Android NumberPicker：設置最小值，最大值，來自XML的默認值

Question

有沒有方法根據XML佈局設置NumberPicker的最小值，最大值和默認值？

我從活動代碼中做它：

np = (NumberPicker) findViewById(R.id.np); 
np.setMaxValue(120); 
np.setMinValue(0); 
np.setValue(30); 

XML顯然是比較合適的，因爲它定義屬性，而不是行爲。

有沒有辦法使用XML佈局來設置它們？

Answer 1

我有同樣的問題，這是我如何解決它（根據MKJParekh的評論）：

1. 我創建了自己NumberPicker級

   package com.exaple.project; 
   
   import android.annotation.TargetApi; 
   import android.content.Context; 
   import android.os.Build; 
   import android.util.AttributeSet; 
   import android.widget.NumberPicker; 
   
   @TargetApi(Build.VERSION_CODES.HONEYCOMB)//For backward-compability 
   public class MyNumberPicker extends NumberPicker { 
   
       public MyNumberPicker(Context context) { 
        super(context); 
       } 
   
       public MyNumberPicker(Context context, AttributeSet attrs) { 
        super(context, attrs); 
        processAttributeSet(attrs); 
       } 
   
       public MyNumberPicker(Context context, AttributeSet attrs, int defStyle) { 
        super(context, attrs, defStyle); 
        processAttributeSet(attrs); 
       } 
       private void processAttributeSet(AttributeSet attrs) { 
        //This method reads the parameters given in the xml file and sets the properties according to it 
        this.setMinValue(attrs.getAttributeIntValue(null, "min", 0)); 
        this.setMaxValue(attrs.getAttributeIntValue(null, "max", 0)); 
       } 
   } 
   

2. 現在，您可以在您的xml佈局文件中使用此NumberPicker

   <com.exaple.project.myNumberPicker 
       android:id="@+id/numberPicker1" 
       android:layout_width="match_parent" 
       android:layout_height="wrap_content" 
       android:layout_gravity="center" 
       android:orientation="vertical" 
       max="100" 
       min="1" /> 
   

感謝MKJParekh對他有用的評論

Answer 2

這裏是下面的Android Docs
（從而支持主題&的Android Studio設計預覽）的更新版本

值/ attrs.xml：

<?xml version="1.0" encoding="utf-8"?> 
<resources> 

    <declare-styleable name="NumberPickerWithXml"> 
     <attr name="maxValue" format="integer" /> 
     <attr name="minValue" format="integer" /> 
     <attr name="defaultValue" format="integer" /> 
    </declare-styleable> 

</resources> 

NumberPickerWithXml.kt：

package com.example.library.ui 

import android.content.Context 
import android.util.AttributeSet 
import android.widget.NumberPicker 
import com.example.library.ui.R 

class NumberPickerWithXml : NumberPicker { 

    constructor(context: Context) : super(context) 

    constructor(context: Context, attrs: AttributeSet) : super(context, attrs) { 
     processXmlAttributes(attrs) 
    } 

    constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int) : super(context, attrs, defStyleAttr) { 
     processXmlAttributes(attrs, defStyleAttr) 
    } 

    constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int, defStyleRes: Int) : super(context, attrs, defStyleAttr, defStyleRes) { 
     processXmlAttributes(attrs, defStyleAttr, defStyleRes) 
    } 

    private fun processXmlAttributes(attrs: AttributeSet, defStyleAttr: Int = 0, defStyleRes: Int = 0) { 
     val attributes = context.theme.obtainStyledAttributes(attrs, R.styleable.NumberPickerWithXml, defStyleAttr, defStyleRes) 

     try { 
      this.minValue = attributes.getInt(R.styleable.NumberPickerWithXml_minValue, 0) 
      this.maxValue = attributes.getInt(R.styleable.NumberPickerWithXml_maxValue, 0) 
      this.value = attributes.getInt(R.styleable.NumberPickerWithXml_defaultValue, 0) 
     } finally { 
      attributes.recycle() 
     } 
    } 

} 

......或NumberPickerWithXml.java（未經測試）：

package com.example.library.ui 

import android.content.Context 
import android.util.AttributeSet 
import android.widget.NumberPicker 
import com.example.library.ui.R 

public class NumberPickerWithXml extends NumberPicker { 

    public NumberPickerWithXml(Context context) { 
     super(context); 
    } 

    public NumberPickerWithXml(Context context, AttributeSet: attrs) { 
     super(context, attrs); 
     processXmlAttributes(attrs, 0, 0); 
    } 

    public NumberPickerWithXml(Context context, AttributeSet: attrs, int: defStyleAttr) { 
     super(context, attrs, defStyleAttr); 
     processXmlAttributes(attrs, defStyleAttr, 0); 
    } 

    public NumberPickerWithXml(Context context, AttributeSet: attrs, int: defStyleAttr, int: defStyleRes) { 
     super(context, attrs, defStyleAttr, defStyleRes); 
     processXmlAttributes(attrs, defStyleAttr, defStyleRes); 
    } 

    private void processXmlAttributes(AttributeSet: attrs, int: defStyleAttr, int: defStyleRes) { 
     TypedArray attributes = context.getTheme().obtainStyledAttributes(attrs, R.styleable.NumberPickerWithXml, defStyleAttr, defStyleRes) 

     try { 
      this.minValue = attributes.getInt(R.styleable.NumberPickerWithXml_minValue, 0); 
      this.maxValue = attributes.getInt(R.styleable.NumberPickerWithXml_maxValue, 0); 
      this.value = attributes.getInt(R.styleable.NumberPickerWithXml_defaultValue, 0); 
     } finally { 
      attributes.recycle(); 
     } 
    } 

} 

使用你的佈局：

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

    <com.example.library.ui.NumberPickerWithXml 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     custom:defaultValue="30" 
     custom:maxValue="120" 
     custom:minValue="0" /> 

</LinearLayout>