Android 自定义圆角的实现

1.概述：

本文所说的方法是继承ImageView,使用Xfermode实现。
步骤：
在values目录下新建attrs文件，

1.自定义属性，可以定制颜色，半径，字体颜色和大小，例如：

<declare-styleable name="mView">
<attr name="round_radius" format="dimension" />
<attr name="round_color" format="color" />
<attr name="text_color" format="color" />
<attr name="text_size" format="dimension" />
</declare-styleable>

但是暂时不需要定义那么多属性
下面定义圆角的度数：



2.然后在构造方法获得属性对应的值



3.重写ondraw方法：

@Override
public void draw(Canvas canvas) {
//创建bitmap
final Bitmap composedBitmap;
final Bitmap originalBitmap;
//创建画布
final Canvas composedCanvas;
final Canvas originalCanvas;
final Paint paint;
final int height;
final int width;

width = getWidth();

height = getHeight();
//ARGB_4444 代表16位Alpha的位图
//ARGB_8888 代表32位ARGB位图
composedBitmap = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);
originalBitmap = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);

originalCanvas = new Canvas(originalBitmap);

paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);

super.draw(originalCanvas);

composedCanvas.drawARGB(0, 0, 0, 0);
//指定RectF对象以及圆角半径来实现，该方法是绘制圆形的主要方法，同时也可以通过设置画笔的空心效果来绘制空心的圆形
//thi,roundness 分别是x,y方向的圆角半径
composedCanvas.drawRoundRect(new RectF(0, 0, width, height),
this.roundness, this.roundness, paint);

paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));

composedCanvas.drawBitmap(originalBitmap, 0, 0, paint);

canvas.drawBitmap(composedBitmap, 0, 0, new Paint());
}

4.在xml使用自己定义的attr，要定义一个xml的命名空间然后再给自定义属性赋值，可以统一用： http://schemas.android.com/apk/res-auto   res-auto是所有的自定义包名

也就是：



使用：xmlns:app="http://schemas.android.com/apk/App的Package名"应该也可以

5.最后再xml使用自定义view:



rectRoundRadius这个值可以任意设置自己想要的值。

最后附上自定义RoundedCornerImageView类：

public class RoundedCornerImageView extends ImageView {

private final float density = getContext().getResources().getDisplayMetrics().density;
private float roundness;
private static final int DEFAULT_RECT_ROUND_RADIUS = 0;

public RoundedCornerImageView(Context context) {
//                super(context);
this(context, null);
//   init();
}

public RoundedCornerImageView(Context context, AttributeSet attrs) {
//                super(context, attrs);
this(context, attrs, 0);
//   init();
}

public RoundedCornerImageView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
//获取attr文件下，名为RoundedCornerImageView
TypedArray ta = context.getTheme().obtainStyledAttributes(attrs, R.styleable.RoundedCornerImageView, defStyle, 0);
//获取值
roundness = ta.getDimensionPixelSize(R.styleable.RoundedCornerImageView_rectRoundRadius, dip2p
4000
x(DEFAULT_RECT_ROUND_RADIUS));
ta.recycle();

//  init();
}

@Override
public void draw(Canvas canvas) {
//创建bitmap
final Bitmap composedBitmap;
final Bitmap originalBitmap;
//创建画布
final Canvas composedCanvas;
final Canvas originalCanvas;
final Paint paint;
final int height;
final int width;

width = getWidth();

height = getHeight();
//ARGB_4444 代表16位Alpha的位图
//ARGB_8888 代表32位ARGB位图
composedBitmap = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);
originalBitmap = Bitmap.createBitmap(width, height,
Bitmap.Config.ARGB_8888);

composedCanvas = new Canvas(composedBitmap);
originalCanvas = new Canvas(originalBitmap);

paint = new Paint();
paint.setAntiAlias(true);
paint.setColor(Color.BLACK);

super.draw(originalCanvas);

composedCanvas.drawARGB(0, 0, 0, 0);
//指定RectF对象以及圆角半径来实现，该方法是绘制圆形的主要方法，同时也可以通过设置画笔的空心效果来绘制空心的圆形
//thi,roundness 分别是x,y方向的圆角半径
composedCanvas.drawRoundRect(new RectF(0, 0, width, height),
this.roundness, this.roundness, paint);

paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));

composedCanvas.drawBitmap(originalBitmap, 0, 0, paint);

canvas.drawBitmap(composedBitmap, 0, 0, new Paint());
}

//    public float getRoundness() {
//        return this.roundness / this.density;
//    }
//
//    public void setRoundness(float roundness) {
//        this.roundness = roundness * this.density;
//    }

//    private void init() {
//        setRoundness(5);
//    }
//dp转px
private int dip2px(int dipVal) {
float scale = getResources().getDisplayMetrics().density;
return (int) (dipVal * scale + 0.5f);
}
}

效果如下：