实现自定义view的自定义属性

如自定义了一个圆形头像的imageview,代码如下：

注意xml布局文件中的命名空间的书写和引用规范，否则自定义属性不能正常使用

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Shader;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.net.Uri;
import android.util.AttributeSet;
import android.widget.ImageView;


/** * 第三方View，显示圆形图片 * * 注意：attrs中有该自定义视图的属性 * * */
public class CircleImageView extends ImageView {

    private static final ScaleType SCALE_TYPE = ScaleType.CENTER_CROP;

    private static final Bitmap.Config BITMAP_CONFIG = Bitmap.Config.ARGB_8888;
    private static final int COLORDRAWABLE_DIMENSION = 2;

    private static final int DEFAULT_BORDER_WIDTH = 0;
    private static final int DEFAULT_BORDER_COLOR = Color.BLACK;

    private final RectF mDrawableRect = new RectF();
    private final RectF mBorderRect = new RectF();

    private final Matrix mShaderMatrix = new Matrix();
    private final Paint mBitmapPaint = new Paint();
    private final Paint mBorderPaint = new Paint();

    private int mBorderColor = DEFAULT_BORDER_COLOR;
    private int mBorderWidth = DEFAULT_BORDER_WIDTH;

    private Bitmap mBitmap;
    private BitmapShader mBitmapShader;
    private int mBitmapWidth;
    private int mBitmapHeight;

    private float mDrawableRadius;
    private float mBorderRadius;

    private ColorFilter mColorFilter;

    private boolean mReady;
    private boolean mSetupPending;

    public CircleImageView(Context context) {
        super(context);

        init();
    }

    public CircleImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CircleImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView, defStyle, 0);

        mBorderWidth = a.getDimensionPixelSize(R.styleable.CircleImageView_border_width, DEFAULT_BORDER_WIDTH);
        mBorderColor = a.getColor(R.styleable.CircleImageView_border_color, DEFAULT_BORDER_COLOR);

        a.recycle();

        init();
    }

    private void init() {
        super.setScaleType(SCALE_TYPE);
        mReady = true;

        if (mSetupPending) {
            setup();
            mSetupPending = false;
        }
    }

    @Override
    public ScaleType getScaleType() {
        return SCALE_TYPE;
    }

    @Override
    public void setScaleType(ScaleType scaleType) {
        if (scaleType != SCALE_TYPE) {
            throw new IllegalArgumentException(String.format("ScaleType %s not supported.", scaleType));
        }
    }

    @Override
    public void setAdjustViewBounds(boolean adjustViewBounds) {
        if (adjustViewBounds) {
            throw new IllegalArgumentException("adjustViewBounds not supported.");
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (getDrawable() == null) {
            return;
        }

        canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius, mBitmapPaint);
        if (mBorderWidth != 0) {
            canvas.drawCircle(getWidth() / 2, getHeight() / 2, mBorderRadius, mBorderPaint);
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        setup();
    }

    public int getBorderColor() {
        return mBorderColor;
    }

    public void setBorderColor(int borderColor) {
        if (borderColor == mBorderColor) {
            return;
        }

        mBorderColor = borderColor;
        mBorderPaint.setColor(mBorderColor);
        invalidate();
    }

    public int getBorderWidth() {
        return mBorderWidth;
    }

    public void setBorderWidth(int borderWidth) {
        if (borderWidth == mBorderWidth) {
            return;
        }

        mBorderWidth = borderWidth;
        setup();
    }

    @Override
    public void setImageBitmap(Bitmap bm) {
        super.setImageBitmap(bm);
        mBitmap = bm;
        setup();
    }

    @Override
    public void setImageDrawable(Drawable drawable) {
        super.setImageDrawable(drawable);
        mBitmap = getBitmapFromDrawable(drawable);
        setup();
    }

    @Override
    public void setImageResource(int resId) {
        super.setImageResource(resId);
        mBitmap = getBitmapFromDrawable(getDrawable());
        setup();
    }

    @Override
    public void setImageURI(Uri uri) {
        super.setImageURI(uri);
        mBitmap = getBitmapFromDrawable(getDrawable());
        setup();
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        if (cf == mColorFilter) {
            return;
        }

        mColorFilter = cf;
        mBitmapPaint.setColorFilter(mColorFilter);
        invalidate();
    }

    private Bitmap getBitmapFromDrawable(Drawable drawable) {
        if (drawable == null) {
            return null;
        }

        if (drawable instanceof BitmapDrawable) {
            return ((BitmapDrawable) drawable).getBitmap();
        }

        try {
            Bitmap bitmap;

            if (drawable instanceof ColorDrawable) {
                bitmap = Bitmap.createBitmap(COLORDRAWABLE_DIMENSION, COLORDRAWABLE_DIMENSION, BITMAP_CONFIG);
            } else {
                bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), BITMAP_CONFIG);
            }

