我在Android上遇到了问题
我保存了一些图片的数据库网址。我想下载图片以查看viewpager。当我有URL时，我将使用ImageLoader下载图像。
当我想从服务器下载图像的URL时，会出现问题。我正在使用Asyntask但不知何故aplicaión失败了。
如何下载URL以便以后使用ImageLoader下载图像？
我留下了我正在使用的部分代码。
package com.cinemappstop;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.Toast;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.cinemappstop.libraries.UserFunctions;
import com.cinemappstop.utils.Utils;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.FailReason;
import com.nostra13.universalimageloader.core.assist.ImageLoadingListener;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
public class ActivityGallery extends SherlockFragmentActivity {
// Create instance of list and ListAdapter
ListView list;
ProgressDialog pDialog;
LinearLayout lytRetry;
private ViewPager pager;
private DisplayImageOptions options;
// Array to url of my images
String[] actorImages;
// Create an instance of ActionBar
ActionBar actionbar;
private int intLengthData;
String mIdActor ;
// Declare object of JSONObject class
JSONObject json;
Context context;
public String[] mImage;
ImagePagerAdapter sla;
// Declare object of userFunctions and Utils class
UserFunctions userFunction;
Utils utils;
private ImageLoader imageLoader;
DetailOnPageChangeListener listener;
/* String[] imageUrls = {
"http://4.bp.blogspot.com/-dCQSa1pig0M/TgbxHWWS2zI/AAAAAAAAABk/Rtnv6PyXYqI/s748/5.jpg",
"http://static.yousaytoo.com/post_images/de/38/50/1198542/remote_image_1326117775.jpg",
"http://im1.indiancolleges.com/uploaded_images/article/CBSE-12-resultsIC_348X264.jpg",
"http://thumbnail.craftkeys.com/t/336x280/f05af81c9d3c71046c07e138756c8ab885d3d74e.jpg",
"http://4.bp.blogspot.com/--2tylWQhA6Y/TY920P3ivyI/AAAAAAAAACo/pI9kArldvm0/s1600/Wearable_Technology%2528GtuGuru%2529.jpg",
"http://1.bp.blogspot.com/-gPY9kcs7w9w/T9W3W62TaSI/AAAAAAAAAM8/nEXldUDIJhc/s1600/gtu-mca-android-tutorial-logo-four.jpg",
"http://gtu-mca.weebly.com/uploads/9/1/5/6/9156517/8037790_orig.png",
"http://gtu-mca.weebly.com/uploads/9/1/5/6/9156517/_6068527.png",
"http://gtu-mca.weebly.com/uploads/9/1/5/6/9156517/3898239.png",
"http://4.bp.blogspot.com/-tXQSSpN5z8o/TfdJViDk9XI/AAAAAAAAAAY/LbY0hbrezKU/s1600/mcahelp.bmp",
"http://i.ytimg.com/vi/yeWf4zvxRTo/0.jpg",
"http://english.globalgujaratnews.com/uploads/news/09_2012/1348840805_ADMISSION_STUDENTS.jpg" };
*/
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gallery);
context = this;
// Get id actor to download images
Intent i = getIntent();
mIdActor = i.getStringExtra("idActor");
new downLoadUrl().execute();
imageLoader = ImageLoader.getInstance();
imageLoader.init(ImageLoaderConfiguration.createDefault(context));
options = new DisplayImageOptions.Builder()
.showImageForEmptyUri(R.drawable.ic_launcher).cacheOnDisc()
.imageScaleType(ImageScaleType.IN_SAMPLE_INT).build();
pager = (ViewPager) findViewById(R.id.view_pager);
pager.setAdapter(new ImagePagerAdapter(actorImages));
listener = new DetailOnPageChangeListener();
pager.setOnPageChangeListener(listener);
}
public void btnClick(View view) {
Toast.makeText(ActivityGallery.this,
"Current Page :: " + listener.getCurrentPage(),
Toast.LENGTH_LONG).show();
System.out.println(">>>>>>>>>>>>>>>>>>>>>" + listener.getCurrentPage());
}
public class DetailOnPageChangeListener extends
ViewPager.SimpleOnPageChangeListener {
private int currentPage;
@Override
public void onPageSelected(int position) {
currentPage = position;
}
public int getCurrentPage() {
return currentPage;
}
}
@Override
protected void onStop() {
imageLoader.stop();
super.onStop();
}
private class ImagePagerAdapter extends PagerAdapter {
private String[] images;
private LayoutInflater inflater;
