Android之绘图

一直对画画相关不感冒，但是Android的绘图机制还是要硬着头皮学绘画主要是使用paint(画笔)在canvas(画布)进行各种图形的绘制，画矩形、圆、三角形等点线构成的2维图形

//矩形  drawRect (float left, float top, float right, float bottom, Paint paint)
canvas.drawRect(50, 100, 200, 200, paint);

//圆  drawCircle (float cx, float cy, float radius, Paint paint)
canvas.drawCircle(width / 2, height / 2, 100, paint);

//三角形（画线）
//实例化路径
Path path = new Path();
path.moveTo(80, 300);// 此点为多边形的起点
path.lineTo(120, 250);
path.lineTo(80, 250);
path.close(); // 使这些点构成封闭的多边形
canvas.drawPath(path, paint);

//扇形 RectF (float left, float top, float right, float bottom)
RectF rectF = new RectF(160, 200, 400, 400);
// drawArc (RectF oval, float startAngle 起始弧度, float sweepAngle 扫过的弧度, boolean useCenter, Paint paint)
canvas.drawArc(rectF, 200, 130, true, paint);

//椭圆
rectF = new RectF(300, 300, 600, 600);
//  set (float left, float top, float right, float bottom)
rectF.set(210,100,450,200);
// drawOval (RectF oval, Paint paint)
canvas.drawOval(rectF, paint);

//曲线
//设置空心
paint.setStyle(Paint.Style.STROKE);
path = new Path();
path.moveTo(500, 500);//设置Path的起点
path.quadTo(550, 510, 670, 600);  //设置路径点和终点
canvas.drawPath(path, paint);

//文字+ 图片
paint.setTextSize(30);
//文本 drawText (String text, float x, float y, Paint paint)
canvas.drawText("slack", 350, 330, paint);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
//图片 drawBitmap (Bitmap bitmap, float left, float top, Paint paint)
canvas.drawBitmap(bitmap, 320, 360, paint);

canvas有几个重要的方法，画图时会使用到，类似ps里的图层，旋转，位移的概念

/*
*  Canvas.save() 将之前的图像保存起来，让后续的操作能像在新的画布一样操作
*  Canvas.restore() 合并图层
*  Canvas.translate() 平移 我们绘制的时候默认坐标点事左上角的起始点，那么我们调用translate（x,y）之后，
则将原点（0,0）移动到（x,y）之后的所有绘图都是在这一点上执行的
*  Canvas.roate() 旋转
* */

画一个时钟，就把这些理解了

//画时钟
// 画外圆
Paint paintCircle = new Paint();
paintCircle.setAntiAlias(true);
paintCircle.setStyle(Paint.Style.STROKE);
paintCircle.setStrokeWidth(5);
canvas.drawCircle(width / 2, height / 2, width / 3, paintCircle);
// 画刻度
Paint paintDegree = new Paint();
paintDegree.setStrokeWidth(3);
canvas.rotate(30, width / 2, height / 2);
for (int i = 1; i <= 12; i++) {
// 区别整点和非整点
if (i == 3 || i == 6 || i == 9 || i == 12 ) {
paintDegree.setStrokeWidth(5);
paintDegree.setTextSize(30);
// drawLine (float startX, float startY, float stopX, float stopY, Paint paint)
canvas.drawLine(width / 2, height / 2 - width / 3,
width / 2, height / 2 - width / 3 + 60, paintDegree);
String degree = String.valueOf(i);
canvas.drawText(degree,
width / 2 - paintDegree.measureText(degree) / 3,
height / 2 - width / 3 + 90, paintDegree);
} else {
paintDegree.setStrokeWidth(3);
paintDegree.setTextSize(15);
// 圆上的一点（x = 屏幕宽一半, y = 屏幕的一半 - 半径）
canvas.drawLine(width / 2, height / 2 - width / 3,
width / 2, height / 2 - width / 3 + 30, paintDegree);
String degree = String.valueOf(i);
canvas.drawText(degree,
width / 2 - paintDegree.measureText(degree) / 3,
height / 2 - width / 3 + 60, paintDegree);
}
// 通过旋转画布——实际上是旋转了画图的坐标轴 简化坐标运算
canvas.rotate(30, width / 2, height / 2);
}

canvas.save();
// 画指针
Paint paintHour = new Paint();
paintHour.setStrokeWidth(15);
Paint paintMinute = new Paint();
paintMinute.setStrokeWidth(10);
//绘制的时候默认坐标点事左上角的起始点，那么我们调用translate（x,y）之后，则将原点（0,0）移动到（x,y）之后的所有绘图都是在这一点上执行的
canvas.translate(width / 2, height / 2);
canvas.drawPoint(0, 0, paintHour);//圆点
canvas.drawLine(0, 0, 100, 100, paintHour);
canvas.drawLine(0, 0, 100, -200, paintMinute);
canvas.restore();

