import android.content.Context
import android.graphics.*
import android.support.annotation.ColorInt
import android.support.annotation.ColorRes
import android.text.TextPaint
import android.util.AttributeSet
import android.widget.TextView
import com.ans.utilactivity.R


class GradientTextView @JvmOverloads constructor(
  context: Context?,
  attrs: AttributeSet? = null
) : TextView(context, attrs) {


  private var mPaint: TextPaint? = null
  private var mLinearGradient: LinearGradient? = null
  private var mMeasureWidth = 0
  private var mTextMatrix: Matrix? = null

  @ColorInt
  private var mStartColor: Int = 0xFF333333.toInt()
  @ColorInt
  private var mEndColor: Int = 0xFF333333.toInt()

  init {
    if (attrs != null) {
      val attrArray = getContext().obtainStyledAttributes(attrs, R.styleable.GradientTextView)
      mStartColor = attrArray.getColor(R.styleable.GradientTextView_startColor, mStartColor)
      mEndColor = attrArray.getColor(R.styleable.GradientTextView_endColor, mEndColor)
    }
  }

  /**
   * 復(fù)寫onSizeChanged方法
   *
   */
  override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
    super.onSizeChanged(w, h, oldw, oldh)
    mMeasureWidth = measuredWidth
    if (mMeasureWidth > 0) {
      mPaint = paint
      //(x0,y0)：漸變起始點(diǎn)坐標(biāo)
      //(x1,y1):漸變結(jié)束點(diǎn)坐標(biāo)
      //color0:漸變開始點(diǎn)顏色,16進(jìn)制的顏色表示，必須要帶有透明度
      //color1:漸變結(jié)束顏色
      //colors:漸變數(shù)組
      //positions:位置數(shù)組，position的取值范圍[0,1],作用是指定某個(gè)位置的顏色值，如果傳null，漸變就線性變化。
      //tile:用于指定控件區(qū)域大于指定的漸變區(qū)域時(shí)，空白區(qū)域的顏色填充方法。
      mLinearGradient = LinearGradient(
        0f
        , 0f
        , mMeasureWidth.toFloat()
        , 0f
        , intArrayOf(mStartColor, mEndColor)
        , null
        , Shader.TileMode.CLAMP
      )
      mPaint?.shader = mLinearGradient
      mTextMatrix = Matrix()
    }
  }
}

<declare-styleable name="GradientTextView">
  <attr name="startColor" format="color"/>
  <attr name="endColor" format="color"/>
</declare-styleable>

<前綴.GradientTextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!"
    app:startColor="@color/colorPrimary"
    app:endColor="@color/colorAccent"
    />