自定义ImageView，实现圆角矩形、原型、固定宽高比样式

最近，项目中动态展示图片的样式做了调整，宽高比从原来的16:9替换成了2:1。有些地方就要重新计算了。突然觉得，要是ImageView可以自己判断就好了。不想去获取宽度（或者高度），然后利用LayoutParams去修改。

在此基础上，我又加了圆角度数和原型的适配。算是一个小综合吧。

展示图片，我用的Glide。相关Glide，我这里就不做过多解释了。有兴趣的请看

http://blog.csdn.net/u014620028/article/details/78363484

代码实现简单，就直接上代码了

原图：

效果图：

res\values\styles.xml

<declare-styleable name="MyImageViewRatio">
        <attr name="ratio" format="float"/>
        <attr name="angle" format="integer"/>
        <attr name="isCircle" format="boolean"/>
    declare-styleable>

MyImageView

package com.chen.demo;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.RectF;
import android.graphics.Shader.TileMode;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.ImageView;

public class MyImageView extends ImageView {

    //图片的宽高比
    private float ratio = 0;

    private boolean imgType;

    /**
     * 圆角的半径
     */
    private int mRadius;
    /**
     * 3x3 矩阵，主要用于缩小放大
     */
    private Matrix mMatrix;

    /**
     * 绘图的Paint
     */
    private Paint mBitmapPaint;

    /**
     * 圆角的大小
     */
    private int mBorderRadius;

    /**
     * 渲染图像，使用图像为绘制图形着色
     */
    private BitmapShader mBitmapShader;

    private RectF mRoundRect;

    private int widthSize;

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

    public MyImageView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, -1);
    }

    public MyImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.MyImageViewRatio);
        ratio = ta.getFloat(R.styleable.MyImageViewRatio_ratio, 0);
        mBorderRadius = ta.getInteger(R.styleable.MyImageViewRatio_angle, 0);
        imgType = ta.getBoolean(R.styleable.MyImageViewRatio_isCircle, false);

        ta.recycle();

        mMatrix = new Matrix();
        mBitmapPaint = new Paint();
        mBitmapPaint.setAntiAlias(true);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        widthSize = MeasureSpec.getSize(widthMeasureSpec);

        /**
         * 如果类型是圆形，则强制改变view的宽高一致，以小值为准
         */
        if (imgType) {
            widthSize = Math.min(getMeasuredWidth(), getMeasuredHeight());
            mRadius = widthSize / 2;
            setMeasuredDimension(widthSize, widthSize);
        } else {

            if (ratio != 0) {
                // 告诉系统我要申请这么多的宽高
                setMeasuredDimension(widthSize, (int) (widthSize / ratio));
            }

        }

    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        Log.e("onSizeChanged=", "onSizeChanged");
        // 圆角图片的范围
        if (!imgType)
            mRoundRect = new RectF(0, 0, w, h);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        setUpShader();

        if (imgType) {
            canvas.drawCircle(mRadius, mRadius, mRadius, mBitmapPaint);
        } else {
            canvas.drawRoundRect(mRoundRect, mBorderRadius, mBorderRadius, mBitmapPaint);
        }

    }

    /**
     * 初始化BitmapShader
     */
    private void setUpShader() {
        Drawable drawable = getDrawable();
        if (drawable == null) {
            return;
        }

        Bitmap bmp = drawableToBitamp(drawable);
        // 将bmp作为着色器，就是在指定区域内绘制bmp
        mBitmapShader = new BitmapShader(bmp, TileMode.CLAMP, TileMode.CLAMP);
        float scale = 1.0f;
        if (imgType) {
            // 拿到bitmap宽或高的小值
            int bSize = Math.min(bmp.getWidth(), bmp.getHeight());
            scale = widthSize * 1.0f / bSize;

        } else {
            if (!(bmp.getWidth() == getWidth() && bmp.getHeight() == getHeight())) {
                // 如果图片的宽或者高与view的宽高不匹配，计算出需要缩放的比例；缩放后的图片的宽高，一定要大于我们view的宽高；所以我们这里取大值；
                scale = Math.max(getWidth() * 1.0f / bmp.getWidth(),
                        getHeight() * 1.0f / bmp.getHeight());
            }

