Android自定义控件View（二）继承控件

来源：互联网发布：零起点学通c语言 pdf 编辑：程序博客网时间：2024/04/24 22:32

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_colorcustom:border_outside_colorcustom:border_thickness

源码下载

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