基本用法：
public class MyGlideModule implements GlideModule {
@Override
public void applyOptions(Context context, GlideBUilder builder) {
}
@Override
public void registerComponents(Context context, Glide glide) {
}
}
以上这两个需要我们重写的方法就是来更改Glide配置以及替换Glide组件的，注意：目前Glide还不能识别我们自定义的MyGlideModule，还需要在AndroidManifest.xml中做一下配置
<manifest>
...
<application>
<meta-data>
这个name是指我们自定义的MyGlideModule的完整路径
android:name="com.example.glidetest.MyGlideModule"
这个value必须指定为GlideMoudle，这样glide在builde的时候才能识别到
android:value="GlideModule" />
...
</application>
</manifest>
源码分析：先来看Glide的构建glide对象：
public static Glide get(Context context) {
if (glide == null) {
// 通过单例模式来获取glide对象
synchronized (Glide.class) {
if (glide == null) {
Context applicationContext = context.getApplicationContext();
// 通过ManifestParser.parse()来解析AndiordManifest.xml中的文件配置
List<GlideModule> modules = new ManifestParser(applicationContext).parse();
GlideBuilder builder = new GlideBuilder(applicationContext);
for (GlideModule module : modules) {
// 循环的调用每一个GlideModule的中的applyOptions()，这里也就是我们自定义逻辑的地方
module.applyOptions(applicationContext, builder);
}
// 构建glide
glide = builder.createGlide();
for (GlideModule module : modules) {
// 在获取到glide对象后，通过循环调用每个GlideModule的redisterComponents()来实现glide的逻辑替换
module.registerComponents(applicationContext, glide);
}
}
}
}
return glide;
}
说明了为什要将value指定为GlideModule
private static final String GLIDE_MODULE_VALUE = "GlideModule";
public List<GlideModule> parse() {
List<GlideModule> modules = new ArrayList<GlideModule>();
try {
ApplicationInfo appInfo = context.getPackageManager().getApplicationInfo(
context.getPackageName(), PackageManager.GET_META_DATA);
if (appInfo.metaData != null) {
// 通过循环来获取所有的值为GlideModule的配置，返回一个GlideModule的集合
for (String key : appInfo.metaData.keySet()) {
if (GLIDE_MODULE_VALUE.equals(appInfo.metaData.get(key))) {
modules.add(parseModule(key));
}
}
}
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException("Unable to find metadata to parse GlideModules", e);
}
return modules;
}
构建glide：
Glide createGlide() {
if (sourceService == null) {
final int cores = Math.max(1, Runtime.getRuntime().availableProcessors());
sourceService = new FifoPriorityThreadPoolExecutor(cores);
}
if (diskCacheService == null) {
diskCacheService = new FifoPriorityThreadPoolExecutor(1);
}
MemorySizeCalculator calculator = new MemorySizeCalculator(context);
if (bitmapPool == null) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
int size = calculator.getBitmapPoolSize();
bitmapPool = new LruBitmapPool(size);
} else {
bitmapPool = new BitmapPoolAdapter();
}
}
if (memoryCache == null) {
memoryCache = new LruResourceCache(calculator.getMemoryCacheSize());
}
if (diskCacheFactory == null) {
diskCacheFactory = new InternalCacheDiskCacheFactory(context);
}
if (engine == null) {
engine = new Engine(memoryCache, diskCacheFactory, diskCacheService, sourceService);
}
if (decodeFormat == null) {
decodeFormat = DecodeFormat.DEFAULT;
}
return new Glide(engine, memoryCache, bitmapPool, context, decodeFormat);
}
会创建BitmapPool、MemoryCache、DiskCache、DecodeDroamt、Engine等对象的实例，并在最后返回的Glide对象中将创建的实例传入进去，以供后续的图片加载操作使用。在创建对象的时候首先回去判断是否为null只有为null的才会创建，所以我们可以自己在applyOptions()中提前初始化并赋值，在createGlide的时候就不会去创建了，从而就实现的glide的配置的更改功能
更改Glide的配置：
只需在applyOptions()中提前将Glide的配置项进行初始化
1、setMemoryCache()
用于设置Glide的内存缓存策略，默认为LruResourceCache
2、setBitmapPool()
配置Glide的Bitmap缓存池，默认为LruBitmapPool
3、setDisCache()
配置Glide的硬盘缓存策略，默认为InternalCacheDiskCacheFactory
4、setDiskCacheService()
配置Glide读取缓存中图片的异步执行器，默认配置是FifoPriorityThreadPoolExecutor，也就是先入先出原则
5、setResizeService()
配置Glide读取非缓存中的图片的异步执行器，默认也是FifoPriorityThreadPoolExecutor
6、setDecodeFormat()
配置Glide加载图片的解码模式，默认为PREFER_RGB_565
不过以上的配置我们几乎都不需要去更改
替换Glide组件：
查看Glide中的组件：
Glide(Engine engine, MemoryCache memoryCache, BitmapPool bitmapPool, Context context, DecodeFormat decodeFormat) {
...
register(File.class, ParcelFileDescriptor.class, new FileDescriptorFileLoader.Factory());
register(File.class, InputStream.class, new StreamFileLoader.Factory());
register(int.class, ParcelFileDescriptor.class, new FileDescriptorResourceLoader.Factory());
register(int.class, InputStream.class, new StreamResourceLoader.Factory());
register(Integer.class, ParcelFileDescriptor.class, new FileDescriptorResourceLoader.Factory());
register(Integer.class, InputStream.class, new StreamResourceLoader.Factory());
register(String.class, ParcelFileDescriptor.class, new FileDescriptorStringLoader.Factory());
register(String.class, InputStream.class, new StreamStringLoader.Factory());
register(Uri.class, ParcelFileDescriptor.class, new FileDescriptorUriLoader.Factory());
register(Uri.class, InputStream.class, new StreamUriLoader.Factory());
register(URL.class, InputStream.class, new StreamUrlLoader.Factory());
register(GlideUrl.class, InputStream.class, new HttpUrlGlideUrlLoader.Factory());
register(byte[].class, InputStream.class, new StreamByteArrayLoader.Factory());
...
