Canvas
重新onDraw(Canvas canvas)方法时涉及绘图API ：Canvas
Canvas绘制方法
drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter, Paint paint
//绘制弧
drawBitmap(Bitmap bitmap,Rect src, Rect dst,Paint paint)
//在指定点绘制从源位图中“挖取”的一块
drawBitmap(Bitmap bitmap, float left, float top, Paint paint)
//在指定点绘制位图
drawCircle(float cx, float cy, float radius, Paint paint)
//在指定点绘制一个圆
drawLine(float startX, float startY, float stopX, float stopY, Paint paint)
//绘制一条线
drawLines(float[] pts, int offset, int count, Paint paint)
//绘制多条线
drawOval(RectF oval, Paint paint)
//绘制椭圆
drawPath(Path path, Paint paint)
//沿着指定Path绘制任意形状
drawPoint(float x, float y, Paint paint)
//绘制一个点
drawPoints(float[] pts, int offset, int count, Paint paint)
//绘制多个点
drawRect(float left, float top, float right, float bottom, Paint paint)
//绘制一个矩形
drawRoundRect(RectF rect, float rx, float ry, Paint paint)
//绘制一个圆角矩形
drawText(String text, float x, float y, Paint paint)
//绘制字符串
drawTextOnPath(char[] text, int index, int count, Path path, float hOffset, float vOffset, Paint paint)
//沿着路径绘制字符串
clipRect(float left, float top, float right, float bottom)
//剪切一个矩形区域
除上表定义的方法以外，Canvas还提供如下方法：
1.rotate(float degrees, float px, float py)对Canvas旋转
2.scale(float sx, float sy, float px, float py)对Canvas放缩
3.translate(float dx, float dy)对Canvas移动。dx为X轴方向移动，dy为Y轴方向移动。
Paint 画笔
setARGB();/setColor();//设置颜色
setAlpha(int a) //设置透明度
setAntiAlias(boolean aa) //设置是否抗锯齿
setColor(int color)//设置颜色
setPathEffect(PathEffect effect)//设置绘制路径是路径效果
setShader(Shader shader)//设置画笔填充效果
setShadowLayer(float radius, float dx, float dy, int shadowColor)//设置阴影
setStrokeWidth(float width)//设置画笔触宽度
setStrokeJoin(Paint.Join join)//设置画笔转弯处的连接风格
setStyle(Paint.Style style)//设置Paint的填充风格
setTextAlign(Paint.Align align)//设置绘制文本时的文字对齐方式
setTextSize(float textSize)//设置绘制文本时的文字大小
PathEffect 类
PathEffect为路径提供不同效果，包含如下子类：
1.ComposePathEffect
2.CornerPathEffect
3.DashPathEffect
4.DiscretePathEffect
5.PathDashPathEffect
6.SumPathEffect
例子：
float phase;
PathEffect[] effects = new PathEffect[7];
int[] colors;
private Paint paint;
Path path;
public MyView(Context context) {
super(context);
init();
}
public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public MyView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init(){
paint = new Paint();
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(4);
//创建Path
path = new Path();
path.moveTo(0,0);
for(int i = 1; i <= 15; i++){
path.lineTo(i*20, (float)(Math.random() * 100));
}
colors = new int[]{
Color.BLACK, Color.BLUE, Color.CYAN, Color.GREEN, Color.MAGENTA,
Color.RED, Color.YELLOW
};
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);//白色背景
//七种路径效果
effects[0] = null;
effects[1] = new CornerPathEffect(10);
effects[2] = new DiscretePathEffect(3.0f, 5.0f);
effects[3] = new DashPathEffect(new float[]{20,10,5,10}, phase);
Path p = new Path();
p.addRect(0, 0, 8, 8, Path.Direction.CCW);
effects[4] = new PathDashPathEffect(p, 12, phase, PathDashPathEffect.Style.ROTATE);
effects[5] = new ComposePathEffect(effects[2], effects[4]);
effects[6] = new SumPathEffect(effects[4], effects[3]);
canvas.translate(8,8);
for(int i = 0; i < effects.length; i++){
paint.setPathEffect(effects[i]);
paint.setColor(colors[i]);
canvas.drawPath(path, paint);
canvas.translate(0,100);
}
phase += 1;
invalidate();
}
效果如图：
