Android---服务的最佳实践（完整版的下载实例）

public interface DownloadListener {

/*
* 接口类，使用回调
*/
void onProgress(int progress);
void onSuccess();
void onFailed();
void onPaused();
void onCanceled();
}

package com.mycompany.servicebestpractice;

import android.os.AsyncTask;
import android.os.Environment;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

/**
* Created by sstek_mars on 2017/9/8.
*/

/**
* AsyncTask的三个泛型参数
* 第一个参数指定为String，表示在执行AsyncTask的时候需要传入一个字符串参数给后台任务
* 第二个泛型参数指定为Integer，表示使用整数型数据来作为进度显示单位
* 第三个泛型参数指定为Integer，表示使用整型数据来反馈执行结果
*/
public abstract class DownloadTask extends AsyncTask<String, Integer, Integer> {

public static final int TYPE_SUCCESS = 0;
public static final int TYPE_FAILED = 1;
public static final int TYPE_PAUSED = 2;
public static final int TYPE_CANCELED = 3;

private DownloadListener listener;
private boolean isCanceled = false;
private boolean isPaused = false;
private int lastProgress;

public DownloadTask(DownloadListener listener) {
this.listener = listener;
}

/**
* 重写doInBackground() onProgressUpdate() onPostExecute()
* doInBackground():用于在后台执行具体的下载逻辑
* onProgressUpdate()：用于在界面上更新当前的下载进度
* onPostExecute()：用于通知最终的下载结果
*/

@Override
protected Integer doInBackground(String... params) {
InputStream is = null;
RandomAccessFile saveFile = null;
File file = null;
try {
long downloadedLength = 0; // 记录下载的文件长度
String dowloadUrl = params[0];
// 从URL中解析出下载的文件名
String fileName = dowloadUrl.substring(dowloadUrl.lastIndexOf("/"));
// 将文件下载的指定位置
String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
// 判断文件是否存在，已经存在的就无需下载了
file = new File(directory + fileName);
if (file.exists()) {
// 如果已存在，读取已下载的字节数，用于启动断点下载功能
downloadedLength = file.length();
}
long contentLength = getContentLength(dowloadUrl);
if (contentLength == 0) {
return TYPE_FAILED;
}else if(contentLength == downloadedLength){
// 已下载的字节和文件总字节相等，说明已经下载完成了
return TYPE_SUCCESS;
}

OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
// 添加header用于告诉服务器我们想从哪个字节开始下载，开始断点下载，知道从哪个字节开始下载
.addHeader("RANGE", "bytes=" + downloadedLength + "-")
.url(dowloadUrl)
.build();
Response response = client.newCall(request).execute();
if (response != null) {
// 使用jiava文件流的方式，不断的从网络读取数据，不断的写入本地
is = response.body().byteStream();
saveFile = new RandomAccessFile(file, "rw");
saveFile.seek(downloadedLength);
byte[] b = new byte[1024];
int total = 0;
int len;
while ((len = is.read(b)) != -1) {
if (isCanceled) {
return TYPE_CANCELED;
}else if (isPaused) {
return TYPE_PAUSED;
}else {
total += len;
saveFile.write(b, 0, len);
// 计算已下载的百分比
int progress = (int) ((total + downloadedLength) * 100 / contentLength);
publishProgress(progress);
}
}

response.body().close();
return TYPE_SUCCESS;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (is != null) {
is.close();
}

if (saveFile != null) {
saveFile.close();
}

if (isCanceled && file != null) {
file.delete();
}
} catch (Exception e) {
e.printStackTrace();
}
}
return TYPE_FAILED;
}

// 获取当前下载的进度
@Override
protected void onProgressUpdate(Integer... values) {
int progress = values[0];
if (progress > lastProgress) {
listener.onProgress(progress);
lastProgress = progress;
}
}

// 获取是否下载完成
@Override
protected void onPostExecute(Integer integer) {
switch (integer) {
case TYPE_SUCCESS:
listener.onSuccess();
break;
case TYPE_FAILED:
listener.onFailed();
break;
case TYPE_PAUSED:
listener.onPaused();
break;
case TYPE_CANCELED:
listener.onCanceled();
break;
default:
break;
}
}

public void pauseDownload() {
isPaused = true;
}

public void cancelDownload() {
isCanceled = true;
}

private long getContentLength(String downloadUrl) throws IOException {
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder().url(downloadUrl).build();
Response response = client.newCall(request).execute();
if (response != null && response.isSuccessful()) {
long contentLength = response.body().contentLength();
response.close();
return contentLength;
}
return 0;
}
}

package com.mycompany.servicebestpractice;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.graphics.BitmapFactory;
import android.os.Binder;
import android.os.Environment;
import android.os.IBinder;
import android.support.annotation.Nullable;
import android.support.v4.app.NotificationCompat;
import android.widget.Toast;

import java.io.File;

public class DownloadService extends Service {

private DownloadTask downloadTask;
private String downloadUrl;

private DownloadListener listener = new DownloadListener() {
@Override
public void onProgress(int progress) {
getNotificationManager().notify(1, getNotification("下载中。。。", progress));
}

