Android 下载网络url文件并显示进度

深藏阁楼爱情的钟 2022-08-17 14:18 265阅读 0赞

首先需要加上权限——访问网络跟存储卡：

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

activity\_main.xml：

MainActivity：

import java.io.File;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.RandomAccessFile;
    import java.net.MalformedURLException;
    import java.net.URL;
    import java.net.URLConnection;
    
    import android.app.Activity;
    import android.os.Bundle;
    import android.os.Environment;
    import android.os.Handler;
    import android.os.Message;
    import android.util.Log;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button; 
    import android.widget.ProgressBar;
    import android.widget.TextView;
    import android.widget.Toast;
    
    /**
     * 文件下载
     * @author 胡汉三
     *
     */
    public class MainActivity extends Activity {
    
    	private static final String Path="文件的HTTP地址/ttt.mp3";
    	private static String fileName = "ttt.mp3";
    	private static String filePath= "/download/";
    	private ProgressBar progressBar; 
    	private TextView textView;
    	private Button button;
    	private int FileLength;  
    	private int DownedFileLength=0;
    	private InputStream inputStream;
    	private URLConnection connection;
    
    	@Override
    	protected void onCreate(Bundle savedInstanceState) {
    		super.onCreate(savedInstanceState);
    		setContentView(R.layout.activity_main);
    		progressBar=(ProgressBar) findViewById(R.id.download_main_progressBarlist);
    		textView=(TextView) findViewById(R.id.download_main_Text);
    		button=(Button) findViewById(R.id.download_main_Button);
    		button.setOnClickListener(new ButtonListener());
    
    	}
    	class ButtonListener implements OnClickListener{
    		@Override
    		public void onClick(View v) {
    			DownedFileLength=0;
    			Thread thread=new Thread(){
    				public void run(){
    					try {
    						DownFile(Path);
    					} catch (Exception e) { }
    				} 
    			};
    			thread.start();
    		}   
    	}
    
    	private Handler handler=new Handler()
    	{
    		public void handleMessage(Message msg)
    		{
    			if (!Thread.currentThread().isInterrupted()) {
    				switch (msg.what) {
    				case 0:
    					progressBar.setMax(FileLength);
    					Log.i("文件长度----------->", progressBar.getMax()+"");  
    					break;
    				case 1:
    					progressBar.setProgress(DownedFileLength);
    					int x=DownedFileLength*100/FileLength;
    					textView.setText(x+"%");
    					break;
    				case 2:
    					Toast.makeText(getApplicationContext(), "下载完成", Toast.LENGTH_LONG).show();
    					break;
    
    				default:
    					break;
    				}
    			}   
    		}
    
    	};
    
    	private void DownFile(String urlString)
    	{
    
    		/*
    		 * 连接到服务器
    		 */
    
    		try {
    			URL url=new URL(urlString);
    			connection=url.openConnection();
    			if (connection.getReadTimeout()==5) {
    				Log.i("---------->", "当前网络有问题");
    				// return;
    			}
    			inputStream=connection.getInputStream();
    
    		} catch (MalformedURLException e1) {
    			// TODO Auto-generated catch block
    			e1.printStackTrace();
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    
    		/*
    		 * 文件的保存路径和和文件名其中Nobody.mp3是在手机SD卡上要保存的路径，如果不存在则新建
    		 */
    		String savePAth=Environment.getExternalStorageDirectory()+filePath;
    		File file1=new File(savePAth);
    		if (!file1.exists()) {
    			file1.mkdir(); 
    		}
    		String savePathString=Environment.getExternalStorageDirectory()+filePath+fileName;
    		File file =new File(savePathString);
    		if (!file.exists()) { 
    			try {
    				file.createNewFile();
    			} catch (IOException e) {
    				// TODO Auto-generated catch block
    				e.printStackTrace();
    			}   
    		}
    		/*
    		 * 向SD卡中写入文件,用Handle传递线程
    		 */
    		Message message=new Message();
    		try {
    			RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rwd");
    			randomAccessFile.setLength(FileLength);
    			byte[]buf = new byte[1024*4];
    			FileLength=connection.getContentLength();
    			message.what=0;
    			handler.sendMessage(message);
    			int length = 0;
    			while ((length=inputStream.read(buf))!=-1) {
    				randomAccessFile.write(buf,0,length);
    				DownedFileLength+=length;
    				Log.i("-------->", DownedFileLength+"");
    				Message message1=new Message();
    				message1.what=1;  
    				handler.sendMessage(message1);
    			}
    			inputStream.close(); 
    			randomAccessFile.close();
    			Message message2=new Message();
    			message2.what=2;
    			handler.sendMessage(message2);
    			
    		} catch (FileNotFoundException e) {   
    			// TODO Auto-generated catch block 
    			e.printStackTrace(); 
    		} catch (IOException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    	}

如此这般，下载文件显示进度条就OK了