            Canvas canvas = new Canvas(bitmap);
            drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
            drawable.draw(canvas);
            return bitmap;
        } catch (OutOfMemoryError e) {
            return null;
        }
    }

    private void setup() {
        if (!mReady) {
            mSetupPending = true;
            return;
        }

        if (mBitmap == null) {
            return;
        }

        mBitmapShader = new BitmapShader(mBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);

        mBitmapPaint.setAntiAlias(true);
        mBitmapPaint.setShader(mBitmapShader);

        mBorderPaint.setStyle(Paint.Style.STROKE);
        mBorderPaint.setAntiAlias(true);
        mBorderPaint.setColor(mBorderColor);
        mBorderPaint.setStrokeWidth(mBorderWidth);

        mBitmapHeight = mBitmap.getHeight();
        mBitmapWidth = mBitmap.getWidth();

        mBorderRect.set(0, 0, getWidth(), getHeight());
        mBorderRadius = Math.min((mBorderRect.height() - mBorderWidth) / 2, (mBorderRect.width() - mBorderWidth) / 2);

        mDrawableRect.set(mBorderWidth, mBorderWidth, mBorderRect.width() - mBorderWidth, mBorderRect.height() - mBorderWidth);
        mDrawableRadius = Math.min(mDrawableRect.height() / 2, mDrawableRect.width() / 2);

        updateShaderMatrix();
        invalidate();
    }

    private void updateShaderMatrix() {
        float scale;
        float dx = 0;
        float dy = 0;

        mShaderMatrix.set(null);

        if (mBitmapWidth * mDrawableRect.height() > mDrawableRect.width() * mBitmapHeight) {
            scale = mDrawableRect.height() / (float) mBitmapHeight;
            dx = (mDrawableRect.width() - mBitmapWidth * scale) * 0.5f;
        } else {
            scale = mDrawableRect.width() / (float) mBitmapWidth;
            dy = (mDrawableRect.height() - mBitmapHeight * scale) * 0.5f;
        }

        mShaderMatrix.setScale(scale, scale);
        mShaderMatrix.postTranslate((int) (dx + 0.5f) + mBorderWidth, (int) (dy + 0.5f) + mBorderWidth);

        mBitmapShader.setLocalMatrix(mShaderMatrix);
    }

}

attrs文件；

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <declare-styleable name="CircleImageView">
        <attr name="border_width" format="dimension" />
        <attr name="border_color" format="color" />
    </declare-styleable>
</resources>

