DownloadManager系统自带下载实现apk后台下载功能

DownloadManager是android2.3以后，系统下载的方法，是处理长期运行的HTTP下载的系统服务。客户端可以请求的URI被下载到一个特定的目标文件。客户端将会在后台与http交互进行下载，或者在下载失败，或者连接改变，重新启动系统后重新下载。还可以进入系统的下载管理界面查看进度。DownloadManger有两个内部类，Request 和Query。Request类可设置下载的一些属性。Query类可查询当前下载的进度，下载地址，文件存放目录等数据。

DownloadManager

1、所需权限

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

 2、获得对象，开始下载

DownloadManager downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(apkUrl));
long id = downloadManager.enqueue(request);
//每下载的一个文件对应一个id，通过此id可以查询数据。

 3、取消下载

downloadManager.remove(REFERENCE_1, REFERENCE_2, REFERENCE_3);  

 该方法返回成功取消的下载的个数，如果一个下载被取消了，所有相关联的文件，部分下载的文件和完全下载的文件都会被删除.

---

Request类

1.指定下载位置，及文件名称

 　　　　 /**
         * 方法1: 
         * 目录: Android -> data -> com.app -> files -> Download -> dxtj.apk
         * 这个文件是你的应用所专用的,软件卸载后，下载的文件将随着卸载全部被删除
         */
　　request.setDestinationInExternalFilesDir( this , Environment.DIRECTORY_DOWNLOADS ,  "dxtj.apk" );  

        /**
         * 方法2:
         * 下载的文件存放地址  SD卡 download文件夹，dxtj.apk
         * 软件卸载后，下载的文件会保留
         */
        //在SD卡上创建一个文件夹
    request.setDestinationInExternalPublicDir(  "/epmyg/"  , "dxtj.apk" ) ;  


        /**
         * 方法3:
         * 如果下载的文件希望被其他的应用共享
         * 特别是那些你下载下来希望被Media Scanner扫描到的文件（比如音乐文件）
         */
     request.setDestinationInExternalPublicDir( Environment.DIRECTORY_MUSIC,  "告白气球.mp3" );  

        /**
         * 方法4
         * 文件将存放在外部存储的确实download文件内，如果无此文件夹，创建之，如果有，下面将返回false。
         * 系统有个下载文件夹，比如小米手机系统下载文件夹  SD卡--> Download文件夹
         */
        //创建目录
     Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).mkdir() ; 

        //设置文件存放路径
     request.setDestinationInExternalPublicDir(  Environment.DIRECTORY_DOWNLOADS  , "dxtj.apk" ) ;
    }

 2、指定下载的网络类型

//指定在WIFI状态下，执行下载操作。
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
//指定在MOBILE状态下，执行下载操作
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE);
//是否允许漫游状态下，执行下载操作
request.setAllowedOverRoaming(boolean);
//是否允许“计量式的网络连接”执行下载操作
request.setAllowedOverMetered(boolean); //默认是允许的。

 3、定制Notification样式

//设置Notification的标题和描述
request.setTitle("标题");  
request.setDescription("描述"); 
//设置Notification的显示，和隐藏。
request.setNotificationVisibility(visibility);

 VISIBILTY_HIDDEN: Notification:将不会显示，如果设置该属性的话，必须要添加权限

Android.permission.DOWNLOAD_WITHOUT_NOTIFICATION. 

