如何在Android应用中实现自定义View

本篇文章为大家展示了如何在Android应用中实现自定义View，内容简明扼要并且容易理解，绝对能使你眼前一亮，通过这篇文章的详细介绍希望你能有所收获。

Android自定义view的种类

自定义view大概可以分为四个大类，主要是通过实现方式来区分

      1.自绘控件，继承view,重写onDraw方法，在其中进行绘制，需要自己适配边距等等

      2.继承ViewGroup派生的特殊Layout,主要用于实现自定义布局，也需要自己适配边距等

      3.继承特定的View(如TextView等），不用自己适配支持wrap_conten,match_parent,可以给其加入新的功能

      4.继承特定的ViewGroup,例如linearlayout,多用于多个控件的组合view,也不用自己去做适配

自绘控件

这种自定义view是最复杂的一种，因为既要适配wrap_conten,match_parent又要通过条件判断来在屏幕上绘制不同的内容，主要就是重写onDraw方法

以下是一个简单的onDraw重写代码

@Override protected void onDraw(canvas canvas) {  super.onDraw(canvas);   final int paddingLeft = getPaddingLeft();  final int paddingRight = getPaddingRight();  final int paddingTop = getPaddingTop();  final int paddingBottom = getPaddingBottom();   //get the view's width and height and decide the radiu  int width = getWidth() - paddingLeft - paddingRight;  int height = getHeight() - paddingTop - paddingBottom;  radiu = Math.min(width , height) / 2 - boundWidth - progressWidth;   //setup the paint  paint.setStyle(Paint.Style.STROKE);  paint.setStrokeWidth(boundWidth);  paint.setColor(Color.BLACK);   //draw the inner circle  int centerX = paddingLeft + getWidth()/2;  int centerY = paddingTop + getHeight() / 2;  canvas.drawCircle(centerX,centerY, radiu, paint);     float totalRadiu = radiu +boundWidth +progressWidth/2;   //draw the circlr pic  if (drawable != null&&bitmap == null) {   image = ((BitmapDrawable) drawable).getBitmap();    bitmap = Bitmap.createBitmap((int)(2*totalRadiu),(int)(2*totalRadiu), Bitmap.Config.ARGB_8888);   Canvas bitmapCanvas = new Canvas(bitmap);    Paint bitmapPaint = new Paint();   bitmapPaint.setAntiAlias(true);    bitmapCanvas.drawCircle(totalRadiu, totalRadiu, radiu, bitmapPaint);    bitmapPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));   bitmapCanvas.drawBitmap(image,null,new RectF(0,0,2*totalRadiu,2*totalRadiu) , bitmapPaint);    }  Rect rect = new Rect((int)(centerX -totalRadiu),(int)(centerY-totalRadiu),(int)(centerX+totalRadiu),(int)(centerY+ totalRadiu));  canvas.save();  if(isRotate)  canvas.rotate(rotateDegree,centerX,centerY);  canvas.drawBitmap(bitmap,null ,rect, paint);   canvas.restore();  //set paint for arc  paint.setStrokeWidth(progressWidth);  paint.setStrokeCap(Paint.Cap.ROUND);   //prepare for draw arc  RectF oval = new RectF();  oval.left = centerX -totalRadiu ;  oval.top =centerY- totalRadiu ;  oval.right = centerX + totalRadiu;  oval.bottom = centerY+ totalRadiu;  paint.setColor(progressBackColor);   //draw background arc  canvas.drawArc(oval, arcStar, arcEnd, false, paint);   //draw progress arc  paint.setColor(progressColor);  canvas.drawArc(oval, arcStar, progress, false, paint); }