最近项目完成就开始搞一些有用没用的东西，以前面试的时候有人问我那种圆弧效果怎么做，还问我翻牌效果，我只看过，没有做过，现在有空了，而且想到可能会用到就做个简单的
圆弧很简单，自定义个View,创建个Paint，设置 arcPaint.setStyle(Paint.Style.STROKE)再设置圆弧的宽，再在onDraw内调用canvas.drawArc()就好了
现在只做一个带刻度的圆弧和一个开口地方是圆角的圆弧。其他各种效果以后再摸索

ArcView.java

public class ArcView extends View {
    private Paint textPaint;
    private Paint arcPaint;
    private Shader backGradient;
    private Xfermode xfermode;
    private RectF oval = new RectF();
    public ArcView(Context context) {
        super(context);
        init();
    }

    public ArcView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    private int type = 0;

    public void setType(int type) {
        this.type = type;
        if(type == 1){
            start = 10;
        }
    }
    private void init(){
        arcPaint = new Paint();
        arcPaint.setAntiAlias(true);
        if(type == 0){
            xfermode = new PorterDuffXfermode(PorterDuff.Mode.CLEAR);
        }

        textPaint = new Paint();
        textPaint.setAntiAlias(true);
        textPaint.setColor(Color.WHITE);
        textPaint.setTextSize(50);
        textPaint.setStyle(Paint.Style.FILL);
        textPaint.setTextAlign(Paint.Align.CENTER);

    }

    private int strokeWidth = 40;

    public void setStrokeWidth(int strokeWidth) {
        this.strokeWidth = strokeWidth;
    }

    private int max = 100;

    public void setMax(int max) {
        this.max = max;
    }

    private int progress;

    public void setProgress(int progress) {
        this.progress = progress;
        postInvalidate();
    }

    private int start = 0;

    public void setStart(int start) {
        if(type == 1){
            if(start < 10){
                start = 10;
            }
        }else{
            if(start < 0){
                start = 0;
            }
        }

        this.start = start;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if(getWidth() != 0){
            int width = getWidth();
            int height = getHeight();
            int cx = width/2;
            int cy = height/2;
            if(backGradient == null){
                oval.set( strokeWidth/2, strokeWidth/2,
                        width - strokeWidth/2, height - strokeWidth/2);
                int colorStart = getResources().getColor(R.color.colorPrimary);
                int color2 = Color.GREEN;
                int colorEnd = Color.RED;

                backGradient = new SweepGradient(cx,cy,new int[]{color2 ,colorStart, colorEnd},new float[]{0.1f,0.4f,0.9f});

                postInvalidate();
            }else{
                int sc = 0;
                if(type == 0){
                    sc = canvas.saveLayer(0, 0, canvas.getWidth(), canvas.getHeight(), null, Canvas.ALL_SAVE_FLAG);
                }else{
                    canvas.save();
                }

                canvas.rotate(90,cx,cy);
                arcPaint.setColor(Color.GRAY);
                arcPaint.setStyle(Paint.Style.STROKE);
                arcPaint.setStrokeWidth(strokeWidth);
                if(type == 1){
                    arcPaint.setStrokeCap(Paint.Cap.ROUND);
                }

                int s =start;
                int e = start*2;
                //底色
                canvas.drawArc(oval,s,360 - e,false,arcPaint);
                arcPaint.setShader(backGradient);
                //渐变
                int sweep = (int) (progress*1.0f/max*(360 - e));
                canvas.drawArc(oval,s,sweep,false,arcPaint);

                arcPaint.setShader(null);


                if(type == 0){
                    //刻度
                    arcPaint.setXfermode(xfermode);
                    arcPaint.setStyle(Paint.Style.STROKE);
                    arcPaint.setStrokeWidth(5);

                    for (int i = 0; i < 36;i++){
                        canvas.drawLine(0,cy,getWidth(),cy,arcPaint);
                        canvas.rotate(5,cx,cy);
                    }
                    arcPaint.setXfermode(null);
                    canvas.restoreToCount(sc);
                }else{
                    canvas.restore();
                }

                Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
                float top = fontMetrics.top;
                float bottom = fontMetrics.bottom;
                int baseLineY = (int) (cy - top/2 - bottom/2);
                canvas.drawText(progress+"%",cx,baseLineY,textPaint);

                //十字线，用来参考的，可删除
                canvas.drawLine(cx,0,cx,height,textPaint);
                canvas.drawLine(0,cy,width,cy,textPaint);

            }

        }

    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.hyq.hm.testdraw.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:gravity="center_horizontal">

        <SeekBar
            android:id="@+id/seek_bar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="20dp"
            android:max="100"/>
        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal">
            <com.hyq.hm.testdraw.ArcView
                android:id="@+id/arc_view_0"
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:layout_margin="5dp"
                android:background="#885453"
                />
            <com.hyq.hm.testdraw.ArcView
                android:id="@+id/arc_view_1"
                android:layout_width="100dp"
                android:layout_height="100dp"
                android:layout_margin="5dp"
                />
        </LinearLayout>
    </LinearLayout>


</android.support.constraint.ConstraintLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {

    private SeekBar seekBar;
    private ArcView arcView0;
    private ArcView arcView1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        arcView0 = findViewById(R.id.arc_view_0);
        arcView1 = findViewById(R.id.arc_view_1);
        arcView0.setType(0);
        arcView1.setType(1);
        arcView0.setStart(10);
        arcView1.setStart(0);

        seekBar = findViewById(R.id.seek_bar);
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                arcView0.setProgress(progress);
                arcView1.setProgress(progress);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });
    }
}