Android下载示例

菜鸟一只，写点文章，保证自己学到的东西不会忘记

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添加OkHttp依赖

dependencies {    compile fileTree(dir: 'libs', include: ['*.jar'])    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {        exclude group: 'com.android.support', module: 'support-annotations'    })    compile 'com.android.support:appcompat-v7:25.3.1'    compile 'com.android.support.constraint:constraint-layout:1.0.2'    testCompile 'junit:junit:4.12'    compile 'com.squareup.okhttp3:okhttp:3.4.1'}

网络功能采用OkHttp来实现

定义回调接口

public interface DownloadListener {    void onProgress(int progress);    void onSuccess();    void onFailed();    void onPause();    void onCanceled();}

一共定义5个回调方法，onProgress()方法用于通知当前的下载进度，onSuccess()方法用于通知下载完成事件，onFailed()用于通知下载失败事件，onPause()用于通知下载暂停事件，onCanceled()用于通知下载取消事件。

编写下载功能

通过AsyncTask来实现下载功能

package com.slience.downloaddemo.downloadtask;import android.os.AsyncTask;import android.os.Environment;import android.util.Log;import com.slience.downloaddemo.downloadinterface.DownloadListener;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.io.RandomAccessFile;import okhttp3.OkHttpClient;import okhttp3.Request;import okhttp3.Response;/** * Created by Slience on 2017/10/20. */public class DownloadTask extends AsyncTask<String , Integer , Integer> {    public static final int TYPE_SUCCESS = 0;    public static final int TYPE_FAILED = 1;    public static final int TYPE_PAUSED = 2;    public static final int TYPE_CANCELED = 3;    public static final String TAG = "DownloadTask";    private DownloadListener listener;    private boolean isCanceled = false;    private boolean isPaused = false;    private int lastProgress;    public DownloadTask(DownloadListener listener){        this.listener = listener;    }    @Override    protected Integer doInBackground(String... params) {        InputStream is = null;        RandomAccessFile savedFile = null;        File file = null;        try {            long downloadedLength = 0;          //记录已下载的文件长度            String downloadUrl = params[0];            Log.i(TAG , "DownloadUrl = " + downloadUrl);            String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));            Log.i(TAG , "FileName = " + fileName);            String dirctory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();            Log.i(TAG , "Dirctory = " + dirctory);            file = new File(dirctory + fileName);            if(file.exists()){                downloadedLength = file.length();            }            long contentLength = getContentLength(downloadUrl);            Log.i(TAG , "ContentLength = " + contentLength);            if(contentLength == 0){                return TYPE_FAILED;            }else if(contentLength == downloadedLength){                return TYPE_SUCCESS;            }            OkHttpClient client = new OkHttpClient();            Request request = new Request.Builder()                    .addHeader("RANGE" , "bytes = " + downloadedLength + "-")                    .url(downloadUrl)                    .build();            Response response = client.newCall(request).execute();            if(response != null){                is = response.body().byteStream();                savedFile = new RandomAccessFile(file , "rw");                savedFile.seek(downloadedLength);                byte[] b = new byte[1024];                int total = 0;                int len;                while((len = is.read(b)) != -1){                    if(isCanceled){                        return TYPE_CANCELED;                    }else if(isPaused){                        return TYPE_PAUSED;                    }else{                        total += len;                        savedFile.write(b , 0 , len);                        //计算下载百分比                        int progress = (int)((total + downloadedLength) * 100 / contentLength);                        publishProgress(progress);                    }                }                response.body().close();                return TYPE_SUCCESS;            }        }catch (Exception e){            e.printStackTrace();        }finally {            try {                if(is != null){                    is.close();                }                if(savedFile != null){                    savedFile.close();                }                if(isCanceled && file != null){                    file.delete();                }            }catch (Exception e){                e.printStackTrace();            }        }        return TYPE_FAILED;    }    @Override    protected void onProgressUpdate(Integer... values) {        int progress = values[0];        if(progress > lastProgress){            listener.onProgress(progress);            lastProgress = progress;        }    }    @Override    protected void onPostExecute(Integer integer) {        switch (integer){            case TYPE_SUCCESS:                listener.onSuccess();                break;            case TYPE_CANCELED:                listener.onCanceled();                break;            case TYPE_PAUSED:                listener.onPause();                break;            case TYPE_FAILED:                listener.onFailed();                break;            default:                break;        }    }    public void pauseDownload(){        isPaused = true;    }    public void cancelDownload(){        isCanceled = true;    }    private long getContentLength(String downloadUrl) throws IOException{        OkHttpClient client = new OkHttpClient();        Request request = new Request.Builder()                .url(downloadUrl)                .build();        Response response = client.newCall(request).execute();        if(response != null && response.isSuccessful()){            long contentLength = response.body().contentLength();            response.close();            Log.i(TAG , "response is not null");            return contentLength;        }else{            Log.i(TAG , "response is null");        }        return 0;    }}

