DownloadUtil
单例模式：主要作用是保证在Java应用程序中，一个类Class只有一个实例存在。 使用Singleton的好处还在于可以节省内存，因为它限制了实例的个数，有利于Java垃圾回收（garbage collection）。
记得在子线程中开启。在ui线程中处理数据
/**
* Created by wanglingsheng on 2018/5/29.
* 文件下载工具类（单例模式）
*/
public class DownloadUtil {
private static DownloadUtil downloadUtil;
private final OkHttpClient okHttpClient;
public static DownloadUtil get() {
if (downloadUtil == null) {
downloadUtil = new DownloadUtil();
}
return downloadUtil;
}
public DownloadUtil() {
okHttpClient = new OkHttpClient();
}
/**
* @param url 下载连接
* @param destFileDir 下载的文件储存目录
* @param destFileName 下载文件名称
* @param listener 下载监听
*/
public void download(final String url, final String destFileDir, final String destFileName, final OnDownloadListener listener) {
Request request = new Request.Builder()
.url(url)
.build();
OkHttpClient client = new OkHttpClient();
try {
Response response = client.newCall(request).execute();
} catch (IOException e) {
e.printStackTrace();
}
//异步请求
okHttpClient.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
// 下载失败监听回调
listener.onDownloadFailed(e);
}
@Override
public void onResponse(Call call, Response response) throws IOException {
InputStream is = null;
byte[] buf = new byte[2048];
int len = 0;
FileOutputStream fos = null;
//储存下载文件的目录
File dir = new File(destFileDir);
if (!dir.exists()) {
dir.mkdirs();
}
File file = new File(dir, destFileName);
try {
is = response.body().byteStream();
long total = response.body().contentLength();
fos = new FileOutputStream(file);
long sum = 0;
while ((len = is.read(buf)) != -1) {
fos.write(buf, 0, len);
sum += len;
int progress = (int) (sum * 1.0f / total * 100);
//下载中更新进度条
listener.onDownloading(progress);
}
fos.flush();
//下载完成
listener.onDownloadSuccess(file);
} catch (Exception e) {
listener.onDownloadFailed(e);
}finally {
try {
if (is != null) {
is.close();
}
if (fos != null) {
fos.close();
}
} catch (IOException e) {
}
}
}
});
}
public interface OnDownloadListener{
/**
* 下载成功之后的文件
*/
void onDownloadSuccess(File file);
/**
* 下载进度
*/
void onDownloading(int progress);
/**
* 下载异常信息
*/
void onDownloadFailed(Exception e);
}
}
使用：
/**
* 文件下载
*/
private void downFile(String url) {
DownloadUtil.get().download(url, Environment.getExternalStorageDirectory().getAbsolutePath(), "dtwb2.apk",
new DownloadUtil.OnDownloadListener() {
@Override
public void onDownloadSuccess(File file) {
if (progressDialog != null && progressDialog.isShowing()) {
progressDialog.dismiss();
}
//下载完成进行相关逻辑操作
Message msg = mHandler.obtainMessage();
msg.what = 0;
mHandler.sendMessage(msg);
}
@Override
public void onDownloading(int progress) {
// progressDialog.setProgress(progress);
Message msg = mHandler.obtainMessage();
msg.what = 11;
msg.obj = progress;
mHandler.sendMessage(msg);
}
@Override
public void onDownloadFailed(Exception e) {
//下载异常进行相关提示操作
Message msg = mHandler.obtainMessage();
msg.what = 1;
msg.obj = e;
mHandler.sendMessage(msg);
}
});
}
progressDialog的配置：
progressDialog = new ProgressDialog(DownloadActivity.this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setCancelable(false);
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.setTitle("正在下载");
progressDialog.setMessage("请稍后...");
progressDialog.setMax(100);
progressDialog.show();
setProgress的更新用过handler处理message，切换到主线程中更新UI
