How to solve Log cat Error? Project ImageViewExample_问答_开发者

Hi Now trying to create folder in my gallery....normally my grid view display images in separately but I need folder in my gallery. so, I am using file class....if i run my project log cat indicate error how to solve these error? please check my coding also.....

ImageViewExample.java

package ImageViewExample.ImageViewExample;

import java.io.File;
import android.R.string;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.provider.MediaStore;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.GridView;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemClickListener;

public class ImageViewExample extends Activity {
  /** Called when the activity is first created. */
  private Cursor imagecursor, actualimagecursor;
  private int image_column_index, actual_image_column_index;
  GridView imagegrid;
  private int count;
@Override
public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      init_phone_image_grid();
}
private void init_phone_image_grid() {
      String[] img = { MediaStore.Images.Thumbnails._ID };
      imagecursor = managedQuery(
      MediaStore.Images.Thumbnails.EXTERNAL_CONTENT_URI, img, null,
      null, MediaStore.Images.Thumbnails.IMAGE_ID + "");
      image_column_index = imagecursor
     .getColumnIndexOrThrow(MediaStore.Images.Thumbnails._ID);
      count = imagecursor.getCount();
      imagegrid = (GridView) findViewById(R.id.PhoneImageGrid);
      imagegrid.setAdapter(new ImAdapterh(this));
      imagegrid.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView parent, View v,
      int position, long id) {
                  System.gc();
                  String[] proj = { MediaStore.Images.Media.DATA };
                  actualimagecursor = managedQuery(
      MediaStore.Images.Media.EXTERNAL_CONTENT_URI, proj,
      null, null, null);
                  actual_image_column_index = actualimagecursor
     .getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
                  actualimagecursor.moveToPosition(position);
                  String i = actualimagecursor.getString(actual_image_column_index);
                  System.gc();
                  Intent intent = new Intent(getApplicationContext(), ViewImage.class);
                  intent.putExtra("filename", i);
                  startActivity(intent);
             }
       });
      }


      public class ImAdapterh extends BaseAdapter{

      File dir=new File(Environment.getExternalStorageDirectory(),"/myImages/");

      int count=dir.list().length; 

      String[] fileNames = dir.list();

      private Context mContext;

      public ImAdapterh(Context c) {
       mContext = c;
       }

   public int getCount() {
       return count;
   }

   public Object getItem(int position) {
       return null;
   }

   public long getItemId(int position) {
       return 0;
   }

   // create a new ImageView for each item referenced by the Adapter
   public View getView(int position, View convertView, ViewGroup parent) {
       ImageView imageView = null;        


     for(String bitmapFileName : fileNames)
     {
          if (convertView == null) 
          {  // if it's not recycled, initialize some attributes
              imageView = new ImageView(mContext);
              imageView.setLayoutParams(new Gallery.LayoutParams(85, 85));
              imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
              imageView.setPadding(8, 8, 8, 8);                   

              Bitmap bmp = BitmapFactory.decodeFile(dir.getPath() + "/" +  
              bitmapFileName);
              System.out.println(dir);
              imageView.setImageBitmap(bmp);  
           }else 
           {
           imageView = (ImageView) convertView;            

           }
   } 
       return imageView;
       }
      }}

Logcat Error:

