Android绘图技巧 Android绘图技巧使用详解
黎明前的硝烟 人气:0想了解Android绘图技巧使用详解的相关内容吗,黎明前的硝烟在本文为您仔细讲解Android绘图技巧的相关知识和一些Code实例,欢迎阅读和指正,我们先划重点:Android,绘图,下面大家一起来学习吧。
XML绘图
Bitmap
<?xml version="1.0" encoding="utf-8"?> <bitmap xmlns:android="http://schemas.android.com/apk/res/android" android:src="@drawable/giao"/>
Shape
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle"> <gradient android:startColor="#FF5DA2FF" android:endColor="#805FBBEF" android:angle="45"/> <padding android:bottom="7dp" android:top="7dp" android:left="7dp" android:right="7dp"/> <corners android:radius="8dp"/> </shape>
Layer(实现Photoshop中类似图层的概念)
<?xml version="1.0" encoding="utf-8"?> <layer-list xmlns:android="http://schemas.android.com/apk/res/android"> <item android:drawable="@drawable/default_head"/> <item android:drawable="@drawable/default_head" android:left="10dip" android:right="10dip" android:top="10dip" android:bottom="10dip"/> <item android:drawable="@drawable/giao" android:left="200dp" android:right="200dp" android:top="200dp" android:bottom="200dp"/> <!-- 图层效果--> </layer-list>
Selector(帮助开发者实现静态绘图中的时间反馈)
<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android"> <item android:state_pressed="true"> <shape android:shape="rectangle"> <solid android:color="#33FD0000"/> <corners android:radius="5dp"/> <padding android:left="10dp" android:right="10dp" android:top="10dp" android:bottom="10dp"/> </shape> </item> <item> <shape android:shape="rectangle"> <solid android:color="#ffffffff"/> <corners android:radius="5dp"/> <padding android:left="10dp" android:right="10dp" android:top="10dp" android:bottom="10dp"/> </shape> </item> <!-- 点击反馈效果--> </selector>
Android绘图技巧
Canvas(作为绘制图形的直接对象)
Canvas.save();
可以理解为保存画布,作用是将之前的所有已经绘制图像保存起来,让后续的操作就好像在一个新的图层上操作一样
Canvas.restore();
可以理解为Photoshop中的合并图层操作,作用是将save()之后绘制的所有的图像与save()之前的图像进行合并
Canvas.translate();
坐标系的平移
Canvas.rotate();
坐标系的旋转
Layer图层
特别注意的是 saveLayerAlpha()与restore()要同时使用,才能够在canvas 画出多个层次,就是花多少层就要有多少对两个函数!
@Override protected void onDraw(Canvas canvas) { //super.onDraw(canvas); drawLayer(canvas); //图层同样是基于栈的结构进行管理的 @SuppressLint("DrawAllocation") Paint paint=new Paint(); canvas.drawColor(Color.WHITE); paint.setColor(Color.BLUE); canvas.drawCircle(150,150,100,paint); canvas.saveLayerAlpha(0,0,400,400,127);//入栈(创建新图层) paint.setColor(Color.RED); canvas.drawCircle(200,200,100,paint); canvas.restore();//出栈 }
像素点分析
bitmap.getPixels(pixels,offset,stride,x,y,width,height);
参数含义如下:
- pixels:接受位图颜色值的数组
- offset:写入到pixels[]中的第一个索引值
- stride:pixels[]的行间距
- x:从位图中读取的第一个像素的x坐标值
- y:从位图中读取的第一个像素的y坐标值
- width:每一行中读取的像素宽度
- height:读取的行数
画笔特效处理
PorterDuffXfermode
public class FilletView extends View { private Bitmap bitmap,out; private Paint paint; public FilletView(Context context) { super(context); inView(); } public FilletView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); inView(); } public FilletView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); inView(); } private void inView(){ bitmap= BitmapFactory.decodeResource(getResources(), R.drawable.ask); out=Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight(),Bitmap.Config.ARGB_8888); Canvas canvas=new Canvas(out); paint=new Paint(); paint.setAntiAlias(true); canvas.drawRoundRect(0,0,bitmap.getWidth(),bitmap.getHeight(),80,80,paint); paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN)); canvas.drawBitmap(bitmap,0,0,paint); } @Override protected void onDraw(Canvas canvas) { canvas.drawBitmap(out,0,0,null); } }
Shader
- BitmapShader:位图Shader
- LinearGradient:线性Shader
- RadialGradient:光束Shader
- SweepGradient:梯度Shader
- ComposeShader:混合Shader