        }
        // shader的变换矩阵，我们这里主要用于放大或者缩小
        mMatrix.setScale(scale, scale);
        // 设置变换矩阵
        mBitmapShader.setLocalMatrix(mMatrix);
        // 设置shader
        mBitmapPaint.setShader(mBitmapShader);
    }

    /**
     * drawable转bitmap
     *
     * @param drawable
     * @return
     */
    private Bitmap drawableToBitamp(Drawable drawable) {
        if (drawable instanceof BitmapDrawable) {
            BitmapDrawable bd = (BitmapDrawable) drawable;
            return bd.getBitmap();
        }
        int w = drawable.getIntrinsicWidth();
        int h = drawable.getIntrinsicHeight();

        try {
            Bitmap bitmap = Bitmap.createBitmap(w, h, drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888 : Bitmap.Config.RGB_565);
            Canvas canvas = new Canvas(bitmap);
            drawable.setBounds(0, 0, w, h);
            drawable.draw(canvas);

            return bitmap;
        } catch (OutOfMemoryError outOfMemoryError) {
            System.gc();
            return BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
        }
    }


}

image_item.xml

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

    <TextView
        android:id="@+id/item_tv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:padding="5dp"
        android:textSize="25sp"/>

    <View
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:background="#55ff0000"
        />

    <com.chen.demo.MyImageView
        android:id="@+id/iv_1"
        xmlns:chen="http://schemas.android.com/apk/res/com.chen.demo"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:scaleType="fitXY"
        chen:angle="50"
        chen:ratio="2"
        />

    <View
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:background="#5500ff00"
        />

    <com.chen.demo.MyImageView
        android:id="@+id/iv_2"
        xmlns:chen="http://schemas.android.com/apk/res/com.chen.demo"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:scaleType="fitXY"
        chen:angle="30"
        />

    <View
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:background="#550000ff"
        />

    <com.chen.demo.MyImageView
        android:id="@+id/iv_3"
        xmlns:chen="http://schemas.android.com/apk/res/com.chen.demo"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:layout_gravity="center_horizontal"
        android:scaleType="fitXY"
        chen:angle="30"
        chen:isCircle="true"
        chen:ratio="2"
        />

LinearLayout>

在Activity中使用

package com.chen.demo;

import android.app.Activity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.bumptech.glide.Glide;

public class MainActivity extends Activity {

    private ListView listview;

    private String imgUrl = "";

    private MyListViewAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        listview = findViewById(R.id.listview);

        imgUrl = "http://pic72.nipic.com/file/20150716/21422793_144600530000_2.jpg";

        adapter = new MyListViewAdapter();

        listview.setAdapter(adapter);

    }

    //ListView数据适配器
    private class MyListViewAdapter extends BaseAdapter {

        @Override
        public int getCount() {
            return 20;
        }

        @Override
        public Object getItem(int position) {
            return position;
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder;
            if (convertView == null) {
                convertView = LayoutInflater.from(MainActivity.this).inflate(R.layout.image_item, null);
                viewHolder = new ViewHolder();

                viewHolder.item_tv = (TextView) convertView.findViewById(R.id.item_tv);
                viewHolder.iv_1 = (MyImageView) convertView.findViewById(R.id.iv_1);
                viewHolder.iv_2 = (MyImageView) convertView.findViewById(R.id.iv_2);
                viewHolder.iv_3 = (MyImageView) convertView.findViewById(R.id.iv_3);

                convertView.setTag(viewHolder);
            } else {
                viewHolder = (ViewHolder) convertView.getTag();
            }
            viewHolder.item_tv.setText("item==" + position);
            Glide.with(MainActivity.this).load(imgUrl).into(viewHolder.iv_1);
            Glide.with(MainActivity.this).load(imgUrl).into(viewHolder.iv_2);
            Glide.with(MainActivity.this).load(imgUrl).into(viewHolder.iv_3);

            return convertView;
        }

        private class ViewHolder {
            private TextView item_tv;
            private MyImageView iv_1;
            private MyImageView iv_2;
            private MyImageView iv_3;
        }
    }

}