Android 自定義控件或多或少都會用到Canvas，那么我們就需要熟悉它的API。Canvas給我們提供了大量的的DrawXXX方法，通過這些方法我們就可以繪制出我們想要的效果。接下來看看官方是怎么說的：
The Canvas class holds the "draw" calls. To draw something, you need 4 basic components: A Bitmap to hold the pixels, a Canvas to host the draw calls (writing into the bitmap), a drawing primitive (e.g. Rect, Path, text, Bitmap), and a paint (to describe the colors and styles for the drawing).
大致意思就是說：
Canvas類持有“draw”調(diào)用。 要繪制一些東西瘦赫，你需要4個基本組件：一個位圖來保存像素，一張畫布（Canvas）來主持繪圖調(diào)用（寫入位圖）啸箫，一個繪圖圖元（如Rect耸彪，Path，text忘苛，Bitmap）和一支畫筆（描述繪圖的顏色和樣式）蝉娜。
首先介紹下畫筆（Paint）的常用API:
private void initPaint() {
// 設(shè)置最基本的屬性
// 設(shè)置畫筆顏色
// 可直接引入Color類，如Color.red等
mPaint.setColor(int color);
// 設(shè)置畫筆模式
mPaint.setStyle(Style style);
// Style有3種類型：
// 類型1：Paint.Style.FILLANDSTROKE（描邊+填充）
// 類型2：Paint.Style.FILL（只填充不描邊）
// 類型3：Paint.Style.STROKE（只描邊不填充）
//設(shè)置畫筆的粗細
mPaint.setStrokeWidth(float width);
// 如設(shè)置畫筆寬度為10px
mPaint.setStrokeWidth(10f);
// 不常設(shè)置的屬性
// 得到畫筆的顏色
mPaint.getColor();
// 設(shè)置Shader
// 即著色器扎唾，定義了圖形的著色召川、外觀
mPaint.setShader(Shader shader);
//設(shè)置畫筆的a,r,p,g值
mPaint.setARGB(int a, int r, int g, int b);
//設(shè)置透明度
mPaint.setAlpha(int a);
//得到畫筆的Alpha值
mPaint.getAlpha();
// 對字體進行設(shè)置（大小、顏色）
//設(shè)置字體大小
mPaint.setTextSize(float textSize)
// 設(shè)置對齊方式
mPaint.setTextAlign(Algin algin);
// LEFT：左對齊
// CENTER：居中對齊
// RIGHT：右對齊
//設(shè)置文本的下劃線
mPaint.setUnderlineText(boolean underlineText);
//設(shè)置文本的刪除線
mPaint.setStrikeThruText(boolean strikeThruText);
//設(shè)置文本粗體
mPaint.setFakeBoldText(boolean fakeBoldText);
// 設(shè)置斜體
mPaint.setTextSkewX(-0.5f);
// 設(shè)置文字陰影
mPaint.setShadowLayer(5,5,5,Color.YELLOW);
}
Paint默認的字體大小為12px胸遇，在繪制文本時我們往往要考慮密度density設(shè)置合適的字體大小荧呐。畫筆的默認顏色為黑色，默認的style為FILL纸镊，默認的cap為BUTT倍阐，默認的線寬為0。
一 坐標(biāo)系
- Canvas坐標(biāo)系
Canvas坐標(biāo)系即Canvas本身的坐標(biāo)系逗威。Canvas坐標(biāo)原點（0,0）在View的左上角峰搪，向右為X軸正方向，向下為Y軸正方向凯旭。Canvas坐標(biāo)系唯一且不會改變概耻。 - 繪圖坐標(biāo)系
繪圖坐標(biāo)系區(qū)別于Canvas坐標(biāo)系，以我們繪圖起始點為坐標(biāo)原點（0,0）罐呼，繪圖坐標(biāo)系默認與Canvas坐標(biāo)系重合鞠柄。繪圖坐標(biāo)系原點位置可以更改，Canvas的 translate嫉柴、rotate厌杜、scale 操作都是基于繪圖坐標(biāo)系變化。
//繪制坐標(biāo)系
private void drawAxis(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int translate = width / 5;
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(10);
//設(shè)置筆觸樣式
mPaint.setStrokeCap(Paint.Cap.ROUND);
//繪制默認繪圖坐標(biāo)系（此時與Canvas坐標(biāo)系重合）
//繪制紅色X軸
mPaint.setColor(Color.RED);
canvas.drawLine(0, 0, width, 0, mPaint);
//繪制藍色Y軸
mPaint.setColor(Color.BLUE);
canvas.drawLine(0, 0, 0, height, mPaint);
//平移
canvas.translate(translate, translate);
//繪制平移后繪圖坐標(biāo)系
//繪制紅色X軸
mPaint.setColor(Color.RED);
canvas.drawLine(0, 0, width, 0, mPaint);
