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Android如何通過組合的方式自定義View_Android

作者：東土也 ? 更新時間： 2022-11-06 編程語言

前言：

自定義View可以分為兩種方式：

  • 第一種通過繼承ViewGroup，內部通過addView的方式將其他的View組合到一起。
  • 第二種則是通過繼承View，重啟View的onMeasure，onLayout，onDraw方法來繪制不規則圖形，如折線圖等。

本文介紹的是第一種方式通過組合的方式去實現自定義View。

實現自定義View首先要自定義屬性。對于自定義屬性，第一步是在項目res/values文件夾中新建attrs.xml文件，在文件中設置自定義屬性的名稱和類型，

代碼如下：

<resources>
    <declare-styleable name="InputItemLayout">
        <attr name="hint" format="string"></attr>
        <attr name="title" format="string"/>
        <attr name="inputType" format="enum">
            <enum name="text" value="0"/>
            <enum name="password" value="1"/>
            <enum name="number" value="2"/>
        </attr>
        <attr name="inputTextAppearance" format="reference"/>
        <attr name="titleTextAppearance" format="reference"/>
        <attr name="topLineAppearance" format="reference"/>
        <attr name="bottomLineAppearance" format="reference"/>
    </declare-styleable>
    <declare-styleable name="inputTextAppearance">
        <attr name="hintColor" format="color" />
        <attr name="inputColor" format="color" />
        <attr name="textSize" format="dimension" />
        <attr name="maxInputLength" format="integer" />
    </declare-styleable>
    <declare-styleable name="titleTextAppearance">
        <attr name="titleColor" format="color" />
        <attr name="titleSize" format="dimension" />
        <attr name="minWidth" format="dimension" />
    </declare-styleable>


    <declare-styleable name="lineAppearance">
        <attr name="color" format="color" />
        <attr name="height" format="dimension" />
        <attr name="leftMargin" format="dimension" />
        <attr name="rightMargin" format="dimension" />
        <attr name="enable" format="boolean" />
    </declare-styleable>
</resources>

自定義屬性都需要包裹在declare-styleable標簽中，name屬性標志這個屬性集合的名字，其中的attr標志屬性。對于自定義屬性的類型，主要的有以下幾種

string字符串類型 reference引用類型，一般是指向另外的一個資源屬性 color顏色代碼 dimension尺寸 float浮點型 boolean布爾型 integer整型 enum枚舉型

當你定義完上面的文件，接下來我們需要在自定義View中解析它們，從而獲得用戶傳遞進來的屬性。 屬性的解析可以使用以下代碼完成

val array = context.obtainStyledAttributes(attributeSet, R.styleable.InputItemLayout)
val title = array.getString(R.styleable.InputItemLayout_title)
val titleResId = array.getResourceId(R.styleable.InputItemLayout_titleTextAppearance, 0)

上面的代碼中，第一句是通過obtainStyledAttributes解析上面XML文件中屬性名為InputItemLayout的屬性內容，并返回TypedArray，后續該命名空間中的所有屬性都可以通過TypedArray.getXX()來獲得XX是屬性類型。

但是引用類型除外，因為引用類型中還包含了其他屬性，所以需要如下代碼去提取屬性。

val array1 = context.obtainStyledAttributes(attributeSet, R.styleable.InputItemLayout)
val titleResId = array1.getResourceId(R.styleable.InputItemLayout_titleTextAppearance, 0)
val array = context.obtainStyledAttributes(titleResId, R.styleable.titleTextAppearance)
val titleColor = array.getColor(
    R.styleable.titleTextAppearance_titleColor,
    resources.getColor(R.color.color_565)
)

如上代碼，我們先獲取在InputItemLayout屬性中titleTextAppearance的屬性，這時候發現titleTextAppearance是一個引用類型的屬性，在使用 context.obtainStyledAttributes(titleResId, R.styleable.titleTextAppearance)獲取titleTextAppearance中的屬性值，第一個參數titleResId是titleTextAppearance的資源ID。 最終我們獲取了所有的屬性，這時候就可以開始自定義你的View了。

當我們最終完成了所有的代碼，怎么在布局文件中使用呢。對于普通的屬性，如String Int等就和平常一樣，但是對于引用類型，我們需要在style.xml文件中定義資源文件