VISIBILITY_VISIBLE： Notification显示，但是只是在下载任务执行的过程中显示，下载完成自动消失。（默认值）
VISIBILITY_VISIBLE_NOTIFY_COMPLETED : Notification显示，下载进行时，和完成之后都会显示。
VISIBILITY_VISIBLE_NOTIFY_ONLY_COMPLETION ：只有当任务完成时，Notification才会显示。
对Notification的设定方法相对较少。

4、设置下载文件类型：

request.setMimeType("application/vnd.android.package-archive");

这是安卓.apk文件的类型。有些机型必须设置此方法，才能在下载完成后，点击通知栏的Notification时，才能正确的打开安装界面。不然会弹出一个Toast（can not open file）.其他文件类型的MimeType ,去百度一下 。

5、添加请求下载的网络链接的http头，比如User-Agent，gzip压缩等：

request.addRequestHeader(String header, String value)；

---

Query 类

我们的需求，可能不只是在Notification 中显示进度就好了，也许，在app中也需要获取实时下载进度。所以Query类就是提供查询的一些方法。
但API中就只有两个方法，原来，他把数据保存在数据库中去了。我们需要获得一个Cursor 结果集，通过结果集获得我们想要的数据。

DownloadManager.Query query = new DownloadManager.Query();
 Cursor cursor = downloadManager.query(query.setFilterById(id));
                if (cursor != null && cursor.moveToFirst()) {
                    //下载的文件到本地的目录
                    String address = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
                    //已经下载的字节数
                    int bytes_downloaded = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                    //总需下载的字节数
                    int bytes_total = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
                    //Notification 标题
                    String title =cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_TITLE));
                    //描述
                    String description =cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_DESCRIPTION));
                    //下载对应id
                    long id =cursor.getLong(cursor.getColumnIndex(DownloadManager.COLUMN_ID));
                    //下载文件名称
                    String filename =cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME));
                    //下载文件的URL链接
                    String url =cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_URI));
}

这只能获取一次，数据库中的信息。我们可以使用Timer类，每隔一段时间去查询数据库即可。也可以使用ContentProvider去访问。

不足之处：

1、我发现，在下载的时候，发送Notification时 是没有声音的。也没有设置声音的方法。不过这影响不大。主要的功能实现就好。
2、因为这是系统的类，每个系统的Notification界面是不一样的。这就是每个rom厂家的自定义了。小米和魅族的就大不一样。魅族Notification上有一个下载暂停的按钮，而小米没有。所以导致Notification是不能统一的。其实，暂停的话用户可以点击notification,进入到下载管理界面，就有暂停按钮了。

---

实现代码

import android.app.DownloadManager;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;

import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private TextView                down;
    private TextView                progress;
    private TextView                file_name;
    private ProgressBar             pb_update;
    private DownloadManager         downloadManager;
    private DownloadManager.Request request;
    public static String downloadUrl = "http://ucdl.25pp.com/fs08/2017/01/20/2/2_87a290b5f041a8b512f0bc51595f839a.apk";
    Timer     timer;
    long      id;
    TimerTask task;
    Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            Bundle bundle = msg.getData();
            int pro = bundle.getInt("pro");
            String name = bundle.getString("name");
            pb_update.setProgress(pro);
            progress.setText(String.valueOf(pro) + "%");
            file_name.setText(name);
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        down = (TextView) findViewById(R.id.down);
        progress = (TextView) findViewById(R.id.progress);
        file_name = (TextView) findViewById(R.id.file_name);
        pb_update = (ProgressBar) findViewById(R.id.pb_update);
        down.setOnClickListener(this);
        downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
        request = new DownloadManager.Request(Uri.parse(downloadUrl));

        request.setTitle("大象投教");
        request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
        request.setAllowedOverRoaming(false);
        request.setMimeType("application/vnd.android.package-archive");
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
        //创建目录
        Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).mkdir();

