简单实现圆角图片CircleView

效果:

CircleImageView代码：

public class CircleImageView extends AppCompatImageView {

private Path mPath;

private RectF mRectF;

private Paint mPaint;

public CircleImageView(Context context) {

this(context, null);

}

public CircleImageView(Context context, AttributeSet attrs) {

this(context, attrs, 0);

}

public CircleImageView(Context context, AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

init();

}

private void init() {

mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);

mPaint.setColor(Color.RED);

mPaint.setStyle(Paint.Style.STROKE);

mPaint.setStrokeWidth(15);

mPath = new Path();

}

@Override

protected void onDraw(Canvas canvas) {

//设置外框的矩形区域，不可再init()初始化，构造器中width和height还未确定，可在onMesure()中获取并设置

mRectF = new RectF(0,0, getWidth(),getHeight());

//path划出一个圆角矩形，容纳图片,图片矩形区域设置比红色外框小，否则会覆盖住外框，随意控制

mPath.addRoundRect(new RectF(10, 10, mRectF.right-10,mRectF.bottom-10), 50, 50, Path.Direction.CW);

canvas.drawRoundRect(mRectF, 50, 50, mPaint); //画出红色外框圆角矩形

canvas.clipPath(mPath);//将canvas裁剪到path设定的区域，往后的绘制都只能在此区域中，

//这一句应该放在canvas.clipPath(path)之后,canvas.clipPath(path)只对裁剪之后的绘制起作用，

// 这个方法在ImageView中会画出xml设置的Drawable,落在刚才设置的path中

super.onDraw(canvas);

}

}

整个原理就是用Path划出一个圆角矩形区域，调用super.onDraw(canvas)就可以让Drawable 落在那个区域。

使用，xml:

xmlns:app="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="com.example.why.traing2.MainActivity">

android:id="@+id/img_circle"

android:layout_width="200dp"

android:layout_height="200dp"

android:src="@drawable/gakki"

android:scaleType="centerCrop"

app:layout_constraintTop_toTopOf="parent"

android:layout_marginTop="8dp"

app:layout_constraintBottom_toBottomOf="parent"

android:layout_marginBottom="8dp"

android:layout_marginLeft="8dp"

app:layout_constraintLeft_toLeftOf="parent"

app:layout_constraintVertical_bias="0.501"

android:layout_marginRight="8dp"

app:layout_constraintRight_toRightOf="parent"

/>

Activivty:

public class MainActivity extends AppCompatActivity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

CircleImageView circleImageView = (CircleImageView)findViewById(R.id.img_circle);

}

}

看了些参考资料，发现上篇写错了，发现思路比较简单的，记录下。也可以用Shader, Xfermode实现,参考:https://enggm.wordpxress.com/...