color文件：

<resources>  
<color name="white">#FFFFFF</color><!--白色 -->  
<color name="ivory">#FFFFF0</color><!--象牙色 -->  
<color name="lightyellow">#FFFFE0</color><!--亮黄色 -->  
<color name="yellow">#FFFF00</color><!--黄色 -->  
<color name="snow">#FFFAFA</color><!--雪白色 -->  
<color name="floralwhite">#FFFAF0</color><!--花白色 -->  
<color name="lemonchiffon">#FFFACD</color><!--柠檬绸色 -->  
<color name="cornsilk">#FFF8DC</color><!--米绸色 -->  
<color name="seashell">#FFF5EE</color><!--海贝色 -->  
<color name="lavenderblush">#FFF0F5</color><!--淡紫红 -->  
<color name="papayawhip">#FFEFD5</color><!--番木色 -->  
<color name="blanchedalmond">#FFEBCD</color><!--白杏色 -->  
<color name="mistyrose">#FFE4E1</color><!--浅玫瑰色 -->  
<color name="bisque">#FFE4C4</color><!--桔黄色 -->  
<color name="moccasin">#FFE4B5</color><!--鹿皮色 -->  
<color name="navajowhite">#FFDEAD</color><!--纳瓦白 -->  
<color name="peachpuff">#FFDAB9</color><!--桃色 -->  
<color name="gold">#FFD700</color><!--金色 -->  
<color name="pink">#FFC0CB</color><!--粉红色 -->  
<color name="lightpink">#FFB6C1</color><!--亮粉红色 -->  
<color name="orange">#FFA500</color><!--橙色 -->  
<color name="lightsalmon">#FFA07A</color><!--亮肉色 -->  
<color name="darkorange">#FF8C00</color><!--暗桔黄色 -->  
<color name="coral">#FF7F50</color><!--珊瑚色 -->  
<color name="hotpink">#FF69B4</color><!--热粉红色 -->  
<color name="tomato">#FF6347</color><!--西红柿色 -->  
<color name="orangered">#FF4500</color><!--红橙色 -->  
<color name="deeppink">#FF1493</color><!--深粉红色 -->  
<color name="fuchsia">#FF00FF</color><!--紫红色 -->  
<color name="magenta">#FF00FF</color><!--红紫色 -->  
<color name="red">#FF0000</color><!--红色 -->  
<color name="oldlace">#FDF5E6</color><!--老花色 -->  
<color name="lightgoldenrodyellow">#FAFAD2</color><!--亮金黄色 -->  
<color name="linen">#FAF0E6</color><!--亚麻色 -->  
<color name="antiquewhite">#FAEBD7</color><!--古董白 -->  
<color name="salmon">#FA8072</color><!--鲜肉色 -->  
<color name="ghostwhite">#F8F8FF</color><!--幽灵白 -->  
<color name="mintcream">#F5FFFA</color><!--薄荷色 -->  
<color name="whitesmoke">#F5F5F5</color><!--烟白色 -->  
<color name="beige">#F5F5DC</color><!--米色 -->  
<color name="wheat">#F5DEB3</color><!--浅黄色 -->  
<color name="sandybrown">#F4A460</color><!--沙褐色 -->  
<color name="azure">#F0FFFF</color><!--天蓝色 -->  
<color name="honeydew">#F0FFF0</color><!--蜜色 -->  
<color name="aliceblue">#F0F8FF</color><!--艾利斯兰 -->  
<color name="khaki">#F0E68C</color><!--黄褐色 -->  
<color name="lightcoral">#F08080</color><!--亮珊瑚色 -->  
<color name="palegoldenrod">#EEE8AA</color><!--苍麒麟色 -->  
<color name="violet">#EE82EE</color><!--紫罗兰色 -->  
<color name="darksalmon">#E9967A</color><!--暗肉色 -->  
<color name="lavender">#E6E6FA</color><!--淡紫色 -->  
<color name="lightcyan">#E0FFFF</color><!--亮青色 -->  
<color name="burlywood">#DEB887</color><!--实木色 -->  
<color name="plum">#DDA0DD</color><!--洋李色 -->  
<color name="gainsboro">#DCDCDC</color><!--淡灰色 -->  
<color name="crimson">#DC143C</color><!--暗深红色 -->  
<color name="palevioletred">#DB7093</color><!--苍紫罗兰色 -->  
<color name="goldenrod">#DAA520</color><!--金麒麟色 -->  
<color name="orchid">#DA70D6</color><!--淡紫色 -->  
<color name="thistle">#D8BFD8</color><!--蓟色 -->  
<color name="lightgray">#D3D3D3</color><!--亮灰色 -->  
<color name="lightgrey">#D3D3D3</color><!--亮灰色 -->  
<color name="tan">#D2B48C</color><!--茶色 -->  
<color name="chocolate">#D2691E</color><!--巧可力色 -->  
<color name="peru">#CD853F</color><!--秘鲁色 -->  
<color name="indianred">#CD5C5C</color><!--印第安红 -->  
<color name="mediumvioletred">#C71585</color><!--中紫罗兰色 -->  
<color name="silver">#C0C0C0</color><!--银色 -->  
<color name="darkkhaki">#BDB76B</color><!--暗黄褐色 -->  
<color name="rosybrown">#BC8F8F</color><!--褐玫瑰红 -->  
<color name="mediumorchid">#BA55D3</color><!--中粉紫色 -->  
<color name="darkgoldenrod">#B8860B</color><!--暗金黄色 -->  
<color name="firebrick">#B22222</color><!--火砖色 -->  
<color name="powderblue">#B0E0E6</color><!--粉蓝色 -->  
<color name="lightsteelblue">#B0C4DE</color><!--亮钢兰色 -->  
<color name="paleturquoise">#AFEEEE</color><!--苍宝石绿 -->  
<color name="greenyellow">#ADFF2F</color><!--黄绿色 -->  
<color name="lightblue">#ADD8E6</color><!--亮蓝色 -->  