//繪制藍色Y軸
mPaint.setColor(Color.BLUE);
canvas.drawLine(0, 0, 0, height, mPaint);
//平移 旋轉(zhuǎn)30度
canvas.translate(translate, translate);
canvas.rotate(30);
//繪制平移旋轉(zhuǎn)后繪圖坐標(biāo)系
//繪制紅色X軸
mPaint.setColor(Color.RED);
canvas.drawLine(0, 0, width, 0, mPaint);
//繪制藍色Y軸
mPaint.setColor(Color.BLUE);
canvas.drawLine(0, 0, 0, height, mPaint);
}
二 Canvas繪制顏色
單一顏色填充Canvas畫布
- drawColor
- drawRGB
- drawARGB
//繪制畫布顏色
private void drawCanvasColor(Canvas canvas) {
//drawARGB
canvas.drawARGB(255, 47, 140, 150);
}
三 繪制點
- drawPoint 繪制點
- drawPoints 繪制一組點
//繪制點
private void drawPoint(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int translateY = height/5;
//設(shè)置畫筆顏色
mPaint.setColor(Color.RED);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(200);
//設(shè)置筆觸樣式
mPaint.setStrokeCap(Paint.Cap.BUTT);
//保存當(dāng)前畫布狀態(tài)（坐標(biāo)系）
canvas.save();
canvas.drawPoint(width / 3, height / 3, mPaint);
//恢復(fù)上次畫布保存狀態(tài)（坐標(biāo)系）
canvas.restore();
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setColor(Color.GREEN);
canvas.save();
canvas.translate(0, translateY);
canvas.drawPoint(width / 3, height / 3, mPaint);
canvas.restore();
mPaint.setStrokeCap(Paint.Cap.SQUARE);
mPaint.setColor(Color.BLUE);
canvas.save();
canvas.translate(translateY, translateY);
canvas.drawPoint(width / 3, height / 3, mPaint);
canvas.restore();
}
四 繪制線
- drawLine 繪制線
- drawLines 繪制一組線
//繪制線
private void drawLine(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int startX = width / 5;
int startY = height / 5;
//設(shè)置畫筆顏色
mPaint.setColor(Color.RED);
mPaint.setStrokeWidth(20);
//設(shè)置筆觸樣式
mPaint.setStrokeCap(Paint.Cap.BUTT);
//畫筆觸為BUTT的線
canvas.drawLine(startX, startY, width - startX, startY, mPaint);
//向下平移20
canvas.translate(0, 60);
mPaint.setColor(Color.GREEN);
mPaint.setStrokeCap(Paint.Cap.ROUND);
//畫筆觸為ROUND的線
canvas.drawLine(startX, startY, width - startX, startY, mPaint);
canvas.translate(0, 60);
mPaint.setColor(Color.BLUE);
mPaint.setStrokeCap(Paint.Cap.SQUARE);
//畫筆觸為SQUARE的線
canvas.drawLine(startX, startY, width - startX, startY, mPaint);
canvas.translate(0, 80);
mPaint.setColor(Color.BLACK);
float[] pts = new float[]{startX, startY, width - startX, startY, startX, startY + 60, width - startX, startY + 60};
canvas.drawLines(pts, mPaint);
}
五 繪制矩形
- drawRect 繪制矩形
- drawRoundRect 繪制圓角矩形
//繪制矩形
private void drawRect(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
//設(shè)置畫筆顏色
mPaint.setColor(Color.RED);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(16);
//設(shè)置畫筆樣式
mPaint.setStyle(Paint.Style.FILL);
canvas.drawRect(20, 20, 400, 200, mPaint);
//繪制矩形 API21
//canvas.drawRoundRect(220, 220, 400, 400, 10, 10, mPaint);
