Android实现圆形头像效果

本文主要是介绍Android实现圆形头像效果，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

效果截图

实现原理

对于圆形头像的实现，其实就是对方形图像做某些处理，以达到圆形头像的效果。一般我们会通过Canvas和Paint结合来实现这种效果。
##自定义View来实现
因为圆形头像是视觉方面的需求，一般我们会考虑能否从自定义View的角度来解决问题。自定义的核心有两点：视觉和交互。视觉由onMeasure、onLayout、onDraw这三个方法来完成，而交互则是由dispatchTouchEvent、onInterceptTouchEvent、onTouchEvent等这几个方法来控制，只要处理好这几个方法，就能实现形态各异的自定义View了。

方式一 BitmapShader

package com.yds.myapplication;import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;import androidx.appcompat.widget.AppCompatImageView;/*** Created by yds* on 2020/3/10.*/
public class CircleImageView extends AppCompatImageView {private int mSize;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();mPaint.setDither(true);mPaint.setAntiAlias(true);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);int width = getMeasuredWidth();int height = getMeasuredHeight();mSize = Math.min(width,height);  //取宽高的最小值setMeasuredDimension(mSize,mSize);    //设置CircleImageView为等宽高}@Overrideprotected void onDraw(Canvas canvas) {//获取sourceBitmap，即通过xml或者java设置进来的图片Drawable drawable = getDrawable();if (drawable == null) return;Bitmap sourceBitmap = ((BitmapDrawable)getDrawable()).getBitmap();if (sourceBitmap != null){//对图片进行缩放，以适应控件的大小Bitmap bitmap = resizeBitmap(sourceBitmap,getWidth(),getHeight());drawCircleBitmapByShader(canvas,bitmap);    //利用BitmapShader实现}}private Bitmap resizeBitmap(Bitmap sourceBitmap,int dstWidth,int dstHeight){int width = sourceBitmap.getWidth();int height = sourceBitmap.getHeight();float widthScale = ((float)dstWidth) / width;float heightScale = ((float)dstHeight) / height;//取最大缩放比float scale = Math.max(widthScale,heightScale);Matrix matrix = new Matrix();matrix.postScale(scale,scale);return Bitmap.createBitmap(sourceBitmap,0,0,width,height,matrix,true);}private void drawCircleBitmapByShader(Canvas canvas,Bitmap bitmap){BitmapShader shader = new BitmapShader(bitmap,BitmapShader.TileMode.CLAMP,BitmapShader.TileMode.CLAMP);mPaint.setShader(shader);canvas.drawCircle(mSize / 2,mSize /2 ,mSize / 2,mPaint);}
}

方式二 PorterDuffXfermode

package com.yds.myapplication;import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.util.AttributeSet;import androidx.appcompat.widget.AppCompatImageView;/*** Created by yds* on 2020/3/10.*/
public class CircleImageViewPD extends AppCompatImageView {private int mWidth;private int mHeight;private Paint mPaint;private Bitmap CircleBitmap;public CircleImageViewPD(Context context) {super(context);}public CircleImageViewPD(Context context, AttributeSet attrs) {super(context, attrs);}public CircleImageViewPD(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}private void ImgCircle(){Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);paint.setAntiAlias(true);paint.setFilterBitmap(true);paint.setColor(Color.GRAY);paint.setStrokeWidth(5);paint.setStyle(Paint.Style.FILL);CircleBitmap = Bitmap.createBitmap(mWidth,mHeight, Bitmap.Config.ARGB_8888);Canvas canvas = new Canvas(CircleBitmap);canvas.drawCircle(mWidth/2,mHeight/2,mWidth/2,paint);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);mWidth = getMeasuredWidth();mHeight = getMeasuredHeight();mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setFilterBitmap(true);ImgCircle();}@Overrideprotected void onDraw(Canvas canvas) {int count = canvas.saveLayerAlpha(0, 0, mWidth, mHeight, 250, Canvas.ALL_SAVE_FLAG);super.onDraw(canvas);mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));canvas.drawBitmap(CircleBitmap,0,0, mPaint);canvas.restoreToCount(count);}
}

方式三继承自Drawable

package com.yds.myapplication;import android.graphics.Bitmap;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.Shader;
import android.graphics.drawable.Drawable;/*** Created by yds* on 2020/3/10.*/
public class CircleImageViewDrawable extends Drawable {private Paint mPaint;private BitmapShader mBitmapShader;private int mSize;private int mRadius;public CircleImageViewDrawable(Bitmap bitmap){mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);mBitmapShader = new BitmapShader(bitmap, Shader.TileMode.CLAMP,Shader.TileMode.CLAMP);mPaint.setShader(mBitmapShader);mSize = Math.min(bitmap.getWidth(),bitmap.getHeight());mRadius = mSize/2;}@Overridepublic void draw(Canvas canvas) {canvas.drawCircle(mRadius,mRadius,mRadius,mPaint);}@Overridepublic void setAlpha(int alpha) {mPaint.setAlpha(alpha);}@Overridepublic void setColorFilter(ColorFilter colorFilter) {mPaint.setColorFilter(colorFilter);}@Overridepublic int getOpacity() {return PixelFormat.TRANSLUCENT;}@Overridepublic int getIntrinsicHeight() {return mSize;}@Overridepublic int getIntrinsicWidth() {return mSize;}
}

使用

public class MainActivity extends AppCompatActivity {private ImageView mImageView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mImageView = findViewById(R.id.img);Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.drawable.img);Drawable drawable = new CircleImageViewDrawable(bitmap);mImageView.setImageDrawable(drawable);}
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical"tools:context=".MainActivity"><ImageViewandroid:id="@+id/img"android:layout_width="120dp"android:layout_height="120dp" /><com.yds.myapplication.CircleImageViewandroid:layout_width="120dp"android:layout_height="120dp"android:src="@drawable/img"/><com.yds.myapplication.CircleImageViewPDandroid:layout_width="120dp"android:layout_height="120dp"android:src="@drawable/img"/>
</LinearLayout>