Android自定义控件之圆形、圆角ImageView

2019-12-12 03:19:27

字体：大中小

来源：转载

供稿：网友

一、问题在哪里？

问题来源于app开发中一个很常见的场景――用户头像要展示成圆的：

二、怎么搞？

机智的我，第一想法就是，切一张中间圆形透明、四周与底色相同、尺寸与头像相同的蒙板图片，盖在头像上不就完事了嘛，哈哈哈！

在背景纯色的前提下，这的确能简单解决问题，但是如果背景没有这么简单呢？

在这种不规则背景下，有两个问题：

1)、背景图常常是适应手机宽度缩放，而头像的尺寸又是固定宽高DP的，所以固定的蒙板图片是没法保证在不同机型上都和背景图案吻合的。

2)、在这种非纯色背景下，哪天想调整一下头像位置就得重新换图片蒙板，实在是太难维护了……

所以呢，既然头像图片肯定是方的，那就就让ImageView圆起来吧。

三、开始干活

基本思路是，自定义一个ImageView，通过重写onDraw方法画出一个圆形的图片来：

public class ImageViewPlus extends ImageView{  private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);  private Bitmap mRawBitmap;  private BitmapShader mShader;  private Matrix mMatrix = new Matrix();    public ImageViewPlus(Context context, AttributeSet attrs) {    super(context, attrs);  }    @Override  protected void onDraw(Canvas canvas) {    Bitmap rawBitmap = getBitmap(getDrawable());    if (rawBitmap != null){      int viewWidth = getWidth();      int viewHeight = getHeight();      int viewMinSize = Math.min(viewWidth, viewHeight);      float dstWidth = viewMinSize;      float dstHeight = viewMinSize;      if (mShader == null || !rawBitmap.equals(mRawBitmap)){        mRawBitmap = rawBitmap;        mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);      }      if (mShader != null){        mMatrix.setScale(dstWidth / rawBitmap.getWidth(), dstHeight / rawBitmap.getHeight());        mShader.setLocalMatrix(mMatrix);      }      mPaintBitmap.setShader(mShader);      float radius = viewMinSize / 2.0f;      canvas.drawCircle(radius, radius, radius, mPaintBitmap);    } else {      super.onDraw(canvas);    }  }  private Bitmap getBitmap(Drawable drawable){    if (drawable instanceof BitmapDrawable){      return ((BitmapDrawable)drawable).getBitmap();    } else if (drawable instanceof ColorDrawable){      Rect rect = drawable.getBounds();      int width = rect.right - rect.left;      int height = rect.bottom - rect.top;      int color = ((ColorDrawable)drawable).getColor();      Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);      Canvas canvas = new Canvas(bitmap);      canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));      return bitmap;    } else {      return null;    }  }}

