使用第三方框架Glide显示网络图片

<?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="www.itcast.com.testglide.MainActivity">

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Glide" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <ImageView
                android:id="@+id/iv1"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />

            <ImageView
                android:id="@+id/iv2"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />

            <ImageView
                android:id="@+id/iv3"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />
        </LinearLayout>
    </ScrollView>
</LinearLayout>

     //显示普通图片
                Glide
                        .with(this) // 指定Context
                        .load(url)// 指定图片的URL
                        .placeholder(R.mipmap.ic_launcher)// 指定图片未成功加载前显示的图片
                        .error(R.mipmap.ic_launcher)// 指定图片加载失败显示的图片
                        .override(300, 300)//指定图片的尺寸
                        .fitCenter()//指定图片缩放类型为fitCenter
                        .centerCrop()// 指定图片缩放类型为centerCrop
                        .skipMemoryCache(true)// 跳过内存缓存
                        .diskCacheStrategy(DiskCacheStrategy.NONE)//跳过磁盘缓存
                        .diskCacheStrategy(DiskCacheStrategy.SOURCE)//仅仅只缓存原来的全分辨率的图像
                        .diskCacheStrategy(DiskCacheStrategy.RESULT)//仅仅缓存最终的图像
                        .diskCacheStrategy(DiskCacheStrategy.ALL)//缓存所有版本的图像
                        .priority(Priority.HIGH)//指定优先级.Glide 将会用他们作为一个准则，并尽可能的处理这些请求，但是它不能保证所有的图片都会按照所要求的顺序加载。优先级排序:IMMEDIATE > HIGH > NORMAL >　LOW
                        .into(iv1);//指定显示图片的ImageView

   //显示圆形图片
                class GlideCircleTransform extends BitmapTransformation {
                    public GlideCircleTransform(Context context) {
                        super(context);
                    }

                    @Override
                    protected Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
                        return circleCrop(pool, toTransform);
                    }

                    private Bitmap circleCrop(BitmapPool pool, Bitmap source) {
                        if (source == null) return null;

                        int size = Math.min(source.getWidth(), source.getHeight());
                        int x = (source.getWidth() - size) / 2;
                        int y = (source.getHeight() - size) / 2;

                        // TODO this could be acquired from the pool too
                        Bitmap squared = Bitmap.createBitmap(source, x, y, size, size);

                        Bitmap result = pool.get(size, size, Bitmap.Config.ARGB_8888);
                        if (result == null) {
                            result = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888);
                        }

                        Canvas canvas = new Canvas(result);
                        Paint paint = new Paint();
                        paint.setShader(new BitmapShader(squared, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP));
                        paint.setAntiAlias(true);
                        float r = size / 2f;
                        canvas.drawCircle(r, r, r, paint);
                        return result;
                    }

                    @Override
                    public String getId() {
                        return getClass().getName();
                    }
                }

                Glide
                        .with(this) // 指定Context
                        .load(url)// 指定图片的URL
                        .transform(new GlideCircleTransform(this)) // 指定自定义BitmapTransformation
                        .into(iv2);//指定显示图片的ImageView

 //显示圆角图片
                class GlideRoundTransform extends BitmapTransformation {

                    private float radius = 0f;

                    public GlideRoundTransform(Context context) {
                        this(context, 4);
                    }

                    public GlideRoundTransform(Context context, int dp) {
                        super(context);
                        this.radius = Resources.getSystem().getDisplayMetrics().density * dp;
                    }

                    @Override protected Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
                        return roundCrop(pool, toTransform);
                    }

                    private Bitmap roundCrop(BitmapPool pool, Bitmap source) {
                        if (source == null) return null;

                        Bitmap result = pool.get(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);
                        if (result == null) {
                            result = Bitmap.createBitmap(source.getWidth(), source.getHeight(), Bitmap.Config.ARGB_8888);
                        }

                        Canvas canvas = new Canvas(result);
                        Paint paint = new Paint();
                        paint.setShader(new BitmapShader(source, BitmapShader.TileMode.CLAMP, BitmapShader.TileMode.CLAMP));
                        paint.setAntiAlias(true);
                        RectF rectF = new RectF(0f, 0f, source.getWidth(), source.getHeight());
                        canvas.drawRoundRect(rectF, radius, radius, paint);
                        return result;
                    }

                    @Override public String getId() {
                        return getClass().getName() + Math.round(radius);
                    }
                }

                Glide
                        .with(this) // 指定Context
                        .load(url)// 指定图片的URL
                        .transform(new GlideRoundTransform(this,30)) // 指定自定义BitmapTransformation
                        .into(iv3);//指定显示图片的ImageView