Android Preference的使用以及解析

简单使用

values.arrays.xml

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="list_entries">
        <item>Option 1</item>
        <item>Option 2</item>
        <item>Option 3</item>
    </string-array>
    <string-array name="list_values">
        <item>1</item>
        <item>2</item>
        <item>3</item>
    </string-array>
</resources>

xml.preferences.xml

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <Preference
        android:key="simple_preference"
        android:summary="This is a simple preference"
        android:title="Simple Preference" />
    <CheckBoxPreference
        android:defaultValue="false"
        android:key="checkbox_preference"
        android:summary="This is a CheckBox"
        android:title="Check Box Preference" />
    <EditTextPreference
        android:dialogTitle="Enter Text"
        android:key="edittext_preference"
        android:summary="Enter your text here"
        android:title="Edit Text Preference" />
    <ListPreference
        android:defaultValue="1"
        android:entries="@array/list_entries"
        android:entryValues="@array/list_values"
        android:key="list_preference"
        android:summary="Select an option"
        android:title="List Preference" />
    <com.example.kotlinlearn.Preference.CustomSeekBarPreference
        android:defaultValue="50"
        android:key="seekbar_preference"
        android:title="SeekBar Preference" />
</PreferenceScreen>

SettingsFragment

kotlin 复制代码

package com.example.kotlinlearn.Preference
import android.os.Bundle
import android.util.Log
import androidx.preference.CheckBoxPreference
import androidx.preference.EditTextPreference
import androidx.preference.Preference
import androidx.preference.PreferenceFragmentCompat
import com.example.kotlinlearn.R
class SettingsFragment : Preference.OnPreferenceClickListener,
    Preference.OnPreferenceChangeListener, PreferenceFragmentCompat() {
    var TAG = "SettingsFragment"
    override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
        setPreferencesFromResource(R.xml.preferences, rootKey)
        var findPreference = findPreference<EditTextPreference>("edittext_preference")
        findPreference?.onPreferenceClickListener = this
        findPreference?.onPreferenceChangeListener = this
    }

    override fun onPreferenceClick(preference: Preference?): Boolean {
        Log.d(TAG, "onPreferenceClick: ")
        return false
    }

    override fun onPreferenceChange(preference: Preference?, newValue: Any?): Boolean {
        Log.d(TAG, "onPreferenceChange: ")
        return false
    }
}

PreferenceActivity

java 复制代码

package com.example.kotlinlearn.Preference

import android.os.Bundle
import androidx.activity.enableEdgeToEdge
import androidx.appcompat.app.AppCompatActivity
import androidx.core.view.ViewCompat
import androidx.core.view.WindowInsetsCompat
import com.example.kotlinlearn.R

class PreferenceActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_preference)

        // Display the fragment as the main content.
        supportFragmentManager
            .beginTransaction()
            .replace(R.id.fragment_container, SettingsFragment())
            .commit()
    }
}

效果

原理

布局：RecyclerView进行布局，PreferenceGroupAdapter，重写onCreateViewHolder()、onBindViewHolder()、getItemCount()
在onCreateViewHolder(ViewGroup parent, int viewType) 中根据viewType判断获取不同的preference。
Preference：底层调用SharedPreferences进行保存。通过以下方法持久化数值。
persistString，persistStringSet，persistInt，persistFloat，persistLong，persistBoolean

自定义Preference

重点在监听view变化，在变化后通过回调，将终值写入SharedPreferences，在初始化的时候读出值并赋给view。

kotlin 复制代码

package com.example.kotlinlearn.Preference


import android.content.Context
import android.content.res.TypedArray
import android.util.AttributeSet
import androidx.preference.Preference
import androidx.preference.PreferenceViewHolder
import android.widget.SeekBar
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.kotlinlearn.R

class CustomSeekBarPreference(context: Context, attrs: AttributeSet) : Preference(context, attrs) {

    private var currentValue: Int = 0
    private var maxValue: Int = 100

    init {
        widgetLayoutResource = R.layout.preference_seekbar
    }

    override fun onBindViewHolder(holder: PreferenceViewHolder) {
        super.onBindViewHolder(holder)
        val seekBar = holder.findViewById(R.id.seekbar) as SeekBar
        val valueText = holder.findViewById(R.id.seekbar_value) as TextView

        seekBar.max = maxValue
        seekBar.progress = currentValue

        valueText.text = currentValue.toString()

        seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
            override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
                currentValue = progress
                valueText.text = progress.toString()
                persistInt(progress)
            }

            override fun onStartTrackingTouch(seekBar: SeekBar?) {}
            override fun onStopTrackingTouch(seekBar: SeekBar?) {}
        })
    }

    override fun onGetDefaultValue(a: TypedArray, index: Int): Any {
        return a.getInt(index, 0)
    }

    override fun onSetInitialValue(defaultValue: Any?) {
        currentValue = getPersistedInt(defaultValue as? Int ?: 0)
    }
}

ex：

1.当xml中设置组件的id相同时，会导致多个preference的值相同。