private void useBitmapShader(Canvas canvas){ @SuppressLint("DrawAllocation") Bitmap bitmap= BitmapFactory.decodeResource(getResources(), R.drawable.default_head); @SuppressLint("DrawAllocation") BitmapShader shader=new BitmapShader(bitmap, Shader.TileMode.REPEAT,Shader.TileMode.REPEAT); @SuppressLint("DrawAllocation") Paint paint=new Paint(); paint.setShader(shader); canvas.drawCircle(500,200,200,paint); }
- Shader.TileMode.REPEAT:重复——横向、纵向不断重复
- Shader.TileMode.CLAMP:拉伸——拉伸的图片最后的那个像素,不断重复
- Shader.TileMode.MIRROR:镜像——横向不断翻转重复,横向不断翻转重复
PathEffect(各种笔触绘制一个路径)
- CornerPathEffect:拐角处变得圆滑
- DiscretePathEffect:线段上会产生许多杂点
- DashPathEffect:绘制虚线
- PathDashPathEffect:比DashPathEffect的功能更加强大,可以设置如方形点的虚线,圆形点的虚线。
- ComposePathEffect:组合任意两种PathEffect路径组合形成新的效果
public class PathEffectView extends View { private Paint paint; private Path mainPath; private PathEffect[] effects; public PathEffectView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); inView(); } private void inView(){ paint=new Paint(); paint.setStyle(Paint.Style.STROKE); paint.setStrokeWidth(5); paint.setColor(Color.DKGRAY); mainPath=new Path(); mainPath.moveTo(0,0); for (int i = 0; i <= 30; i++) { mainPath.lineTo(i*35, (float) (Math.random()*100)); } effects=new PathEffect[6]; } @SuppressLint("DrawAllocation") @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); effects[0]=null; effects[1]=new CornerPathEffect(30); effects[2]=new DiscretePathEffect(3,5); effects[3]=new DashPathEffect(new float[]{20,10,5,10},0); Path path=new Path(); path.addRect(0,0,8,8,Path.Direction.CCW); effects[4]=new PathDashPathEffect(path,12,0,PathDashPathEffect.Style.ROTATE); effects[5]=new ComposePathEffect(effects[3],effects[1]); for (PathEffect effect : effects) { paint.setPathEffect(effect); canvas.drawPath(mainPath, paint); canvas.translate(0, 200); } } }
SurfaceView
SurfaceView与View的区别:
1、View主要适用于主动更新的情况下,而SurfaceView主要适用于被动更新,例如频繁的更新
2、View在主线程中对画面进行更新,而SurfaceView通常会通过一个子线程来进行页面的刷新
3、View在绘图时没有使用双缓冲机制,而SurfaceView在底层机制中就已经实现了双缓冲机制
总结:SurfaceView适合需要频繁刷新,或者刷新时数据处理量比较大
public class SurfaceViewTemplate extends SurfaceView implements SurfaceHolder.Callback ,Runnable{ //SurfaceHolder private SurfaceHolder holder; //用于绘画的Canvas private Canvas canvas; //子线程标志位 private boolean isDrawing; private Paint paint; private Path path; private int x,y; public SurfaceViewTemplate(Context context) { super(context); inView(); } public SurfaceViewTemplate(Context context, AttributeSet attrs) { super(context, attrs); inView(); } public SurfaceViewTemplate(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); inView(); } private void inView(){ holder=getHolder(); holder.addCallback(this); setFocusable(false);//焦点 setFocusableInTouchMode(true); this.setKeepScreenOn(true); path=new Path(); paint=new Paint(Paint.ANTI_ALIAS_FLAG); paint.setColor(Color.RED); paint.setStyle(Paint.Style.STROKE); paint.setStrokeWidth(10); paint.setStrokeCap(Paint.Cap.ROUND); paint.setStrokeJoin(Paint.Join.ROUND); } @Override public void surfaceCreated(@NonNull SurfaceHolder surfaceHolder) { isDrawing=true; path.moveTo(0,400); new Thread(this).start(); } @Override public void surfaceChanged(@NonNull SurfaceHolder surfaceHolder, int i, int i1, int i2) { } @Override public void surfaceDestroyed(@NonNull SurfaceHolder surfaceHolder) { isDrawing=false; } @Override public void run() { while (isDrawing){ drawSome(); x+=1; y= (int) (100*Math.sin(x*2*Math.PI/180)+400); path.lineTo(x,y); } } private void drawSome(){ try { canvas=holder.lockCanvas(); //draw something... canvas.drawColor(Color.WHITE); canvas.drawPath(path,paint); } catch (Exception e) { e.printStackTrace(); } finally { if (canvas!=null){ holder.unlockCanvasAndPost(canvas); } } } }
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