ImagePagerAdapter(String[] images) {
this.images = images;
inflater = getLayoutInflater();
}
@Override
public void destroyItem(View container, int position, Object object) {
((ViewPager) container).removeView((View) object);
}
@Override
public void finishUpdate(View container) {
}
@Override
public int getCount() {
return images.length;
}
@Override
public Object instantiateItem(View view, int position) {
final View imageLayout = inflater.inflate(
R.layout.item_pager_image, null);
final ImageView imageView = (ImageView) imageLayout
.findViewById(R.id.image);
imageLoader.displayImage(images[position], imageView, options,
new ImageLoadingListener() {
@Override
public void onLoadingFailed(FailReason failReason) {
String message = null;
switch (failReason) {
case IO_ERROR:
message = "Input/Output error";
break;
case OUT_OF_MEMORY:
message = "Out Of Memory error";
break;
case UNKNOWN:
message = "Unknown error";
break;
}
Toast.makeText(ActivityGallery.this, message,
Toast.LENGTH_SHORT).show();
imageView
.setImageResource(android.R.drawable.ic_delete);
}
@Override
public void onLoadingComplete(Bitmap loadedImage) {
Animation anim = AnimationUtils.loadAnimation(
ActivityGallery.this, R.anim.fade_in);
imageView.setAnimation(anim);
anim.start();
}
@Override
public void onLoadingCancelled() {
// Do nothing
}
@Override
public void onLoadingStarted() {
// TODO Auto-generated method stub
}
});
((ViewPager) view).addView(imageLayout, 0);
return imageLayout;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view.equals(object);
}
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
@Override
public Parcelable saveState() {
return null;
}
@Override
public void startUpdate(View container) {
}
}
// Load first 10 videos
private class downLoadUrl extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(
context);
pDialog.setMessage("Buscando...");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show();
}
protected Void doInBackground(Void... unused) {
// Call method getDataFromServer
getDataUrlFromServer();
return (null);
}
protected void onPostExecute(Void unused) {
// Closing progress dialog
pDialog.dismiss();
}
}
// Method get data from server
public void getDataUrlFromServer(){
try {
Log.d("Value idActor", mIdActor);
json = userFunction.searchImageActor(mIdActor);
if(json != null){
JSONArray dataLocationArray =
json.getJSONArray(userFunction.array_list_actor_images);
intLengthData = dataLocationArray.length();
actorImages = new String[intLengthData];
// Store data to variable array
for (int i = 0; i < intLengthData; i++) {
JSONObject locationObject = dataLocationArray.getJSONObject(i);
actorImages[i] = userFunction.URLImagesActor + locationObject.getString(userFunction.key_images_actor);
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.d("NULO", "Null");
}
}
}
logCat。有时它失败并且没有显示消息
07-27 09:55:51.806: I/MemoryCache(10592): cache size=4916800 length=3
07-27 09:55:52.576: D/dalvikvm(10592): GC_FOR_ALLOC freed 10842K, 47% free 16309K/30672K, paused 31ms, total 31ms
07-27 09:55:52.696: I/MemoryCache(10592): cache size=7060800 length=4
07-27 09:55:52.946: I/MemoryCache(10592): cache size=8980800 length=5
07-27 09:55:53.366: D/dalvikvm(10592): GC_FOR_ALLOC freed 180K, 34% free 20251K/30672K, paused 24ms, total 24ms
07-27 09:55:53.386: I/MemoryCache(10592): cache size=10900800 length=6
07-27 09:55:54.316: I/MemoryCache(10592): cache size=13044800 length=7
07-27 09:55:55.616: D/Valor id_actor(10592): 11
07-27 09:55:55.616: D/Valor id_actor(10592): 11
07-27 09:55:55.816: D/Click(10592): id_actor
07-27 09:55:55.886: D/Value idActor(10592): 11
07-27 09:55:55.886: W/dalvikvm(10592): threadid=11: thread exiting with uncaught exception (group=0x415f68b0)
