Android高级UI开发（四十三）Canvas基本知识（1）
【摘要】 直接贴代码，注释很详细。源码下载：https://download.csdn.net/download/gaoxiaoweiandy/12371948
package com.xiaowei.lsn7_canvas; import android.content.Context;import android.graphics.Bitmap;import android.g...
直接贴代码，注释很详细。源码下载：https://download.csdn.net/download/gaoxiaoweiandy/12371948
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package com.xiaowei.lsn7_canvas;
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import android.content.Context;
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import android.graphics.Bitmap;
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import android.graphics.Canvas;
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import android.graphics.Color;
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import android.graphics.Paint;
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import android.graphics.RectF;
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import android.graphics.drawable.BitmapDrawable;
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import android.util.AttributeSet;
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import android.view.View;
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import com.xiaowei.lsn7_canvas.R;
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/**
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* Created by John on 2017/5/14.
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*/
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public class MyView2 extends View {
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private Bitmap mBitmap;
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public MyView2(Context context) {
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this(context,null);
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}
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public MyView2(Context context, AttributeSet attrs) {
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super(context, attrs);
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mBitmap = ((BitmapDrawable)getResources().getDrawable(R.drawable.xyjy2)).getBitmap();
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}
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@Override
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protected void onDraw(Canvas canvas) {
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super.onDraw(canvas);
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//绘制直线
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Paint paint = new Paint();
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paint.setColor(Color.RED);
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//paint.setStyle(Paint.Style.FILL);//
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paint.setAntiAlias(true);
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paint.setDither(true);
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paint.setStyle(Paint.Style.STROKE);
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paint.setStrokeWidth(20);
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/*gxw-s for 画线段2点之间
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canvas.drawLine(0, 0, 100, 100, paint);
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gxw-e*/
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/*gxw-s for 画多段线段，4个值为1条线段，4个值分别是起点的x,y与终点的x',y'。
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float []pts = {0,0,100,100,200,200,300,300,0,0};
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canvas.drawLines(pts, paint);
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gxw-e*/
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/*gxw-s for 画多段线段，可以跳过几个值（这里为6），跳过之后再去绘制几个值（这里为4，即(300,300,0,0)）,最终就只画了这条起点为300，300终点为0，0的线段
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float []pts = {0,0,100,100,200,200,300,300,0,0,100,100};
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canvas.drawLines(pts, 6, 4, paint);
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gxw-e*/
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/*gxw-s for 画1个点与画多个点
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canvas.drawPoint(500, 500, paint);
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float []pts = {0,0,100,100,200,200,300,300,0,0};
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canvas.drawPoints(pts, paint);
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gxw-e */
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/*gxw-s for 画矩形
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RectF r = new RectF(100, 100, 500, 500);
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canvas.drawRect(r, paint);
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canvas.drawRect(100, 100, 400, 500, paint);
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gxw-e*/
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/*gxw-s for 绘制圆角矩形，30，30为圆角半径,x,y
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RectF r = new RectF(100, 100, 400, 500);
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canvas.drawRoundRect(r, 30, 30, paint);
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gxw-e*/
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//画圆canvas.drawCircle(300, 300, 200, paint);
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/*gxw-s for 绘制椭圆的2种方法
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// canvas.drawOval(100,100,400,300, paint);
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RectF r = new RectF(100, 100, 400, 300);
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canvas.drawOval(r, paint);
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gxw-e*/
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/*gxw-s for 画弧形
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// paint.setStyle(Paint.Style.FILL);
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RectF r = new RectF(100, 100, 400, 500);
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canvas.drawArc(r, 0, 90, false, paint);//顺时针旋转90度
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gxw-e */
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/*gxw-s for 绘制路径，这里为直线路径与贝塞尔曲线*/
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/* 绘制直线路径
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Path path = new Path();
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path.moveTo(100, 100);//画笔落笔的位置
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path.lineTo(200, 100);
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path.lineTo(200, 200);
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path.close();//封闭路径,在这里如果不封闭，绘制的将是一个直角，不能成为一个三角形。
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*/
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/* gxw-s for 绘制贝塞尔曲线路径
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Path path = new Path();
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path.cubicTo(250, 200, 350, 300, 450, 400);//绘制贝塞尔曲线
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canvas.drawPath(path, paint);gxw-e for 绘制贝塞尔曲线路径*/
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/*gxw-e */
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/*gxw-s for 圆角矩形路径
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RectF r = new RectF(100, 100, 600, 800);
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Path path = new Path();
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float radii[] = {10,10,10,10,10,10,50,60}; //圆角半径，分别为左上，右上，右下，左下。
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path.addRoundRect(r, radii, Path.Direction.CCW);
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canvas.drawPath(path, paint);
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gxw-e */
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/*gxw-s for 区域:将椭圆绘制成多个小矩形组成，高等数学中的微积分
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RectF r = new RectF(100, 100, 600, 800);
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Path path = new Path();
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path.addOval(r, Path.Direction.CCW);
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//创建一块矩形的区域