AsyncTask三个泛型参数，第一个String类型参数表示在执行AsyncTask的时候需要传入一个字符串参数给后台任务，第二个int类型参数表示用整数来作为进度显示单位，第三个int类型参数用来反馈执行结果

创建下载服务

package com.slience.downloaddemo.downloadservice;import android.app.Notification;import android.app.NotificationManager;import android.app.PendingIntent;import android.app.Service;import android.content.Intent;import android.graphics.BitmapFactory;import android.os.Binder;import android.os.Environment;import android.os.IBinder;import android.support.v4.app.NotificationCompat;import android.widget.Toast;import com.slience.downloaddemo.MainActivity;import com.slience.downloaddemo.R;import com.slience.downloaddemo.downloadinterface.DownloadListener;import com.slience.downloaddemo.downloadtask.DownloadTask;import java.io.File;public class DownloadService extends Service {    private DownloadTask downloadTask;    private String downloadUrl;    private DownloadListener listener = new DownloadListener() {        @Override        public void onProgress(int progress) {            getNotificationManager().notify(1,getNotification("Downloading..." , progress));        }        @Override        public void onSuccess() {            downloadTask = null;            stopForeground(true);            getNotificationManager().notify(1,getNotification("Download Success" , -1));            Toast.makeText(DownloadService.this , "Download Success" , Toast.LENGTH_SHORT).show();        }        @Override        public void onFailed() {            downloadTask = null;            //下载失败将前台服务关闭，并创建一个下载失败的通知            stopForeground(true);            getNotificationManager().notify(1,getNotification("Download Failed" , -1));            Toast.makeText(DownloadService.this , "Download Failed" , Toast.LENGTH_SHORT).show();        }        @Override        public void onPause() {            downloadTask = null;            Toast.makeText(DownloadService.this , "Paused" , Toast.LENGTH_SHORT).show();        }        @Override        public void onCanceled() {            downloadTask = null;            stopForeground(true);            Toast.makeText(DownloadService.this , "Canceled" , Toast.LENGTH_SHORT).show();        }    };    public DownloadService() {    }    private DownloadBinder mBinder = new DownloadBinder();    @Override    public IBinder onBind(Intent intent) {        return mBinder;    }    public class DownloadBinder extends Binder{        public void startDownload(String url){            if(downloadTask == null){                downloadUrl = url;                downloadTask = new DownloadTask(listener);                downloadTask.execute(downloadUrl);                startForeground(1 , getNotification("Downloading..." , 0));                Toast.makeText(DownloadService.this , "Downloading" , Toast.LENGTH_SHORT).show();            }        }        public void pauseDownload(){            if(downloadTask != null){                downloadTask.pauseDownload();            }        }        public void cancelDownload(){            if(downloadTask != null){                downloadTask.cancelDownload();            }else{                if(downloadUrl != null){                    String fileName = downloadUrl.substring(downloadUrl.lastIndexOf("/"));                    String directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();                    File file = new File(directory + fileName);                    if(file.exists()){                        file.delete();                    }                    getNotificationManager().cancel(1);                    stopForeground(true);                    Toast.makeText(DownloadService.this , "Canceled" , Toast.LENGTH_SHORT).show();                }            }        }    }    private NotificationManager getNotificationManager(){        return (NotificationManager)getSystemService(NOTIFICATION_SERVICE);    }    private Notification getNotification(String title , int progress){        Intent intent = new Intent(this , MainActivity.class);        PendingIntent pi = PendingIntent.getActivity(this , 0 , intent , 0);        NotificationCompat.Builder builder = new NotificationCompat.Builder(this);        builder.setSmallIcon(R.mipmap.ic_launcher);        builder.setLargeIcon(BitmapFactory.decodeResource(getResources() , R.mipmap.ic_launcher));        builder.setContentIntent(pi);        builder.setContentTitle(title);        if(progress > 0){            builder.setContentText(progress + "%");            builder.setProgress(100 , progress , false);        }        return builder.build();    }}

