Android绘图技巧使用详解

本文实例为大家分享了Android绘图技巧使用的具体代码，供大家参考，具体内容如下

XML绘图

Bitmap

<?xml version='1.0' encoding='utf-8'?><bitmap xmlns:android='http://schemas.android.com/apk/res/android' android:src='https://www.haobala.com/bcjs/@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); } } }}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持好吧啦网。