07-27 09:55:55.886: E/AndroidRuntime(10592): FATAL EXCEPTION: AsyncTask #1
07-27 09:55:55.886: E/AndroidRuntime(10592): java.lang.RuntimeException: An error occured while executing doInBackground()
07-27 09:55:55.886: E/AndroidRuntime(10592): at android.os.AsyncTask$3.done(AsyncTask.java:299)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
07-27 09:55:55.886: E/AndroidRuntime(10592): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.lang.Thread.run(Thread.java:841)
07-27 09:55:55.886: E/AndroidRuntime(10592): Caused by: java.lang.NullPointerException
07-27 09:55:55.886: E/AndroidRuntime(10592): at com.cinemappstop.ActivityGallery.getDataUrlFromServer(ActivityGallery.java:285)
07-27 09:55:55.886: E/AndroidRuntime(10592): at com.cinemappstop.ActivityGallery$downLoadUrl.doInBackground(ActivityGallery.java:265)
07-27 09:55:55.886: E/AndroidRuntime(10592): at com.cinemappstop.ActivityGallery$downLoadUrl.doInBackground(ActivityGallery.java:1)
07-27 09:55:55.886: E/AndroidRuntime(10592): at android.os.AsyncTask$2.call(AsyncTask.java:287)
07-27 09:55:55.886: E/AndroidRuntime(10592): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
07-27 09:55:55.886: E/AndroidRuntime(10592): ... 4 more
07-27 09:55:55.896: D/AndroidRuntime(10592): Shutting down VM
07-27 09:55:55.896: W/dalvikvm(10592): threadid=1: thread exiting with uncaught exception (group=0x415f68b0)
07-27 09:55:55.896: I/Process(10592): Sending signal. PID: 10592 SIG: 9
解决方案
package com.cinemappstop;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Parcelable;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.Toast;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.cinemappstop.libraries.UserFunctions;
import com.cinemappstop.utils.Utils;
import com.nostra13.universalimageloader.core.DisplayImageOptions;
import com.nostra13.universalimageloader.core.ImageLoader;
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration;
import com.nostra13.universalimageloader.core.assist.FailReason;
import com.nostra13.universalimageloader.core.assist.ImageLoadingListener;
import com.nostra13.universalimageloader.core.assist.ImageScaleType;
public class ActivityGallery extends SherlockFragmentActivity {
// Create instance of list and ListAdapter
ListView list;
ProgressDialog pDialog;
LinearLayout lytRetry;
private ViewPager pager;
private DisplayImageOptions options;
// Array to url of my images
String[] actorImages;
// Create an instance of ActionBar
ActionBar actionbar;
String name;
private int intLengthData;
String mIdActor ;
// Declare object of JSONObject class
JSONObject json;
Context context;
public String[] mImage;
ImagePagerAdapter sla;
// Declare object of userFunctions and Utils class
UserFunctions userFunction;
Utils utils;
private ImageLoader imageLoader;
DetailOnPageChangeListener listener;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gallery);
context = this;
// Get id actor to download images
Intent i = getIntent();
mIdActor = i.getStringExtra("idActor");
name = i.getStringExtra("name");
// Declare object of userFunctions class
userFunction = new UserFunctions();
new downLoadUrl().execute();
}
public void btnClick(View view) {
Toast.makeText(ActivityGallery.this,
"Current Page :: " + listener.getCurrentPage(),
Toast.LENGTH_LONG).show();
System.out.println(">>>>>>>>>>>>>>>>>>>>>" + listener.getCurrentPage());
}
public class DetailOnPageChangeListener extends
ViewPager.SimpleOnPageChangeListener {
private int currentPage;
@Override
public void onPageSelected(int position) {
currentPage = position;
}
public int getCurrentPage() {
return currentPage;
}
}
@Override
