assistant-android/app/src/main/java/com/gh/download/cache/CacheManager.java

package com.gh.download.cache;

import com.danikula.videocache.file.FileNameGenerator;
import com.danikula.videocache.file.Md5FileNameGenerator;
import com.gh.common.AppExecutor;
import com.halo.assistant.HaloApp;
import com.shuyu.gsyvideoplayer.utils.StorageUtils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicReference;

import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class CacheManager {
    private static final AtomicReference<CacheManager> INSTANCE = new AtomicReference<>();
    private volatile ConcurrentHashMap<String, Call> downCalls;
    private OkHttpClient mClient;
    private File cacheDirectory = StorageUtils.getIndividualCacheDirectory(HaloApp.getInstance().getApplication());
    private FileNameGenerator generator = new Md5FileNameGenerator();
    private final String TEMP_POSTFIX = ".download";
//    private final int preLength = 5 * 1024 * 1024;//预加载大小


    public static CacheManager getInstance() {
        for (; ; ) {
            CacheManager current = INSTANCE.get();
            if (current != null) {
                return current;
            }
            current = new CacheManager();
            if (INSTANCE.compareAndSet(null, current)) {
                return current;
            }
        }
    }

    private CacheManager() {
        downCalls = new ConcurrentHashMap<>();
        mClient = new OkHttpClient.Builder().build();
    }

    private synchronized ConcurrentHashMap<String, Call> getDownCalls() {
        return downCalls;
    }

    public void download(String url, CacheObserver cacheObserver) {
        //当前url已下载完成则不再下载
        for (File file : getAllFile()) {
            if (file.getName().equals(generator.generate(url))) {
                return;
            }
        }
        Observable.just(url)
                .filter(s -> !getDownCalls().containsKey(s))//call的map已经有了,就证明正在下载,则这次不下载
                .flatMap(s -> Observable.just(createDownInfo(s)))
                .map(this::getRealFileName)
                .flatMap(cacheInfo -> Observable.create(new DownloadSubscribe(cacheInfo)))
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeOn(Schedulers.io())
                .subscribe(cacheObserver);

    }

    public void cancel(String url) {
        Call call = getDownCalls().get(url);
        if (call != null) {
            call.cancel();
        }
        getDownCalls().remove(url);
    }

    /**
     * 创建DownInfo
     *
     * @param url 请求网址
     * @return DownInfo
     */
    private CacheInfo createDownInfo(String url) {
        CacheInfo cacheInfo = new CacheInfo(url);
        long contentLength = getContentLength(url);//获得文件大小
        cacheInfo.setTotal(contentLength);
        String fileName = generator.generate(url) + TEMP_POSTFIX;
        cacheInfo.setFileName(fileName);
        return cacheInfo;
    }

    private CacheInfo getRealFileName(CacheInfo cacheInfo) {
        String fileName = cacheInfo.getFileName();
        long downloadLength = 0;
        if (!cacheDirectory.exists()) {
            cacheDirectory.mkdir();
        }
        File file = new File(cacheDirectory, fileName);
        if (file.exists()) {
            //找到了文件,代表已经下载过,则获取其长度
            downloadLength = file.length();
        }
        //设置改变过的文件名/大小
        cacheInfo.setProgress(downloadLength);
        cacheInfo.setFileName(file.getName());
        return cacheInfo;
    }


    private class DownloadSubscribe implements ObservableOnSubscribe<CacheInfo> {
        private CacheInfo cacheInfo;

        public DownloadSubscribe(CacheInfo cacheInfo) {
            this.cacheInfo = cacheInfo;
        }

        @Override
        public void subscribe(ObservableEmitter<CacheInfo> e) throws Exception {
            String url = cacheInfo.getUrl();
            final long[] downloadLength = {cacheInfo.getProgress()};//已经下载好的长度
            long contentLength = cacheInfo.getTotal();//文件的总长度
//            if (downloadLength[0] >= preLength) {
            if (downloadLength[0] >= contentLength) {
                e.onComplete();
                return;
            }
            e.onNext(cacheInfo);
            Request request = new Request.Builder()
//                    .addHeader("RANGE", "bytes=" + downloadLength[0] + "-" + (contentLength > preLength ? preLength : contentLength))
                    .addHeader("RANGE", "bytes=" + downloadLength[0] + "-" + contentLength)
                    .url(url)
                    .build();
            Call call = mClient.newCall(request);
            getDownCalls().put(url, call);
            call.enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {

                }

                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    File file = new File(cacheDirectory, cacheInfo.getFileName());
                    InputStream is = null;
                    FileOutputStream fileOutputStream = null;
                    try {
                        is = response.body().byteStream();
                        fileOutputStream = new FileOutputStream(file, true);
                        byte[] buffer = new byte[2048];
                        int len;
                        while (downCalls.get(url) != null && !call.isCanceled() && (len = is.read(buffer)) != -1) {
                            fileOutputStream.write(buffer, 0, len);
                            downloadLength[0] += len;
                            cacheInfo.setProgress(downloadLength[0]);
                            e.onNext(cacheInfo);
                        }
                        fileOutputStream.flush();
                        getDownCalls().remove(url);
                    } catch (Exception ex) {
                        ex.printStackTrace();
                    } finally {
                        if (is != null) {
                            is.close();
                        }
                        if (fileOutputStream != null) {
                            fileOutputStream.close();
                        }
                    }
                    if (file.length() == contentLength) {
                        file.renameTo(new File(file.getPath().substring(0, file.getPath().lastIndexOf(TEMP_POSTFIX))));
                    }
                    e.onComplete();
                }
            });

        }
    }

    /**
     * 获取下载长度
     *
     * @param downloadUrl
     * @return
     */
    public long getContentLength(String downloadUrl) {
        long contentLength = CacheInfo.TOTAL_ERROR;
        Request request = new Request.Builder()
                .url(downloadUrl)
                .build();
        Response response = null;
        try {
            response = mClient.newCall(request).execute();
            if (response.isSuccessful() && response.body() != null) {
                long length = response.body().contentLength();
                contentLength = length == 0 ? CacheInfo.TOTAL_ERROR : length;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return contentLength;
    }

    public void removeAllCall() {
        AppExecutor.getIoExecutor().execute(() -> {
            for (Map.Entry<String, Call> entry : getDownCalls().entrySet()) {
                entry.getValue().cancel();
            }
            AppExecutor.getUiExecutor().execute(() -> getDownCalls().clear());
        });
    }

    private List<File> getAllFile() {
        try {
            if (cacheDirectory.exists() && cacheDirectory.isDirectory()) {
                File[] files = cacheDirectory.listFiles();
                return Arrays.asList(files);
            }
        } catch (Exception e) {
            e.printStackTrace();
            return new ArrayList<>();
        }
        return new ArrayList<>();
    }

}