求适配AndroidX PreferenceScreen的Java自定义Preference示例

以下是适配AndroidX Preference Library的Java自定义Preference示例，包含ColorPickerPreference和NumberPickerPreference，直接基于AndroidX组件扩展，无需依赖第三方库。

1. ColorPickerPreference 实现 #

点击后弹出颜色选择对话框，选中颜色自动保存到SharedPreferences，同时在Preference项上展示颜色预览与色值。

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AlertDialog;
import androidx.preference.DialogPreference;
import androidx.preference.PreferenceViewHolder;

public class ColorPickerPreference extends DialogPreference {
    private int mCurrentColor;
    private static final int DEFAULT_COLOR = Color.WHITE;

    public ColorPickerPreference(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        setDialogLayoutResource(R.layout.dialog_color_picker);
        setPositiveButtonText(android.R.string.ok);
        setNegativeButtonText(android.R.string.cancel);
    }

    @Override
    protected void onBindViewHolder(@NonNull PreferenceViewHolder holder) {
        super.onBindViewHolder(holder);
        // 更新预览区域的颜色和色值文本
        ImageView colorPreview = (ImageView) holder.findViewById(R.id.color_preview);
        TextView colorValue = (TextView) holder.findViewById(R.id.color_value);
        if (colorPreview != null) {
            colorPreview.setBackground(new ColorDrawable(mCurrentColor));
        }
        if (colorValue != null) {
            colorValue.setText(String.format("#%06X", (0xFFFFFF & mCurrentColor)));
        }
    }

    @Override
    protected void onSetInitialValue(@Nullable Object defaultValue) {
        mCurrentColor = getPersistedInt(defaultValue != null ? (Integer) defaultValue : DEFAULT_COLOR);
    }

    @Override
    protected Object onGetDefaultValue(@NonNull TypedArray a, int index) {
        return a.getColor(index, DEFAULT_COLOR);
    }

    @Override
    protected void showDialog(@Nullable Bundle state) {
        super.showDialog(state);
        AlertDialog dialog = (AlertDialog) getDialog();
        if (dialog != null) {
            android.widget.ColorPickerView colorPicker = dialog.findViewById(R.id.color_picker);
            if (colorPicker != null) {
                colorPicker.setColor(mCurrentColor);
                colorPicker.setOnColorChangedListener(color -> mCurrentColor = color);
            }
            dialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(v -> {
                if (callChangeListener(mCurrentColor)) {
                    persistInt(mCurrentColor);
                    notifyChanged();
                    dialog.dismiss();
                }
            });
        }
    }
}

对应对话框布局res/layout/dialog_color_picker.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="16dp">

    <android.widget.ColorPickerView
        android:id="@+id/color_picker"
        android:layout_width="match_parent"
        android:layout_height="200dp" />

</LinearLayout>

2. NumberPickerPreference 实现 #

点击后弹出带滚轮选择器的对话框，支持自定义数值范围，选中数值自动保存并更新Preference摘要。

import android.content.Context;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.View;
import android.widget.NumberPicker;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AlertDialog;
import androidx.preference.DialogPreference;

public class NumberPickerPreference extends DialogPreference {
    private int mCurrentValue;
    private int mMinValue = 0;
    private int mMaxValue = 100;
    private static final int DEFAULT_VALUE = 50;

    public NumberPickerPreference(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        setDialogLayoutResource(R.layout.dialog_number_picker);
        setPositiveButtonText(android.R.string.ok);
        setNegativeButtonText(android.R.string.cancel);

        // 读取xml中配置的数值范围属性
        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.NumberPickerPreference);
        mMinValue = a.getInt(R.styleable.NumberPickerPreference_minValue, mMinValue);
        mMaxValue = a.getInt(R.styleable.NumberPickerPreference_maxValue, mMaxValue);
        a.recycle();
    }

    @Override
    protected void onSetInitialValue(@Nullable Object defaultValue) {
        mCurrentValue = getPersistedInt(defaultValue != null ? (Integer) defaultValue : DEFAULT_VALUE);
        setSummary(String.valueOf(mCurrentValue));
    }

    @Override
    protected Object onGetDefaultValue(@NonNull TypedArray a, int index) {
        return a.getInt(index, DEFAULT_VALUE);
    }

    @Override
    protected void showDialog(@Nullable Bundle state) {
        super.showDialog(state);
        AlertDialog dialog = (AlertDialog) getDialog();
        if (dialog != null) {
            NumberPicker numberPicker = dialog.findViewById(R.id.number_picker);
            if (numberPicker != null) {
                numberPicker.setMinValue(mMinValue);
                numberPicker.setMaxValue(mMaxValue);
                numberPicker.setValue(mCurrentValue);
                // 禁用手动输入，仅保留滚轮选择
                numberPicker.setDescendantFocusability(NumberPicker.FOCUS_BLOCK_DESCENDANTS);
            }
            dialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(v -> {
                if (numberPicker != null) {
                    int newValue = numberPicker.getValue();
                    if (callChangeListener(newValue)) {
                        mCurrentValue = newValue;
                        persistInt(mCurrentValue);
                        setSummary(String.valueOf(mCurrentValue));
                        dialog.dismiss();
                    }
                }
            });
        }
    }
}

对应对话框布局res/layout/dialog_number_picker.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:padding="16dp">

    <NumberPicker
        android:id="@+id/number_picker"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

</LinearLayout>

添加自定义属性到res/values/attrs.xml：

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

在PreferenceScreen中使用 #

在你的偏好设置xml中直接引用自定义Preference：

<?xml version="1.0" encoding="utf-8"?>
<androidx.preference.PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <com.yourpackage.ColorPickerPreference
        android:key="theme_color"
        android:title="主题颜色"
        android:defaultValue="#FFFFFF"/>

    <com.yourpackage.NumberPickerPreference
        android:key="count_value"
        android:title="数量设置"
        android:defaultValue="50"
        app:minValue="0"
        app:maxValue="200"/>

</androidx.preference.PreferenceScreen>

依赖配置 #

确保模块级build.gradle中包含AndroidX Preference依赖：

dependencies {
    implementation 'androidx.preference:preference:1.2.0'
}

内容的提问来源于stack exchange，提问作者tm1701