<com.slowtd.tcommon.InputItemLayout
   android:layout_marginTop="10dp"
   android:layout_width="match_parent"
   android:layout_height="55dp"
   app:hint="請輸入密碼"
   app:title="密碼"
   app:inputType="text"
   app:titleTextAppearance="@style/titleTextAppearance"
   app:inputTextAppearance="@style/inputTextAppearance_limitLength"
   app:topLineAppearance="@style/lineAppearance"
   app:bottomLineAppearance="@style/lineAppearance"
   />
<style name="inputTextAppearance">
   <item name="hintColor">@color/color_C1B</item>
   <item name="inputColor">@color/color_565</item>
   <item name="textSize">15sp</item>
</style>

<style name="inputTextAppearance_limitLength" parent="inputTextAppearance">
   <item name="maxInputLength">4</item>
</style>
<style name="titleTextAppearance">
   <item name="titleColor">@color/color_565</item>
   <item name="titleSize">15sp</item>
   <item name="minWidth">100dp</item>
</style>
<style name="lineAppearance">
   <item name="color">@color/black</item>
   <item name="height">2dp</item>
   <item name="leftMargin">0dp</item>
   <item name="rightMargin">0dp</item>
   <item name="enable">true</item>
</style>

下面的代碼是一個簡單的自定義輸入框代碼，供大家參考，配合上面的XML屬性資源就可以使用了。

class InputItemLayout : LinearLayout {
   private lateinit var titleView: TextView
   private lateinit var editText: EditText
   private var bottomLine: Line
   private var topLine: Line
   private var topPaint = Paint(Paint.ANTI_ALIAS_FLAG)
   private var bottomPaint = Paint(Paint.ANTI_ALIAS_FLAG)

   constructor(context: Context) : this(context, null)
   constructor(context: Context, attributeSet: AttributeSet?) : this(context, attributeSet, 0)
   constructor(context: Context, attributeSet: AttributeSet?, defStyle: Int) : super(
       context,
       attributeSet,
       defStyle
   ) {
       dividerDrawable = ColorDrawable()
       showDividers = SHOW_DIVIDER_BEGINNING

       //去加載 去讀取 自定義sytle屬性
       orientation = HORIZONTAL
       val array = context.obtainStyledAttributes(attributeSet, R.styleable.InputItemLayout)

       //解析title 屬性
       val title = array.getString(R.styleable.InputItemLayout_title)
       val titleResId = array.getResourceId(R.styleable.InputItemLayout_titleTextAppearance, 0)
       parseTitleStyle(title, titleResId)

       //解析右側的輸入框屬性
       val hint = array.getString(R.styleable.InputItemLayout_hint)
       val inputResId = array.getResourceId(R.styleable.InputItemLayout_inputTextAppearance, 0)
       val inputType = array.getInteger(R.styleable.InputItemLayout_inputType, 0)
       parseInputStyle(hint, inputResId, inputType)
       //上下分割線屬性
       val topResId = array.getResourceId(R.styleable.InputItemLayout_topLineAppearance, 0)
       val bottomResId = array.getResourceId(R.styleable.InputItemLayout_bottomLineAppearance, 0)
       topLine = parseLineStyle(topResId)
       bottomLine = parseLineStyle(bottomResId)

       if (topLine.enable) {
           topPaint.color = topLine.color
           topPaint.style = Paint.Style.FILL_AND_STROKE
           topPaint.strokeWidth = topLine.height
       }
       if (bottomLine.enable) {
           bottomPaint.color = bottomLine.color
           bottomPaint.style = Paint.Style.FILL_AND_STROKE
           bottomPaint.strokeWidth = bottomLine.height
       }
       array.recycle()
   }
   @SuppressLint("CustomViewStyleable")
   private fun parseLineStyle(resId: Int): Line {
       val line = Line()
       val array = context.obtainStyledAttributes(resId, R.styleable.lineAppearance)
       line.color =
           array.getColor(
               R.styleable.lineAppearance_color,
               ContextCompat.getColor(context, R.color.color_d1d2)
           )
       line.height = array.getDimensionPixelOffset(R.styleable.lineAppearance_height, 0).toFloat()
       line.leftMargin =
           array.getDimensionPixelOffset(R.styleable.lineAppearance_leftMargin, 0).toFloat()
       line.rightMargin =
           array.getDimensionPixelOffset(R.styleable.lineAppearance_rightMargin, 0).toFloat()
       line.enable = array.getBoolean(R.styleable.lineAppearance_enable, false)

