Android——断点续传（下载）

DownloadUtils

public class DownloadUtils {
    private static final String TAG = "DownloadUtils";
    private static volatile DownloadUtils instance;
    private File file;
    private String filePath;

    private OkHttpClient client;
    private File downloadFile;
    private long startPosition;
    private Call call;

    private DownloadUtils() {
        client = new OkHttpClient();
    }

    private DownloadListener listener;

    public void setListener(DownloadListener listener) {
        this.listener = listener;
    }

    /**
     * 初始化下载父路径
     *
     * @param path
     */
    public void initDownload(String path) {
        file = new File(path);
        if (!file.getParentFile().exists()) {
            file.getParentFile().mkdir();
        }
        if (!file.exists()) {
            file.mkdir();
        }
        filePath = file.getAbsolutePath();
        Log.i(TAG, "initDownload: " + filePath);
    }

    public static DownloadUtils getInstance() {
        if (null == instance) {
            synchronized (DownloadUtils.class) {
                if (instance == null) {
                    instance = new DownloadUtils();
                }
            }
        }
        return instance;
    }

    public void startDownload(String url) {
        if (TextUtils.isEmpty(url)) {
            return;
        }


        if (url.contains(".")) {
            String typeName = url.substring(url.lastIndexOf(".") + 1);
            if (url.contains("/")) {
                String name = url.substring(url.lastIndexOf("/") + 1, url.lastIndexOf("."));
                String fn = name + "." + typeName;

                downloadFile = new File(file, fn);
            }
        }
        startPosition = 0;
        if (downloadFile.exists()) {
            startPosition = downloadFile.length();
        }

        Request request = new Request.Builder()
                .addHeader("RANGE", "bytes=" + startPosition + "-")
                .url(url)
                .build();

        call = client.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                listener.startDownload();
                ResponseBody body = response.body();
                long totalLength = body.contentLength() + startPosition;
                Log.i(TAG, "totalLength: " + totalLength + "----");
                InputStream is = body.byteStream();
                byte[] buf = new byte[2048];
                int length = 0;
                long totalNum = startPosition;
                RandomAccessFile raf = new RandomAccessFile(downloadFile, "rw");
                raf.seek(totalNum);
                while ((length = is.read(buf, 0, buf.length)) != -1) {
                    raf.write(buf, 0, length);
                    totalNum += length;
                    listener.downloadProgress(totalNum * 100 / totalLength);

                }
                Log.i(TAG, "totalNum==" + totalNum + "---");
                listener.finishDownload(downloadFile.getAbsolutePath());
                body.close();
            }
        });


    }

    public void pauseDownload() {
        listener.pauseDownload();
        if (call != null && call.isExecuted()) {
            call.cancel();
        }
    }
}

DownloadListener

public interface DownloadListener {
    void startDownload();

    void pauseDownload();

    void finishDownload(String path);

    void downloadProgress(long progress);
}

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private TextView tv_pro;
    private ProgressBar progressBar;
    private Button btn_start;
    private Button btn_pause;
    private String downloadUrl = "http://acj3.pc6.com/pc6_soure/2017-12/com.yek.android.kfc.activitys_3820.apk";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_pro = findViewById(R.id.tv_pro);
        progressBar = findViewById(R.id.progressbar);
        btn_start = findViewById(R.id.start);
        btn_pause = findViewById(R.id.pause);
        btn_start.setOnClickListener(this);
        btn_pause.setOnClickListener(this);
        if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            File storageDirectory = Environment.getExternalStorageDirectory();
            String absolutePath = storageDirectory.getAbsolutePath();
            final String path = absolutePath + "/Download/";
            Log.i("zzz", "下载路径 " + path);
            DownloadUtils.getInstance().initDownload(path);
            DownloadUtils.getInstance().setListener(new DownloadListener() {
                @Override
                public void startDownload() {

                }

                @Override
                public void pauseDownload() {

                }

                @Override
                public void finishDownload(String path) {
                    installApk(new File(path));
                }


                @Override
                public void downloadProgress(final long progress) {
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            tv_pro.setText((int)progress + "%");
                            progressBar.setProgress((int) progress);
                        }
                    });
                }
            });
        }
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.start:
                DownloadUtils.getInstance().startDownload(downloadUrl);
                break;
            case R.id.pause:
                DownloadUtils.getInstance().pauseDownload();
                break;
        }
    }
    /**
     * 安装apk
     *
     * @param file
     */
    private void installApk(File file) {
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_VIEW);
        intent.addCategory("android.intent.category.DEFAULT");
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
        startActivity(intent);
        android.os.Process.killProcess(android.os.Process.myPid());
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.bwie.com.wangruixin20171227.MainActivity">

    <TextView
        android:id="@+id/tv_pro"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:text="0%" />

    <ProgressBar
        android:id="@+id/progressbar"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/tv_pro"
        android:layout_marginTop="12dp"
        android:max="100"
        android:progress="0" />

    <Button
        android:id="@+id/start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/progressbar"
        android:layout_marginTop="15dp"
        android:text="开始下载" />

    <Button
        android:id="@+id/pause"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/start"
        android:layout_marginTop="26dp"
        android:text="暂停下载" />


</RelativeLayout>