RectF rect = new RectF(20, 420, 800, 600);
canvas.drawRoundRect(rect, 10, 10, mPaint);
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Paint.Style.STROKE);
canvas.drawRect(20, 800, 400, 1000, mPaint);
RectF rect1 = new RectF(20, 1200, 800, 1400);
canvas.drawRoundRect(rect1, 10, 10, mPaint);
}
六 繪制圓
- drawCircle 繪制圓
//繪制圓形
private void drawCircle(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int halfWidth = width / 2;
int d = height / 3;
int r = d / 2 - 10;
//設(shè)置畫筆顏色
mPaint.setColor(Color.RED);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(2);
//設(shè)置畫筆樣式
mPaint.setStyle(Paint.Style.FILL);
//繪制圓
canvas.drawCircle(halfWidth, (float) (d * 0.5), r, mPaint);
//繪制兩個圓實現(xiàn)圓環(huán)效果
mPaint.setColor(Color.GREEN);
canvas.drawCircle(halfWidth, (float) (d * 1.5), r, mPaint);
mPaint.setColor(Color.WHITE);
canvas.drawCircle(halfWidth, (float) (d * 1.5), r - 40, mPaint);
//繪制一個圓實現(xiàn)圓環(huán)效果
mPaint.setStrokeWidth(40);
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Paint.Style.STROKE);
//半徑減去畫筆畫筆寬度的一半 圓的大小和前面一致
canvas.drawCircle(halfWidth, (float) (d * 2.5), r - 20, mPaint);
}
七 繪制橢圓
- drawOval 繪制橢圓
跟繪制圓差不多计螺，唯一不同就是繪制圓是指定圓心和半徑夯尽，繪制橢圓是指定左上右下4個距離侧馅。
//繪制橢圓
private void drawOval(Canvas canvas) {
//設(shè)置畫筆顏色
mPaint.setColor(Color.RED);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(2);
//設(shè)置畫筆樣式
mPaint.setStyle(Paint.Style.FILL);
RectF overRect = new RectF(20, 20, 400, 200);
canvas.drawOval(overRect, mPaint);
mPaint.setColor(Color.GREEN);
mPaint.setStrokeWidth(20);
mPaint.setStyle(Paint.Style.STROKE);
overRect = new RectF(20, 220, 200, 600);
canvas.drawOval(overRect, mPaint);
}
八 繪制圓弧
- drawArc 繪制弧
繪制圓弧，可以繪制弧面和弧線呐萌。弧面即用弧圍成的填充面谊娇，弧線即為弧面的輪廓線肺孤。
//繪制弧
private void drawAcr(Canvas canvas) {
int width = canvas.getWidth();
//設(shè)置畫筆顏色
mPaint.setColor(Color.RED);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(2);
//設(shè)置畫筆樣式
mPaint.setStyle(Paint.Style.FILL);
//和前面繪制橢圓的矩形一致（正方形也可）
RectF arcRect = new RectF(20, 20, 400, 200);
//根據(jù)矩形繪制弧形 開始角度0 掃過角度360 通過中心點首尾連接：true
// 和前面繪制的橢圓效果一致
canvas.drawArc(arcRect, 0, 360, true, mPaint);
canvas.translate(0, width / 5);
canvas.drawArc(arcRect, 0, 90, true, mPaint);
canvas.translate(0, width / 5);
canvas.drawArc(arcRect, 0, 90, false, mPaint);
//正方形
arcRect = new RectF(20, 20, 220, 220);
mPaint.setStrokeWidth(4);
mPaint.setStyle(Paint.Style.STROKE);
canvas.translate(0, width / 5);
//根據(jù)矩形繪制弧形 角度從0-1800 首尾連接
canvas.drawArc(arcRect, 0, 180, true, mPaint);
canvas.translate(0, width / 5);
//根據(jù)矩形繪制弧形 角度從0-1800 首尾不連接
canvas.drawArc(arcRect, 0, 180, false, mPaint);
mPaint.setStrokeWidth(10);
canvas.translate(width / 2, width / 5);