模拟刮刮乐

// PorterDuffXfermode 刮刮乐 通过DST_IN.SRC_IN模式来实现将一个矩形变成圆角图片的效果
mPaint = new Paint();
mPaint.setAlpha(0);
mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeWidth(50);
mPaint.setStrokeCap(Paint.Cap.ROUND);

mPath = new Path();
// createBitmap (int width, int height, Bitmap.Config config)
mFgBitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mFgBitmap);
mCanvas.drawColor(Color.GRAY);

/**
* 触摸事件
* 画一条透明的线  曲线
* @param event
* @return
*/
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mPath.reset();
lastX = event.getX();
lastY = event.getY();
mPath.moveTo(lastX, lastY);//起点
break;
case MotionEvent.ACTION_UP:
mPath.lineTo(event.getX(), event.getY());
break;
case MotionEvent.ACTION_MOVE:
//移动时，记录这一次的点位置
mPath.quadTo(lastX, lastY, event.getX(), event.getY());  //设置曲线路径点和终点
lastX = event.getX();
lastY = event.getY();
break;
}
mCanvas.drawPath(mPath, mPaint);
invalidate();
return true;
}

@Override
public void draw(Canvas canvas) {
super.draw(canvas);

//刮刮乐
canvas.drawBitmap(mFgBitmap, 0, 0, null);
}

SurfaceView主要用于频繁刷新处，做一个画板

SurfaceView的简单使用也简单

public class SurfaView extends SurfaceView implements SurfaceHolder.Callback, Runnable

在线程里处理绘画的事件，贴上代码

import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Path;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.SurfaceHolder;import android.view.SurfaceView;/*** SurfaceView的使用* Created by chenling on 2016/5/9.* 1.View主要用于自动更新的情况下,而surfaceVicw主要适用于被动更新,例如频繁刷新* 2.View在主线程中刷新，而surfaceView通常会通过一 个子线程来进行页面刷新。* 3.View在绘制的时候没有双缓冲机制,而surfaceVicw在底层实现机制中就已经实现了双缓冲机制；*/public class SurfaView extends SurfaceView implements SurfaceHolder.Callback, Runnable{//SurfaceHolderprivate SurfaceHolder mHolder;//用于绘制的Canvasprivate Canvas mCanvas;//子线程标志位private boolean mIsDrawing;private float lastX,lastY;private Path mPath;private Paint mPaint;/*** 构造方法** @param context* @param attrs*/public SurfaView(Context context, AttributeSet attrs) {super(context, attrs);mPath = new Path();mPaint = new Paint();mPaint.setStrokeWidth(20);mPaint.setAntiAlias(true);mPaint.setStyle(Paint.Style.STROKE);mHolder = getHolder();mHolder.addCallback(this);setFocusable(true);setFocusableInTouchMode(true);setKeepScreenOn(true);}// 创建@Overridepublic void surfaceCreated(SurfaceHolder holder) {mIsDrawing = true;new Thread(this).start();}// 改变@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}//销毁@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {mIsDrawing = false;}@Overridepublic void run() {while (mIsDrawing) {draw();//            lastX += 1;//            lastY = (int) (100 * Math.sin(lastX * 2 * Math.PI / 180) + 400);//            mPath.lineTo(lastX, lastY);}}// 负责绘画，频繁刷新private void draw() {try {mCanvas = mHolder.lockCanvas();mCanvas.drawColor(Color.WHITE);mCanvas.drawPath(mPath, mPaint);} catch (Exception e) {} finally {if (mCanvas != null) {//提交mHolder.unlockCanvasAndPost(mCanvas);}}}/*** 触摸事件** @param event* @return*/@Overridepublic boolean onTouchEvent(MotionEvent event) {lastX =  event.getX();lastY =  event.getY();switch (event.getAction()) {case MotionEvent.ACTION_DOWN:mPath.moveTo(lastX, lastY);break;case MotionEvent.ACTION_MOVE:mPath.lineTo(lastX,lastY);break;case MotionEvent.ACTION_UP:break;}return true;}}

附件：源码：https://github.com/CL-window/android_paint