Android 基礎圖形繪製API詳解

Canvas類常用的方法：

API 功能	方法
顏色	drawARGB(), drawRGB(), drawColor()
畫點	drawPoint()，
畫線(多條)	drawLine()，drawLines()
矩形（圓角矩形）	drawRect(), drawRoundRect()
圖片	drawBitmap()，
文本	drawText()，drawPosText()，drawTextOnPath()
圓	drawCircle()
橢圓	drawOval()
圓弧	drawArc()
路徑	drawPath()

### 下面通過例子詳細說明上述方法：
####1. **畫點 drawPoint**

<font color=#ff0000 size=4 face="黑體">(1) 單點：</font>

####```drawPoint(float x, float y, Paint paint) ```
><font color=#aa33ff size=3 face="黑體">參數：</font>
**float X：**點的X座標
**float Y：**點的Y座標

```java
Paint paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStrokeWidth(30);
canvas.drawPoint(100, 100, paint);




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(2) 填充整個Canvas：

drawPoint(Paint paint)

參數：
Paint paint：填充Canvas的畫筆

Paint paint = new Paint();
paint.setColor(Color.BLUE);
canvas.drawPaint(paint);




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(3) 多個點 ：

public void drawPoints(float[] pts, Paint paint)

參數：
float[] pts: 點的集合，從第一個開始兩兩一組爲一個點，元素個數必須是偶數，形如：pts = {x1, y1, x2, y2, x3, y3, ……｝;

Paint paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStrokeWidth(30);
float [] points = new float[]{20, 20, 100, 100, 250, 250, 450, 450};
canvas.drawPoints(points, paint);




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public void drawPoints(float[] pts, int offset, int count, Paint paint)

參數：
float[] pts: 點的集合，從第一個開始兩兩一組爲一個點，元素個數必須是偶數，形如：pts = {x1, y1, x2, y2, x3, y3, ……｝;
int offset: 點的集合 pts 數組中省去不繪製的數的個數，兩個數爲一個點；可以爲奇數，但繪製的點會位置不正確；
count: 參與繪製的 pts 數組中數的個數，兩個數爲一個點，必需爲偶數；

Paint paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStrokeWidth(30);
float [] points = new float[]{20, 20, 100, 100, 250, 250, 450, 450};
canvas.drawPoints(points, 2, 4, paint);




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如果將 offset 改爲 1，即：

Paint paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStrokeWidth(30);
float [] points = new float[]{20, 20, 100, 100, 250, 250, 450, 450};
canvas.drawPoints(points, 1, 4, paint);




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效果如下：

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2. 畫直線 drawLine()

(1) 一條直線：

public void drawLine(float startX, float startY, float stopX, float stopY, Paint paint)

參數：
float startX : 起點橫座標;
float startY : 起點縱座標;
float stopX : 終點橫座標;
float stopY : 終點縱座標;
Paint paint : 畫筆;

Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth(20);
canvas.drawLine(30, 30, 150, 150, paint);




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(1) 多條直線：

public void drawLines(float[] pts, Paint paint)

參數：
float[] pts: 點的集合，從第一個開始兩兩一組爲一個點，元素個數必須是偶數，形如：pts = {x1, y1, x2, y2, x3, y3, ……｝;
Paint paint : 畫筆;

Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth(20);
float[] points = new float[]{30, 30, 150, 150, 250, 250, 400, 400};
canvas.drawLines(points, paint);




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public void drawLines(float[] pts, int offset, int count, Paint paint)

參數：
float[] pts: 點的集合，從第一個開始兩兩一組爲一個點，元素個數必須是偶數，形如：pts = {x1, y1, x2, y2, x3, y3, ……｝;
int offset: 點的集合 pts 數組中省去不繪製的數的個數，兩個數爲一個點；可以爲奇數，但繪製的點會位置不正確；
count: 參與繪製的 pts 數組中數的個數，兩個數爲一個點，必需爲偶數；
Paint paint : 畫筆;

Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth(20);
float[] points = new float[]{30, 30, 150, 150, 250, 250, 400, 400};
canvas.drawLines(points, paint);




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3. 畫矩形 drawRect

public void drawRect(RectF rect, Paint paint)

參數：
RectF rect 矩形區域
Paint paint : 畫筆;

Paint paint = new Paint();
paint.setColor(Color.GREEN);
paint.setStrokeWidth(20);
paint.setStyle(Paint.Style.STROKE);

RectF rectF = new RectF();
rectF.left = 50;
rectF.top = 50;
rectF.right = 400;
rectF.bottom = 200;

canvas.drawRect(rectF, paint);




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4. 畫橢圓 drawOval

public void drawRect(RectF rect, Paint paint)

參數：
RectF rect 矩形區域, 橢圓的繪製是在一個矩形區域完成的
Paint paint : 畫筆;

public void drawOval(float left, float top, float right, float bottom, Paint paint)

Paint paint = new Paint(); //橢圓畫筆
paint.setColor(Color.GREEN);
paint.setStrokeWidth(5);
paint.setStyle(Paint.Style.STROKE);

Paint paint1 = new Paint(); //橢圓所在矩形區域畫筆
paint1.setColor(Color.RED);
paint1.setStrokeWidth(5);
paint1.setStyle(Paint.Style.STROKE);

RectF rectF = new RectF();
rectF.left = 50;
rectF.top = 50;
rectF.right = 400;
rectF.bottom = 200;

canvas.drawRect(rectF, paint1);//畫出矩形，爲了更加形象顯示橢圓的繪製規則
canvas.drawOval(rectF, paint);//繪製橢圓

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