当屏幕方向改变时，ProgressDialog 退出更新。我已经实施了一个修复程序，该修复程序可以挽救 asynctask 并将 asynctask 的活动设置为在它被销毁和重建后的新活动。进度对话框上的完成百分比保持在方向更改之前的百分比。
我错过了什么？
package net.daleroy.fungifieldguide.activities;
import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.Window;
import android.view.View.OnClickListener;
import android.widget.Toast;
import net.daleroy.fungifieldguide.R;
import net.daleroy.fungifieldguide.fungifieldguideapplication;
public class FungiFieldGuide extends Activity {
//static final int PROGRESS_DIALOG = 0;
//ProgressThread progressThread;
private final static String LOG_TAG = FungiFieldGuide.class.getSimpleName();
fungifieldguideapplication appState;
private DownloadFile mTask;
public boolean mShownDialog;
ProgressDialog progressDialog;
private final static int DIALOG_ID = 1;
@Override
protected void onPrepareDialog(int id, Dialog dialog) {
super.onPrepareDialog(id, dialog);
if ( id == DIALOG_ID ) {
mShownDialog = true;
}
}
private void onTaskCompleted() {
Log.i(LOG_TAG, "Activity " + this + " has been notified the task is complete.");
//Check added because dismissDialog throws an exception if the current
//activity hasn't shown it. This Happens if task finishes early enough
//before an orientation change that the dialog is already gone when
//the previous activity bundles up the dialogs to reshow.
if ( mShownDialog ) {
dismissDialog(DIALOG_ID);
Toast.makeText(this, "Finished..", Toast.LENGTH_LONG).show();
}
}
@Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case DIALOG_ID:
progressDialog = new ProgressDialog(this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading Database (only first run)...");
return progressDialog;
default:
return super.onCreateDialog(id);
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.main);
appState = ((fungifieldguideapplication)this.getApplication());
Object retained = getLastNonConfigurationInstance();
if ( retained instanceof DownloadFile ) {
Log.i(LOG_TAG, "Reclaiming previous background task.");
mTask = (DownloadFile) retained;
mTask.setActivity(this);
//showDialog(DIALOG_ID);
}
else {
if(!appState.service.createDataBase())
{
Log.i(LOG_TAG, "Creating new background task.");
//showDialog(DIALOG_ID);
mTask = new DownloadFile(this);
mTask.execute("http://www.codemarshall.com/Home/Download");
}
}
//showDialog(PROGRESS_DIALOG);
View btn_Catalog = findViewById(R.id.btn_Catalog);
btn_Catalog.setOnClickListener(new OnClickListener()
{
public void onClick(View v)
{
Intent i = new Intent(getBaseContext(), Cat_Genus.class);//new Intent(this, Total.class);
startActivity(i);
}
});
View btn_Search = findViewById(R.id.btn_Search);
btn_Search.setOnClickListener(new OnClickListener()
{
public void onClick(View v)
{
Intent i = new Intent(getBaseContext(), Search.class);//new Intent(this, Total.class);
startActivity(i);
}
});
}
@Override
public Object onRetainNonConfigurationInstance() {
mTask.setActivity(null);
return mTask;
}
@Override
public void onDestroy()
{
super.onDestroy();
//progressDialog.dismiss();
//progressDialog = null;
appState.service.ClearSearchParameters();
}
private class DownloadFile extends AsyncTask<String, Integer, Boolean>{
private FungiFieldGuide activity;
private boolean completed;
private String Error = null;
private String Content;
private DownloadFile(FungiFieldGuide activity) {
this.activity = activity;
}
@Override
protected void onPreExecute()
{
showDialog(DIALOG_ID);
}
@Override
protected Boolean doInBackground(String... urlarg) {
int count;
try {
URL url = new URL(urlarg[0]);
URLConnection conexion = url.openConnection();
conexion.setDoInput(true);
conexion.setUseCaches(false);
// this will be useful so that you can show a tipical 0-100% progress bar
int lenghtOfFile = conexion.getContentLength();
// downlod the file
InputStream input = new BufferedInputStream(conexion.getInputStream());
OutputStream output = new FileOutputStream("/data/data/net.daleroy.fungifieldguide/databases/Mushrooms.db");
byte data[] = new byte[1024];
long total = 0;
while ((count = input.read(data)) != -1) {
total += count;
// publishing the progress....
publishProgress((int)total*100/lenghtOfFile);
output.write(data, 0, count);
}
output.flush();
output.close();
input.close();
} catch (Exception e) {
Log.i(LOG_TAG, e.getMessage());
}
return null;
}
@Override
public void onProgressUpdate(Integer... args){
progressDialog.setProgress(args[0]);
}
@Override
protected void onPostExecute(Boolean result)
{
completed = true;
notifyActivityTaskCompleted();
}
private void notifyActivityTaskCompleted() {
if ( null != activity ) {
activity.onTaskCompleted();
}
}
private void setActivity(FungiFieldGuide activity) {
this.activity = activity;
if ( completed ) {
notifyActivityTaskCompleted();
}
}
}
}