHolder, actionState)
}
interface ItemTouchHelperCallback {
fun onItemDelete(positon: Int)
fun onMove(fromPosition: Int, toPosition: Int)
}
}NoteAdapter接口实现
拖拽排序和滑动删除后即更新一次，这种方法并不好，毕竟没有用到MVVM中的高级组件，包括观察者，Livedata，ViewModel察觉数据变化并提示更新。建议在这种方法的前提下可以考虑在从Activity离开后，再数据更新。
注：千万不要在**onPause()**中涉及数据更新和保存！！！
//拖拽排序
override fun onMove(fromPosition: Int, toPosition: Int) {
val noteDao = AppDatabase.getDatabase(context).noteDao()
if (fromPosition < toPosition) {
for (i in fromPosition until toPosition) {
Collections.swap(noteList, i, i + 1)
for (i in noteList){
Log.d("title", i.title)
}
Log.d("tag2", fromPosition.toString()+"->"+toPosition)
}
} else {
for (i in fromPosition downTo toPosition + 1) {
Collections.swap(noteList, i, i - 1)
}
}
//排序后的数据更新
thread {
var templist = noteDao.loadAllNotes().toMutableList()
for (i in 0 until templist.size){
templist[i].title = noteList[i].title
templist[i].content = noteList[i].content
noteDao.updateNote(templist[i])
}
}
notifyItemMoved(fromPosition, toPosition)
}简易闹钟实现
broadcast类需要自己实现
class MyReceiver : BroadcastReceiver() {
override fun onReceive(context: Context, intent: Intent) {
// This method is called when the BroadcastReceiver is receiving an Intent broadcast.
Toast.makeText(context,"You have a task to do!!!", Toast.LENGTH_LONG).show()
}
}这里只是发个广播通知，并没有提示声音，可以采取发到通知栏的方式，系统会有提示音。涉及到AlarmManager类
NoteActivity中的实现：
setBtn.setOnClickListener { view ->
val c = Calendar.getInstance()
//调整为中国时区，不然有8小时差比较麻烦
val tz = TimeZone.getTimeZone("Asia/Shanghai")
c.timeZone = tz
//获取当前时间
if (setHour.text.toString()!=""&&setMin.text.toString()!="") {
c.set(Calendar.HOUR_OF_DAY, setHour.text.toString().toInt());//小时
c.set(
Calendar.MINUTE, setMin.text.toString().toInt()
);//分钟
c.set(Calendar.SECOND, 0);//秒
}
//计时发送通知
val mIntent = Intent(this, MyReceiver::class.java)
val mPendingIntent =
PendingIntent.getBroadcast(this, 0, mIntent, PendingIntent.FLAG_UPDATE_CURRENT)
am = this
.getSystemService(Context.ALARM_SERVICE) as AlarmManager
if (setHour.text.toString()==""||setMin.text.toString()==""||
setHour.text.toString().toInt() > 24 || setMin.text.toString().toInt() > 60) {
Toast.makeText(this, "请输入正确的时间格式！", Toast.LENGTH_SHORT).show()
} else {
Log.d("fuck10", c.timeInMillis.toString())
am!!.setExactAndAllowWhileIdle(
AlarmManager.RTC_WAKEUP, c.timeInMillis,
mPendingIntent
)
Toast.makeText(this, "设置成功", Toast.LENGTH_SHORT).show()
}
}其它方面如点击recyclerView中的Item重新编辑时对原数据的展现，用到了setText()，这里注意不要跟kotlin中setText()和getText()搞混。
大概所有功能差不多就这些了，毕竟只是个记事本应用
看完上述内容，是不是对Android如何实现记事本功能有进一步的了解，如果还想学习更多内容，欢迎关注亿速云行业资讯频道。
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