以下代码下载了一些文件（视频和图像）。下载文件后，将重新启动活动以完成重新加载过程。问题是，即使正确显示消息，活动有时也不会重新启动。这似乎发生在播放视频时。
public class FastFTPDownloader extends DownloaderBase {
public FastFTPDownloader(Activity activity, Intent intent) {
super(activity, intent);
}
@Override
protected String doInBackground(String... params) {
FastFTPDownloader.setDoing(true);
FTPClient client = new FTPClient();
FTPFile[] files = null;
client.setType(FTPClient.TYPE_BINARY);
try {
client.connect(params[0]);
client.login(params[1], params[2]);
client.changeDirectory(params[3]);
File alphalist = new File(ConfigLoader.ALPHA_PATH + "list.txt");
File betalist = new File(ConfigLoader.BETA_PATH + "list.txt");
// Step 1: download list.txt to alpha folder
client.download("list.txt", alphalist);
Log.d("Pankaj " + this.getClass().toString(),
"Downloading list.txt");
// Step 2: compare list.txt in alpha with list.txt in beta
// if both are same size return and do nothing
if (betalist.length() == alphalist.length()) {
// FastFTPDownloader.setDoing(false);
Log.d("Pankaj " + this.getClass().toString(),
"Nothing to download");
return "Nothing to download";
}
// Step 3: get a list of files from the server
files = client.list();
// for each file in list if file exists move on to next file
for (FTPFile f : files) {
File betafile = new File(ConfigLoader.BETA_PATH + f.getName());
if (betafile.exists()) {
if (betafile.length() == f.getSize()) {
continue;
}
}
// Step 4: the file does not exist in beta so download to alpha
// if it is not there
File alphaFile = new File(ConfigLoader.ALPHA_PATH + f.getName());
if (alphaFile.exists()) {
// if files are same size move on to next file.
if (alphaFile.length() == f.getSize()) {
continue;
}
// if existing file is less than the remote file continue
// download
// for files having size > remote file do a complete
// download.
if (alphaFile.length() < f.getSize()) {
client.download(f.getName(), alphaFile,
alphaFile.length());
continue;
}
}
client.download(f.getName(), alphaFile);
}
} catch (IllegalStateException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (IOException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (FTPIllegalReplyException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (FTPException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (FTPDataTransferException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (FTPAbortedException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (FTPListParseException e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
} catch (Exception e) {
Log.e(getClass().getName(), e.getMessage());
// FastFTPDownloader.setDoing(false);
return e.getMessage();
}
File alpha = new File(ConfigLoader.ALPHA_PATH);
File beta = new File(ConfigLoader.BETA_PATH);
File[] betaFiles = beta.listFiles();
activity.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(activity, "Restarting Please Wait...",
Toast.LENGTH_LONG).show();
}
});
// Step 5: shutdown the activity to complete the reconfiguration
VideoView video = ConfigLoader.getVideo();
if (video.isPlaying()) {
video.stopPlayback();
}
activity.overridePendingTransition(0, 0);
intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
activity.finish();
// ConfigLoader.getResources().reload();
// Step 6: if the file is not in list then delete it from beta
for (File f : betaFiles) {
if (!existsInList(f.getName())) {
f.delete();
}
}
File[] alphaFiles = alpha.listFiles();
// Step 7: move the remaining files in alpha to beta.
for (File f : alphaFiles) {
moveToBeta(f);
}
// Step 8: restart the application with new configurations.
