Android繪圖技巧使用詳解

更新時(shí)間：2020年09月24日 17:31:38 作者：黎明前的硝煙

這篇文章主要為大家詳細(xì)介紹了Android繪圖技巧的使用，文中示例代碼介紹的非常詳細(xì)，具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下

本文實(shí)例為大家分享了Android繪圖技巧使用的具體代碼，供大家參考，具體內(nèi)容如下

XML繪圖

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(實(shí)現(xiàn)Photoshop中類似圖層的概念)

<?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"/>
<!-- 圖層效果-->
</layer-list>

Selector(幫助開發(fā)者實(shí)現(xiàn)靜態(tài)繪圖中的時(shí)間反饋)

<?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>
<!-- 點(diǎn)擊反饋效果-->
</selector>

Android繪圖技巧

Canvas(作為繪制圖形的直接對象)

Canvas.save();

可以理解為保存畫布，作用是將之前的所有已經(jīng)繪制圖像保存起來，讓后續(xù)的操作就好像在一個(gè)新的圖層上操作一樣

Canvas.restore();

可以理解為Photoshop中的合并圖層操作，作用是將save()之后繪制的所有的圖像與save()之前的圖像進(jìn)行合并

Canvas.translate();

坐標(biāo)系的平移

Canvas.rotate();

坐標(biāo)系的旋轉(zhuǎn)

Layer圖層

特別注意的是 saveLayerAlpha()與restore()要同時(shí)使用，才能夠在canvas 畫出多個(gè)層次，就是花多少層就要有多少對兩個(gè)函數(shù)！

@Override
 protected void onDraw(Canvas canvas) {
 //super.onDraw(canvas);
 drawLayer(canvas);
 //圖層同樣是基于棧的結(jié)構(gòu)進(jìn)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);//入棧(創(chuàng)建新圖層)
 paint.setColor(Color.RED);
 canvas.drawCircle(200,200,100,paint);
 canvas.restore();//出棧
 }

像素點(diǎn)分析

bitmap.getPixels(pixels,offset,stride,x,y,width,height);

參數(shù)含義如下：

pixels：接受位圖顏色值的數(shù)組
offset：寫入到pixels[]中的第一個(gè)索引值
stride：pixels[]的行間距
x:從位圖中讀取的第一個(gè)像素的x坐標(biāo)值
y:從位圖中讀取的第一個(gè)像素的y坐標(biāo)值
width:每一行中讀取的像素寬度
height:讀取的行數(shù)

畫筆特效處理

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：位圖Shader
LinearGradient：線性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：重復(fù)——橫向、縱向不斷重復(fù)
Shader.TileMode.CLAMP：拉伸——拉伸的圖片最后的那個(gè)像素，不斷重復(fù)
Shader.TileMode.MIRROR：鏡像——橫向不斷翻轉(zhuǎn)重復(fù)，橫向不斷翻轉(zhuǎn)重復(fù)

PathEffect（各種筆觸繪制一個(gè)路徑）

CornerPathEffect：拐角處變得圓滑
DiscretePathEffect：線段上會產(chǎn)生許多雜點(diǎn)
DashPathEffect：繪制虛線
PathDashPathEffect：比DashPathEffect的功能更加強(qiáng)大，可以設(shè)置如方形點(diǎn)的虛線，圓形點(diǎn)的虛線。
ComposePathEffect：組合任意兩種PathEffect路徑組合形成新的效果

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與View的區(qū)別：

1、View主要適用于主動更新的情況下，而SurfaceView主要適用于被動更新，例如頻繁的更新
2、View在主線程中對畫面進(jìn)行更新，而SurfaceView通常會通過一個(gè)子線程來進(jìn)行頁面的刷新
3、View在繪圖時(shí)沒有使用雙緩沖機(jī)制，而SurfaceView在底層機(jī)制中就已經(jīng)實(shí)現(xiàn)了雙緩沖機(jī)制

總結(jié)：SurfaceView適合需要頻繁刷新，或者刷新時(shí)數(shù)據(jù)處理量比較大

public class SurfaceViewTemplate extends SurfaceView implements SurfaceHolder.Callback ,Runnable{
 //SurfaceHolder
 private SurfaceHolder holder;
 //用于繪畫的Canvas
 private Canvas canvas;
 //子線程標(biāo)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);//焦點(diǎn)
 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內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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