Android 画一个太极图实例代码

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今天练手一下，一起来画个太极图吧~

最终效果如下：

最终效果

一般都是先讲原理，我就反其道而行，先讲实现吧。

1.继承实现初始化方法

继承View，实现基本的构造函数：

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

public TestView(Context context, AttributeSet attrs) {
  this(context, attrs, 0);
}

public TestView(Context context, AttributeSet attrs, int defStyleAttr) {
  this(context, attrs, defStyleAttr, 0);
}

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
public TestView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
  super(context, attrs, defStyleAttr, defStyleRes);
  init();
}

在init()方法中，进行初始化操作，这里初始化一下画笔就好。

private Paint mPaint;

private void init() {
  initPaint();
}

/**
 * 初始化画笔
 */
private void initPaint() {
  mPaint = new Paint();        //创建画笔对象
  mPaint.setColor(Color.BLACK);    //设置画笔颜色
  mPaint.setStyle(Paint.Style.FILL); //设置画笔模式为填充
  mPaint.setStrokeWidth(10f);     //设置画笔宽度为10px
  mPaint.setAntiAlias(true);     //设置抗锯齿
  mPaint.setAlpha(255);        //设置画笔透明度
}

在onSizeChanged()方法中获取高宽，便于之后绘制计算。

private int mWidth;
private int mHeight;  

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
  super.onSizeChanged(w, h, oldw, oldh);
  mWidth = w;
  mHeight = h;
}

创建两个路径，一下计算就在这两个路径中进行。

private Path path0 = new Path();
private Path path1 = new Path();

然后到最关键的onDraw()方法了，这里会分几步来演示。

1.移动布局到中间

@Override
protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //移动布局到中间
  canvas.translate(mWidth / 2, mHeight / 2);
}

ps：为了简洁，之后的代码都是在onDraw()中逐层增加的，之后就不写onDraw()的外出括号了。

2.画背景黄色

mPaint.setColor(0xffffff00);
  path0.addRect(-400, -400, 400, 400, Path.Direction.CW);
  canvas.drawPath(path0, mPaint);

第二步.png

3.画白色圆背景，即太极图的白鱼部分。

mPaint.setColor(0xffffffff);
path0.rewind();
path0.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);

4.画黑色圆背景，即太极图的黑鱼部分，和白鱼一样大小位置，只是把白鱼盖住了，这里就需要用一些boolean运算进行绘制了。

//白鱼的背景
mPaint.setColor(0xffffffff);
path0.rewind();
path0.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);

//黑鱼的背景
mPaint.setColor(0xff000000);
path1.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);//这一段注意，之后要删除

第四步.png

5.对黑鱼（path1）进行boolean计算，把不需要的部分去掉。这里就是要把圆的右半边消除，这里就需要用到path.op()方法了。

mPaint.setColor(0xffffffff);
path0.rewind();
path0.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);

mPaint.setColor(0xff000000);
path1.addCircle(0, 0, 200, Path.Direction.CW);

path0.rewind();
path0.addRect(0, -200, 200, 200, Path.Direction.CW);
path1.op(path0, Path.Op.DIFFERENCE);
canvas.drawPath(path0, mPaint);//这一段注意，之后要删除

第五步.png

6.这时候我们已经把不需要的另一半黑色去掉了，但是黑鱼应该有个圆的头，那么我们就拼接一个头给它。

mPaint.setColor(0xffffffff);
path0.rewind();
path0.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);

mPaint.setColor(0xff000000);
path1.addCircle(0, 0, 200, Path.Direction.CW);

path0.rewind();
path0.addRect(0, -200, 200, 200, Path.Direction.CW);
path1.op(path0, Path.Op.DIFFERENCE);

path0.rewind();
path0.addCircle(0, -100, 100, Path.Direction.CW);
path1.op(path0, Path.Op.UNION);

canvas.drawPath(path1, mPaint);//这一段注意，之后要删除

第六步.png

7.到这里，我们看到，只需要在绘制一个白鱼的头就可以了，那么也和第五步一样，使用一个boolean运算把多余的黑色去掉即可。

mPaint.setColor(0xffffffff);
path0.rewind();
path0.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);

mPaint.setColor(0xff000000);
path1.addCircle(0, 0, 200, Path.Direction.CW);

path0.rewind();
path0.addRect(0, -200, 200, 200, Path.Direction.CW);
path1.op(path0, Path.Op.DIFFERENCE);

path0.rewind();
path0.addCircle(0, -100, 100, Path.Direction.CW);
path1.op(path0, Path.Op.UNION);

path0.rewind();
path0.addCircle(0, 100, 100, Path.Direction.CW);
path1.op(path0, Path.Op.DIFFERENCE);
canvas.drawPath(path1, mPaint);

