Android系统自带更新DownloadManager用法

效果图如下：

added in API level 9.

包路径: java.lang.Object
↳	android.app.DownloadManager

下载管理器是一个处理长时间运行的HTTP下载的系统服务，通过此API请求下载的应用程序应为ACTION_NOTIFICATION_CLICKED注册一个广播接收器，以便在用户单击通知中的正在运行的下载或从下载UI中正确处理。

此类的实例必须使用Context.getSystemService（Class），参数为DownloadManager.class或Context.getSystemService（String），参数为Context.DOWNLOAD_SERVICE。

注意：使用时需要添加下面两个权限

a、网络访问权限 

b、外部存储写权限

本例程主要实现的几个步骤：

1、添加权限和配置广播接收器（用于接收点击和下载完成后发出的系统广播）

2、广播接收器中主要实现点击事件和下载完成事件的响应；即未完成时点击跳转到下载查看页面，完成后自动调用安装应用。

public class DownloadReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {

        if (intent.getAction().equals(DownloadManager.ACTION_DOWNLOAD_COMPLETE)) {
            long id = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            installApk(context, id);
        } else if (intent.getAction().equals(DownloadManager.ACTION_NOTIFICATION_CLICKED)) {
            // DownloadManager manager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
            //获取所有下载任务Ids组
            //long[] ids = intent.getLongArrayExtra(DownloadManager.EXTRA_NOTIFICATION_CLICK_DOWNLOAD_IDS);
            ////点击通知栏取消所有下载
            //manager.remove(ids);
            //Toast.makeText(context, "下载任务已取消", Toast.LENGTH_SHORT).show();
            //处理 如果还未完成下载，用户点击Notification ，跳转到下载中心
            Intent viewDownloadIntent = new Intent(DownloadManager.ACTION_VIEW_DOWNLOADS);
            viewDownloadIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(viewDownloadIntent);
        }
    }

    private static void installApk(Context context, long downloadApkId) {
        DownloadManager dManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
        Intent install = new Intent(Intent.ACTION_VIEW);
        Uri downloadFileUri = dManager.getUriForDownloadedFile(downloadApkId);
        if (downloadFileUri != null) {
            Log.d("DownloadManager", downloadFileUri.toString());
            install.setDataAndType(downloadFileUri, "application/vnd.android.package-archive");
            install.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(install);
        } else {
            Log.e("DownloadManager", "download error");
        }
    }

3、Activity中调用更新操作

public class MainActivity extends AppCompatActivity {

    private String url = "https://downpack.baidu.com/appsearch_AndroidPhone_v8.0.3(1.0.65.172)_1012271b.apk";
    private String title = "测试应用.apk";
    private String desc = "下载完成后，点击安装";

    private Button btn;
    private DownloadManagerUtil downloadManagerUtil;

    long downloadId = 0;

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

    private void findViews() {
        btn = findViewById(R.id.btn);
    }

    private void initView() {
        downloadManagerUtil = new DownloadManagerUtil(this);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (downloadId != 0) {
                    adownloadManagerUtil.clearCurrentTask(downloadId);
                }
                downloadId = downloadManagerUtil.download(url, title, desc);
            }
        });
    }

4、下载工具类DownloadManagerUtil，主要完成DownloadManager的参数设置及启动下载任务

public class DownloadManagerUtil {
    private Context mContext;

    public DownloadManagerUtil(Context context) {
        mContext = context;
    }

    public long download(String url, String title, String desc) {
        Uri uri = Uri.parse(url);
        DownloadManager.Request req = new DownloadManager.Request(uri);
        //设置WIFI下进行更新
        req.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
        //下载中和下载完后都显示通知栏
        req.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
        //使用系统默认的下载路径 此处为应用内 /android/data/packages ,所以兼容7.0
        req.setDestinationInExternalFilesDir(mContext, Environment.DIRECTORY_DOWNLOADS, title);
        //通知栏标题
        req.setTitle(title);
        //通知栏描述信息
        req.setDescription(desc);
        //设置类型为.apk
        req.setMimeType("application/vnd.android.package-archive");
        //获取下载任务ID
        DownloadManager dm = (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);
        return dm.enqueue(req);
    }

    /**
     * 下载前先移除前一个任务，防止重复下载
     * @param downloadId
     */
    public void clearCurrentTask(long downloadId) {
        DownloadManager dm = (DownloadManager) mContext.getSystemService(Context.DOWNLOAD_SERVICE);
        try {
            dm.remove(downloadId);
        } catch (IllegalArgumentException ex) {
            ex.printStackTrace();
        }
    }