Android set listview addapter null exception_问答_开发者

I need to find a way to set ListView addapter to null.The reason I want to do that is that I have 4 child activities in Tab and each one of these activities are lazy loading lists.In OnDestroy method of the activity I do this :

@Override
public void onDestroy()
{
    adapter.imageLoader.stopThread();
    listView.setAdapter(null);
    super.onDestroy();
}

But when I do this I get this exception :

08-13 15:29:43.115: ERROR/AndroidRuntime(10381): FATAL EXCEPTION: main
08-13 15:29:43.115: ERROR/AndroidRuntime(10381): java.lang.RuntimeException: Unable to destroy activity {com.stampii.stampii/com.stampii.stampii.mystampii.OwnedStampii}: java.lang.NullPointerException
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3874)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.开发者_开发知识库ActivityThread.performDestroyActivity(ActivityThread.java:3784)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.LocalActivityManager.performDestroy(LocalActivityManager.java:355)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.LocalActivityManager.destroyActivity(LocalActivityManager.java:381)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at com.stampii.stampii.TabGroupActivity.finishFromChild(TabGroupActivity.java:46)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.Activity.finish(Activity.java:3290)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at com.stampii.stampii.mystampii.OwnedStampii$1.onClick(OwnedStampii.java:38)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.view.View.performClick(View.java:2408)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.view.View$PerformClick.run(View.java:8817)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.os.Handler.handleCallback(Handler.java:587)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.os.Handler.dispatchMessage(Handler.java:92)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.os.Looper.loop(Looper.java:144)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.ActivityThread.main(ActivityThread.java:4937)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at java.lang.reflect.Method.invokeNative(Native Method)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at java.lang.reflect.Method.invoke(Method.java:521)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at dalvik.system.NativeStart.main(Native Method)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381): Caused by: java.lang.NullPointerException
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at com.stampii.stampii.mystampii.OwnedStampii.onDestroy(OwnedStampii.java:102)
08-13 15:29:43.115: ERROR/AndroidRuntime(10381):     at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3861)

at line 102 I have this : listView.setAdapter(null);

If I remove that code I get :

08-13 15:33:36.545: ERROR/AndroidRuntime(10511): FATAL EXCEPTION: main
08-13 15:33:36.545: ERROR/AndroidRuntime(10511): java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at java.util.Vector.elementAt(Vector.java:329)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at java.util.Vector.get(Vector.java:443)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at com.stampii.stampii.tableview.ImageLoader$PhotosQueue.Clean(ImageLoader.java:126)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at com.stampii.stampii.tableview.ImageLoader.queuePhoto(ImageLoader.java:59)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at com.stampii.stampii.tableview.ImageLoader.DisplayImage(ImageLoader.java:51)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at com.stampii.stampii.tableview.LazyAdapter.getView(LazyAdapter.java:62)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.AbsListView.obtainView(AbsListView.java:1294)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1198)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.ListView.onMeasure(ListView.java:1109)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:521)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3140)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.View.measure(View.java:8172)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewRoot.performTraversals(ViewRoot.java:805)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1744)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.os.Looper.loop(Looper.java:144)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at android.app.ActivityThread.main(ActivityThread.java:4937)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at java.lang.reflect.Method.invokeNative(Native Method)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at java.lang.reflect.Method.invoke(Method.java:521)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
08-13 15:33:36.545: ERROR/AndroidRuntime(10511):     at dalvik.system.NativeStart.main(Native Method)

And here is ImageLoader.class :

package com.stampii.stampii.tableview;

import java.io.File;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Stack;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import com.stampii.stampii.R;
import android.app.Activity;
import android.content.Context;
import android.content.res.AssetManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.widget.ImageView;

public class ImageLoader extends Activity {

    //the simplest in-memory cache implementation. This should be replaced with something like SoftReference or BitmapOptions.inPurgeable(since 1.6)
    private HashMap<String, Bitmap> cache=new HashMap<String, Bitmap>();

    private File cacheDir;
    private AssetManager mAssetManager;


    public ImageLoader(Context context){
        //Make the background thead low priority. This way it will not affect the UI performance
        photoLoaderThread.setPriority(Thread.NORM_PRIORITY-1);
        mAssetManager = context.getAssets();

