1）新建一个dowmloadfile的项目
2）在app/build中添加Okhttp的依赖
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-v7:24.2.1' testCompile 'junit:junit:4.12' compile 'com.squareup.okhttp3:okhttp:3.4.1'//添加依赖 }
3）定义一个回掉接口DownloadListener 用于事件的监听
public interface DownloadListener { void onProgress(int progress);//通知当前下载进度 void onSuccess();//通知下载成功 void onFiled();//通知下载失败 void onPaused();//下载暂停 void inCanceled();//下载取消 }
4）使用来实现下载
package com.example.dowmloadfile.Myclass; import android.os.AsyncTask; import android.os.Environment; import com.example.dowmloadfile.imp.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 海绵宝宝 on 2019/5/13. */ /**三个参数第一个为需要传入给后台的数据类型，第二个是进度显示类型，第三个为使用Integer作为反馈结果类型**/ 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; private DownloadListener downloadListener; private boolean isCanceled=false; private boolean isPaused=false; private int lastProgress; //通过DownLoadTask回调下载状态 public DownLoadTask(DownloadListener listener){ downloadListener=listener; } @Override//后台执行具体的下载逻辑 protected Integer doInBackground(String... params) { InputStream is=null; RandomAccessFile savedFile=null; File file=null; try{ long downloadLength=0; String downloadUrl=params[0]; String fileName=downloadUrl.substring(downloadUrl.lastIndexOf("/"));//解析出下载的文件名 String derectory= Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).getPath();//获取本地的下载文件夹的路径 file=new File(derectory+fileName); if (file.exists()){ downloadLength=file.length(); } long contentLength=getContentLength(downloadUrl);//读取下载文件的字节数 if (contentLength==0){ return TYPE_FAILED; }else if (contentLength==downloadLength){ return TYPE_SUCCESS; } OkHttpClient client=new OkHttpClient(); Request request=new Request.Builder().addHeader("RANGE","bytes="+downloadLength+"-").url(downloadUrl).build();//head用于告诉服务器我们从那个字节开始下载 Response response=client.newCall(request).execute(); if (response!=null){ is=response.body().byteStream(); savedFile=new RandomAccessFile(file,"rw"); savedFile.seek(downloadLength);//跳过已经下载的字节 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); int progress=(int)((total+downloadLength)*100/contentLength); publishProgress(progress); } } response.body().close(); return TYPE_SUCCESS; }; }catch (Exception e){ e.printStackTrace(); }finally { try { if (is!=null){ is.close(); }else if (savedFile!=null){ savedFile.close(); }else if (isCanceled&&file!=null){ file.delete(); } }catch (Exception e){ e.printStackTrace(); } } return TYPE_FAILED; } @Override//用于比较下载进度然后使用onProgress来更改下载进度的通知 protected void onProgressUpdate(Integer... values) { int progress=values[0]; if (progress>lastProgress){ downloadListener.onProgress(progress); lastProgress=progress; } } @Override//根据传入的参数进行回调 protected void onPostExecute(Integer integer) { switch (integer) { case TYPE_SUCCESS: downloadListener.onSuccess(); break; case TYPE_FAILED: downloadListener.onFiled(); break; case TYPE_PAUSED: downloadListener.onPaused(); break; case TYPE_CANCELED: downloadListener.inCanceled(); default: break; }; } public void pauseDownload(){ isPaused=true; } public void cancelDownload(){ isCanceled=true; } //获取需要下载的文件长度 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(); return contentLength; } return 0; } }
5）为了保证下载可以一直运行我们需要创建一个服务
package com.example.dowmloadfile.Myservice; 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.example.dowmloadfile.MainActivity; import com.example.dowmloadfile.Myclass.DownLoadTask; import com.example.dowmloadfile.R; import com.example.dowmloadfile.imp.DownloadListener; import java.io.File; public class DownloadService extends Service { private DownLoadTask downLoadTask; private String downloadUrl; //创建一个DownloadListener并实现其中的方法 private DownloadListener downloadListener=new DownloadListener() { @Override//以通知的方式显示进度条 public void onProgress(int progress) { //使用getNotificationManager函数构建一个用于显示下载进度的通知 //使用notify去触发这个通知 getNotificationManager().notify(1,getNotification("Download...",progress)); } @Override public void onSuccess() { downLoadTask=null; //关闭前台服务通知 