本文主演参照前一篇文章打造了一个自定义的进度条，仅作代码记录。
实现效果：

1645079823700.gif

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="ProcessBarView">
        <attr name="innerColor" format="color"/>
        <attr name="outerColor" format="color"/>
        <attr name="borderWidth" format="dimension"/>
        <attr name="NumTextColor" format="color"/>
        <attr name="NumTextSize" format="dimension"/>
    </declare-styleable>
</resources>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.example.view04.ProcessBarView
        app:NumTextSize="22sp"
        app:outerColor="#C0C0C0"
        android:id="@+id/processBarView"
        android:layout_width="200dp"
        android:layout_height="200dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:text="开始"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="startAnimator"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/processBarView"
        tools:ignore="OnClick" />
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private ProcessBarView mProcessView;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mProcessView=findViewById(R.id.processBarView);

    }
    public void startAnimator(View view){
        mProcessView.setSweepAngle(0);
        ValueAnimator valueAnimator= ObjectAnimator.ofFloat(0,100);
        valueAnimator.setDuration(10000);
        valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener(){

            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float mSweepAngle= (float) animation.getAnimatedValue();
                //保留两位小数
                BigDecimal b = new BigDecimal(mSweepAngle);
                double f1 = b.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();
                mProcessView.setSweepAngle((float) f1);
            }
        });
        valueAnimator.start();
    }
}

ProcessBarView.java

public class ProcessBarView extends View {
    private Context mContext;
    private int mOutColor;
    private int mInnerColor;
    private int mBorderWidth;
    private int mNumTextSize;
    private int mNumTextColor;
    private Paint mOutPaint;
    private Paint mInnerPaint;
    private Paint mTextPaint;



    private float mSweepAngle=0;
    private int mMaxAngle=100;

    public ProcessBarView(Context context) {
        this(context, null);
    }

    public ProcessBarView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ProcessBarView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ProcessBarView);
        mOutColor = typedArray.getColor(R.styleable.ProcessBarView_outerColor, Color.RED);
        mInnerColor = typedArray.getColor(R.styleable.ProcessBarView_innerColor, Color.BLUE);
        mBorderWidth = (int) typedArray.getDimension(R.styleable.ProcessBarView_borderWidth, 20);
        mNumTextColor = typedArray.getColor(R.styleable.ProcessBarView_NumTextColor, Color.RED);
        mNumTextSize = typedArray.getDimensionPixelSize(R.styleable.ProcessBarView_NumTextSize, 20);

        mOutPaint=new Paint();
        mOutPaint.setAntiAlias(true);
        mOutPaint.setStrokeWidth(mBorderWidth);
        mOutPaint.setColor(mOutColor);
        mOutPaint.setStyle(Paint.Style.STROKE);
        mOutPaint.setStrokeCap(Paint.Cap.ROUND);

        mInnerPaint=new Paint();
        mInnerPaint.setAntiAlias(true);
        mInnerPaint.setStrokeWidth(mBorderWidth);
        mInnerPaint.setColor(mInnerColor);
        mInnerPaint.setStyle(Paint.Style.STROKE);
        mInnerPaint.setStrokeCap(Paint.Cap.ROUND);

        mTextPaint=new Paint();
        mTextPaint.setAntiAlias(true);
        mTextPaint.setColor(mNumTextColor);
        mTextPaint.setTextSize(mNumTextSize);

        typedArray.recycle();
    }

    public ProcessBarView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        mContext=context;
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        setMeasuredDimension(widthSize > heightSize ? heightSize : widthSize, widthSize > heightSize ? heightSize : widthSize);
    }

    @Override
    public void draw(Canvas canvas) {
        //画外圆
        super.draw(canvas);
        RectF rectf=new RectF(50,50,getWidth()-2*mBorderWidth,getHeight()-2*mBorderWidth);
        canvas.drawArc(rectf,0,360,false,mOutPaint);
        //画内圆
        canvas.drawArc(rectf,0,mSweepAngle/mMaxAngle*360,false,mInnerPaint);
        //画文字
        String stepText = mSweepAngle+"%";
        Rect textBounds = new Rect();
        mTextPaint.getTextBounds(stepText, 0, stepText.length(), textBounds);//测量文字画笔长度
        int dx = getWidth() / 2 - textBounds.width() / 2;
        Paint.FontMetricsInt fontMetricsInt = mTextPaint.getFontMetricsInt();
        int dy = (fontMetricsInt.bottom - fontMetricsInt.top) / 2 - fontMetricsInt.bottom;
        int baseLine = getHeight() / 2 + dy;
        canvas.drawText(stepText, dx, baseLine, mTextPaint);
    }
    public void setSweepAngle(float sweepAngle){
        this.mSweepAngle=sweepAngle;
        invalidate();
    }
}

