运行结果 
文章图片
文章图片
文章图片
文件结构 【Android|Android studio 多线程网络文件下载】
文章图片
主要代码
MainActivity
package cn.edu.sicnu.threadfiledownload;
import android.app.ProgressDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {EditText editText_url;
ListView listView;
//heap堆，可以被整个对象所有方法访问
TextView textView;
ProgressBar progressBar;
ArrayList arrayList = new ArrayList<>();
ArrayList localImages = new ArrayList<>();
ArrayAdapter arrayAdapter;
MyAsyncTask asyncTask;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
arrayList.add("http://img2.imgtn.bdimg.com/it/u=500808421,1575925585&fm=200&gp=0.jpg");
arrayList.add("http://img1.imgtn.bdimg.com/it/u=2883138594,3332343437&fm=27&gp=0.jpg");
arrayList.add("http://img0.imgtn.bdimg.com/it/u=2779717376,1807907918&fm=200&gp=0.jpg");
arrayList.add("http://img0.imgtn.bdimg.com/it/u=416447706,3692155938&fm=27&gp=0.jpg");
arrayList.add("http://img3.imgtn.bdimg.com/it/u=2058241956,1502683125&fm=27&gp=0.jpg");
arrayList.add("http://img0.imgtn.bdimg.com/it/u=2779717376,1807907918&fm=200&gp=0.jpg");
arrayList.add("http://img0.imgtn.bdimg.com/it/u=2779717376,1807907918&fm=200&gp=0.jpg");
editText_url = findViewById(R.id.editText_url);
listView = findViewById(R.id.listView);
arrayAdapter = new ArrayAdapter(this,android.R.layout.simple_list_item_1,arrayList);
listView.setAdapter(arrayAdapter);
textView = findViewById(R.id.textView);
progressBar = findViewById(R.id.progressBar);
asyncTask = new MyAsyncTask();
}public void add(View view){
arrayList.add(editText_url.getText().toString());
arrayAdapter.notifyDataSetChanged();
}public void download(View view){switch (asyncTask.getStatus()){
case PENDING:
asyncTask.execute(0);
break;
case RUNNING:
break;
case FINISHED:
asyncTask = new MyAsyncTask();
asyncTask.execute(0);
break;
}}class MyAsyncTask extends AsyncTask{@Override
protected void onPreExecute() {
super.onPreExecute();
localImages.clear();
}@Override
protected Integer doInBackground(Integer... integers) {
//在另外一个线程里面！！！
for(int i=0;
itry {
URL url = new URL(s);
URLConnection connection = url.openConnection();
int size = connection.getContentLength();
//图片大小publishProgress(0,i+1,size);
InputStream inputStream = connection.getInputStream();
//流
byte[] bytes = new byte[100];
int len = -1;
//准备好外部存储文件
File file = getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS);
String filename = file.getAbsolutePath()+"/"+i+".jpg";
FileOutputStream fileOutputStream = new FileOutputStream(filename);
while ((len=inputStream.read(bytes))!=-1){
fileOutputStream.write(bytes,0,len);
//Thread.sleep(1);
publishProgress(1,len);
}fileOutputStream.close();
inputStream.close();
localImages.add(filename);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}return null;
}@Override
protected void onProgressUpdate(Integer... values) {
super.onProgressUpdate(values);
switch (values[0]){
case 0:
textView.setText("正在下载第"+values[1]+"个文件！！！");
progressBar.setMax(values[2]);
progressBar.setProgress(0);
break;
case 1:
progressBar.incrementProgressBy(values[1]);
break;
}}@Override
protected void onPostExecute(Integer integer) {
super.onPostExecute(integer);
textView.setText("下载完成！！！");
progressBar.setProgress(0);
}
}public void showImages(View view){
Intent intent = new Intent(this,Main2Activity.class);
intent.putExtra("images",localImages);
startActivity(intent);
}} Main2Activity
package cn.edu.sicnu.threadfiledownload;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.LinearLayout;
import java.util.ArrayList;
public class Main2Activity extends AppCompatActivity {LinearLayout layout;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
layout = findViewById(R.id.layout);
Intent intent = getIntent();
ArrayList images = (ArrayList) intent.getSerializableExtra("images");
for(int i=0;
iactivity_main.xml
activity_main2.xml