//drawArc繪制出圓環(huán)
canvas.drawArc(arcRect, 0, 270, false, mPaint);
mPaint.setColor(Color.GREEN);
canvas.drawArc(arcRect, 270, 90, false, mPaint);
}
九 繪制文字
- drawText 繪制文本
- drawPosText 根據(jù)位置繪制文本
- drawTextOnPath 根據(jù)路徑繪制文本
//繪制文字
private void drawText(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int textHeight = 32;
int halfWidth = width / 2;
//設(shè)置畫筆顏色
mPaint.setColor(Color.GRAY);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(2);
canvas.drawLine(halfWidth, 0, halfWidth, height, mPaint);
mPaint.setColor(Color.BLACK);
//設(shè)置文本大小
mPaint.setTextSize(textHeight);
//繪制普通文本
canvas.drawText("繪制普通文本", 0, textHeight, mPaint);
mPaint.setColor(Color.RED);
mPaint.setTextAlign(Paint.Align.LEFT);
//存儲畫布狀態(tài) 坐標(biāo)系
canvas.save();
//平移
canvas.translate(halfWidth, textHeight);
//繪制左對齊文本
canvas.drawText("繪制左對齊文本", 0, textHeight, mPaint);
//恢復(fù)上次存儲狀態(tài)
canvas.restore();
mPaint.setColor(Color.GREEN);
mPaint.setTextAlign(Paint.Align.CENTER);
//存儲畫布狀態(tài) 坐標(biāo)系
canvas.save();
//平移
canvas.translate(halfWidth, textHeight * 2);
//繪制居中對齊文本(對齊是根據(jù)繪圖坐標(biāo)系而言)
canvas.drawText("繪制居中對齊文本", 0, textHeight, mPaint);
//恢復(fù)上次存儲狀態(tài)
canvas.restore();
mPaint.setColor(Color.BLUE);
mPaint.setTextAlign(Paint.Align.RIGHT);
//存儲畫布狀態(tài) 坐標(biāo)系
canvas.save();
//平移
canvas.translate(halfWidth, textHeight * 3);
//繪制右對齊文本
canvas.drawText("繪制右對齊文本", 0, textHeight, mPaint);
//恢復(fù)上次存儲狀態(tài)
canvas.restore();
mPaint.setColor(Color.BLACK);
//恢復(fù)默認對齊方式
mPaint.setTextAlign(Paint.Align.LEFT);
//設(shè)置下劃線
mPaint.setUnderlineText(true);
//設(shè)置加粗
mPaint.setFakeBoldText(true);
//設(shè)置刪除線
mPaint.setStrikeThruText(true);
//存儲畫布狀態(tài) 坐標(biāo)系
canvas.save();
//平移
canvas.translate(halfWidth, textHeight * 4);
//繪制下劃線加粗文本
canvas.drawText("繪制下劃線加粗文本", 0, textHeight, mPaint);
//恢復(fù)上次存儲狀態(tài)
canvas.restore();
mPaint.reset();
mPaint.setColor(Color.BLACK);
//設(shè)置文本大小
mPaint.setTextSize(textHeight);
//存儲畫布狀態(tài) 坐標(biāo)系
canvas.save();
canvas.translate(width / 3, height / 3);
//旋轉(zhuǎn)
canvas.rotate(45);
//繪制傾斜文本
canvas.drawText("繪制傾斜文本", 0, textHeight, mPaint);
//恢復(fù)上次存儲狀態(tài)
canvas.restore();
float[] pos = new float[]{40, 40, 80, 80, 120, 120, 160, 160, 200, 200, 240, 240};
//存儲畫布狀態(tài) 坐標(biāo)系
canvas.save();
canvas.translate(width / 3, height / 2);
canvas.drawPosText("繪制位置文本", pos, mPaint);
//恢復(fù)上次存儲狀態(tài)
canvas.restore();
Path path = new Path();
path.cubicTo(550, 750, 350, 250, 850, 800);
//畫路徑
mPaint.setColor(Color.RED);
mPaint.setStyle(Paint.Style.STROKE);
canvas.drawPath(path,mPaint);
canvas.drawTextOnPath("繪制文本OnPath繪制文本OnPath繪制文本OnPath繪制文本OnPath繪制文本OnPath", path, 50, 0, mPaint);
