自定义ImageView实现圆角图片

自定义ImageView实现圆角图片,满足以下需求:
1、四个角的度数均要支持自定义
2、可以在布局当中添加自定义的度数

实现步骤:
1、自定义一个ImageView,继承自AppCompatImageView。
(关于AppCompatImageView,继承自ImageView,是一个在平台的旧版本上支持兼容功能的imageView。)
实现它的构造方法,创建一个init()方法,保证构造方法里面都会调用。
2、在onLayout方法里面获取到ImageView的width和height。
3、在onDraw方法里面对Canvas进行裁剪。
4、让四个角的度数支持自定义,并且支持在xml中设置。

实现代码如下:

public class CircleImageView extends AppCompatImageView {
    float width, height;
    private int defaultRadius = 0;
    private int radius;
    private int leftTopRadius;
    private int rightTopRadius;
    private int rightBottomRadius;
    private int leftBottomRadius;

    public CircleImageView(Context context) {
        super(context);
        init(context, null);
    }

    public CircleImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs);
    }

    public CircleImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.circle_image_view);
        radius = array.getDimensionPixelOffset(R.styleable.circle_image_view_radius, defaultRadius);
        leftTopRadius = array.getDimensionPixelOffset(R.styleable.circle_image_view_left_top_radius, leftTopRadius);
        rightTopRadius = array.getDimensionPixelOffset(R.styleable.circle_image_view_right_top_radius, rightTopRadius);
        rightBottomRadius = array.getDimensionPixelOffset(R.styleable.circle_image_view_right_bottom_radius, rightBottomRadius);
        leftBottomRadius = array.getDimensionPixelOffset(R.styleable.circle_image_view_left_bottom_radius, leftBottomRadius);

        if (defaultRadius == leftTopRadius) {
            leftTopRadius = radius;
        }
        if (defaultRadius == rightTopRadius) {
            rightTopRadius = radius;
        }
        if (defaultRadius == rightBottomRadius) {
            rightBottomRadius = radius;
        }
        if (defaultRadius == leftBottomRadius) {
            leftBottomRadius = radius;
        }
        array.recycle();
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        width = getWidth();
        height = getHeight();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        int maxLeft = Math.max(leftTopRadius, leftBottomRadius);
        int maxRight = Math.max(rightTopRadius, rightBottomRadius);
        int minWidth = maxLeft + maxRight;
        int maxTop = Math.max(leftTopRadius, rightTopRadius);
        int maxBottom = Math.max(leftBottomRadius, rightBottomRadius);
        int minHeight = maxTop + maxBottom;
        if (width >= minWidth && height > minHeight) {
            Path path = new Path();
            //四个角:右上,右下,左下,左上
            path.moveTo(leftTopRadius, 0);
            path.lineTo(width - rightTopRadius, 0);
            path.quadTo(width, 0, width, rightTopRadius);

            path.lineTo(width, height - rightBottomRadius);
            path.quadTo(width, height, width - rightBottomRadius, height);

            path.lineTo(leftBottomRadius, height);
            path.quadTo(0, height, 0, height - leftBottomRadius);

            path.lineTo(0, leftTopRadius);
            path.quadTo(0, 0, leftTopRadius, 0);

            canvas.clipPath(path);
        }
        super.onDraw(canvas);
    }
}

attrs.xml,位于values文件夹下,内容如下:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="circle_image_view">
        <attr name="radius" format="dimension"/>
        <attr name="left_top_radius" format="dimension"/>
        <attr name="right_top_radius" format="dimension"/>
        <attr name="right_bottom_radius" format="dimension"/>
        <attr name="left_bottom_radius" format="dimension"/>
    </declare-styleable>
</resources>

使用:

<com.example.custom_view.CircleImageView
            android:id="@+id/civ"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:scaleType="centerCrop"
            android:layout_marginTop="8dp"
            android:layout_marginBottom="8dp"
            app:radius="20dp"/>

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