Interpretation of the technical principles of the CircleImageView framework in the Java library (Decoding The Technical Principles of CircleImageView Framework in Java Class Libraries)

Interpret the technical principles of the CircleImageView framework in the Java class library In the Java library, CircleImageView is a commonly used framework to display round pictures.This article will analyze the technical principles of the CircleImageView framework and provide examples of Java code. 1. Technical background In order to achieve the effect of displaying circular pictures, developers usually need to perform some additional processing, such as using ImageView in the layout file, and then turning the picture into a circular shape by code.To simplify this process, the CircleImageView framework came into being. 2. Technical principles The key technical principle of the CircleImageView framework is to display a round picture using the custom imageView.It extends the Android native ImageView class and achieves a circular tailoring effect by rewriting the ONDRAW method. The specific implementation steps are as follows: 2.1 Inherit ImageView First of all, you need to create a custom CircleImageView class to inherit the ImageView class of Android.This custom class will add the logic of round cutting. 2.2 Rewrite the ONDRAW method Next, rewrite the ONDRAW method in the CircleImageView class.In this method, you can use Canvas to draw a circular image and cut it into a circular. The following is a simplified CircleImageView class: public class CircleImageView extends ImageView { public CircleImageView(Context context) { super(context); } public CircleImageView(Context context, AttributeSet attrs) { super(context, attrs); } public CircleImageView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } @Override protected void onDraw(Canvas canvas) { // Get Drawable in ImageView Drawable drawable = getDrawable(); if (drawable == null) { return; } // Converted drawable to Bitmap object Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap(); // Tie the picture into a circular Bitmap circleBitmap = getCircleBitmap(bitmap); // Draw a circular image in Canvas canvas.drawBitmap(circleBitmap, 0, 0, null); } // Tie the picture into a circular private Bitmap getCircleBitmap(Bitmap bitmap) { Bitmap output = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888); Canvas canvas = new Canvas(output); final Paint paint = new Paint(); final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight()); paint.setAntiAlias(true); canvas.drawARGB(0, 0, 0, 0); canvas.drawCircle(bitmap.getWidth() / 2, bitmap.getHeight() / 2, bitmap.getWidth() / 2, paint); paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN)); canvas.drawBitmap(bitmap, rect, rect, paint); return output; } } 3. Use CircleImageView Once the implementation of the CircleImageView is completed, it can be used as an ordinary ImageView in the layout file to display a round picture. <com.example.CircleImageView android:layout_width="120dp" android:layout_height="120dp" android:src="@drawable/profile_picture" /> In the above code, CircleImageView is a custom ImageView class, specifically specified the picture resources to be displayed through the `Android: src`. Through the above steps, the CircleImageView framework can easily achieve the display effect of circular pictures without additional code. Summarize This article interprets the technical principles of the CircleImageView framework in the Java class library.By inheriting the ImageView class and rewriting the ONDraw method, the CircleImageView framework implements the function of displaying circular pictures.This framework simplifies the process of developers to achieve circular tailoring, making the display of round pictures simpler and efficient.