Diycode开源项目 Glide图片加载分析

1.使用Glide前的准备

1.1.首先要build.gradle中添加

　　github原地址点击我。

　　参考博客：Glide-开始！

　　参考博客：android图片加载库Glide的使用介绍。

　　参考博客：Google推荐的图片加载库Glide介绍。

　　所有有关Glide的源头都是来自于github，首先亮一手，可以自己去看看。

1.2.有必要添加混淆

　　为了APP的安全，现在一般都要求添加混淆

　　在github上复制粘贴即可。

1.3.最简单的用法==>对于一个简单的view

　　了解这么多就行了。

2.用Module自定义Glide

2.1.Glide Module存在的意义

　　Glide Module是一个抽象方法，全局改变Glide行为的一个方法。如果你需要GlideBuilder，它要在你要做的地方

　　创建Glide实例。这是要做的一种方法。为了定制Glide，你需要去实现一个GlideModule接口的公共类。

2.2.需要在AndroidManifest.xml中声明这个Glide module。

2.3.然后就可以对这个Module为所欲为了。

　　有这些方法可以用的。

　　实际的项目中是这样用的。

　　设置了内存缓存==10M

　　设置了磁盘缓存==250M

2.4.还可以增加Glide的图片质量，用的也比较多

3.自定义Drawable实现Drawable.Callback

3.1.首先了解一下Drawable

　关于自定义Drawable，可以参考一下这篇文章。

3.2.然后了解一下Drawble.Callback回调接口

3.3.本项目的源代码

/*
 * Copyright 2017 GcsSloop
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Last modified 2017-03-11 22:24:02
 *
 * GitHub:  https://github.com/GcsSloop
 * Website: http://www.gcssloop.com
 * Weibo:   http://weibo.com/GcsSloop
 */

package com.gcssloop.diycode.base.glide;

import android.graphics.Canvas;
import android.graphics.ColorFilter;
import android.graphics.drawable.Drawable;

import com.bumptech.glide.load.resource.drawable.GlideDrawable;

/**
 * 为 {@link GlideImageGetter} 服务
 */
public class UrlDrawable extends Drawable implements Drawable.Callback {

    private GlideDrawable mDrawable;

    @Override
    public void draw(Canvas canvas) {
        if (mDrawable != null) {
            mDrawable.draw(canvas);
        }
    }

    @Override
    public void setAlpha(int alpha) {
        if (mDrawable != null) {
            mDrawable.setAlpha(alpha);
        }
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
        if (mDrawable != null) {
            mDrawable.setColorFilter(cf);
        }
    }

    @Override
    public int getOpacity() {
        if (mDrawable != null) {
            return mDrawable.getOpacity();
        }
        return 0;
    }

    public void setDrawable(GlideDrawable drawable) {
        if (this.mDrawable != null) {
            this.mDrawable.setCallback(null);
        }
        drawable.setCallback(this);
        this.mDrawable = drawable;
    }

    @Override
    public void invalidateDrawable(Drawable who) {
        if (getCallback() != null) {
            getCallback().invalidateDrawable(who);
        }
    }

    @Override
    public void scheduleDrawable(Drawable who, Runnable what, long when) {
        if (getCallback() != null) {
            getCallback().scheduleDrawable(who, what, when);
        }
    }

    @Override
    public void unscheduleDrawable(Drawable who, Runnable what) {
        if (getCallback() != null) {
            getCallback().unscheduleDrawable(who, what);
        }
    }
}

View Code

3.4.本项目实现Drawable中4个必须实现的函数

　　其实这里的主角已经悄悄替换成了Glide中的一个GlideDrawble方法了

　　这个UrlDrawable就是起一个替换作用，就是自定义一个Drawable可以完美实现GlideDrawable中的所有方法。

3.5.最关键的setDrawable函数

　　仅仅这个函数被外部调用了，所以这里既设置了Callback回调，也将外部传进来的GlideDrawable完美附上了值。

3.6.然后是看一下Drawable.Callback

　　这里没有做什么改变，只是因为GlideDrawable要实现这些回调，只能被动去实现3个复写的方法。

4.用Glide加载网络图片，并在textView中显示

4.1.要实现的功能预览。

　　如上图，评论中有一张截图+下方的文字。

　　整个评论其实是一个TextView。

　　问题是如何实现这个功能呢？

4.2.回顾之前的准备

　　我自定义了一个GlideModule，并在清单文件中配置好，有这个东西就行了。　　

　　然后我自定义了一个UrlDrawable，都是为GlideImageGetter做准备的。

　　这个是那个评论实现图文混排的关键代码。

　　所以我还要定义GlideImageGetter，将content注入这种特殊功能。

4.3.然后就来关注一下如何实现GlideImageGetter的吧。

/*
 * Copyright 2017 GcsSloop
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Last modified 2017-03-31 14:20:42
 *
 * GitHub:  https://github.com/GcsSloop
 * Website: http://www.gcssloop.com
 * Weibo:   http://weibo.com/GcsSloop
 */