}
十 繪制Path
- drawPath 繪制路徑
//path拐點集合
List<Point> points = new ArrayList<>();
//繪制Path
private void drawPath(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int deltaX = width / 4;
int deltaY = (int) (deltaX * 0.75);
//設(shè)置畫筆顏色
mPaint.setColor(Color.GRAY);
//設(shè)置畫筆寬度
mPaint.setStrokeWidth(4);
//Fill模式畫面
Path path1 = new Path();
RectF arcRect = new RectF(0, 0, deltaX, deltaY);
path1.addArc(arcRect, 0, 360);
path1.addRect(deltaX, 0, deltaX << 1, deltaY, Path.Direction.CW);
canvas.drawPath(path1, mPaint);
//STROKE模式畫線
mPaint.setColor(Color.RED);
mPaint.setStyle(Paint.Style.STROKE);
canvas.translate(0, deltaY << 1);
canvas.drawPath(path1, mPaint);
mPaint.setColor(Color.BLUE);
// mPaint.setStyle(Paint.Style.FILL);
canvas.translate(0, deltaY << 1);
Path path2 = new Path();
path2.lineTo(100, 0); //畫線
points.add(new Point(100, 0)); //終點 X: 100 Y: 0
RectF overRect = new RectF(100, -50, 300, 50);
path2.arcTo(overRect, 180, -90); //畫橢圓 左下部分
points.add(new Point(200, 50)); //終點 X: 250 Y: 50
overRect = new RectF(200, 0, 400, 100);
path2.arcTo(overRect, 180, 90); //畫橢圓右上部分
points.add(new Point(300, 0)); //終點 X: 300 Y: 0
path2.lineTo(350, 50); //畫線
points.add(new Point(350, 50)); //終點 X: 350 Y: 50
//畫二階貝塞爾曲線 第一個坐標(biāo)為控制點 最后為終點
path2.quadTo(450, -50, 500, 150);
points.add(new Point(500, 150)); //終點 X: 500 Y: 150
//畫三階階貝塞爾曲線 前兩個坐標(biāo)為控制點 最后為終點
path2.cubicTo(600, 150, 700, 0, 380, -200);
points.add(new Point(380, -200)); //終點 X: 480 Y: -200
path2.rLineTo(0, 100);
points.add(new Point(380, -200 + 100)); //終點 X: 480 Y: -100
canvas.drawPath(path2, mPaint);
mPaint.setStrokeWidth(10);
mPaint.setColor(Color.RED);
mPaint.setStrokeCap(Paint.Cap.ROUND);
for (Point point : points) {
canvas.drawPoint(point.x, point.y, mPaint);
}
}
十一 繪制Bitmap
- drawBitmap 繪制Bitmap
//繪制Bitmap
private void drawBitmap(Canvas canvas) {
BitmapDrawable drawable = (BitmapDrawable) getResources().getDrawable(R.mipmap.ic_launcher);
Bitmap bitmap = drawable.getBitmap();
//如果bitmap不存在，那么就不執(zhí)行下面的繪制代碼
if (bitmap == null) {
return;
}
//直接完全繪制Bitmap
canvas.drawBitmap(bitmap, 0, 0, mPaint);
//繪制Bitmap的一部分济欢，并對其拉伸
//srcRect定義了要繪制Bitmap的哪一部分
Rect srcRect = new Rect();
srcRect.left = 0;
srcRect.right = bitmap.getWidth();
srcRect.top = 0;
srcRect.bottom = (int) (0.33 * bitmap.getHeight());
float radio = (float) (srcRect.bottom - srcRect.top) / bitmap.getWidth();
//dstRecF定義了要將繪制的Bitmap拉伸到哪里
RectF dstRecF = new RectF();
dstRecF.left = 0;
dstRecF.right = canvas.getWidth();
dstRecF.top = bitmap.getHeight();
float dstHeight = (dstRecF.right - dstRecF.left) * radio;
dstRecF.bottom = dstRecF.top + dstHeight;
canvas.drawBitmap(bitmap, srcRect, dstRecF, mPaint);
