implementation 'com.qw.download:download:1.0.0-alpha01'

public class MyApplication extends Application{
    @Override
    public void onCreate() {
        super.onCreate();
        //初始化下載組件(可在子線程中做)
        DownloadManager.init(this);
    }    
}

public class DownloadManager {
    private static DownloadManager mInstance;
    private final Context context;
    
    private DownloadManager(Context context) {}
    //初始化組件
    public static void init(Context context) {}
    //開啟下載
    public static void add(DownloadEntry entry) {}  
    //暫停下載
    public static void pause(DownloadEntry entry) {}    
    //暫停所有任務
    public static void pauseAll() {}
    //恢復下載
    public static void resume(DownloadEntry entry) {}   
    //恢復所有任務
    public static void recoverAll() {}
}

private DownloadWatcher watcher = new DownloadWatcher() {
    @Override
    protected void onDataChanged(DownloadEntiry entry) {
	    //這里監(jiān)聽下載的實時信息
        mDownloadInfoLabel.setText(entry.toString());
        Log.e("MainActivity", entry.toString());
    }
};

@Override
protected void onResume() {
    super.onResume();
    //注冊觀察者
    DownloadManager.addObserver(watcher);
}

@Override
protected void onPause() {
    super.onPause();
    //移除觀察者
    DownloadManager.removeObserver(watcher);
}

public class DownloadEntry implements Serializable {
    public String id;//下載的唯一標識
    public String url;//下載文件的url地址
    public boolean isSupportRange;//是否支持斷點續(xù)傳
    public long contentLength;//文件長度
    public long currentLength;//已下載文件長度
    public State state;//任務狀態(tài)
    public HashMap<Integer, Long> ranges;//存儲每個線程下載開始區(qū)塊
    public int speed;//下載速度 單位s
}

public enum State {
    IDLE,//空閑
    CONNECT,//連接中(用戶預取文件信息)
    ING,//下載中
    PAUSED,//已暫停
    CANCELLED,//已取消
    ERROR,//錯誤
    DONE,//完成
    WAIT//等待
}

public void addDownload(String id,String url){
    //id為任務的一個唯一標識，url為文件地址
    DownloadEntry entry = DownloadEntry.obtain(id,url)
    //添加一個下載任務
    DownloadManager.add(entry)    
}

public void pauseDownload(DownloadEntry entry){
    //添加一個下載任務
    DownloadManager.pause(entry)    
}

public void resumeDownload(DownloadEntry entry){
    //添加一個下載任務
    DownloadManager.resume(entry)    
}

public void pauseAll(DownloadEntry entry){
    //添加一個下載任務
    DownloadManager.resume(entry)    
}

public void recoverAll(DownloadEntry entry){
    //添加一個下載任務
    DownloadManager.recoverAll(entry)    
}

public class ApkEntry {
    public String id;//包id
    public String cover;//apk 圖標
    public String name;//apk 名稱
    public String url;//apk 下載地址
    public long length;//apk 大小

    public String id() {
        if (TextUtils.isEmpty(id)) {
            //如果服務端沒有返回唯一標記則用url的md5值作為下載唯一標識
            id = FileUtilities.getMd5FileName(url);
        }
        return id;
    }
}

public void downloadApk(ApkEntry apkEntry){
    //1、先check當前apk是否在下載
    DownloadEntry entry = DownloadManager.findById(apkEntry.id())
    if(entry==null || entry.state==State.PAUSED || entry.state==State.ERROR || entry.state==State.CANCELLED){
        //這四種情況：沒有下載任務 || 任務是暫停 || 下載失敗 || 任務已被取消
        DownloadManager.add(entry)
    }
}

public void pauseDownloadApk(ApkEntry apkEntry){
    //1、先check當前apk是否在下載任務中
    DownloadEntry entry = DownloadManager.findById(apkEntry.id())
    if(entry!=null){
        DownloadManager.pause(entry)
    }
}