stopForeground(true); getNotificationManager().notify(1,getNotification("download succeed",-1)); Toast.makeText(DownloadService.this,"Download Succeed",Toast.LENGTH_LONG).show(); } @Override public void onFiled() { downLoadTask=null; //关闭前台服务通知 stopForeground(true); getNotificationManager().notify(1,getNotification("download filed",-1)); Toast.makeText(DownloadService.this,"Download failed",Toast.LENGTH_LONG).show(); } @Override public void onPaused() { downLoadTask=null; Toast.makeText(DownloadService.this,"Download Paused",Toast.LENGTH_LONG).show(); } @Override public void inCanceled() { downLoadTask=null; //关闭前台服务通知 stopForeground(true); Toast.makeText(DownloadService.this,"Download canceled",Toast.LENGTH_LONG).show(); } }; private DownloadBinder mBinder=new DownloadBinder(); @Override public IBinder onBind(Intent intent) { // TODO: Return the communication channel to the service. return mBinder; } //用于使服务可以和活动通信 public class DownloadBinder extends Binder{ public void startDownload(String url){ if(downLoadTask==null){ downloadUrl=url; downLoadTask=new DownLoadTask(downloadListener); //使用execute开启下载 downLoadTask.execute(downloadUrl); //startForeground使服务成为一个前台服务以创建持续运行的通知 startForeground(1,getNotification("download...",0)); Toast.makeText(DownloadService.this,"Download",Toast.LENGTH_LONG).show(); } } public void pauseDownload(){ if (downLoadTask!=null){ downLoadTask.pauseDownload(); } } //取消下载后需要将下载中的任务取消 public void cancelDownload(){ if(downLoadTask!=null){ downLoadTask.cancelDownload(); }else { if (downloadUrl!=null) { //取消需要将文件删除并将通知关闭 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_LONG).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);//最大进度，当前进度，是否使用模糊进度条 } return builder.build(); } }
6）前台xml文件
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <Button android:id="@+id/start" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="start download"/> <Button android:id="@+id/pause" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="start pause"/> <Button android:id="@+id/cancel" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="start cancel"/> </LinearLayout>
7）MainActivity.java中设置具体逻辑和按钮的触发事件
package com.example.dowmloadfile; import android.Manifest; import android.content.ComponentName; import android.content.Context; import android.content.Intent; import android.content.ServiceConnection; import android.content.pm.PackageManager; import android.os.IBinder; 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 com.example.dowmloadfile.Myservice.DownloadService; public class MainActivity extends AppCompatActivity implements View.OnClickListener{ private DownloadService.DownloadBinder downloadBinder; private ServiceConnection connection=new ServiceConnection() { @Override public void onServiceConnected(ComponentName name, IBinder service) { //获取实例以便于在活动中调用其中的方法 downloadBinder=(DownloadService.DownloadBinder) service; } @Override public void onServiceDisconnected(ComponentName name) { } }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Button start=(Button)findViewById(R.id.start); Button pause=(Button)findViewById(R.id.pause); Button cancel=(Button)findViewById(R.id.cancel); start.setOnClickListener(this); pause.setOnClickListener(this); cancel.setOnClickListener(this); Intent intent=new Intent(this, DownloadService.class); startService(intent);//启动服务保证服务一直运行 bindService(intent,connection,BIND_AUTO_CREATE);//绑定服务保证数据在服务和活动中传递 //申请运行时权限 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 view){ if(downloadBinder==null) { return; } switch (view.getId()){ case R.id.start: String url="http://icon.nipic.com/BannerPic/20190513/original/20190513111935_1.jpg"; downloadBinder.startDownload(url); break; case R.id.pause: downloadBinder.pauseDownload(); break; case R.id.cancel: downloadBinder.cancelDownload(); break; default: break; } } @Override protected void onDestroy() { super.onDestroy(); unbindService(connection); } }
8）申请权限
<uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
