Android 绘制太极图实例详解

package com.jackie.taijicircle; 
 
import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.RectF; 
import android.util.AttributeSet; 
import android.view.View; 
 
/** 
 * Created by Administrator on 2016/11/14. 
 */ 
 
public class TaijiCircleView extends View { 
  private Paint mPaint; 
  private int mWidth; 
 
  public TaijiCircleView(Context context) { 
    this(context, null); 
  } 
 
  public TaijiCircleView(Context context, AttributeSet attrs) { 
    this(context, attrs, 0); 
  } 
 
  public TaijiCircleView(Context context, AttributeSet attrs, int defStyleAttr) { 
    super(context, attrs, defStyleAttr); 
 
    initPaint(); 
  } 
 
  private void initPaint() { 
    mPaint = new Paint(); 
    mPaint.setColor(Color.BLACK); 
    mPaint.setStrokeWidth(5); 
    mPaint.setAntiAlias(true); 
    mPaint.setDither(true); 
    mPaint.setStyle(Paint.Style.FILL); 
  } 
 
  private void drawCircle(Canvas canvas) { 
    mPaint.setColor(Color.BLACK); 
    //x轴正轴为0° 
//    canvas.drawArc(new RectF(0, 0, width, width), 90, 180, true, mPaint); 
    canvas.drawArc(new RectF(0, 0, mWidth, mWidth), 270, -180, true, mPaint); 
 
    mPaint.setColor(Color.WHITE); 
//    canvas.drawArc(new RectF(0, 0, width, width), 90, -180, true, mPaint); 
    canvas.drawArc(new RectF(0, 0, mWidth, mWidth), 270, 180, true, mPaint); 
  } 
 
  private void drawHalfCircle(Canvas canvas) { 
    mPaint.setColor(Color.BLACK); 
    canvas.drawArc(new RectF(mWidth / 4, 0, mWidth / 2 + mWidth / 4, mWidth / 2), 
        270, 180, true, mPaint); 
 
    mPaint.setColor(Color.WHITE); 
    canvas.drawArc(new RectF(mWidth / 4, mWidth / 2, mWidth / 2 + mWidth / 4, mWidth), 
        270, -180, true, mPaint); 
  } 
 
  private void drawSmallCircle(Canvas canvas) { 
    mPaint.setColor(Color.BLACK); 
    canvas.drawCircle(mWidth / 2, mWidth * 3 / 4, 20, mPaint); 
 
    mPaint.setColor(Color.WHITE); 
    canvas.drawCircle(mWidth / 2, mWidth / 4, 20, mPaint); 
  } 
 
  @Override 
  protected void onDraw(Canvas canvas) { 
    super.onDraw(canvas); 
 
    mWidth = Math.min(getWidth(), getHeight()); 
    drawCircle(canvas); 
    drawHalfCircle(canvas); 
    drawSmallCircle(canvas); 
  } 
}