Android实现记事本小功能

本文实例为大家分享了Android实现记事本功能的具体代码，供大家参考，具体内容如下

首先声明，本人是android的小白，主要是新人项目写了这个程序，思路可能不是很清晰，可优化的地方也有很多，望路过的大佬不吝赐教。
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。
所有代码放在github上面了，如有需要，请自取

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。