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Android PorterDuff 圆形和圆角 ImageView

本章我们使用 PorterDuff.Mode 中的 DST_IN 模式来实现圆形&圆角 ImageView

Xfermode 无非是两层图构成，先绘制的叫 DST 图(目标图)，后绘制的叫 SRC 图(原图)

我们要实现圆形或者圆角，可以先把要显示的图片绘制出来 (DST)，通过 src 的属性进行设置

接着再绘制出圆形和圆角 (SRC)，因为要显示的部分是他们相交的地方，而且是图片部分的内容，所以选择： DST_IN 模式

PorterDuff 圆形和圆角 ImageView

下图就是我们要实现的一个效果，通过这个 PorterDuff.Mode.DST_IN 模式来实现

这里最重要的就是获取图片的高宽了：首先假如我们设置的是圆形的话，则需要让宽高一致，以最小值为准，我们可以在 onMesure() 方法调用 getMeasuredXxx() 获得宽高，看谁小一点，调用 setMeasuredDimension(x, x) 设置宽高

创建一个空的 Android 项目 cn.twle.android.PorterDuffDstIn
下载 /static/i/meimei_160x360.jpg 和 /static/i/android/avatar.png 都放到 /res/drawable 目录下

然后在 res/drawable 目录下自定义控件属性 res/values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="CircleImageView">
        <attr name="Radius" format="dimension"/>
        <attr name="type">
            <enum name="circle" value="0"/>
            <enum name="round" value="1"/>
        </attr>
    </declare-styleable>
</resources>

在 MainActivity.java 目录下自定义 ImageView CircleImageView.java

package cn.twle.android.porterduffdstin;

import android.content.Context;
import android.content.res.TypedArray;
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.graphics.RectF;
import android.graphics.Xfermode;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.ImageView;

import java.lang.ref.WeakReference;

public class CircleImageView extends ImageView {

    private Paint mPaint;
    private Xfermode mXfermode = new PorterDuffXfermode(PorterDuff.Mode.DST_IN);
    private Bitmap mMaskBitmap;
    private WeakReference<Bitmap> mWeakBitmap;

    //图片相关的属性
    private int type;                           //类型，圆形或者圆角
    public static final int TYPE_CIRCLE = 0;
    public static final int TYPE_ROUND = 1;
    private static final int BODER_RADIUS_DEFAULT = 10;     //圆角默认大小值
    private int mBorderRadius;                  //圆角大小

    public CircleImageView(Context context) {
        this(context, null);
    }

    public CircleImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        //取出attrs中我们为View设置的相关值
        TypedArray tArray = context.obtainStyledAttributes(attrs, R.styleable.CircleImageView);
        mBorderRadius = tArray.getDimensionPixelSize(R.styleable.CircleImageView_Radius, BODER_RADIUS_DEFAULT);
        type = tArray.getInt(R.styleable.CircleImageView_type, TYPE_CIRCLE);
        tArray.recycle();
    }

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

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        if (type == TYPE_CIRCLE) {
            int width = Math.min(getMeasuredWidth(), getMeasuredHeight());
            setMeasuredDimension(width, width);    //设置当前View的大小
        }
    }

    @Override
    protected void onDraw(Canvas canvas) {

        //在缓存中取出bitmap
        Bitmap bitmap = mWeakBitmap == null ? null : mWeakBitmap.get();
        if (bitmap == null || bitmap.isRecycled()) {
            //获取图片宽高
            Drawable drawable = getDrawable();
            int width = drawable.getIntrinsicWidth();
            int height = drawable.getIntrinsicHeight();

            if (drawable != null) {
                bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
                Canvas drawCanvas = new Canvas(bitmap);
                float scale = 1.0f;
                if (type == TYPE_ROUND) {
                    scale = Math.max(getWidth() * 1.0f / width, getHeight()
                            * 1.0f / height);
                } else {
                    scale = getWidth() * 1.0F / Math.min(width, height);
                }
                //根据缩放比例，设置bounds，相当于缩放图片了
                drawable.setBounds(0, 0, (int) (scale * width),
                        (int) (scale * height));

                drawable.draw(drawCanvas);
                if (mMaskBitmap == null || mMaskBitmap.isRecycled()) {
                    mMaskBitmap = getBitmap();
                }

                mPaint.reset();
                mPaint.setFilterBitmap(false);
                mPaint.setXfermode(mXfermode);

                //绘制形状
                drawCanvas.drawBitmap(mMaskBitmap, 0, 0, mPaint);

                //bitmap缓存起来，避免每次调用onDraw，分配内存
                mWeakBitmap = new WeakReference<Bitmap>(bitmap);

                //绘制图片
                canvas.drawBitmap(bitmap, 0, 0, null);
                mPaint.setXfermode(null);

            }
        }
        if (bitmap != null) {
            mPaint.setXfermode(null);
            canvas.drawBitmap(bitmap, 0.0f, 0.0f, mPaint);
            return;
        }
    }

    //缓存Bitmap，避免每次OnDraw都重新分配内存与绘图
    @Override
    public void invalidate() {
        mWeakBitmap = null;
        if (mWeakBitmap != null) {
            mMaskBitmap.recycle();
            mMaskBitmap = null;
        }
        super.invalidate();
    }

    //定义一个绘制形状的方法

    private Bitmap getBitmap() {
        Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(),
                Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);   //抗锯齿
        paint.setColor(Color.BLACK);
        if (type == TYPE_ROUND) {
            canvas.drawRoundRect(new RectF(0, 0, getWidth(), getHeight()),
                    mBorderRadius, mBorderRadius, paint);
        } else {
            canvas.drawCircle(getWidth() / 2, getWidth() / 2, getWidth() / 2, paint);
        }
        return bitmap;
    }
}

修改 activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <cn.twle.android.porterduffdstin.CircleImageView
        android:layout_width="128dp"
        android:layout_height="120dp"
        android:layout_margin="10dp"
        android:src="@drawable/avatar"
        app:type="circle" />

    <cn.twle.android.porterduffdstin.CircleImageView
        android:layout_width="160dp"
        android:layout_height="360dp"
        android:layout_margin="10dp"
        android:src="@drawable/meimei_160x360"
        app:Radius="30dp"
        app:type="round" />

</LinearLayout>

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简单教程

Android PorterDuff 圆形和圆角 ImageView

PorterDuff 圆形和圆角 ImageView

Android 基础教程