Android Retrofit下载MP4并保存本地教程
作为一名经验丰富的开发者,我将教会你如何使用Retrofit库来实现在Android平台上下载MP4文件并将其保存到本地。下面是整个过程的详细步骤:
1. 添加依赖库
首先,你需要在项目的build.gradle文件中添加Retrofit库的依赖。打开你的项目级别的build.gradle文件,找到dependencies
块并添加以下代码:
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
implementation 'com.squareup.okhttp3:logging-interceptor:3.12.1'
这些依赖库将帮助我们实现Retrofit的功能。
2. 创建Retrofit实例
下一步,我们将创建一个Retrofit实例,用于发起HTTP请求。在你的代码中创建一个RetrofitClient类,并添加以下代码:
public class RetrofitClient {
private static Retrofit retrofit;
public static Retrofit getClient() {
if (retrofit == null) {
OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
httpClient.addInterceptor(loggingInterceptor);
retrofit = new Retrofit.Builder()
.baseUrl("
.addConverterFactory(GsonConverterFactory.create())
.client(httpClient.build())
.build();
}
return retrofit;
}
}
以上代码创建了一个Retrofit实例,并设置了基本的URL和Gson转换器。你需要将your-api-base-url.com
替换为你实际使用的API的基本URL。
3. 创建API接口
接下来,我们将创建一个API接口,用于定义下载MP4文件的网络请求。在你的代码中创建一个ApiService接口,并添加以下代码:
public interface ApiService {
@Streaming
@GET("download/{file_name}")
Call<ResponseBody> downloadFile(@Path("file_name") String fileName);
}
该接口包含一个downloadFile
方法,用于请求下载文件。使用@Streaming
注解可以确保下载文件时不会将整个文件读入内存。
4. 下载并保存文件
现在,我们将实现文件下载和保存的代码。在你的代码中创建一个DownloadManager类,并添加以下代码:
public class DownloadManager {
private static final String STORAGE_PATH = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
private ApiService apiService;
public DownloadManager() {
apiService = RetrofitClient.getClient().create(ApiService.class);
}
public void downloadFile(String fileName, final DownloadCallback downloadCallback) {
Call<ResponseBody> call = apiService.downloadFile(fileName);
call.enqueue(new Callback<ResponseBody>() {
@Override
public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
if (response.isSuccessful()) {
boolean writtenToDisk = writeResponseBodyToDisk(response.body(), fileName);
if (writtenToDisk) {
downloadCallback.onDownloadComplete();
} else {
downloadCallback.onDownloadFailed();
}
} else {
downloadCallback.onDownloadFailed();
}
}
@Override
public void onFailure(Call<ResponseBody> call, Throwable t) {
downloadCallback.onDownloadFailed();
}
});
}
private boolean writeResponseBodyToDisk(ResponseBody body, String fileName) {
try {
File file = new File(STORAGE_PATH + File.separator + fileName);
InputStream inputStream = null;
OutputStream outputStream = null;
try {
byte[] fileReader = new byte[4096];
long fileSize = body.contentLength();
long fileSizeDownloaded = 0;
inputStream = body.byteStream();
outputStream = new FileOutputStream(file);
while (true) {
int read = inputStream.read(fileReader);
if (read == -1) {
break;
}
outputStream.write(fileReader, 0, read);
fileSizeDownloaded += read;
}
outputStream.flush();
return true;
} catch (IOException e) {
return false;
} finally {
if (inputStream != null) {
inputStream.close();
}
if (outputStream != null) {
outputStream.close();
}
}
} catch (IOException e) {
return false;
}
}
}
以上代码中,DownloadManager
类使用Retrofit的RetrofitClient实例来创建一个ApiService实例。downloadFile
方法接收文件名和一个DownloadCallback
回调,用于在下载完成或失败时进行通知。writeResponseBodyToDisk
方法用于将下载的文件保存到本地。