}
例如：我们将Glide的网络请求改成OKHttp的register(GlideUrl.class, InputStream.class, new HttpUrlGlideUrlLoader.Factory());直接将这里面的http通讯组件改成okhttp的查看HttpUrlGlideUrlLoader的源码：
public class HttpUrlGlideUrlLoader implements ModelLoader<GlideUrl, InputStream> {
private final ModelCache<GlideUrl, GlideUrl> modelCache;
/**
* The default factory for {@link com.bumptech.glide.load.model.stream.HttpUrlGlideUrlLoader}s.
*/
public static class Factory implements ModelLoaderFactory<GlideUrl, InputStream> {
private final ModelCache<GlideUrl, GlideUrl> modelCache = new ModelCache<GlideUrl, GlideUrl>(500);
@Override
public ModelLoader<GlideUrl, InputStream> build(Context context, GenericLoaderFactory factories) {
return new HttpUrlGlideUrlLoader(modelCache);
}
@Override
public void teardown() {
// Do nothing.
}
}
public HttpUrlGlideUrlLoader() {
this(null);
}
public HttpUrlGlideUrlLoader(ModelCache<GlideUrl, GlideUrl> modelCache) {
this.modelCache = modelCache;
}
@Override
public DataFetcher<InputStream> getResourceFetcher(GlideUrl model, int width, int height) {
// GlideUrls memoize parsed URLs so caching them saves a few object instantiations and time spent parsing urls.
GlideUrl url = model;
if (modelCache != null) {
url = modelCache.get(model, 0, 0);
if (url == null) {
modelCache.put(model, 0, 0, model);
url = model;
}
}
// 主要的网络请求在这里
return new HttpUrlFetcher(url);
}
}
通过查看HttpUrlFetcher源码可以知道：其实就是HttpURLConnection所以我们替换成okhttp来处理：
1、模仿Glide的HttpUrlFetcher写出自己的OkHttpFetcher
public class OkHttpFetcher implements DataFetcher<InputStream> {
private GlideUrl url;
private OkHttpClient client;
private InputStream stream;
private ResponseBody responseBody;
private volatile boolean isCancelled;
public OkHttpFetcher(GlideUrl url, OkHttpClient client) {
this.url = url;
this.client = client;
}
@Override
public InputStream loadData(Priority priority) throws Exception {
Request.Builder requestBuilder = new Request.Builder();
requestBuilder.url(url.toString());
for (Map.Entry<String, String> headerEntry :url.getHeaders().entrySet()) {
String key = headerEntry.getKey();
requestBuilder.addHeader(key, headerEntry.getValue());
}
//这个请求头是测试用，实际项目中可以不用添加
requestBuilder.addHeader("httplib", "OkHttp");
Request request = requestBuilder.build();
if (isCancelled) {
return null;
}
Response response = client.newCall(request).execute();
responseBody = response.body();
if (!response.isSuccessful() || responseBody == null) {
throw new IOException("Request failed with code: " + response.code());
}
stream = ContentLengthInputStream.obtain(responseBody.byteStream(), responseBody.contentLength());
return stream;
}
@Override
public void cleanup() {
try {
if (stream != null) {
stream.close();
}
if (responseBody != null) {
responseBody.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public String getId() {
return url.getCacheKey();
}
@Override
public void cancel() {
isCancelled = true;
}
}
2、模仿Glide的HttpUrlGlideUrlLoader来写出自己的OkHttpGlideUrlLoader
public class OkHttpGlideUrlLoader implements ModelLoader<GlideUrl, InputStream> {
private OkHttpClient okHttpClient;
public OkHttpGlideUrlLoader(OkHttpClient okHttpClient) {
this.okHttpClient = okHttpClient;
}
public static class Factory implements ModelLoaderFactory<GlideUrl, InputStream> {
private OkHttpClient client;
public Factory() {
}
public Factory(OkHttpClient client) {
this.client = client;
}
private synchronized OkHttpClient getOkHttpClient() {
if (client == null) {
client = new OkHttpClient();
}
return client;
}
@Override
public ModelLoader<GlideUrl, InputStream> build(Context context, GenericLoaderFactory factories) {
return new OkHttpGlideUrlLoader(getOkHttpClient());
}
@Override
public void teardown() {
}
}
@Override
public DataFetcher<InputStream> getResourceFetcher(GlideUrl model, int width, int height) {
return new OkHttpFetcher(model, okHttpClient);
}
}
3、将上面创建的OkHttpUrlFetcher和OkHttpGlideUrlLoader注册到Glide中（注意：需要在AndroidManifest中配置）
public class MyGlideModule implements GlideModule {
@Override
public void applyOptions(Context context, GlideBuilder builder) {
}
@Override
public void registerComponents(Context context, Glide glide) {
glide.register(GlideUrl.class, InputStream.class, new OkHttpGlideUrlLoader.Factory());
}
}
以上都是我们自己手写的，Glide有官方的替换方法（其背后的原理也就是我们上面所分析的）利用okhttp3来作为http的通讯：
dependencies {
compile 'com.squareup.okhttp3:okhttp:3.9.0'
compile 'com.github.bumptech.glide:okhttp3-integration:1.5.0@aar'
}
利用volley来作为http通讯：
dependencies {
compile 'com.github.bumptech.glide:volley-integration:1.5.0@aar'
compile 'com.mcxiaoke.volley:library:1.0.19'
}