04-29 14:56:23.011: DEBUG/AndroidRuntime(415): >>>>>>>>>>>>>> AndroidRuntime START 
<<<<<<<<<<<<<<
04-29 14:56:23.021: DEBUG/AndroidRuntime(开发者_Python百科415): CheckJNI is ON
04-29 14:56:23.402: DEBUG/AndroidRuntime(415): --- registering native functions ---
04-29 14:56:24.781: DEBUG/AndroidRuntime(415): Shutting down VM
04-29 14:56:24.791: DEBUG/dalvikvm(415): Debugger has detached; object registry had 1 
entries
04-29 14:56:24.821: INFO/AndroidRuntime(415): NOTE: attach of thread 'Binder Thread 
#3' failed
04-29 14:56:25.761: DEBUG/AndroidRuntime(423): >>>>>>>>>>>>>> AndroidRuntime START 
<<<<<<<<<<<<<<
04-29 14:56:25.761: DEBUG/AndroidRuntime(423): CheckJNI is ON
04-29 14:56:26.141: DEBUG/AndroidRuntime(423): --- registering native functions ---
04-29 14:56:27.552: INFO/ActivityManager(66): Starting activity: Intent { 
act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000   
cmp=ImageViewExample.ImageViewExample/.ImageViewExample }
04-29 14:56:28.182: DEBUG/AndroidRuntime(423): Shutting down VM
04-29 14:56:28.232: DEBUG/dalvikvm(423): Debugger has detached; object registry had 1 
entries
04-29 14:56:28.291: INFO/ActivityManager(66): Start proc 
ImageViewExample.ImageViewExample for activity   
ImageViewExample.ImageViewExample/.ImageViewExample: pid=430 uid=10050 gids={}
04-29 14:56:28.312: INFO/AndroidRuntime(423): NOTE: attach of thread 'Binder Thread 
#3' failed
04-29 14:56:29.641: DEBUG/AndroidRuntime(430): Shutting down VM
04-29 14:56:29.641: WARN/dalvikvm(430): threadid=1: thread exiting with uncaught 
exception (group=0x4001d800)
04-29 14:56:29.711: ERROR/AndroidRuntime(430): FATAL EXCEPTION: main
04-29 14:56:29.711: ERROR/AndroidRuntime(430): java.lang.RuntimeException: Unable to   
start activity  
ComponentInfo{ImageViewExample.ImageViewExample/ImageViewExample.
ImageViewExample.ImageViewExample}: java.lang.NullPointerException
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at  
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at  
android.app.ActivityThread.access$2300(ActivityThread.java:125)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at  
android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
android.os.Handler.dispatchMessage(Handler.java:99)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
android.os.Looper.loop(Looper.java:123)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
android.app.ActivityThread.main(ActivityThread.java:4627)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
java.lang.reflect.Method.invokeNative(Native Method)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at   
java.lang.reflect.Method.invoke(Method.java:521)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at   
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
dalvik.system.NativeStart.main(Native Method)
04-29 14:56:29.711: ERROR/AndroidRuntime(430): Caused by: 
java.lang.NullPointerException
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
ImageViewExample.ImageViewExample.ImageViewExample$ImAdapterh.<init>  
(ImageViewExample.java:73)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at     
 ImageViewExample.ImageViewExample.ImageViewExample.init_phone_image_grid
(ImageViewExample.java:47)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at   
ImageViewExample.ImageViewExample.ImageViewExample.onCreate
(ImageViewExample.java:36)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at 
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     at     
android.app.ActivityThread.performLaunchActivity
(ActivityThread.java:2627)
04-29 14:56:29.711: ERROR/AndroidRuntime(430):     ... 11 more
04-29 14:56:29.751: WARN/ActivityManager(66):   Force finishing activity 
ImageViewExample.ImageViewExample/.ImageViewExample
04-29 14:56:30.292: WARN/ActivityManager(66): Activity pause timeout for 
HistoryRecord{4406aab0 ImageViewExample.ImageViewExample/.ImageViewExample}
04-29 14:56:36.701: DEBUG/dalvikvm(189): GC_EXPLICIT freed 162 objects / 7136 bytes in 
121ms
04-29 14:56:41.568: WARN/ActivityManager(66): Activity destroy timeout for 
HistoryRecord{4406aab0 ImageViewExample.ImageViewExample/.ImageViewExample}

please help me.....

The problem is almost certainly this line:

int count=dir.list().length;

The chain of logic that demonstrates that it has to be that line is follows:

The statement that creates the File object can't throw an exception in the ImAdapterh constructor itself.
This means that dir must be non-null.
This means that dir.list() won't throw an exception in the ImAdapterh constructor.
This just leaves the dereferencing of the String[] reference to get the length value as the culprit.

Finally, the null pointer can be explained by the fact that File.list() returns null if the File (in this case dir) does not exists or doesn't denote a directory ... as per the File.list() javadoc.

Null Pointer exception in your adapter class.

File dir=new File(Environment.getExternalStorageDirectory(),"/myImages/");

      int count=dir.list().length; 

      String[] fileNames = dir.list();

check above lines...that a value returning null.