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Region region = new Region(100, 100, 600, 800);
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Region region1 = new Region();
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region1.setPath(path, region);//path的椭圆区域和矩形区域进行交集
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//结合区域迭代器使用（得到图形里面的所有的矩形区域）
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RegionIterator iterator = new RegionIterator(region1);
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Rect rect = new Rect();
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while (iterator.next(rect)) {
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canvas.drawRect(rect, paint);
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}
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还有区域的合并，交集等操作。
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gxw-e */
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/*
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平移START
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Canvas绘制坐标轴，canvas的坐标系原点永远是View的左上角
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canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
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paint.setColor(Color.BLUE);
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canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴
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//这里实质平移的是Canvas里面的图形（绘图坐标系），然后Canvas并没有平移，它的坐标系原点还是View的左上角。
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canvas.translate(100, 50);
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canvas.save();
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//Canvas平移后再绘制坐标轴，发现“坐标轴图形”确实平移了
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paint.setColor(Color.GREEN);
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//canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
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paint.setColor(Color.BLACK);
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canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴
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===================================================================
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//旋转
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canvas.rotate(45);
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canvas.save();
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//旋转后再绘制坐标轴，发现“坐标轴图形”确实旋转了
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paint.setColor(Color.GREEN);
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canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
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paint.setColor(Color.BLACK);
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canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴
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==================================================================
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//缩放Scale
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canvas.restoreToCount(1);//还原到第一次save的 状态
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canvas.drawColor(Color.BLUE);
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RectF r = new RectF(0, 0, 400, 400);
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paint.setColor(Color.RED);
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//sx,sy：分别对x/y方向的一个缩放系数,画布的缩放会导致里面所有的绘制的东西都会有一个缩放效果
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canvas.scale(1.5f, 1.5f);
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canvas.drawRect(r, paint);
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=====================================================================
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//旋转角度
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canvas.restoreToCount(1);//还原到第一次save的 状态
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canvas.drawColor(Color.BLUE);
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paint.setColor(Color.WHITE);
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RectF rect = new RectF(300, 600, 400, 800);
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canvas.drawRect(rect, paint);
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canvas.rotate(40, 300, 600);
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paint.setColor(Color.YELLOW);
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canvas.drawRect(rect, paint);
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=============================================================================
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*/
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//4. 斜拉画布
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/* canvas.drawColor(Color.BLUE);
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paint.setColor(Color.RED);
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RectF rec2t = new RectF(100, 100, 300, 300);
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canvas.drawRect(rec2t, paint);
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paint.setColor(Color.YELLOW);
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//sx,sy倾斜度：X轴方向上倾斜60度，tan60=根号3
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canvas.skew(1.73f, 0);
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canvas.drawRect(rec2t, paint);
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=========================================================================
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*/
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/*gxw-s for 裁剪
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RectF r = new RectF(200, 200, 400, 500);
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canvas.drawRect(r, paint);
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paint.setColor(Color.BLUE);
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canvas.clipRect(new Rect(250, 250, 300, 400));
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canvas.drawColor(Color.YELLOW);
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=====================================================
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gxw-e for 裁剪*/
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canvas.drawColor(Color.WHITE);
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paint.setColor(Color.GREEN);
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RectF r = new RectF(200, 200, 400, 500);
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canvas.drawRect(r, paint);
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canvas.translate(100,100);
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paint.setColor(Color.RED);
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canvas.drawRect(r, paint);
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int layer = canvas.saveLayer(0,0,canvas.getWidth(),canvas.getHeight(),null,Canvas.ALL_SAVE_FLAG);
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paint.setColor(Color.YELLOW);
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canvas.drawRect(r, paint);
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/*gxw -s for 笔记
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Canvas的状态保存---状态栈、Layer栈
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状态栈--save、 restore方法来保存和还原变换操作Matrix以及Clip剪裁,也可以通过restoretoCount直接还原到对应栈的保存状态
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Layer栈--- saveLayer的时候都会新建一个透明的图层（离屏Bitmap-离屏缓冲），并且会将saveLayer之前的一些Canvas操作延续过来
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后续的绘图操作都在新建的layer上面进行,当我们调用restore 或者 restoreToCount 时 更新到对应的图层和画布上
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*/
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}
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}
文章来源: blog.csdn.net，作者：冉航--小虾米，版权归原作者所有，如需转载，请联系作者。
原文链接：blog.csdn.net/gaoxiaoweiandy/article/details/105832787
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