分析一下代码：

canvas.drawCircle 决定了画出来的形状是圆形，而圆形的内容则是通过 mPaintBitmap.setShader 搞定的。

其中，BitmapShader需要设置Bitmap填充ImageView的方式(CLAMP：拉伸边缘, MIRROR：镜像, REPEAT：整图重复)。

这里其实设成什么不重要，因为我们实际需要的是将Bitmap按比例缩放成跟ImageView一样大，而不是预置的三种效果。

所以，别忘了 mMatrix.setScale 和 mShader.setLocalMatrix 一起用，将图片缩放一下。

四、更多玩法 ―― 支持边框

看下面的效果图，如果想给圆形的头像上加一个边框，该怎么搞呢？

public class ImageViewPlus extends ImageView{  private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);  private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);  private Bitmap mRawBitmap;  private BitmapShader mShader;  private Matrix mMatrix = new Matrix();  private float mBorderWidth = dip2px(15);  private int mBorderColor = 0xFF0080FF;    public ImageViewPlus(Context context, AttributeSet attrs) {    super(context, attrs);  }    @Override  protected void onDraw(Canvas canvas) {    Bitmap rawBitmap = getBitmap(getDrawable());    if (rawBitmap != null){      int viewWidth = getWidth();      int viewHeight = getHeight();      int viewMinSize = Math.min(viewWidth, viewHeight);      float dstWidth = viewMinSize;      float dstHeight = viewMinSize;      if (mShader == null || !rawBitmap.equals(mRawBitmap)){        mRawBitmap = rawBitmap;        mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);      }      if (mShader != null){        mMatrix.setScale((dstWidth - mBorderWidth * 2) / rawBitmap.getWidth(), (dstHeight - mBorderWidth * 2) / rawBitmap.getHeight());        mShader.setLocalMatrix(mMatrix);      }      mPaintBitmap.setShader(mShader);      mPaintBorder.setStyle(Paint.Style.STROKE);      mPaintBorder.setStrokeWidth(mBorderWidth);      mPaintBorder.setColor(mBorderColor);      float radius = viewMinSize / 2.0f;      canvas.drawCircle(radius, radius, radius - mBorderWidth / 2.0f, mPaintBorder);      canvas.translate(mBorderWidth, mBorderWidth);      canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);    } else {      super.onDraw(canvas);    }  }  private Bitmap getBitmap(Drawable drawable){    if (drawable instanceof BitmapDrawable){      return ((BitmapDrawable)drawable).getBitmap();    } else if (drawable instanceof ColorDrawable){      Rect rect = drawable.getBounds();      int width = rect.right - rect.left;      int height = rect.bottom - rect.top;      int color = ((ColorDrawable)drawable).getColor();      Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);      Canvas canvas = new Canvas(bitmap);      canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));      return bitmap;    } else {      return null;    }  }    private int dip2px(int dipVal)  {    float scale = getResources().getDisplayMetrics().density;    return (int)(dipVal * scale + 0.5f);  }}

看代码中，加边框实际上就是用实心纯色的 Paint 画了一个圆边，在此基础上画上原来的头像即可。

需要的注意的地方有三个：

1)、圆框的半径不是 radius ，而应该是 radius - mBorderWidth / 2.0f 。想象着拿着笔去画线，线其实是画在右图中白色圈的位置，只不过它很粗。

2)、在ImageView大小不变的基础上，头像的实际大小要比没有边框的时候小了，所以 mMatrix.setScale 的时候要把边框的宽度去掉。

3)、画头像Bitmap的时候不能直接 canvas.drawCircle(radius, radius, radius - mBorderWidth, mPaintBitmap) ，这样你会发现头像的右侧和下方边缘被拉伸了（右图）

为什么呢？因为 Paint 默认是以左上角为基准开始绘制的，此时头像的实际区域是右图中的红框，而超过红框的部分（圆形的右侧和下方），自然被 TileMode.CLAMP效果沿边缘拉伸了。

所以，需要通过挪动坐标系的位置和调整圆心，才能把头像画在正确的区域（右图绿框）中。

五、更多玩法 ―― 支持xml配置

既然有了边框，那如果想配置边框的宽度和颜色该如何是好呢？

基本上两个思路：

1)、给ImageViewPlus加上set接口，设置完成之后通过 invalidate(); 重绘一下即可；

2)、在xml里就支持配置一些自定义属性，这样用起来会方便很多。

这里重点说一下支持xml配置自定义属性。

自定义控件要支持xml配置自定义属性的话，首先需要在 /res/values 里去定义属性：

<?xml version="1.0" encoding="utf-8"?> <resources>   <attr name="borderColor" format="color" />  <attr name="borderWidth" format="dimension" />  <declare-styleable name="ImageViewPlus">     <attr name="borderColor" />    <attr name="borderWidth" />  </declare-styleable> </resources>

然后在ImageViewPlus的构造函数中去读取这些自定义属性：

private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;  private static final int DEFAULT_BORDER_WIDTH = 0;    public ImageViewPlus(Context context, AttributeSet attrs) {    super(context, attrs);    //取xml文件中设定的参数    TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);    mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);    mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));    ta.recycle();  }

