Android繪圖技巧使用詳解
阿新 • • 發佈：2020-09-24
本文例項為大家分享了Android九宮格圖片展示的具體程式碼，供大家參考，具體內容如下
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(實現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(幫助開發者實現靜態繪圖中的時間反饋)
<?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>
<!-- 點選反饋效果-->
</selector>Android繪圖技巧
Canvas(作為繪製圖形的直接物件)
Canvas.save();
可以理解為儲存畫布，作用是將之前的所有已經繪製圖像儲存起來，讓後續的操作就好像在一個新的圖層上操作一樣
Canvas.restore();
可以理解為Photoshop中的合併圖層操作，作用是將save()之後繪製的所有的影象與save()之前的影象進行合併
Canvas.translate();
座標系的平移
Canvas.rotate();
座標系的旋轉
Layer圖層
特別注意的是 saveLayerAlpha()與restore()要同時使用，才能夠在canvas 畫出多個層次，就是花多少層就要有多少對兩個函式！
@Override
protected void onDraw(Canvas canvas) {
//super.onDraw(canvas);
drawLayer(canvas);
//圖層同樣是基於棧的結構進行管理的
@SuppressLint("DrawAllocation")
Paint paint=new Paint();
canvas.drawColor(Color.WHITE);
paint.setColor(Color.BLUE);
canvas.drawCircle(150,150,100,paint);
canvas.saveLayerAlpha(0,400,127);//入棧(建立新圖層)
paint.setColor(Color.RED);
canvas.drawCircle(200,200,paint);
canvas.restore();//出棧
}
畫素點分析
bitmap.getPixels(pixels,offset,stride,x,y,width,height);
引數含義如下：
- pixels：接受點陣圖顏色值的陣列
- offset：寫入到pixels[]中的第一個索引值
- stride：pixels[]的行間距
- x:從點陣圖中讀取的第一個畫素的x座標值
- y:從點陣圖中讀取的第一個畫素的y座標值
- width:每一行中讀取的畫素寬度
- height:讀取的行數
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,bitmap.getWidth(),80,paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(bitmap,paint);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(out,null);
}
}
Shader
- BitmapShader：點陣圖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,paint);
}
- Shader.TileMode.REPEAT：重複——橫向、縱向不斷重複
- Shader.TileMode.CLAMP：拉伸——拉伸的圖片最後的那個畫素，不斷重複
- Shader.TileMode.MIRROR：映象——橫向不斷翻轉重複，橫向不斷翻轉重複
PathEffect（各種筆觸繪製一個路徑）
- CornerPathEffect：拐角處變得圓滑
- DiscretePathEffect：線段上會產生許多雜點
- DashPathEffect：繪製虛線
- PathDashPathEffect：比DashPathEffect的功能更加強大，可以設定如方形點的虛線，圓形點的虛線。
- 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,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(0,8,Path.Direction.CCW);
effects[4]=new PathDashPathEffect(path,12,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的區別：
1、View主要適用於主動更新的情況下，而SurfaceView主要適用於被動更新，例如頻繁的更新
2、View在主執行緒中對畫面進行更新，而SurfaceView通常會通過一個子執行緒來進行頁面的重新整理
3、View在繪圖時沒有使用雙緩衝機制，而SurfaceView在底層機制中就已經實現了雙緩衝機制
總結：SurfaceView適合需要頻繁重新整理，或者重新整理時資料處理量比較大
public class SurfaceViewTemplate extends SurfaceView implements SurfaceHolder.Callback,Runnable{
//SurfaceHolder
private SurfaceHolder holder;
//用於繪畫的Canvas
private Canvas canvas;
//子執行緒標誌位
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,defStyleAttr);
inView();
}
private void inView(){
holder=getHolder();
holder.addCallback(this);
setFocusable(false);//焦點
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容，希望對大家的學習有所幫助，也希望大家多多支援我們。