package com.gcssloop.diycode.base.glide;

import android.content.Context;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.text.Html;
import android.view.View;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.engine.DiskCacheStrategy;
import com.bumptech.glide.load.resource.drawable.GlideDrawable;
import com.bumptech.glide.request.Request;
import com.bumptech.glide.request.animation.GlideAnimation;
import com.bumptech.glide.request.target.ViewTarget;
import com.gcssloop.diycode.R;
import com.gcssloop.diycode_sdk.log.Logger;

import java.util.HashSet;
import java.util.Set;

/**
 * 用 Glide 加载图片，并在 TextView 中显示
 */
public final class GlideImageGetter implements Html.ImageGetter, Drawable.Callback {

    private final Context mContext;

    private final TextView mTextView;

    private final Set<ImageGetterViewTarget> mTargets;

    public static GlideImageGetter get(View view) {
        return (GlideImageGetter) view.getTag(R.id.drawable_callback_tag);
    }

    public void clear() {
        GlideImageGetter prev = get(mTextView);
        if (prev == null) return;

        for (ImageGetterViewTarget target : prev.mTargets) {
            Glide.clear(target);
        }
    }

    public GlideImageGetter(Context context, TextView textView) {
        this.mContext = context;
        this.mTextView = textView;

        clear();
        mTargets = new HashSet<>();
        mTextView.setTag(R.id.drawable_callback_tag, this);
    }

    @Override
    public Drawable getDrawable(String url) {
        final UrlDrawable urlDrawable = new UrlDrawable();

        Logger.i("Downloading from: " + url);
        Glide.with(mContext)
                .load(url)
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(new ImageGetterViewTarget(mTextView, urlDrawable));


        return urlDrawable;

    }

    @Override
    public void invalidateDrawable(Drawable who) {
        mTextView.invalidate();
    }

    @Override
    public void scheduleDrawable(Drawable who, Runnable what, long when) {

    }

    @Override
    public void unscheduleDrawable(Drawable who, Runnable what) {

    }

    private class ImageGetterViewTarget extends ViewTarget<TextView, GlideDrawable> {

        private final UrlDrawable mDrawable;

        private ImageGetterViewTarget(TextView view, UrlDrawable drawable) {
            super(view);
            mTargets.add(this);
            this.mDrawable = drawable;
        }

        @Override
        public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> glideAnimation) {
            Rect rect;
            if (resource.getIntrinsicWidth() > 100) {
                float width;
                float height;
                Logger.i("Image width is " + resource.getIntrinsicWidth());
                Logger.i("View width is " + view.getWidth());
                if (resource.getIntrinsicWidth() >= getView().getWidth()) {
                    float downScale = (float) resource.getIntrinsicWidth() / getView().getWidth();
                    width = (float) resource.getIntrinsicWidth() / (float) downScale;
                    height = (float) resource.getIntrinsicHeight() / (float) downScale;
                } else {
                    float multiplier = (float) getView().getWidth() / resource.getIntrinsicWidth();
                    width = (float) resource.getIntrinsicWidth() * (float) multiplier;
                    height = (float) resource.getIntrinsicHeight() * (float) multiplier;
                }
                Logger.i("New Image width is " + width);


                rect = new Rect(0, 0, Math.round(width), Math.round(height));
            } else {
                rect = new Rect(0, 0, resource.getIntrinsicWidth() * 2, resource.getIntrinsicHeight() * 2);
            }
            resource.setBounds(rect);

            mDrawable.setBounds(rect);
            mDrawable.setDrawable(resource);


            if (resource.isAnimated()) {
                mDrawable.setCallback(get(getView()));
                resource.setLoopCount(GlideDrawable.LOOP_FOREVER);
                resource.start();
            }

            getView().setText(getView().getText());
            getView().invalidate();
        }

        private Request request;

        @Override
        public Request getRequest() {
            return request;
        }

        @Override
        public void setRequest(Request request) {
            this.request = request;
        }
    }
}