getNotificationManager()方法用来调用NotificationManager的notify()方法，触发通知不停的更新当前的下载进度
DownloadBinder中提供了startDownload()，pauseDownload()，cancelDownload()三个方法，分别用于开始下载，暂停下载，和取消下载

MainActivity

package com.slience.downloaddemo;import android.Manifest;import android.content.ComponentName;import android.content.Intent;import android.content.ServiceConnection;import android.content.pm.PackageManager;import android.os.IBinder;import android.support.annotation.NonNull;import android.support.v4.app.ActivityCompat;import android.support.v4.content.ContextCompat;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.Button;import android.widget.Toast;import com.slience.downloaddemo.downloadservice.DownloadService;public class MainActivity extends AppCompatActivity implements View.OnClickListener{    private DownloadService.DownloadBinder downloadBinder;    private Button startDwonload , pauseDownload , cancelDownload;    private ServiceConnection connection = new ServiceConnection() {        @Override        public void onServiceConnected(ComponentName name, IBinder service) {            downloadBinder = (DownloadService.DownloadBinder)service;        }        @Override        public void onServiceDisconnected(ComponentName name) {        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        startDwonload = (Button)findViewById(R.id.start_download);        pauseDownload = (Button)findViewById(R.id.pause_download);        cancelDownload = (Button)findViewById(R.id.cancel_download);        startDwonload.setOnClickListener(this);        pauseDownload.setOnClickListener(this);        cancelDownload.setOnClickListener(this);        Intent intent = new Intent(this , DownloadService.class);        startService(intent);        bindService(intent , connection , BIND_AUTO_CREATE);        //绑定服务        if(ContextCompat.checkSelfPermission(MainActivity.this , Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED){            ActivityCompat.requestPermissions(MainActivity.this , new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE} , 1);        }    }    @Override    public void onClick(View v) {        if(downloadBinder == null){            return;        }        switch (v.getId()){            case R.id.start_download:                String url = "http://imtt.dd.qq.com/16891/FDC777ED452DD64653166EDFBF9273D4.apk";                downloadBinder.startDownload(url);                break;            case R.id.pause_download:                downloadBinder.pauseDownload();                break;            case R.id.cancel_download:                downloadBinder.cancelDownload();                break;            default:                break;        }    }    @Override    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {        switch (requestCode){            case 1:                if(grantResults.length > 0 && grantResults[0] != PackageManager.PERMISSION_GRANTED){                    Toast.makeText(this , "拒绝权限将无法使用程序" , Toast.LENGTH_SHORT).show();                    finish();                }                break;            default:                break;        }    }    @Override    protected void onDestroy() {        super.onDestroy();        unbindService(connection);    }}

由于程序使用了网络和调用SD卡的功能，需要在Manifest中添加INTERNET和WRITE_EXTERNAL_STORAGE这两个权限

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