       array.recycle()
       return line
   }
   inner class Line {
       var color = 0
       var height = 0f
       var leftMargin = 0f
       var rightMargin = 0f;
       var enable: Boolean = false
   }
   @SuppressLint("CustomViewStyleable")
   private fun parseInputStyle(hint: String?, resId: Int, inputType: Int) {

       val array = context.obtainStyledAttributes(resId, R.styleable.inputTextAppearance)

       val hintColor = array.getColor(
           R.styleable.inputTextAppearance_hintColor,
           ContextCompat.getColor(context, R.color.color_d1d2)
       )
       val inputColor = array.getColor(
           R.styleable.inputTextAppearance_inputColor,
           ContextCompat.getColor(context, R.color.color_565)
       )
       //px
       val textSize = array.getDimensionPixelSize(
           R.styleable.inputTextAppearance_textSize,
           applyUnit(TypedValue.COMPLEX_UNIT_SP, 15f)
       )
       val maxInputLength = array.getInteger(R.styleable.inputTextAppearance_maxInputLength, 0)

       editText = EditText(context)
       if (maxInputLength > 0) {
           editText.filters = arrayOf(InputFilter.LengthFilter(maxInputLength))//最多可輸入的字符數
       }
       editText.setPadding(0, 0, 0, 0)
       val params = LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT)
       params.weight = 1f
       editText.layoutParams = params
       editText.hint = hint
       editText.setTextColor(inputColor)
       editText.setHintTextColor(hintColor)
       editText.gravity = LEFT or (CENTER)
       editText.setBackgroundColor(Color.TRANSPARENT)
       editText.setTextSize(TypedValue.COMPLEX_UNIT_PX, textSize.toFloat())
       /**
        * <enum name="text" value="0"></enum>
        * <enum name="password" value="1"></enum>
        * <enum name="number" value="2"></enum>
        */
       if (inputType == 0) {
           editText.inputType = InputType.TYPE_CLASS_TEXT
       } else if (inputType == 1) {
           editText.inputType =
               InputType.TYPE_TEXT_VARIATION_PASSWORD or (InputType.TYPE_CLASS_TEXT)
       } else if (inputType == 2) {
           editText.inputType = InputType.TYPE_CLASS_NUMBER
       }
       addView(editText)
       array.recycle()
   }
   @SuppressLint("CustomViewStyleable")
   private fun parseTitleStyle(title: String?, resId: Int) {
       val array = context.obtainStyledAttributes(resId, R.styleable.titleTextAppearance)
       val titleColor = array.getColor(
           R.styleable.titleTextAppearance_titleColor,
           resources.getColor(R.color.color_565)
       )
       //px
       val titleSize = array.getDimensionPixelSize(
           R.styleable.titleTextAppearance_titleSize,
           applyUnit(TypedValue.COMPLEX_UNIT_SP, 15f)
       )
       val minWidth = array.getDimensionPixelOffset(R.styleable.titleTextAppearance_minWidth, 0)

       titleView = TextView(context)
       titleView.setTextSize(TypedValue.COMPLEX_UNIT_PX, titleSize.toFloat())  //sp---當做sp在轉換一次
       titleView.setTextColor(titleColor)
       titleView.layoutParams = LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT)
       titleView.minWidth = minWidth
       titleView.gravity = LEFT or (CENTER)
       titleView.text = title
       addView(titleView)
       array.recycle()
   }
   override fun onDraw(canvas: Canvas?) {
       super.onDraw(canvas)


       //巨坑
       if (topLine.enable) {
           canvas!!.drawLine(
               topLine.leftMargin,
               0f,
               measuredWidth - topLine.rightMargin,
               0f,
               topPaint
           )
       }

       if (bottomLine.enable) {
           canvas!!.drawLine(
               bottomLine.leftMargin,
               height - bottomLine.height,
               measuredWidth - bottomLine.rightMargin,
               height - bottomLine.height,
               bottomPaint
           )
       }
   }
   private fun applyUnit(applyUnit: Int, value: Float): Int {
       return TypedValue.applyDimension(applyUnit, value, resources.displayMetrics).toInt()
   }
   fun getTitleView(): TextView {
       return titleView
   }
   fun getEditText(): EditText {
       return editText
   }
}

原文鏈接：https://juejin.cn/post/7142758407844397063

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