在xml布局中使用自定义属性：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:background="@drawable/wallpaper"  android:orientation="vertical"  tools:context="${relativePackage}.${activityClass}" >    <cc.snser.imageviewplus.ImageViewPlus    android:id="@+id/imgplus"    android:layout_width="200dp"    android:layout_height="300dp"    android:layout_marginBottom="50dp"    android:layout_centerHorizontal="true"    android:layout_alignParentBottom="true"    android:src="@drawable/img_square"    snser:borderColor="#FF0080FF"    snser:borderWidth="15dp" />  </RelativeLayout>

六、更多玩法 ―― 圆角ImageView

搞定了圆形ImageView以及对应的边框，那如何实现下面这种圆角的ImageView呢？

其实原理上一样，把 canvas.drawCircle 对应改成 canvas.drawRoundRect 就OK了，直接贴代码吧：

public class ImageViewPlus extends ImageView{  /**   * android.widget.ImageView   */  public static final int TYPE_NONE = 0;  /**   * 圆形   */  public static final int TYPE_CIRCLE = 1;  /**   * 圆角矩形   */  public static final int TYPE_ROUNDED_RECT = 2;      private static final int DEFAULT_TYPE = TYPE_NONE;  private static final int DEFAULT_BORDER_COLOR = Color.TRANSPARENT;  private static final int DEFAULT_BORDER_WIDTH = 0;  private static final int DEFAULT_RECT_ROUND_RADIUS = 0;    private int mType;  private int mBorderColor;  private int mBorderWidth;  private int mRectRoundRadius;    private Paint mPaintBitmap = new Paint(Paint.ANTI_ALIAS_FLAG);  private Paint mPaintBorder = new Paint(Paint.ANTI_ALIAS_FLAG);    private RectF mRectBorder = new RectF();  private RectF mRectBitmap = new RectF();    private Bitmap mRawBitmap;  private BitmapShader mShader;  private Matrix mMatrix = new Matrix();    public ImageViewPlus(Context context, AttributeSet attrs) {    super(context, attrs);    //取xml文件中设定的参数    TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.ImageViewPlus);    mType = ta.getInt(R.styleable.ImageViewPlus_type, DEFAULT_TYPE);    mBorderColor = ta.getColor(R.styleable.ImageViewPlus_borderColor, DEFAULT_BORDER_COLOR);    mBorderWidth = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_borderWidth, dip2px(DEFAULT_BORDER_WIDTH));    mRectRoundRadius = ta.getDimensionPixelSize(R.styleable.ImageViewPlus_rectRoundRadius, dip2px(DEFAULT_RECT_ROUND_RADIUS));    ta.recycle();  }    @Override  protected void onDraw(Canvas canvas) {    Bitmap rawBitmap = getBitmap(getDrawable());        if (rawBitmap != null && mType != TYPE_NONE){      int viewWidth = getWidth();      int viewHeight = getHeight();      int viewMinSize = Math.min(viewWidth, viewHeight);      float dstWidth = mType == TYPE_CIRCLE ? viewMinSize : viewWidth;      float dstHeight = mType == TYPE_CIRCLE ? viewMinSize : viewHeight;      float halfBorderWidth = mBorderWidth / 2.0f;      float doubleBorderWidth = mBorderWidth * 2;            if (mShader == null || !rawBitmap.equals(mRawBitmap)){        mRawBitmap = rawBitmap;        mShader = new BitmapShader(mRawBitmap, TileMode.CLAMP, TileMode.CLAMP);      }      if (mShader != null){        mMatrix.setScale((dstWidth - doubleBorderWidth) / rawBitmap.getWidth(), (dstHeight - doubleBorderWidth) / rawBitmap.getHeight());        mShader.setLocalMatrix(mMatrix);      }            mPaintBitmap.setShader(mShader);      mPaintBorder.setStyle(Paint.Style.STROKE);      mPaintBorder.setStrokeWidth(mBorderWidth);      mPaintBorder.setColor(mBorderWidth > 0 ? mBorderColor : Color.TRANSPARENT);            