• Android自定义控件View(二)继承控件


    在前一篇博客中学习了Android自定义控件View的流程步骤和注意点,不了解的童鞋可以参考Android自定义控件View(一)。这一节开始学习自定义控件View(二)之继承系统已有的控件。我们来自定义一个圆形ImageView。

    这里写图片描述

    RoundImageView

    随着Android UI效果越来越炫,很多系统自带的控件已经无法满足日常开发需求,比如很多应用的头像是圆形的,QQ头像就是圆形的图片。但是Android系统提供的控件当中没有一个是圆形的。那么怎么才能实现圆形头像效果呢?两种方法:

    • 图片直接做成圆形的
    • 自定义一个圆形的view控件来加载图片

    第一种方法有局限性,因为大多数图片都是矩形的,也无法确保用户提供的图片是圆形的。因此此方法直接放弃。
    第二种方法就是我们经常使用的,继承ImageView重新自定义一个RoundImageView。

    根据自定义控件View的流程,我们一步一步来实现RoundImageView吧。

    1.自定义attrs.xml属性文件

    <--圆形轮廓的宽度-->
     <attr name="border_thickness" format="dimension"></attr>
     <--圆形轮廓外边框的颜色-->
     <attr name="border_outside_color" format="color"></attr>
     <--圆形轮廓内边框的颜色-->
     <attr name="border_inside_color" format="color"></attr>

    2.获取View的属性值

     private void setCustomAttributes(AttributeSet attrs) {
            TypedArray a = mContext.obtainStyledAttributes(attrs,
                    R.styleable.RoundImageView);
            mBorderThickness = a.getDimensionPixelSize(
                    R.styleable.RoundImageView_border_thickness, 0);
            mBorderOutsideColor = a
                    .getColor(R.styleable.RoundImageView_border_outside_color,
                            defaultColor);
            mBorderInsideColor = a.getColor(
                    R.styleable.RoundImageView_border_inside_color, defaultColor);
            a.recycle();
        }

    可以看到,我们这里自定义了3个属性,因为RoundImageViwe控件是继承自ImageView的,所以继承了ImageView所有的属性和方法,因此,RoundImageView可以使用ImageView的一切属性。
    3.重写onDraw方法

        @Override
        protected void onDraw(Canvas canvas) {
            Drawable drawable = getDrawable();
            if (drawable == null) {
                return;
            }
    
            if (getWidth() == 0 || getHeight() == 0) {
                return;
            }
            this.measure(0, 0);
            if (drawable.getClass() == NinePatchDrawable.class) {
                return;
            }
            Bitmap b = ((BitmapDrawable) drawable).getBitmap();
            Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);
    
            int radius = getRadius(canvas);
    
            Bitmap roundBitmap = getCroppedRoundBitmap(bitmap, radius);
            canvas.drawBitmap(roundBitmap, requestWH / 2 - radius, requestWH
                    / 2 - radius, null);
        }

    根据控件的布局大小,获得圆形图片的半径值大小,然后根据图片的半径大小裁剪出圆形图片,最后canvas.drawBitmap画出圆形图片。

    最后贴出所有代码

    package com.xjp.customview;
    
    import android.content.Context;
    import android.content.res.TypedArray;
    import android.graphics.Bitmap;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.graphics.PorterDuff;
    import android.graphics.PorterDuffXfermode;
    import android.graphics.Rect;
    import android.graphics.drawable.BitmapDrawable;
    import android.graphics.drawable.Drawable;
    import android.graphics.drawable.NinePatchDrawable;
    import android.util.AttributeSet;
    import android.util.Log;
    import android.widget.ImageView;
    