下面是两个类的kotlin代码实现：
MainActivity

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        start.setOnClickListener { startAnimator() }
    }

    private fun startAnimator() {
        processBarView!!.setSweepAngle(0.00)
        val valueAnimator = ObjectAnimator.ofFloat(0f, 100f)
        valueAnimator.duration = 10000
        valueAnimator.addUpdateListener { animation ->
            val mSweepAngle = animation.animatedValue
            //保留两位小数
            val b: BigDecimal = BigDecimal(mSweepAngle.toString())
            val f1 = b.setScale(2, BigDecimal.ROUND_HALF_UP).toDouble()
            processBarView!!.setSweepAngle(f1)
        }
        valueAnimator.start()
    }
}

ProcessBarView

class ProcessBarView : View {
    private var mContext: Context? = null
    private var mOutColor = 0
    private var mInnerColor = 0
    private var mBorderWidth = 0
    private var mNumTextSize = 0
    private var mNumTextColor = 0
    private var mOutPaint: Paint? = null
    private var mInnerPaint: Paint? = null
    private var mTextPaint: Paint? = null
    private var mSweepAngle = 0.00
    private val mMaxAngle = 100

    @JvmOverloads
    constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) : super(
        context,
        attrs,
        defStyleAttr
    ) {
        val typedArray = context.obtainStyledAttributes(attrs, R.styleable.ProcessBarView)
        mOutColor = typedArray.getColor(R.styleable.ProcessBarView_outerColor, Color.RED)
        mInnerColor = typedArray.getColor(R.styleable.ProcessBarView_innerColor, Color.BLUE)
        mBorderWidth = typedArray.getDimension(R.styleable.ProcessBarView_borderWidth, 20f).toInt()
        mNumTextColor = typedArray.getColor(R.styleable.ProcessBarView_NumTextColor, Color.RED)
        mNumTextSize = typedArray.getDimensionPixelSize(R.styleable.ProcessBarView_NumTextSize, 20)
        mOutPaint = Paint()
        mOutPaint!!.isAntiAlias = true
        mOutPaint!!.strokeWidth = mBorderWidth.toFloat()
        mOutPaint!!.color = mOutColor
        mOutPaint!!.style = Paint.Style.STROKE //该属性代表非实心圆
        mOutPaint!!.strokeCap = Paint.Cap.ROUND

        mInnerPaint = Paint()
        mInnerPaint!!.isAntiAlias = true
        mInnerPaint!!.strokeWidth = mBorderWidth.toFloat()
        mInnerPaint!!.color = mInnerColor
        mInnerPaint!!.style = Paint.Style.STROKE
        mInnerPaint!!.strokeCap = Paint.Cap.ROUND

        mTextPaint = Paint()
        mTextPaint!!.isAntiAlias = true
        mTextPaint!!.color = mNumTextColor
        mTextPaint!!.textSize = mNumTextSize.toFloat()
        typedArray.recycle()
    }

    constructor(
        context: Context?,
        attrs: AttributeSet?,
        defStyleAttr: Int,
        defStyleRes: Int
    ) : super(context, attrs, defStyleAttr, defStyleRes) {
        mContext = context
    }

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        val widthSize = MeasureSpec.getSize(widthMeasureSpec)
        val heightSize = MeasureSpec.getSize(heightMeasureSpec)
        setMeasuredDimension(widthSize.coerceAtMost(heightSize), widthSize.coerceAtMost(heightSize))
    }

    override fun draw(canvas: Canvas) {
        //画外圆
        super.draw(canvas)
        val rectf = RectF(
            50F,
            50F,
            (width - 2 * mBorderWidth).toFloat(),
            (height - 2 * mBorderWidth).toFloat()
        )
        canvas.drawArc(rectf, 0f, 360f, false, mOutPaint!!)
        //画内圆
        canvas.drawArc(rectf, 0f, (mSweepAngle / mMaxAngle * 360).toFloat(), false, mInnerPaint!!)
        //画文字
        val stepText = "$mSweepAngle%"
        val textBounds = Rect()
        mTextPaint!!.getTextBounds(stepText, 0, stepText.length, textBounds) //测量文字画笔长度
        val dx = width / 2 - textBounds.width() / 2
        val fontMetricsInt = mTextPaint!!.fontMetricsInt
        val dy = (fontMetricsInt.bottom - fontMetricsInt.top) / 2 - fontMetricsInt.bottom
        val baseLine = height / 2 + dy
        canvas.drawText(stepText, dx.toFloat(), baseLine.toFloat(), mTextPaint!!)
    }

    fun setSweepAngle(sweepAngle: Double) {
        mSweepAngle = sweepAngle
        invalidate()
    }
}

使用kotlin代码时，别忘了在app目录下的build.gradle中添加插件

id 'kotlin-android-extensions'