Android---服务的最佳实践（完整版的下载实例）

一、定义回调接口

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

二、定义下载类

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;    }}

三、定义服务

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();    }}

四、调用

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);    }}