Android 畫一個太極圖實例代碼

今天練手一下，一起來畫個太極圖吧~

最終效果如下：

最終效果

一般都是先講原理，我就反其道而行，先講實現吧。

1.繼承實現初始化方法

繼承View，實現基本的構造函數：

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，進行初始化操作，這裡初始化一下畫筆就好。

private Paint mPaint;

private void init() {
  initPaint();
}

/**
 * 初始化畫筆
 */
private void initPaint() {
  mPaint = new Paint();        //創建畫筆對象
  mPaint.setColor(Color.BLACK);    //設置畫筆顏色
  mPaint.setStyle(Paint.Style.FILL); //設置畫筆模式為填充
  mPaint.setStrokeWidth(10f);     //設置畫筆寬度為10px
  mPaint.setAntiAlias(true);     //設置抗鋸齒
  mPaint.setAlpha(255);        //設置畫筆透明度
}

在onSizeChanged()方法中獲取高寬，便於之後繪制計算。

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;
}

創建兩個路徑，一下計算就在這兩個路徑中進行。

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

然後到最關鍵的onDraw()方法了，這裡會分幾步來演示。

1.移動布局到中間

@Override
protected void onDraw(Canvas canvas) {
  super.onDraw(canvas);
  //移動布局到中間
  canvas.translate(mWidth / 2, mHeight / 2);
}

ps：為了簡潔，之後的代碼都是在onDraw()中逐層增加的，之後就不寫onDraw()的外出括號了。

2.畫背景黃色  

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

第二步.png

3.畫白色圓背景，即太極圖的白魚部分。

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

4.畫黑色圓背景，即太極圖的黑魚部分，和白魚一樣大小位置，只是把白魚蓋住了，這裡就需要用一些boolean運算進行繪制了。

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

//黑魚的背景
mPaint.setColor(0xff000000);
path1.addCircle(0, 0, 200, Path.Direction.CW);
canvas.drawPath(path0, mPaint);//這一段注意，之後要刪除

第四步.png

5.對黑魚（path1）進行boolean計算，把不需要的部分去掉。這裡就是要把圓的右半邊消除，這裡就需要用到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);//這一段注意，之後要刪除

第五步.png

6.這時候我們已經把不需要的另一半黑色去掉了，但是黑魚應該有個圓的頭，那麼我們就拼接一個頭給它。

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);//這一段注意，之後要刪除

第六步.png

7.到這裡，我們看到，只需要在繪制一個白魚的頭就可以了，那麼也和第五步一樣，使用一個boolean運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，已經繪制好了八卦圖的背景了，只需要在繪制魚的眼睛即可。

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

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

第八步.png

完成，最後上完整的代碼。代碼寫得有點亂，不過也是練習而已，哈哈。至於其中的boolean運算什麼的，之後在我的自定義View的筆記中在寫吧。

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: [email protected]
 */
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();
  }

  /**
   * 初始化畫筆
   */
  private void initPaint() {
    mPaint = new Paint();        //創建畫筆對象
    mPaint.setColor(Color.BLACK);    //設置畫筆顏色
    mPaint.setStyle(Paint.Style.FILL); //設置畫筆模式為填充
    mPaint.setStrokeWidth(10f);     //設置畫筆寬度為10px
    mPaint.setAntiAlias(true);     //設置抗鋸齒
    mPaint.setAlpha(255);        //設置畫筆透明度
  }

  @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);
    //移動布局到中間
    canvas.translate(mWidth / 2, mHeight / 2);

    //畫大背景顏色
    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);

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

    //畫白色小圓
    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

以上就是對Android 實現太極的實例代碼，有興趣朋友可以參考下，謝謝大家對本站的支持！