        //Find the dir to save cached images
        if (android.os.Environment.getExternalStorageState().equals(android.os.Environment.MEDIA_MOUNTED))
            cacheDir=new File(android.os.Environment.getExternalStorageDirectory(),"LazyList");
        else
            cacheDir=context.getCacheDir();
        if(!cacheDir.exists())
            cacheDir.mkdirs();
    }


    final int stub_id=R.drawable.default_img;
    public void DisplayImage(String url, Activity activity, ImageView imageView)
    {
        if(cache.containsKey(url))
            imageView.setImageBitmap(cache.get(url));
        else
        {
            queuePhoto(url, activity, imageView);
            imageView.setImageResource(stub_id);
        }    
    }

    private void queuePhoto(String url, Activity activity, ImageView imageView)
    {
        //This ImageView may be used for other images before. So there may be some old tasks in the queue. We need to discard them. 
        photosQueue.Clean(imageView);
        PhotoToLoad p=new PhotoToLoad(url, imageView);
        synchronized(photosQueue.photosToLoad){
            photosQueue.photosToLoad.push(p);
            photosQueue.photosToLoad.notifyAll();
        }

        //start thread if it's not started yet
        if(photoLoaderThread.getState()==Thread.State.NEW)
            photoLoaderThread.start();
    }

    private Bitmap getBitmap(String src) {
        Bitmap myBitmap = null;


                //Decryption
                try {
                Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
                SecretKeySpec keySpec = new SecretKeySpec("01234567890abcde".getBytes(), "AES");
                IvParameterSpec ivSpec = new IvParameterSpec("fedcba9876543210".getBytes());
                cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);

                InputStream input = mAssetManager.open(src);
                CipherInputStream cis = new CipherInputStream(input, cipher);

                myBitmap = BitmapFactory.decodeStream(cis);

                }
                catch(Exception e){
                    e.printStackTrace();
                    Log.v("ERROR","Error : "+e);
                }


                return myBitmap;


        }

    //Task for the queue
    private class PhotoToLoad
    {
        public String url;
        public ImageView imageView;
        public PhotoToLoad(String u, ImageView i){
            url=u; 
            imageView=i;
        }
    }

    PhotosQueue photosQueue=new PhotosQueue();

    public void stopThread()
    {
        photoLoaderThread.interrupt();
    }

    //stores list of photos to download
    class PhotosQueue
    {
        private Stack<PhotoToLoad> photosToLoad=new Stack<PhotoToLoad>();

        //removes all instances of this ImageView
        public void Clean(ImageView image)
        {
            for(int j=0 ;j<photosToLoad.size();){
                if(photosToLoad.get(j).imageView==image)
                    photosToLoad.remove(j);
                else
                    ++j;
            }
        }
    }

    class PhotosLoader extends Thread {
        public void run() {
            try {
                while(true)
                {
                    //thread waits until there are any images to load in the queue
                    if(photosQueue.photosToLoad.size()==0)
                        synchronized(photosQueue.photosToLoad){
                            photosQueue.photosToLoad.wait();
                        }
                    if(photosQueue.photosToLoad.size()!=0)
                    {
                        PhotoToLoad photoToLoad;
                        synchronized(photosQueue.photosToLoad){
                            photoToLoad=photosQueue.photosToLoad.pop();
                        }
                        Bitmap bmp=getBitmap(photoToLoad.url);
                        cache.put(photoToLoad.url, bmp);
                        Object tag=photoToLoad.imageView.getTag();
                        if(tag!=null && ((String)tag).equals(photoToLoad.url)){
                            BitmapDisplayer bd=new BitmapDisplayer(bmp, photoToLoad.imageView);
                            Activity a=(Activity)photoToLoad.imageView.getContext();
                            a.runOnUiThread(bd);
                        }
                    }
                    if(Thread.interrupted())
                        break;
                }
            } catch (InterruptedException e) {
                //allow thread to exit
            }
        }
    }

    PhotosLoader photoLoaderThread=new PhotosLoader();

    //Used to display bitmap in the UI thread
    class BitmapDisplayer implements Runnable
    {
        Bitmap bitmap;
        ImageView imageView;
        public BitmapDisplayer(Bitmap b, ImageView i){bitmap=b;imageView=i;}
        public void run()
        {
            if(bitmap!=null)
                imageView.setImageBitmap(bitmap);
            else
                imageView.setImageResource(stub_id);
        }
    }

    public void clearCache() {
        //clear memory cache

        long size=0;
            cache.clear();

            //clear SD cache
            File[] files=cacheDir.listFiles();
            for(File f:files){
                size=size+f.length();
                    f.delete();
            }
}




}

Any ideas how to fix that?

You assign null as the adapter. Thats not a valid one and will of course throw a NullPointerException to emphasize this.

The other exception is hard to tell with that small piece of code. Please post some more.