Android实现记事本功能

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，溜了溜了~~
https://github.com/bossjoker1/OrangeNote

本文地址：https://blog.csdn.net/bossshp/article/details/107467797