首先新建一个CircleView类：
package com.example.circleview;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.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.util.AttributeSet;import android.widget.ImageView;/**
* Created by Elsie on 2017/11/1.
*/public class CircleImageView extends android.support.v7.widget.AppCompatImageView { 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 = 1; 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 boolean mReady; private boolean mSetupPending; public CircleImageView(Context context) { super(context);
} public CircleImageView(Context context, AttributeSet attrs) { this(context, attrs, 0);
} public CircleImageView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); super.setScaleType(SCALE_TYPE);
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();
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
protected void onDraw(Canvas canvas) { if (getDrawable() == null) { return;
}
canvas.drawCircle(getWidth() / 2, getHeight() / 2, mDrawableRadius, mBitmapPaint);
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();
} 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) * 5f;
} else {
scale = mDrawableRect.width() / (float) mBitmapWidth;
dy = (mDrawableRect.height() - mBitmapHeight * scale) * 5f;
}
mShaderMatrix.setScale(scale, scale);
mShaderMatrix.postTranslate((int) (dx + 5f) + mBorderWidth, (int) (dy + 5f) + mBorderWidth);
mBitmapShader.setLocalMatrix(mShaderMatrix);
}
}然后在value文件夹下面新建一个attrs.xml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>
最后在activity_main.xml文件中使用：
<?xml version="1.0" encoding="utf-8"?><android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" 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.circleview.MainActivity"> <com.example.circleview.CircleImageView android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/welcome" tools:layout_editor_absoluteY="143dp" tools:layout_editor_absoluteX="26dp" /></android.support.constraint.ConstraintLayout>
这样就可以得到一个圆形图片了~这个其实相当于一个自定义控件，由于里面牵扯到挺多未学的知识，所以现在我先追求会用，等以后学到了相关知识再回来更新该博客，然后对相关代码进行注释~