    /**
     * Description:圆形ImageView,可设置最多两个宽度不同且颜色不同的圆形边框。
     * User: xjp
     * Date: 2015/5/28
     * Time: 16:24
     */
    
    public class RoundImageView extends ImageView {
    
        private static final String TAG = "RoundImageView";
        private static final boolean DEBUG = true;
        private int mBorderThickness = 0;
        private Context mContext;
        private int defaultColor = 0xFFFFFFFF;
        // 如果只有其中一个有值,则只画一个圆形边框
        private int mBorderOutsideColor = 0;
        private int mBorderInsideColor = 0;
        // 控件默认长、宽
        private int defaultWidth = 0;
        private int defaultHeight = 0;
        //控件画圆的宽高。
        private int requestWH = 0;
    
        public RoundImageView(Context context) {
            this(context, null);
        }
    
        public RoundImageView(Context context, AttributeSet attrs) {
            this(context, attrs, 0);
        }
    
        public RoundImageView(Context context, AttributeSet attrs, int defStyle) {
            super(context, attrs, defStyle);
            mContext = context;
            setCustomAttributes(attrs);
        }
    
        /**
         * 获得自定义控件属性值
         *
         * @param attrs
         */
        private void setCustomAttributes(AttributeSet attrs) {
            TypedArray a = mContext.obtainStyledAttributes(attrs,
                    R.styleable.RoundImageView);
            mBorderThickness = a.getDimensionPixelSize(
                    R.styleable.RoundImageView_border_thickness, 0);
            mBorderOutsideColor = a
                    .getColor(R.styleable.RoundImageView_border_outside_color,
                            defaultColor);
            mBorderInsideColor = a.getColor(
                    R.styleable.RoundImageView_border_inside_color, defaultColor);
            a.recycle();
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            Drawable drawable = getDrawable();
            if (drawable == null) {
                return;
            }
    
            if (getWidth() == 0 || getHeight() == 0) {
                return;
            }
            this.measure(0, 0);
            if (drawable.getClass() == NinePatchDrawable.class) {
                return;
            }
            Bitmap b = ((BitmapDrawable) drawable).getBitmap();
            Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);
    
            int radius = getRadius(canvas);
    
            Bitmap roundBitmap = getCroppedRoundBitmap(bitmap, radius);
            canvas.drawBitmap(roundBitmap, requestWH / 2 - radius, requestWH
                    / 2 - radius, null);
        }
    
        /**
         * 获取画园的半径,并且绘制圆的外边框
         *
         * @param canvas
         * @return
         */
        private int getRadius(Canvas canvas) {
            if (defaultWidth == 0) {
                defaultWidth = getWidth();
    
            }
            if (defaultHeight == 0) {
                defaultHeight = getHeight();
            }
            requestWH = defaultHeight > defaultWidth ? defaultWidth : defaultHeight;
    
            int radius = 0;
            if (mBorderInsideColor != defaultColor
                    && mBorderOutsideColor != defaultColor) {// 定义画两个边框,分别为外圆边框和内圆边框
                radius = requestWH / 2 - 2 * mBorderThickness;
                // 画内圆
                drawCircleBorder(canvas, radius + mBorderThickness / 2,
                        mBorderInsideColor);
                // 画外圆
                drawCircleBorder(canvas, radius + mBorderThickness
                        + mBorderThickness / 2, mBorderOutsideColor);
            } else if (mBorderInsideColor != defaultColor
                    && mBorderOutsideColor == defaultColor) {// 定义画一个边框
                radius = requestWH / 2 - mBorderThickness;
                drawCircleBorder(canvas, radius + mBorderThickness / 2,
                        mBorderInsideColor);
            } else if (mBorderInsideColor == defaultColor
                    && mBorderOutsideColor != defaultColor) {// 定义画一个边框
                radius = (defaultWidth < defaultHeight ? defaultWidth
                        : defaultHeight) / 2 - mBorderThickness;
                drawCircleBorder(canvas, radius + mBorderThickness / 2,
                        mBorderOutsideColor);
            } else {// 没有边框
                radius = requestWH / 2;
            }
            return radius;
        }
    
        /**
         * 获取裁剪后的圆形图片
         *
         * @param radius 半径
         */
        private static Bitmap getCroppedRoundBitmap(Bitmap bmp, int radius) {
            Bitmap scaledSrcBmp;
            int diameter = radius * 2;
    
