servicebesttest

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学习目的：1.完整版下载示例 （@verride表示重写方法 无则是新建方法）

添加依赖

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compile 'com.squareup.okhttp3:okhttp:3.4.1'

定义一个回调接口（对下载过程中的各种状态进行监听和回调）
DownloadListenter

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public interface DownloadListener {

    void onProgress(int progress);

    void onSuccess();

    void onFailed();

    void onPaused();

    void onCanceled();

}

AsynsTask实现下载功能

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//三个参数 传入数据 进度显示数据单位 反馈执行结果数据类型
public 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;
    }
    //下载逻辑
    @Override
    protected Integer doInBackground(String... params) {
        InputStream is = null;
        RandomAccessFile savedFile = null;
        File file = null;
        try {
            long downloadedLength = 0; // 记录已下载的文件长度
            String downloadUrl = params[0];
            String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
            String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
            file = new File(directory + fileName);
            if (file.exists()) {
                downloadedLength = file.length();
            }
            long contentLength = getContentLength(downloadUrl);
            if (contentLength == 0) {
                return TYPE_FAILED;
            } else if (contentLength == downloadedLength) {
                // 已下载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()
                    // 断点下载，指定从哪个字节开始下载
                    .addHeader("RANGE", "bytes=" + downloadedLength + "-")
                    .url(downloadUrl)
                    .build();
            Response response = client.newCall(request).execute();
            if (response != null) {
                is = response.body().byteStream();
                savedFile = new RandomAccessFile(file, "rw");
                savedFile.seek(downloadedLength); // 跳过已下载的字节
                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;
                        savedFile.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 (savedFile != null) {
                    savedFile.close();
                }
                if (isCanceled && file != null) {
                    file.delete();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return TYPE_FAILED;
    }
    //界面显示当前下载进度
    @Override
    protected void onProgressUpdate(Integer... values) {
        int progress = values[0];
        if (progress > lastProgress) {
            listener.onProgress(progress);
            lastProgress = progress;
        }
    }
    //通知最终下载结果
    @Override
    protected void onPostExecute(Integer status) {
        switch (status) {
            case TYPE_SUCCESS:
                listener.onSuccess();
                break;
            case TYPE_FAILED:
                listener.onFailed();
                break;
            case TYPE_PAUSED:
                listener.onPaused();
                break;
            case TYPE_CANCELED:
                listener.onCanceled();
            default:
                break;
        }
    }

    public void pauseDownload() {
        isPaused = true;
    }


    public void cancelDownload() {
        isCanceled = true;
    }
    //获取下载文件总长度
    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;
    }

创建下载服务DownloadService（重写5个方法） DownloadBinder内部类（重写3个方法）两个类

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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("Downloading...", progress));
        }

        @Override
        public void onSuccess() {
            downloadTask = null;
            // 下载成功时将前台服务通知关闭，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, "Download Success", Toast.LENGTH_SHORT).show();
        }

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

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

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

    };

    private DownloadBinder mBinder = new DownloadBinder();

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

    class DownloadBinder extends Binder {

        public void startDownload(String url) {
            if (downloadTask == null) {
                downloadUrl = url;
                downloadTask = new DownloadTask(listener);
                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) {
                    // 取消下载时需将文件删除，并将通知关闭
                    String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
                    String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();
                    File file = new File(directory + fileName);
                    if (file.exists()) {
                        file.delete();
                    }
                    getNotificationManager().cancel(1);
                    stopForeground(true);
                    Toast.makeText(DownloadService.this, "Canceled", 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) {
            // 当progress大于或等于0时才需显示下载进度
            builder.setContentText(progress + "%");
            builder.setProgress(100, progress, false);
        }
        return builder.build();
    }

}

MainActivity

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public class MainActivity extends AppCompatActivity implements View.OnClickListener{

    private DownloadService.DownloadBinder downloadBinder;

    private ServiceConnection connection = new ServiceConnection() {

        @Override
        public void onServiceDisconnected(ComponentName name) {
        }

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

    };

    @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 cancelDownload = (Button) findViewById(R.id.cancel_download);
        startDownload.setOnClickListener(this);
        pauseDownload.setOnClickListener(this);
        cancelDownload.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, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this, new String[]{ 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/eclipse-inst-win64.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, String[] permissions, int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(this, "拒绝权限将无法使用程序", Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;
            default:
        }
    }

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

}

权限声明


<service
    android:name=".DownloadService"
    android:enabled="true"
    android:exported="true" />

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