Canvas基础知识

public class TestView1 extends View {
private Bitmap mBitmap;
private BitmapShader mBitmapShader;
public TestView1(Context context) {
super(context);
}

public TestView1(Context context, @Nullable AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
mBitmap = ((BitmapDrawable)getResources().getDrawable(R.drawable.xyjy2)).getBitmap();
mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.REPEAT, Shader.TileMode.REPEAT);
}

public TestView1(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}

@RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
public TestView1(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}

@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//绘制直线
Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.FILL);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(10);
paint.setShader(mBitmapShader);
paint.setAntiAlias(true);

canvas.drawLine(0, 0, 100, 100, paint);

}

}

float []pts = {0,0,100,100,200,200,300,300};
canvas.drawLines(pts, paint);


float []pts = {0,0,100,100,200,200,300,300};

canvas.drawPoint(500, 500, paint);
canvas.drawPoints(pts, paint);


RectF r = new RectF(100, 100, 400, 500);
canvas.drawRect(r, paint);
//canvas.drawRect(left, top, right, bottom, paint);

RectF r = new RectF(100, 100, 400, 500);
// canvas.drawRect(r, paint);
//canvas.drawRect(left, top, right, bottom, paint);

//画圆角矩形
//x-radius ,y-radius圆角的半径
canvas.drawRoundRect(r, 30, 30, paint);



canvas.drawCircle(300, 300, 200, paint);



RectF r = new RectF(100, 100, 400, 500);

paint.setColor(Color.GREEN);
canvas.drawOval(r, paint);


RectF r = new RectF(100, 100, 400, 500);

// canvas.drawArc(
// r,
// startAngle, //其实角度，相对X轴正方向
// sweepAngle, //画多少角度的弧度
// useCenter, //boolean, false：只有一个纯弧线；true：闭合的边
// paint)；
canvas.drawArc(r, 0, 90, true, paint);//顺时针旋转90度


Path path = new Path();
path.moveTo(100, 100);//画笔落笔的位置
//移动
path.lineTo(200, 100);
path.lineTo(200, 200);
path.cubicTo(250, 200, 350, 300, 450, 400);
path.close();

canvas.drawPath(path, paint);



//圆角矩形路径
RectF r = new RectF(100, 100, 600, 800);
Path path = new Path();
float radii[] = {10,10,10,10,10,10,50,60};
path.addRoundRect(r, radii, Path.Direction.CCW);
//path.addArc(oval, startAngle, sweepAngle);
canvas.drawPath(path, paint);


//--------------------Canvas变换技巧--------------------------
//1.平移（Translate）

// 绘制坐标系
RectF r = new RectF(0, 0, 400, 500);
paint.setColor(Color.GREEN);
canvas.drawRect(r, paint);

// 第一次绘制坐标轴
canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
paint.setColor(Color.BLUE);
canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴

//平移--即改变坐标原点
canvas.translate(50, 50);
// 第二次绘制坐标轴
paint.setColor(Color.GREEN);
canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
paint.setColor(Color.BLUE);
canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴

canvas.rotate(45);
// 第三次绘制坐标轴
paint.setColor(Color.GREEN);
canvas.drawLine(0,0,canvas.getWidth(),0,paint);// X 轴
paint.setColor(Color.BLUE);
canvas.drawLine(0,0,0,canvas.getHeight(),paint);// Y 轴

canvas.drawColor(Color.BLUE);
RectF r2 = new RectF(0, 0, 400, 500);
paint.setColor(Color.RED);
//虽然新建了一个画布图层，但是还是会沿用之前设置的平移变换。不可逆的。（save和restore来解决）
canvas.drawRect(r2, paint);

//2.缩放Scale
RectF r = new RectF(0, 0, 400, 500);
canvas.drawRect(r, paint);
paint.setColor(Color.BLUE);
//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
canvas.scale(1.5f, 0.5f);
canvas.drawRect(r, paint);

//3.旋转Rotate
RectF r = new RectF(200, 200, 400, 500);
canvas.drawRect(r, paint);
paint.setColor(Color.BLUE);
canvas.rotate(45);
//canvas.rotate(45, 200, 200);
canvas.drawRect(r, paint);

//4.斜拉画布Skew
RectF r = new RectF(100, 100, 600, 800);
canvas.drawRect(r, paint);
paint.setColor(Color.BLUE);
//sx,sy倾斜度：X轴方向上倾斜60度，tan60=根号3
canvas.skew(1.73f, 0);
canvas.drawRect(r, paint);

//5.裁剪画布clip
RectF r = new RectF(200, 200, 400, 500);
canvas.drawRect(r, paint);
paint.setColor(Color.BLUE);
canvas.clipRect(new Rect(250, 250, 300, 400));
canvas.drawColor(Color.YELLOW);

// save 和 restore

RectF r = new RectF(0, 0, 400, 500);
paint.setColor(Color.GREEN);
canvas.drawRect(r, paint);
canvas.save();
//平移
canvas.translate(50, 50);

paint.setColor(Color.BLUE);
canvas.drawRect(r, paint);

canvas.restore();
canvas.rotate(45);

paint.setColor(Color.YELLOW);
r = new RectF(0, 0, 200, 200);

canvas.drawRect(r, paint);

//当canvas执行saveLayer的时候就会新建一个新的画布图层
int layer = canvas.saveLayer(0,0,canvas.getWidth(),canvas.getHeight(),null,Canvas.ALL_SAVE_FLAG);

canvas.drawColor(Color.YELLOW);
canvas.translate(50, 50);
paint.setColor(Color.BLUE);
canvas.drawRect(r, paint);

canvas.restoreToCount(layer);