Android--完整版的下載下傳示例

在AndroidManifest.xml添權重限和屬性

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.servicebestpractice">

    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:requestLegacyExternalStorage="true"//添加這個屬性才能通路SD卡的Download目錄
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ServiceBestPractice">
        <service
            android:name=".DownloadService"
            android:enabled="true"
            android:exported="true">
        </service>

        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

下載下傳狀态回調接口

public interface DownloadListener {

    void onProgress(int progress);//通知目前下載下傳進度

    void onSuccess();//通知下載下傳成功事件

    void onFailed();//通知下載下傳失敗事件

    void onPause();//通知下載下傳停止事件

    void onCanceled();//通知下載下傳取消事件

}

建立DownloadTask繼承自AsyncTask實作下載下傳功能

public class DownloadTask extends AsyncTask<String, Integer, Integer> {

    //四種下載下傳狀态
    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;//最新的下載下傳進度

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

    @Override
    protected Integer doInBackground(String... params) {
        InputStream is = null;//讀資料
        RandomAccessFile saveFile = null;//寫資料
        File file = null;
        try {
            //記錄已下載下傳的檔案長度
            long downloadedLength = 0;
            //擷取到要下載下傳的URL位址
            String downloadUrl = params[0];
            //根據URL位址解析出要下載下傳的檔案名
            String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
            //然後指定将檔案下載下傳到Environment.DIRECTORY_DOWNLOADS目錄下，也就是SD卡的Download目錄下
            String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath();

            file = new File(directory + fileName);//目錄+檔案名
            //判斷Download目錄下是否存在要下載下傳的檔案
            if (file.exists()) {
                //如果存在該檔案，則讀取已下載下傳的位元組數
                downloadedLength = file.length();
            }
            //擷取待下載下傳檔案的總長度
            long contentLength = getContentLength(downloadUrl);
            //如果待下載下傳檔案長度為0，說明檔案有問題，直接傳回TYPE_FAILED
            if (contentLength == 0) {
                return TYPE_FAILED;
            }//如果已下載下傳位元組數等于待下載下傳檔案總字數，說明下載下傳完成了
            else if (contentLength == downloadedLength){
                return TYPE_SUCCESS;
            }

            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    //斷點下載下傳，告訴伺服器我們想要從哪個位元組開始下載下傳，防止重複下載下傳
                    .addHeader("RANGE", "bytes=" + downloadedLength + "-")
                    .url(downloadUrl)
                    .build();
            Response response = client.newCall(request).execute();
            if (response != null) {
                is = response.body().byteStream();
                saveFile = new RandomAccessFile(file, "rw");
                //跳過已下載下傳的位元組
                saveFile.seek(downloadedLength);

                byte[] b = new byte[1024];
                int total = 0;
                int len;
                while ((len = is.read(b)) != -1) {
                    //前兩個if用于中斷下載下傳
                    if (isCanceled) {
                        return TYPE_CANCELED;
                    } else if (isPaused) {
                        return TYPE_PAUSED;
                    } else {
                        total += len;
                        saveFile.write(b, 0 ,len);
                        //計算已下載下傳的百分比
                        int progress = (int) ((total + downloadedLength) * 100 / contentLength);
                        publishProgress(progress);//自動調用onProgressUpdate()方法
                    }
                }
            }
            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 null;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        //擷取下載下傳進度
        int progress = values[0];
        //和上一次的進度對比
        if (progress > lastProgress) {
            listener.onProgress(progress);
            lastProgress = progress;
        }
    }

    @Override
    protected void onPostExecute(Integer status) {//根據傳入的下載下傳進度進行回調
        switch (status) {
            case TYPE_SUCCESS:
                listener.onSuccess();
                break;
            case TYPE_FAILED:
                listener.onFailed();
                break;
            case TYPE_PAUSED:
                listener.onPause();
                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.body().close();
            return contentLength;
        }
        return 0;
    }

}

建立一個下載下傳的服務保證DownloadTask一直在背景運作

@RequiresApi(api = Build.VERSION_CODES.O)
public class DownloadService extends Service {

    private DownloadTask downloadTask;

    private String downloadUrl;

    private String channelId = "download";

    private DownloadListener listener = new DownloadListener() {
        @Override
        public void onProgress(int progress) {
            //建構一個用于顯示下載下傳進度的通知
            getNotificationManager().notify(1, getNotification("Downloading...", progress));
        }

        @Override
        public void onSuccess() {
            downloadTask = null;
            //下載下傳完成後将前台服務關閉
            stopForeground(true);
            //并建立一個下載下傳成功的通知
            getNotificationManager().notify(1, getNotification("Download Success", -1));
            Toast.makeText(DownloadService.this, "Download Success", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onFailed() {
            downloadTask = null;
            //下載下傳失敗時将前台服務關閉，并建立一個下載下傳失敗的通知
            stopForeground(true);
            getNotificationManager().notify(1, getNotification("Download Failed", -1));
            Toast.makeText(DownloadService.this, "Download Failed", Toast.LENGTH_SHORT).show();
        }

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

        @Override
        public void onCanceled() {
            downloadTask = null;
            //取消下載下傳後關閉前台服務
            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);
                //開啟背景下載下傳
                downloadTask.execute(downloadUrl);
                //同時讓這個下載下傳任務成為一個前台服務
                startForeground(1, getNotification("Download...", 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();
            }
            if (downloadUrl != null) {
                //取消下載下傳時需将檔案删除，并将通知關閉
                String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));
                String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getAbsolutePath();
                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();
            }
        }
    }

    public DownloadService() {
    }

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

    private Notification getNotification(String title, int progress) {
        Intent intent = new Intent(this, DownloadActivity.class);
        PendingIntent pending = PendingIntent.getActivity(this, 0, intent, 0);
        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        NotificationChannel channel = new NotificationChannel(channelId, "task", NotificationManager.IMPORTANCE_HIGH);
        manager.createNotificationChannel(channel);
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this, channelId);
        builder.setContentTitle(title);
        builder.setSmallIcon(R.mipmap.ic_launcher);
        builder.setLargeIcon(BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher));
        builder.setContentIntent(pending);
        //隻有progress大于0時才顯示進度
        if (progress > 0) {
            builder.setContentText(progress + "%");
            builder.setProgress(100, progress, false);
        }
        return builder.build();
    }
}

在活動中申請權限、開啟綁定服務等

public class DownloadActivity extends AppCompatActivity implements View.OnClickListener{

    private DownloadService.DownloadBinder downloadBinder;

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

        @Override
        public void onServiceDisconnected(ComponentName componentName) {

        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_download);
        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);
        //啟動服務
        Intent intent = new Intent(this, DownloadService.class);
        startService(intent);
        //綁定服務
        bindService(intent, connection, BIND_AUTO_CREATE);
        if (ContextCompat.checkSelfPermission(DownloadActivity.this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
                != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(DownloadActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
        }

    }

    @Override
    public void onClick(View view) {
        if (downloadBinder == null) {
            return;
        }
        switch (view.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, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode) {
            case 1:
                if (grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(this, "拒絕權限将無法使用程式", Toast.LENGTH_SHORT).show();
                    finish();
                }
                break;
            default:
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //解綁服務
        unbindService(connection);
    }

}

Android--完整版的下載下傳示例

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