SeekBarPreference for Float with value formatter

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="FloatSeekBarPreference">
        <attr name="minValue"/>
        <attr name="maxValue"/>
        <attr name="valueSpacing"/>
        <attr name="format"/>
    </declare-styleable>
</resources>

FloatSeekBarPreference.kt

package com.example.app

import android.content.Context
import android.content.res.TypedArray
import android.util.AttributeSet
import android.widget.SeekBar
import android.widget.TextView
import androidx.preference.Preference
import androidx.preference.PreferenceViewHolder

class FloatSeekBarPreference(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) :
    Preference(context, attrs, defStyleAttr, defStyleRes), SeekBar.OnSeekBarChangeListener {

    var value: Float
        // Seekbarから値を取得する
        get() = (seekbar?.progress?.times(valueSpacing) ?: 0F) + minValue
        set(v) {
            newValue = v
            persistFloat(v) // SharedPreferenceに保存
            notifyChanged() // UIの更新を要求
        }

    private val minValue: Float
    private val maxValue: Float
    private val valueSpacing: Float // 指定できる値の間隔
    private val format: String // 値のフォーマット

    private var seekbar: SeekBar? = null
    private var textView: TextView? = null

    private var defaultValue = 0F // XMLで設定したデフォルト値
    private var newValue = 0F

    constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : this(context, attrs, defStyleAttr, 0)
    constructor(context: Context, attrs: AttributeSet?) : this(context, attrs, R.attr.seekBarPreferenceStyle)
    constructor(context: Context) : this(context, null)

    init {
        widgetLayoutResource = R.layout.pref_float_seekbar // カスタムレイアウトを指定する

        // XMLの値を取得
        val ta = context.obtainStyledAttributes(attrs, R.styleable.FloatSeekBarPreference, defStyleAttr, defStyleRes)
        minValue = ta.getFloat(R.styleable.FloatSeekBarPreference_minValue, 0F)
        maxValue = ta.getFloat(R.styleable.FloatSeekBarPreference_maxValue, 1F)
        valueSpacing = ta.getFloat(R.styleable.FloatSeekBarPreference_valueSpacing, .1F)
        format = ta.getString(R.styleable.FloatSeekBarPreference_format) ?: "%3.1f"
        ta.recycle()
    }

    // Called when a Preference is being inflated and the default value attribute needs to be read. Since different
    // Preference types have different value types, the subclass should get and return the default value which will be
    // its value type.
    override fun onGetDefaultValue(ta: TypedArray?, i: Int): Any {
        defaultValue = ta!!.getFloat(i, 0F) // XMLで指定したデフォルト値を取得
        return defaultValue
    }

    // Implement this to set the initial value of the Preference.
    override fun onSetInitialValue(initValue: Any?) {
        newValue = getPersistedFloat(
            if (initValue is Float) initValue
            else this.defaultValue
        )
    }

    // onGetDefaultValue -> onSetInitialValue -> onBindViewHolder の順に呼ばれる
    override fun onBindViewHolder(holder: PreferenceViewHolder?) {
        super.onBindViewHolder(holder)

        holder!!.itemView.isClickable = false
        seekbar = holder.findViewById(R.id.seekbar) as SeekBar
        textView = holder.findViewById(R.id.seekbar_value) as TextView

        seekbar!!.setOnSeekBarChangeListener(this)
        // SeekbarはIntのみ受け付けるのでよしなにやる
        seekbar!!.max = ((maxValue - minValue) / valueSpacing).toInt()
        seekbar!!.progress = ((newValue - minValue) / valueSpacing).toInt()
        seekbar!!.isEnabled = isEnabled

        textView!!.text = format.format(newValue)
    }

    // for OnSeekBarChangeListener
    override fun onProgressChanged(seekbar: SeekBar?, progress: Int, fromUser: Boolean) {
        if (!fromUser) return
        val v = minValue + progress * valueSpacing
        textView!!.text = format.format(v)
    }

    // for OnSeekBarChangeListener
    override fun onStartTrackingTouch(seekbar: SeekBar?) {}

    // for OnSeekBarChangeListener
    override fun onStopTrackingTouch(seekbar: SeekBar?) {
        val v = minValue + seekbar!!.progress * valueSpacing
        persistFloat(v)
    }
}

FloatSeekBarPreference.md

SeekBarPreference for Float with value formatter

AndroidX library has SeekBarPreference, but it supports Int only. This FloatSeekBarPreference class supports Float and has formatter.

Usage

Requires library androidx.preference.

<com.example.app.FloatSeekBarPreference android:key="example"
                                        android:icon="@drawable/slow_motion_video"
                                        android:title="Speed"
                                        android:defaultValue="0.8"
                                        app:minValue="0.5"
                                        app:maxValue="1.0"
                                        app:valueSpacing="0.1"
                                        app:format="\u00D7%3.1f"/>

References

• AndroidX Preference API
• SeekBarPreference implementation of AndroidX

LICENSE

MIT License

Copyright (c) 2019 Yuto Tokunaga

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

pref_float_seekbar.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="wrap_content"
              android:gravity="center_vertical">

    <android.support.v7.widget.AppCompatSeekBar android:id="@+id/seekbar"
                                                android:layout_width="0dp"
                                                android:layout_weight="80"
                                                android:layout_height="wrap_content"/>

    <TextView android:id="@+id/seekbar_value"
              android:layout_width="0dp"
              android:layout_weight="20"
              android:layout_height="wrap_content"/>

</LinearLayout>