        //设置文件存放路径
        request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "app-release.apk");
        pb_update.setMax(100);
        final DownloadManager.Query query = new DownloadManager.Query();
        timer = new Timer();
        task = new TimerTask() {
            @Override
            public void run() {
                Cursor cursor = downloadManager.query(query.setFilterById(id));
                if (cursor != null && cursor.moveToFirst()) {
                    if (cursor.getInt(
                            cursor.getColumnIndex(DownloadManager.COLUMN_STATUS)) == DownloadManager.STATUS_SUCCESSFUL) {
                        pb_update.setProgress(100);
                        install(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + "/app-release.apk");
                        task.cancel();
                    }
                    String title = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_TITLE));
                    String address = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
                    int bytes_downloaded = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                    int bytes_total = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
                    int pro = (bytes_downloaded * 100) / bytes_total;
                    Message msg = Message.obtain();
                    Bundle bundle = new Bundle();
                    bundle.putInt("pro", pro);
                    bundle.putString("name", title);
                    msg.setData(bundle);
                    handler.sendMessage(msg);
                }
                cursor.close();
            }
        };
        timer.schedule(task, 0, 1000);
    }

    @Override
    public void onClick(View v) {
        id = downloadManager.enqueue(request);
        task.run();
        down.setClickable(false);
        down.setBackgroundResource(R.drawable.background);

    }

    private void install(String path) {
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(Uri.parse("file://" + path), "application/vnd.android.package-archive");
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);//4.0以上系统弹出安装成功打开界面
        startActivity(intent);
    }
}

 progressbar_color.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:id="@android:id/background">
        <shape>
            <corners android:radius="10dip"/>
            <gradient
                android:angle="0"
                android:centerColor="#e4e4e4"
                android:centerY="0.75"
                android:endColor="#e4e4e4"
                android:startColor="#e4e4e4"/>
        </shape>
    </item>
    <item android:id="@android:id/secondaryProgress">
        <clip>
            <shape>
                <corners android:radius="10dip"/>
                <gradient
                    android:angle="0"
                    android:centerColor="#e4e4e4"
                    android:centerY="0.75"
                    android:endColor="#e4e4e4"
                    android:startColor="#e4e4e4"/>
            </shape>
        </clip>
    </item>
    <item android:id="@android:id/progress">
        <clip>
            <shape>
                <corners android:radius="10dip"/>
                <gradient
                    android:angle="0"
                    android:endColor="@color/red"
                    android:startColor="@color/red"/>
            </shape>
        </clip>
    </item>
</layer-list>

 效果:

---

本文学习来源地址:http://blog.csdn.net/u012209506/article/details/56012744

---

AKP更新案例学习代码:

import android.app.DownloadManager;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AlertDialog;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import com.loaderman.group09.redboy11.R;
import com.loaderman.group09.redboy11.utils.PrefUtils;
import com.zhy.http.okhttp.OkHttpUtils;
import com.zhy.http.okhttp.callback.FileCallBack;
import com.zhy.http.okhttp.callback.StringCallback;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.File;

import okhttp3.Call;

import static com.loaderman.global.GlobalConstants.URL_PREFIX;

/*
 * @author: Ji.C.F
 * Desc   :  关于
 * date   : 2016/12/23 19:29
*/
public class AboutActivity extends BaseActivity {

    private TextView tvVersion;
    private Button   btnUpdateApk;
    private String   mDownloadUrl;
    private String   versionMessage;
    private boolean  isUpdateVersion;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_about);
        ivLeft.setVisibility(View.VISIBLE);
        ivCenter.setVisibility(View.GONE);
        tvCenter.setText("关于");
        tvCenter.setVisibility(View.VISIBLE);
        btnUpdateApk = (Button) findViewById(R.id.btn_update_apk);
        tvVersion = (TextView) findViewById(R.id.tv_version);
        tvVersion.setText(getVersionName());
        isUpdateVersion = PrefUtils.getBoolean(AboutActivity.this, "isUpdateVersion", false);
        if (!isUpdateVersion) {
            btnUpdateApk.setText("当前已经是最新版本");
        } else {
            //Toast.makeText(AboutActivity.this, "有新版本可以更新了", Toast.LENGTH_SHORT).show();
            btnUpdateApk.setText("有新版本可以更新了");
        }
        btnUpdateApk.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (!isUpdateVersion) {
                    Toast.makeText(AboutActivity.this, "当前已经是最新版本了", Toast.LENGTH_SHORT).show();
                } else {
                    updateVersion();
                }
            }
        });
    }