<color name="darkgray">#A9A9A9</color><!--暗灰色 -->  
<color name="darkgrey">#A9A9A9</color><!--暗灰色 -->  
<color name="brown">#A52A2A</color><!--褐色 -->  
<color name="sienna">#A0522D</color><!--赭色 -->  
<color name="darkorchid">#9932CC</color><!--暗紫色 -->  
<color name="palegreen">#98FB98</color><!--苍绿色 -->  
<color name="darkviolet">#9400D3</color><!--暗紫罗兰色 -->  
<color name="mediumpurple">#9370DB</color><!--中紫色 -->  
<color name="lightgreen">#90EE90</color><!--亮绿色 -->  
<color name="darkseagreen">#8FBC8F</color><!--暗海兰色 -->  
<color name="saddlebrown">#8B4513</color><!--重褐色 -->  
<color name="darkmagenta">#8B008B</color><!--暗洋红 -->  
<color name="darkred">#8B0000</color><!--暗红色 -->  
<color name="blueviolet">#8A2BE2</color><!--紫罗兰蓝色 -->  
<color name="lightskyblue">#87CEFA</color><!--亮天蓝色 -->  
<color name="skyblue">#87CEEB</color><!--天蓝色 -->  
<color name="gray">#808080</color><!--灰色 -->  
<color name="grey">#808080</color><!--灰色 -->  
<color name="olive">#808000</color><!--橄榄色 -->  
<color name="purple">#800080</color><!--紫色 -->  
<color name="maroon">#800000</color><!--粟色 -->  
<color name="aquamarine">#7FFFD4</color><!--碧绿色 -->  
<color name="chartreuse">#7FFF00</color><!--黄绿色 -->  
<color name="lawngreen">#7CFC00</color><!--草绿色 -->  
<color name="mediumslateblue">#7B68EE</color><!--中暗蓝色 -->  
<color name="lightslategray">#778899</color><!--亮蓝灰 -->  
<color name="lightslategrey">#778899</color><!--亮蓝灰 -->  
<color name="slategray">#708090</color><!--灰石色 -->  
<color name="slategrey">#708090</color><!--灰石色 -->  
<color name="olivedrab">#6B8E23</color><!--深绿褐色 -->  
<color name="slateblue">#6A5ACD</color><!--石蓝色 -->  
<color name="dimgray">#696969</color><!--暗灰色 -->  
<color name="dimgrey">#696969</color><!--暗灰色 -->  
<color name="mediumaquamarine">#66CDAA</color><!--中绿色 -->  
<color name="cornflowerblue">#6495ED</color><!--菊兰色 -->  
<color name="cadetblue">#5F9EA0</color><!--军兰色 -->  
<color name="darkolivegreen">#556B2F</color><!--暗橄榄绿 -->  
<color name="indigo">#4B0082</color><!--靛青色 -->  
<color name="mediumturquoise">#48D1CC</color><!--中绿宝石 -->  
<color name="darkslateblue">#483D8B</color><!--暗灰蓝色 -->  
<color name="steelblue">#4682B4</color><!--钢兰色 -->  
<color name="royalblue">#4169E1</color><!--皇家蓝 -->  
<color name="turquoise">#40E0D0</color><!--青绿色 -->  
<color name="mediumseagreen">#3CB371</color><!--中海蓝 -->  
<color name="limegreen">#32CD32</color><!--橙绿色 -->  
<color name="darkslategray">#2F4F4F</color><!--暗瓦灰色 -->  
<color name="darkslategrey">#2F4F4F</color><!--暗瓦灰色 -->  
<color name="seagreen">#2E8B57</color><!--海绿色 -->  
<color name="forestgreen">#228B22</color><!--森林绿 -->  
<color name="lightseagreen">#20B2AA</color><!--亮海蓝色 -->  
<color name="dodgerblue">#1E90FF</color><!--闪兰色 -->  
<color name="midnightblue">#191970</color><!--中灰兰色 -->  
<color name="aqua">#00FFFF</color><!--浅绿色 -->  
<color name="cyan">#00FFFF</color><!--青色 -->  
<color name="springgreen">#00FF7F</color><!--春绿色 -->  
<color name="lime">#00FF00</color><!--酸橙色 -->  
<color name="mediumspringgreen">#00FA9A</color><!--中春绿色 -->  
<color name="darkturquoise">#00CED1</color><!--暗宝石绿 -->  
<color name="deepskyblue">#00BFFF</color><!--深天蓝色 -->  
<color name="darkcyan">#008B8B</color><!--暗青色 -->  
<color name="teal">#008080</color><!--水鸭色 -->  
<color name="green">#008000</color><!--绿色 -->  
<color name="darkgreen">#006400</color><!--暗绿色 -->  
<color name="blue">#0000FF</color><!--蓝色 -->  
<color name="mediumblue">#0000CD</color><!--中兰色 -->  
<color name="darkblue">#00008B</color><!--暗蓝色 -->  
<color name="navy">#000080</color><!--海军色 -->  
<color name="black">#000000</color><!--黑色 -->  
</resources> 

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res/com.player" // 命名空间的书写：res后面对应activity的java文件对应包，"app"随便写，但是要和下面对应 android:layout_width="match_parent" android:layout_height="80dp" android:orientation="horizontal" >

    <view.CircleImageView  android:id="@+id/circleimage_header" android:layout_width="70dp" android:layout_height="70dp" android:layout_margin="5dp" android:src="@drawable/ic_launcher" app:border_color="#FFFFFF"//自定义属性的使用方法 app:border_width="1dp" >
    </view.CircleImageView>

</LinearLayout>