For details, the technical principles of the CircleImageView framework in the Java class library

CircleImageView is a commonly used Android framework that is used to achieve circular pictures display.Its technical principles and the implementation methods in the Java library are as follows. First of all, the CircleImageView class is a custom View inherited from the IMAGEVIEW class.It realizes the display of round pictures by rewriting the drawing method of the ImageView class.In the constructive method, we can set attributes such as border color and border width. In the drawing method onDraw (), we first obtain the width and height of the CircleImageView, and then calculate the radius.Then, we set a brush to draw pictures and frames.Use the BitMapShader class to create an object that contains the picture to be drawn and how to fill the style of this picture.We applied this object to the brush and set the scaling method of the picture to the center_crop to ensure that the picture was filled in the CircleImageView. Then, we draw a circular area through Canvas.Drawcircle () method.The radius of this circular area is the radius just calculated.Finally, we use the drawbitMap () method to draw the cut -cut pictures in this circular area, thereby achieving a circular picture display. Below is a simple CircleImageView Java code example: public class CircleImageView extends ImageView { private int borderWidth; private int borderColor; public CircleImageView(Context context, AttributeSet attrs) { super(context, attrs); // Get custom attributes TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CircleImageView, 0, 0); try { borderWidth = typedArray.getDimensionPixelSize(R.styleable.CircleImageView_borderWidth, 0); borderColor = typedArray.getColor(R.styleable.CircleImageView_borderColor, Color.WHITE); } finally { typedArray.recycle(); } } @Override protected void onDraw(Canvas canvas) { // Draw a circular area int radius = Math.min(getWidth() / 2, getHeight() / 2); canvas.drawCircle(getWidth() / 2, getHeight() / 2, radius, getPaint()); // Cutting pictures are round BitmapDrawable drawable = (BitmapDrawable) getDrawable(); Bitmap bitmap = drawable.getBitmap(); BitmapShader shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP); shader.setLocalMatrix(getImageMatrix()); getPaint().setShader(shader); // Draw round pictures int circleRadius = radius - borderWidth; canvas.drawCircle(getWidth() / 2, getHeight() / 2, circleRadius, getPaint()); // Draw the frame Paint borderPaint = new Paint(); borderPaint.setStyle(Paint.Style.STROKE); borderPaint.setStrokeWidth(borderWidth); borderPaint.setColor(borderColor); canvas.drawCircle(getWidth() / 2, getHeight() / 2, circleRadius, borderPaint); } } The above is the technical principles and example code of the CircleImageView framework in the Java class library.Through this framework, we can easily display circular pictures in Android applications, providing a better user experience.