    private void updateVersion() {
        OkHttpUtils.get().addParams("ver", getVersionCode() + "").url(URL_PREFIX + "index/index_checkVersion.html").build().execute(new StringCallback() {
            @Override
            public void onError(Call call, Exception e, int i) {
                e.printStackTrace();
                Toast.makeText(AboutActivity.this, "网络异常", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onResponse(String result, int i) {
                try {
                    JSONObject json = new JSONObject(result);
                    String version = json.optString("version");
                    JSONObject json2 = new JSONObject(version);
                    String versionCode = json2.optString("versionCode");
                    versionMessage = json2.optString("versionMessage");
                    System.out.println(versionMessage);
                    mDownloadUrl = json2.optString("downloadUrl");
                    System.out.println(mDownloadUrl);
                    showUpdateDialog(versionCode);
                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        });

    }

    private void showUpdateDialog(String mVersionName) {
        System.out.println("showUpdateDialog");
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("发现新版本:" + mVersionName);
        builder.setMessage(versionMessage);
        builder.setPositiveButton("前台更新", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                download();
            }
        });
        builder.setNegativeButton("后台更新", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                download(URL_PREFIX + mDownloadUrl);
            }
        });
        AlertDialog dialog = builder.create();
        dialog.show();
    }
    private void download(String downloadUrl) {
        DownloadManager manager = (DownloadManager) getApplicationContext()
                .getSystemService(Context.DOWNLOAD_SERVICE);
        DownloadManager.Request request = new DownloadManager.Request(
                Uri.parse(downloadUrl));
        request.setTitle("红孩子下载中...");
        request.setDescription("让你的购物从此与众不同!!!");
        request.allowScanningByMediaScanner();// 设置可以被扫描到
        request.setVisibleInDownloadsUi(true);// 设置下载可见
        String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));// 解析fileName
        request.setDestinationInExternalPublicDir(
                Environment.DIRECTORY_DOWNLOADS, fileName);// 设置下载位置，sdcard/Download/fileName
        long refernece = manager.enqueue(request);// 加入下载并取得下载ID
        SharedPreferences sPreferences = getApplicationContext()
                .getSharedPreferences("downloadplato", 0);
        sPreferences.edit().putLong("plato", refernece).commit();//保存此次下载ID
    }
    private void download() {
        //设置进度条
        final ProgressDialog progressDialog = new ProgressDialog(this);
        //水平显示
        progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        progressDialog.setTitle("拼命下载中");
        //显示
        progressDialog.show();
        OkHttpUtils.get().url(URL_PREFIX + mDownloadUrl).build().execute(new FileCallBack(Environment.getExternalStorageDirectory().getAbsolutePath(), "RedBoy.apk") {
            @Override
            public void onError(Call call, Exception e, int i) {
                progressDialog.dismiss();
            }

            @Override
            public void inProgress(float progress, long total, int id) {
                super.inProgress(progress, total, id);
                progressDialog.setProgress((int) (progress * 100));
            }

            @Override
            public void onResponse(File file, int i) {
                progressDialog.dismiss();
                installAPK(file);
            }
        });
    }

    private void installAPK(File file) {
        Intent intent = new Intent();
        intent.setAction(Intent.ACTION_VIEW);
        intent.addCategory(Intent.CATEGORY_DEFAULT);
        intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
        startActivityForResult(intent, 0);
    }


    private String getVersionName() {
        PackageManager pm = getPackageManager();
        try {
            PackageInfo info = pm.getPackageInfo(getPackageName(), 0);
            String versionName = info.versionName;
            return versionName;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return "";
    }

    private int getVersionCode() {
        PackageManager pm = getPackageManager();
        try {
            PackageInfo info = pm.getPackageInfo(getPackageName(), 0);
            int versionCode = info.versionCode;
            return versionCode;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return -1;
    }

}