第七步.png

8.至此，已经绘制好了八卦图的背景了，只需要在绘制鱼的眼睛即可。

//画黑色小圆
path0.rewind();
path0.addCircle(0, 100, 50, Path.Direction.CW);
mPaint.setColor(0xff000000);
canvas.drawPath(path0, mPaint);

//画白色小圆
path0.rewind();
path0.addCircle(0, -100, 50, Path.Direction.CW);
mPaint.setColor(0xffffffff);
canvas.drawPath(path0, mPaint);

第八步.png

完成，最后上完整的代码。代码写得有点乱，不过也是练习而已，哈哈。至于其中的boolean运算什么的，之后在我的自定义View的笔记中在写吧。

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;

/**
 * Created by Whitelaning on 2016/6/28.
 * Email: whitelaning@qq.com
 */
public class TestView extends View {

  private Paint mPaint;
  private int mWidth;
  private int mHeight;

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

  public TestView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public TestView(Context context, AttributeSet attrs, int defStyleAttr) {
    this(context, attrs, defStyleAttr, 0);
  }

  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  public TestView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
    init();
  }

  private void init() {
    initPaint();
  }

  /**
   * 初始化画笔
   */
  private void initPaint() {
    mPaint = new Paint();        //创建画笔对象
    mPaint.setColor(Color.BLACK);    //设置画笔颜色
    mPaint.setStyle(Paint.Style.FILL); //设置画笔模式为填充
    mPaint.setStrokeWidth(10f);     //设置画笔宽度为10px
    mPaint.setAntiAlias(true);     //设置抗锯齿
    mPaint.setAlpha(255);        //设置画笔透明度
  }

  @Override
  protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mWidth = w;
    mHeight = h;
  }

  private Path path0 = new Path();
  private Path path1 = new Path();

  @Override
  protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    //移动布局到中间
    canvas.translate(mWidth / 2, mHeight / 2);

    //画大背景颜色
    mPaint.setColor(0xffffff00);
    path0.addRect(-400, -400, 400, 400, Path.Direction.CW);
    canvas.drawPath(path0, mPaint);

    mPaint.setColor(0xffffffff);
    path0.rewind();
    path0.addCircle(0, 0, 200, Path.Direction.CW);
    canvas.drawPath(path0, mPaint);

    mPaint.setColor(0xff000000);
    path1.addCircle(0, 0, 200, Path.Direction.CW);

    path0.rewind();
    path0.addRect(0, -200, 200, 200, Path.Direction.CW);
    path1.op(path0, Path.Op.DIFFERENCE);

    path0.rewind();
    path0.addCircle(0, -100, 100, Path.Direction.CW);
    path1.op(path0, Path.Op.UNION);

    path0.rewind();
    path0.addCircle(0, 100, 100, Path.Direction.CW);
    path1.op(path0, Path.Op.DIFFERENCE);
    canvas.drawPath(path1, mPaint);

    //画黑色小圆
    path0.rewind();
    path0.addCircle(0, 100, 50, Path.Direction.CW);
    mPaint.setColor(0xff000000);
    canvas.drawPath(path0, mPaint);

    //画白色小圆
    path0.rewind();
    path0.addCircle(0, -100, 50, Path.Direction.CW);
    mPaint.setColor(0xffffffff);
    canvas.drawPath(path0, mPaint);
  }
}

Whitelaning
It's very easy to be different but very difficult to be better

以上就是对Android 实现太极的实例代码，有兴趣朋友可以参考下，谢谢大家对本站的支持！

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