protected void onStop() {
imageLoader.stop();
super.onStop();
}
private class ImagePagerAdapter extends PagerAdapter {
private String[] images;
private LayoutInflater inflater;
ImagePagerAdapter(String[] images) {
this.images = images;
inflater = getLayoutInflater();
}
@Override
public void destroyItem(View container, int position, Object object) {
((ViewPager) container).removeView((View) object);
}
@Override
public void finishUpdate(View container) {
}
@Override
public int getCount() {
return images.length;
}
@Override
public Object instantiateItem(View view, int position) {
final View imageLayout = inflater.inflate(
R.layout.item_pager_image, null);
final ImageView imageView = (ImageView) imageLayout
.findViewById(R.id.image);
imageLoader.displayImage(images[position], imageView, options,
new ImageLoadingListener() {
@Override
public void onLoadingFailed(FailReason failReason) {
String message = null;
switch (failReason) {
case IO_ERROR:
message = "Input/Output error";
break;
case OUT_OF_MEMORY:
message = "Out Of Memory error";
break;
case UNKNOWN:
message = "Unknown error";
break;
}
Toast.makeText(ActivityGallery.this, message,
Toast.LENGTH_SHORT).show();
imageView
.setImageResource(android.R.drawable.ic_delete);
}
@Override
public void onLoadingComplete(Bitmap loadedImage) {
Animation anim = AnimationUtils.loadAnimation(
ActivityGallery.this, R.anim.fade_in);
imageView.setAnimation(anim);
anim.start();
}
@Override
public void onLoadingCancelled() {
// Do nothing
}
@Override
public void onLoadingStarted() {
// TODO Auto-generated method stub
}
});
((ViewPager) view).addView(imageLayout, 0);
return imageLayout;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view.equals(object);
}
@Override
public void restoreState(Parcelable state, ClassLoader loader) {
}
@Override
public Parcelable saveState() {
return null;
}
@Override
public void startUpdate(View container) {
}
}
// Load first 10 videos
private class downLoadUrl extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(
context);
pDialog.setMessage("Buscando...");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show();
}
protected Void doInBackground(Void... unused) {
// Call method getDataFromServer
getDataUrlFromServer();
return (null);
}
protected void onPostExecute(Void unused) {
// Closing progress dialog
pDialog.dismiss();
imageLoader = ImageLoader.getInstance();
imageLoader.init(ImageLoaderConfiguration.createDefault(context));
options = new DisplayImageOptions.Builder()
.showImageForEmptyUri(R.drawable.ic_launcher).cacheOnDisc()
.imageScaleType(ImageScaleType.IN_SAMPLE_INT).build();
pager = (ViewPager) findViewById(R.id.view_pager);
pager.setAdapter(new ImagePagerAdapter(actorImages));
listener = new DetailOnPageChangeListener();
pager.setOnPageChangeListener(listener);
}
}
// Method get data from server
public void getDataUrlFromServer(){
try {
Log.d("Value idActor", mIdActor);
json = userFunction.searchImageActor(mIdActor);
if(json != null){
JSONArray dataLocationArray =
json.getJSONArray(userFunction.array_list_actor_images);
intLengthData = dataLocationArray.length();
Log.d("Valor json", String.valueOf(intLengthData));
actorImages = new String[intLengthData];
// Store data to variable array
for (int i = 0; i < intLengthData; i++) {
JSONObject locationObject = dataLocationArray.getJSONObject(i);
actorImages[i] = userFunction.URLImagesActor + locationObject.getString(userFunction.key_images_actor);
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Log.d("NULO", "Null");
}
}
}
答案 0 :(得分：0)
您似乎忘了初始化UserFunctions userFunction，因此在userFunction.searchImageActor(mIdActor)内调用getDataUrlFromServer()时会收到NullPointerException