activity.overridePendingTransition(0, 0);
activity.startActivity(intent);
return "Activity Restarted Successfully";
}
@Override
protected void onPostExecute(String result) {
Toast.makeText(activity, result, Toast.LENGTH_LONG).show();
FastFTPDownloader.setDoing(false);
super.onPostExecute(result);
}
private void moveToBeta(File file) {
File betaFile = new File(ConfigLoader.BETA_PATH + file.getName());
try {
FileInputStream fis = new FileInputStream(file);
FileOutputStream fos = new FileOutputStream(betaFile);
byte[] buffer = new byte[1024];
int len;
while ((len = fis.read(buffer)) > 0) {
fos.write(buffer, 0, len);
}
fis.close();
fos.close();
file.delete();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
下载程序库代码： -
public abstract class DownloaderBase extends AsyncTask<String, Integer, String> {
protected Activity activity;
protected Intent intent;
private static boolean doing = false;
public static boolean isDoing() {
return doing;
}
public static void setDoing(boolean doing) {
DownloaderBase.doing = doing;
}
public DownloaderBase(Activity activity, Intent intent) {
this.activity = activity;
this.intent = intent;
}
protected void deleteSubFolders(String uri) {
File currentFolder = new File(uri);
File files[] = currentFolder.listFiles();
if (files == null) {
return;
}
for (File f : files) {
if (f.isDirectory()) {
deleteSubFolders(f.toString());
}
// no else, or you'll never get rid of this folder!
f.delete();
}
}
protected void copyFromBeta() throws IOException {
File beta = new File(ConfigLoader.BETA_PATH);
File alpha = new File(ConfigLoader.ALPHA_PATH);
File[] files = beta.listFiles();
for (File f : files) {
String fname = f.getName().toLowerCase();
if (!fname.endsWith(".mp4")) {
continue;
}
if (!existsInList(f.getName())) {
continue;
}
FileInputStream fis = new FileInputStream(f);
File copy = new File(alpha + f.getName());
FileOutputStream fos = new FileOutputStream(copy);
byte[] buf = new byte[1024];
int len;
while ((len = fis.read(buf)) > 0) {
fos.write(buf, 0, len);
}
fis.close();
fos.close();
}
}
protected void trimAlpha() {
File alpha = new File(ConfigLoader.ALPHA_PATH);
File[] files = alpha.listFiles();
for (File f : files) {
if (!existsInList(f.getName())) {
f.delete();
}
}
}
protected boolean existsInList(String filename) {
File list = new File(ConfigLoader.ALPHA_PATH + "list.txt");
try {
FileReader fr = new FileReader(list);
BufferedReader br = new BufferedReader(fr);
String s;
while ((s = br.readLine()) != null) {
if (s.equals(filename)) {
return true;
}
}
br.close();
} catch (FileNotFoundException e) {
Log.e(getClass().getName(), e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return false;
}
}
主要活动代码： -
public class MainActivity extends Activity implements Runnable {
private Handler h;
private MediaPlayer player;
private Standee standee;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_main);
ImageView iv = (ImageView) findViewById(R.id.imageView1);
VideoView vv = (VideoView) findViewById(R.id.videoView1);
standee = new Standee(this, vv, iv);
standee.start();
h = new Handler();
h.post(this);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void run() {
if (!FastFTPDownloader.isDoing()) {
h.removeCallbacks(this);
FastFTPDownloader ftp = new FastFTPDownloader(this, getIntent());
ConfigLoader l = ConfigLoader.getInstance();
ftp.execute(l.URL(), l.User(), l.Password(), l.Path());
h.postDelayed(this, l.Delay() * 1000);
}
}
@Override
protected void onDestroy() {
player = standee.getMediaPlayer();
player.stop();
player.release();
player = null;
super.onDestroy();
}
}
感谢任何帮助。提前致谢。如果需要，我正在使用FTP4j库。
答案 0 :(得分：0)
最可能的原因是Android正在销毁和重新创建活动。因此，AsyncTask对活动的引用将变为无效。有一种模式可以解决这个问题。
在AsyncTask中，提供“附加”方法：
public void attach（活动活动）{ this.activity =活动; }
在您的活动类中，总是将当前版本的活动与任务挂钩，如下所示：
static AsyncTask myTask = ....
和onCreate（）或onResume（）
if (myTask != null) myTask.attach(this);