@Override
public void onSuccess() {
downloadTask = null;
// 下载成功时将前台的服务通知关闭，并创建一个下载成功的通知
stopForeground(true);
getNotificationManager().notify(1, getNotification("Download success", -1));
Toast.makeText(DownloadService.this, "下载成功", Toast.LENGTH_SHORT).show();
}

@Override
public void onFailed() {
downloadTask = null;
// 下载失败时将前台的服务通知关闭，并创建一个下载失败的通知
stopForeground(true);
getNotificationManager().notify(1, getNotification("Download success", -1));
Toast.makeText(DownloadService.this, "下载失败", Toast.LENGTH_SHORT).show();
}

@Override
public void onPaused() {
downloadTask = null;
Toast.makeText(DownloadService.this, "下载暂停", Toast.LENGTH_SHORT).show();
}

@Override
public void onCanceled() {
downloadTask = null;
stopForeground(true);
Toast.makeText(DownloadService.this, "下载取消", Toast.LENGTH_SHORT).show();
}
};

private DownloadBinder mBinder = new DownloadBinder();

@Nullable
@Override
public IBinder onBind(Intent intent) {
return mBinder;
}

class DownloadBinder extends Binder {

public void startDownload(String url) {
if (downloadTask == null) {
downloadUrl = url;
downloadTask.execute(downloadUrl);
startForeground(1, getNotification("Downloading...", 0));
Toast.makeText(DownloadService.this, "Downloading...",Toast.LENGTH_SHORT).show();
}
}

public void pauseDownload() {
if (downloadTask != null) {
downloadTask.pauseDownload();
}
}

public void cancelDownload() {
if (downloadTask != null) {
downloadTask.cancelDownload();
} else {
if (downloadUrl != null) {
// 取消下载是需将文件删除，并将通知关闭
String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
String dirdectory = Environment.getExternalStoragePublicDirectory(Environment
.DIRECTORY_DOWNLOADS).getPath();
File file = new File(dirdectory + fileName);
if (file.exists()) {
file.delete();
}
getNotificationManager().cancel(1);
stopForeground(true);
Toast.makeText(DownloadService.this, "取消", Toast.LENGTH_SHORT).show();
}
}
}
}

private NotificationManager getNotificationManager() {
return (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
}

private Notification getNotification(String title, int progress) {
Intent intent = new Intent(this, MainActivity.class);
PendingIntent pi = PendingIntent.getActivity(this, 0, intent, 0);
NotificationCompat.Builder builder = new NotificationCompat.Builder(this);
builder.setSmallIcon(R.mipmap.ic_launcher);
builder.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher));
builder.setContentIntent(pi);
builder.setContentTitle(title);
if (progress > 0) {
builder.setContentText(progress + "%");
builder.setProgress(100, progress, false);
}
return builder.build();
}
}

package com.mycompany.servicebestpractice;

import android.content.ComponentName;
import android.content.Intent;
import android.content.ServiceConnection;
import android.content.pm.PackageManager;
import android.os.IBinder;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.util.jar.Manifest;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

private DownloadService.DownloadBinder downloadBinder;
private ServiceConnection connection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
downloadBinder = (DownloadService.DownloadBinder) service;
}

@Override
public void onServiceDisconnected(ComponentName name) {

}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

Button startDownload = (Button) findViewById(R.id.start_download);
Button pauseDownload = (Button) findViewById(R.id.pause_download);
Button cancleDownload = (Button) findViewById(R.id.cancel_download);

startDownload.setOnClickListener(this);
pauseDownload.setOnClickListener(this);
cancleDownload.setOnClickListener(this);

Intent intent = new Intent(this, DownloadService.class);
startService(intent); // 启动服务
bindService(intent, connection, BIND_AUTO_CREATE); // 绑定服务
if (ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
!= PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(MainActivity.this, new String[]{
android.Manifest.permission.WRITE_EXTERNAL_STORAGE
}, 1);
}
}

@Override
public void onClick(View v) {
if (downloadBinder == null) {
return;
}

switch (v.getId()) {
case R.id.start_download:
String url = "https://raw.githubusercontent.com/guolindev/eclipse/master/ec;o[se=inst-win.exe";
downloadBinder.startDownload(url);
break;
case R.id.pause_download:
downloadBinder.pauseDownload();
break;
case R.id.cancel_download:
downloadBinder.cancelDownload();
break;
default:
break;
}
}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[]
grantResults) {
switch (requestCode) {
case 1:
if (grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED) {
Toast.makeText(this, "权限被拒绝无法使用", Toast.LENGTH_SHORT).show();
finish();
}
break;
default:
break;
}
}

@Override
protected void onDestroy() {
super.onDestroy();
unbindService(connection);
}
}