}
以上就是大部分的繪制操作赠堵，當(dāng)然還有一些沒介紹到，還有一些需要在API21（5.0）以上才能使用法褥，這個使用到的時候可以弄個小demo看下效果茫叭，接下來介紹下針對畫布變換和畫布裁剪做一些介紹。
十二 畫布變換
- translate 平移
- scale 縮放
- rotate 旋轉(zhuǎn)
- skew 錯切
在學(xué)習(xí)繪制操作的時候很多地方都使用到了translate 和rotate 這里就不再對它們進行操作
1.畫布scale
//畫布縮放
private void canvasScale(Canvas canvas) {
int width = canvas.getWidth();
int height = canvas.getHeight();
int hWidth = width / 2;
int hHeight = height / 2;
mPaint.setColor(Color.GRAY);
mPaint.setStrokeWidth(2);
mPaint.setStyle(Paint.Style.STROKE);
//使用path 畫布中心的X Y 軸
Path path = new Path();
path.moveTo(hWidth, 0);
path.lineTo(hWidth, height);
path.moveTo(0, hHeight);
path.lineTo(width, hHeight);
canvas.drawPath(path, mPaint);
//畫布平移
canvas.translate(hWidth, hHeight);
mPaint.setColor(Color.RED);
mPaint.setStrokeWidth(5);
RectF rectF = new RectF(0, 0, 200, 100);
canvas.drawRect(rectF, mPaint);
//默認0,0進行縮放
canvas.scale(1.5f, 1.5f);
mPaint.setColor(Color.BLUE);
canvas.drawRect(rectF, mPaint);
//100,0進行縮放
canvas.scale(1.5f, 1.5f, 100, 0);
mPaint.setColor(Color.GREEN);
canvas.drawRect(rectF, mPaint);
/*
當(dāng)縮放倍數(shù)為負數(shù)時半等，會先進行縮放揍愁，然后根據(jù)不同情況進行圖形翻轉(zhuǎn)：
（設(shè)縮放倍數(shù)為（a,b），旋轉(zhuǎn)中心為（px杀饵，py））：
a<0莽囤，b>0：以px為軸翻轉(zhuǎn)
a>0，b<0：以py為軸翻轉(zhuǎn)
a<0切距，b<0：以旋轉(zhuǎn)中心翻轉(zhuǎn)
*/
//100,0進行縮放 以Y軸翻轉(zhuǎn)
canvas.scale(1f, -1f, 100, 0);
mPaint.setColor(Color.BLACK);
canvas.drawRect(rectF, mPaint);
}
2.畫布skew
//畫布錯切
private void canvasSkew(Canvas canvas) {
mPaint.setColor(Color.RED);
mPaint.setStrokeWidth(5);
mPaint.setStyle(Paint.Style.STROKE);
RectF rectF = new RectF(0, 0, 400, 200);
canvas.translate(100,100);
canvas.drawRect(rectF, mPaint);
canvas.save();
canvas.translate(0,300);
//畫布X正方向錯切45°
canvas.skew(1f, 0);
canvas.drawRect(rectF, mPaint);
canvas.restore();
canvas.save();
canvas.translate(0,600);
//畫布Y負方向錯切45°
canvas.skew(0, -1f);
canvas.drawRect(rectF, mPaint);
canvas.restore();
mPaint.setColor(Color.GREEN);
canvas.drawLine(0,400,600,400,mPaint);
}
十三 畫布裁剪
- clipPath
- clipRect
- clipRegion(過時)
- getClipBounds
//畫布裁剪
private void canvasClip(Canvas canvas) {
canvas.drawColor(Color.RED);
canvas.save();
//矩形裁剪
canvas.clipRect(0, 0, 400, 200);
canvas.drawColor(Color.BLUE);
canvas.restore();
canvas.save();
canvas.translate(20, 400);
Path path = new Path();
path.addRect(0, 0, 400, 200, Path.Direction.CCW);
canvas.drawPath(path, mPaint);
//路徑裁剪
canvas.clipPath(path);
canvas.drawColor(Color.GREEN);
//獲得裁剪邊界
Rect bounds = canvas.getClipBounds();
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(10);
canvas.drawRect(bounds, mPaint);
canvas.restore();
}
這里針對Canvas的API進行了一些說明朽缎，希望對大家有所幫助。沒有添加完整工程上來谜悟，但是每一個方法都是實際跑過的话肖，只需要在onDraw中調(diào)用就可以看到效果了。
