實際演示效果：

Canvas 畫圖基本步驟：

1、布局添加一個SurfaceView<?xml version="1.0" encoding="utf-8"?>

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context=".MainActivity">

android:id="@+id/surfaceView"

android:layout_width="match_parent"

android:layout_height="match_parent" />

2、在onCreate()中，加入：

SurfaceHolder surfaceHolder = SurfaceView.getHolder();surfaceHolder = surfaceView.getHolder();//Canvas畫圖很關鍵的一步3、Paint設置顏色、線寬、文字大小等屬性

penOfGrid.setColor(gridColor); //設置畫筆

penOfGrid.setStrokeWidth(1); //線寬

penOfGrid.setAntiAlias(true); //抗鋸齒

penOfGrid.setTextSize(24); //文字大小，和線寬無關

penOfData.setColor(lineColor);

penOfData.setStrokeWidth(2);

penOfData.setAntiAlias(true);

penOfData.setTextSize(80);

4、開始畫圖：

(---坐標的(0，0)的位置是左上角，而不是為人熟知的左下角---)

Canvas canvas = surfaceHolder.lockCanvas();

canvas.drawLine(x1,y1,x2,y2,paint);//畫線

canvas.drawColor(Color.BLACK);//畫黑色 ...

5、結束畫圖:

surfaceHolder.unlockAndPost(canvas);

/**

* 繪制數據波形操作,數據緩存到了ArrayList中，本方法將其中數據繪制出來

* 用到的其他未在方法中聲明的對象、變量須自己在合適的位置聲明

* @param dataGroup 輸入數據集合

*/private void drawData(ArrayList dataGroup){

//獲得畫布的寬高,繪制網格用到

widthOfCanvas = surfaceView.getWidth();

heightOfCanvas = surfaceView.getHeight();

canvas = surfaceHolder.lockCanvas(); // 鎖定畫布，開始繪圖

canvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG

| Paint.FILTER_BITMAP_FLAG));//抗鋸齒

int xScale = 1; //橫軸幾個像素為一個單位

//bitmap：用于雙緩沖畫圖，解決刷新閃爍問題

if(bitmap == null){//bitmap == null：第一次畫圖，bitmap沒有初始化，就需要初始化，就是下面這一行

bitmap = Bitmap.createBitmap(widthOfCanvas,heightOfCanvas, Bitmap.Config.ARGB_8888);

Canvas tempCanvas = new Canvas(bitmap);//在bitmap中再新建一個畫布Cancas，bitmap相當于SurfaceView了

tempCanvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG

| Paint.FILTER_BITMAP_FLAG));

tempCanvas.drawColor(backColor); //繪制背景色

/**

* 繪制網格

*/

for (int i = 0; i < widthOfCanvas / 30; i++) {

tempCanvas.drawLine(i * 30, 0, i * 30, heightOfCanvas, penOfGrid); //縱

}

for (int i = 0; i < heightOfCanvas / 30; i++) {

tempCanvas.drawLine(0, i * 30, heightOfCanvas, i * 30, penOfGrid); //橫

}

float cx,cy,dx,dy; //畫線需要的起點坐標和終點坐標

for (int i = 0;i

//起點：

cx = i * xScale;

cy = heightOfCanvas - heightOfCanvas * dataGroup.get(i)/3;//由于左上角為(0,0)，需要對畫出來的圖進行上下顛倒，

//并根據Canvas高度對數據進行一定比例的放大

//終點：

dx = (i + 1) * xScale;

dy = heightOfCanvas - heightOfCanvas * dataGroup.get(i+1)/3;

//在起點和重點之間畫一條線段

tempCanvas.drawLine(cx,cy,dx,dy,penOfData);

}

tempCanvas.drawText("心率：--",20,100,penOfData);

//繪制完畢

canvas.drawBitmap(bitmap,0,0,penOfData);

}else { //如果不是第一次繪制，就沒有必要重新初始化bitmap，節約資源，其他操作完全一樣

Canvas tempCanvas = new Canvas(bitmap);

tempCanvas.setDrawFilter(new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG

| Paint.FILTER_BITMAP_FLAG));

tempCanvas.drawColor(backColor); //Draw background color to Black

/**

* Draw grid

*/

for (int i = 0; i < widthOfCanvas / 30; i++) {

tempCanvas.drawLine(i * 30, 0, i * 30, heightOfCanvas, penOfGrid); //vertical lines

}

for (int i = 0; i < heightOfCanvas / 30; i++) {

tempCanvas.drawLine(0, i * 30, heightOfCanvas, i * 30, penOfGrid);

}

float cx,cy,dx,dy;

for (int i = 0;i

cx = i * xScale;

cy = heightOfCanvas - heightOfCanvas * dataGroup.get(i)/3;

dx = (i + 1) * xScale;

dy = heightOfCanvas - heightOfCanvas * dataGroup.get(i+1)/3;

tempCanvas.drawLine(cx,cy,dx,dy,penOfData);

}

tempCanvas.drawText("心率："+falseHeart(),20,100,penOfData);

canvas.drawBitmap(bitmap,0,0,penOfData);

}

//將雙緩沖的圖復制到SurfaceView上顯示

surfaceHolder.unlockCanvasAndPost(canvas);

}

總結

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