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div id=”content” contentScore=”149″>下载文件会阻塞UI主线程，所以需要new一个新线程来执行下载操作，通过handler执行更新UI进度条操作。代码如下：
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ol>
public class AndroidTest extends Activity {
private static final String TAG = “AndroidTest”;
private ProgressBar progressBar = null;
private Button startButton = null;
private EditText filenameText = null;
private MyHandler handler = null;
private Message message = null;
private boolean flag = true;
private int size = 1;
private int hasRead = 0;
private int len = 0;
private byte buffer[] = new byte[10244];
private int index = 0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
progressBar = (ProgressBar)findViewById(R.id.progress_horizontal);
startButton = (Button)findViewById(R.id.mybutton);
startButton.setOnClickListener(new ButtonClick());
filenameText = (EditText)findViewById(R.id.fileNameID);
handler = new MyHandler();
}
public boolean downloadFile(final String urlStr, final String filename) {
new Thread(new Runnable(){
public void run() {
try {
URL url = new URL(urlStr);
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
size = connection.getContentLength();
InputStream inputStream = connection.getInputStream();
OutputStream outputStream = new FileOutputStream(Environment.getExternalStorageDirectory()+“/”+filename);
while((len=inputStream.read(buffer))!=-1){
outputStream.write(buffer);
hasRead+=len;
index = (int)(hasRead100)/size;
message = new Message();
message.what = 1;
handler.sendMessage(message);
Log.d(TAG, “index = “ + index);
System.out.println(“has = “+hasRead+” size = “+size+” index = “+index);
}
inputStream.close();
outputStream.close();
} catch (Exception e) {
flag = false;
e.printStackTrace();
}
}
}).start();
return flag;
}
class ButtonClick implements OnClickListener {
public void onClick(View v) {
String url = filenameText.getText().toString();
String filename = url.substring(url.lastIndexOf(‘/’) + 1);
Log.d(TAG, “url = “ + url);
Log.d(TAG, “filename = “ + filename);
if(!downloadFile(url, filename)) {
String rs = “下载失败 “;
Toast.makeText(AndroidTest.this, rs, Toast.LENGTH_SHORT).show();
}
}
}
class MyHandler extends Handler{
@Override
public void handleMessage(Message msg) {
if (msg.what == 1) {
progressBar.setProgress(index);
Log.d(TAG, “setProgress index:” + index);
if (index >= 99) {
String rs = “下载完成”;
Toast.makeText(AndroidTest.this, rs, Toast.LENGTH_SHORT).show();
}
}
super.handleMessage(msg);
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bjmayor
程序员，码农，php,python,ios,android,go，产品经理，创业。