            // 为了防止宽高不相等,造成圆形图片变形,因此截取长方形中处于中间位置最大的正方形图片
            int bmpWidth = bmp.getWidth();
            int bmpHeight = bmp.getHeight();
            int squareWidth = 0, squareHeight = 0;
            int x = 0, y = 0;
            Bitmap squareBitmap;
            if (DEBUG) {
                Log.d(TAG, "the Bitmap w:" + bmpWidth + " the Bitmap h:" + bmpHeight);
            }
    
            if (bmpHeight > bmpWidth) {// 高大于宽
                squareWidth = squareHeight = bmpWidth;
                x = 0;
                y = (bmpHeight - bmpWidth) / 2;
                // 截取正方形图片
                squareBitmap = Bitmap.createBitmap(bmp, x, y, squareWidth,
                        squareHeight);
            } else if (bmpHeight < bmpWidth) {// 宽大于高
                squareWidth = squareHeight = bmpHeight;
                x = (bmpWidth - bmpHeight) / 2;
                y = 0;
                squareBitmap = Bitmap.createBitmap(bmp, x, y, squareWidth,
                        squareHeight);
            } else {
                squareBitmap = bmp;
            }
    
            if (squareBitmap.getWidth() != diameter
                    || squareBitmap.getHeight() != diameter) {
                scaledSrcBmp = Bitmap.createScaledBitmap(squareBitmap, diameter,
                        diameter, true);
    
            } else {
                scaledSrcBmp = squareBitmap;
            }
            Bitmap output = Bitmap.createBitmap(scaledSrcBmp.getWidth(),
                    scaledSrcBmp.getHeight(), Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(output);
    
            Paint paint = new Paint();
            Rect rect = new Rect(0, 0, scaledSrcBmp.getWidth(),
                    scaledSrcBmp.getHeight());
    
            paint.setAntiAlias(true);
            paint.setFilterBitmap(true);
            paint.setDither(true);
            canvas.drawARGB(0, 0, 0, 0);
            canvas.drawCircle(scaledSrcBmp.getWidth() / 2,
                    scaledSrcBmp.getHeight() / 2, scaledSrcBmp.getWidth() / 2,
                    paint);
            paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
            canvas.drawBitmap(scaledSrcBmp, rect, rect, paint);
            bmp.recycle();
            squareBitmap.recycle();
            scaledSrcBmp.recycle();
            bmp = null;
            squareBitmap = null;
            scaledSrcBmp = null;
            return output;
        }
    
        /**
         * 边缘画圆
         */
        private void drawCircleBorder(Canvas canvas, int radius, int color) {
            Paint paint = new Paint();
            /* 去锯齿 */
            paint.setAntiAlias(true);
            paint.setFilterBitmap(true);
            paint.setDither(true);
            paint.setColor(color);
            /* 设置paint的 style 为STROKE:空心 */
            paint.setStyle(Paint.Style.STROKE);
            /* 设置paint的外框宽度 */
            paint.setStrokeWidth(mBorderThickness);
            canvas.drawCircle(requestWH / 2, requestWH / 2, radius, paint);
        }
    
        /**
         * 设置外边框的宽度
         *
         * @param borderWith
         */
        public void setBorderWith(int borderWith) {
            mBorderThickness = borderWith;
        }
    
        /**
         * 设置外边框的颜色
         *
         * @param outsideColor
         */
        public void setBorderOutsideColor(int outsideColor) {
            mBorderOutsideColor = outsideColor;
        }
    
        /**
         * 设置内边框的颜色
         *
         * @param insideColor
         */
        public void setBorderInsideColor(int insideColor) {
            mBorderInsideColor = insideColor;
        }
    
    }
    

    4.在布局中这么使用

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:custom="http://schemas.android.com/apk/res-auto"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">
    
        <com.xjp.customview.RoundImageView
            android:id="@+id/myCustom"
            android:layout_width="110dp"
            android:layout_height="110dp"
            android:scaleType="fitCenter"
            android:src="@drawable/image"
            custom:border_inside_color="#ff0000"
            custom:border_outside_color="@android:color/black"
            custom:border_thickness="2dp" />
    
    </RelativeLayout>

    当以下三个属性没有设置时,默认圆形图片没有外边框

    custom:border_inside_color
    custom:border_outside_color
    custom:border_thickness

    源码下载

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  • 原文地址:https://www.cnblogs.com/Free-Thinker/p/6113483.html
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