CircleImageView source code analysis and optimization skills
CircleImageView is a commonly used custom ImageView, which can cut the picture into a circular display.This article will analyze the source code of CircleImageView and introduces how to optimize the CircleImageView to improve performance and effect.
1. Source code analysis
CircleImageView is inherited from AppCompatimageView, and AppCompatimageView is inherited from ImageView, so CircleImageView has all the functions of ImageView.
2. Core method:
The core method of CircleImageView is the ONDraw (Canvas) method, which is called during viewing.In the ONDRAW method, CircleImageView calculates the width and height of the picture, and then use Canvas to draw a circular border and cut the picture into a round shape.
3. Custom attributes:
CircleImageView also defines some custom attributes, such as `bordercolor` (border color),` borderWidth` (border width), etc., you can customize these attributes in the XML layout file to customize.
Second, optimization skills
1. Use BitmapShader:
CircleImageView uses BitmapShader to implement the cutting and drawing of the picture. You can make the picture automatically zoom and spread the control by setting the `Scaletype` as the` CENTERCROP`.This can avoid manually calculating the picture size and improve the simplicity of the code.
2. Use cache:
When the picture is large or the loading is slow, you can use memory cache or disk cache to optimize the picture loading speed to avoid frequent IO operations.
3. Asynchronous loading:
When you need to load network pictures, it is recommended to use the asynchronous loading framework (such as GLIDE or Picasso) to avoid the main thread obstruction.Asynchronous loading can improve the user experience, and can automatically process the compression and cache of the picture.
4. Use hardware acceleration:
If the device supports hardware acceleration, the hardware acceleration can be opened to improve the performance of CircleImageView.By adding hardware acceleration by adding `application` tags in the` Application` label in the AndroidManifest.xml file to open the hardware acceleration.
Third, sample code
The following is a simple CircleImageView sample code:
public class CircleImageView extends AppCompatImageView {
public CircleImageView(Context context) {
super(context);
}
public CircleImageView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CircleImageView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onDraw(Canvas canvas) {
if (getDrawable() == null) {
return;
}
Bitmap bitmap = ((BitmapDrawable) getDrawable()).getBitmap();
Bitmap circleBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), Bitmap.Config.ARGB_8888);
float radius = Math.min(bitmap.getWidth(), bitmap.getHeight()) / 2f;
BitmapShader shader = new BitmapShader(bitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
Paint paint = new Paint();
paint.setShader(shader);
Canvas circleCanvas = new Canvas(circleBitmap);
circleCanvas.drawCircle(bitmap.getWidth() / 2f, bitmap.getHeight() / 2f, radius, paint);
canvas.drawBitmap(circleBitmap, 0, 0, null);
}
}
The above code is just a simple example. The actual project may need to make more complicated customization and optimization according to the needs.It is hoped that this article can help the CircleImageView source code analysis and optimization skills and be applied in actual development.