if (mType == TYPE_CIRCLE){        float radius = viewMinSize / 2.0f;        canvas.drawCircle(radius, radius, radius - halfBorderWidth, mPaintBorder);        canvas.translate(mBorderWidth, mBorderWidth);        canvas.drawCircle(radius - mBorderWidth, radius - mBorderWidth, radius - mBorderWidth, mPaintBitmap);      } else if (mType == TYPE_ROUNDED_RECT){        mRectBorder.set(halfBorderWidth, halfBorderWidth, dstWidth - halfBorderWidth, dstHeight - halfBorderWidth);        mRectBitmap.set(0.0f, 0.0f, dstWidth - doubleBorderWidth, dstHeight - doubleBorderWidth);        float borderRadius = mRectRoundRadius - halfBorderWidth > 0.0f ? mRectRoundRadius - halfBorderWidth : 0.0f;        float bitmapRadius = mRectRoundRadius - mBorderWidth > 0.0f ? mRectRoundRadius - mBorderWidth : 0.0f;        canvas.drawRoundRect(mRectBorder, borderRadius, borderRadius, mPaintBorder);        canvas.translate(mBorderWidth, mBorderWidth);        canvas.drawRoundRect(mRectBitmap, bitmapRadius, bitmapRadius, mPaintBitmap);      }    } else {      super.onDraw(canvas);    }  }  private int dip2px(int dipVal)  {    float scale = getResources().getDisplayMetrics().density;    return (int)(dipVal * scale + 0.5f);  }    private Bitmap getBitmap(Drawable drawable){    if (drawable instanceof BitmapDrawable){      return ((BitmapDrawable)drawable).getBitmap();    } else if (drawable instanceof ColorDrawable){      Rect rect = drawable.getBounds();      int width = rect.right - rect.left;      int height = rect.bottom - rect.top;      int color = ((ColorDrawable)drawable).getColor();      Bitmap bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);      Canvas canvas = new Canvas(bitmap);      canvas.drawARGB(Color.alpha(color), Color.red(color), Color.green(color), Color.blue(color));      return bitmap;    } else {      return null;    }  }}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:tools="http://schemas.android.com/tools"  xmlns:snser="http://schemas.android.com/apk/res/cc.snser.imageviewplus"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:background="@drawable/wallpaper"  android:orientation="vertical"  tools:context="${relativePackage}.${activityClass}" >    <cc.snser.imageviewplus.ImageViewPlus    android:id="@+id/imgplus"    android:layout_width="200dp"    android:layout_height="300dp"    android:layout_marginBottom="50dp"    android:layout_centerHorizontal="true"    android:layout_alignParentBottom="true"    android:src="@drawable/img_rectangle"    snser:type="rounded_rect"    snser:borderColor="#FF0080FF"    snser:borderWidth="10dp"    snser:rectRoundRadius="30dp" />  </RelativeLayout>

<?xml version="1.0" encoding="utf-8"?> <resources>   <attr name="type">     <enum name="none" value="0" />     <enum name="circle" value="1" />     <enum name="rounded_rect" value="2" />  </attr>  <attr name="borderColor" format="color" />  <attr name="borderWidth" format="dimension" />  <attr name="rectRoundRadius" format="dimension" />  <declare-styleable name="ImageViewPlus">     <attr name="type" />    <attr name="borderColor" />    <attr name="borderWidth" />    <attr name="rectRoundRadius" />  </declare-styleable></resources>

七、Demo源码

Android自定义圆形ImageView

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持武林网。

上一篇：Android实现图片点击预览效果(zoom动画)

下一篇：Java Base64位编码与String字符串的相互转换,Base64与Bitmap的相互转换实例代码