在gridview中獲取文件夾圖像

從gridview中獲取sdcard文件夾和視圖時出現錯誤。在gridview中獲取文件夾圖像

我班如下：

public class Favourites extends Activity{ 
    String backupPath=Environment.getExternalStorageDirectory().getPath() + "/WallpaperPro"; 
    String name; 
    GridView favgrid; 

    Cursor cursor; 
    int columnIndex; 
    String[] imagenames=new String[100]; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     try{ 
     readfile(); 
     }catch(Exception e) 
     { 

     } 
     setContentView(R.layout.fav); 
     favgrid=(GridView) findViewById(R.id.favgrid); 

     String[] projection = {MediaStore.Images.Media._ID}; 
     // Create the cursor pointing to the SDCard 
     cursor = managedQuery(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, 
       projection, 
       null , 
       null, 
       null); 
     // Get the column index of the image ID 
     Toast.makeText(getApplicationContext(),""+cursor.getCount() , 1).show(); 
     columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media._ID); 
     favgrid.setAdapter(new FavAdapter(this)); 


    } 
    public void readfile() 
    { 
     //File sdCardRoot = Environment.getExternalStorageDirectory(); 
     File yourDir = new File(backupPath); 
     int i=0; 
     for (File f : yourDir.listFiles()) { 
      if (f.isFile()) 
       name = f.getName(); 
      imagenames[i]=backupPath+"/"+name; 
      Log.i("CUTEWALLPAPER", "imagenames["+i+"]= "+name); 
      i++; 

       // make something with the name 
     } 
    } 

    public class FavAdapter extends BaseAdapter { 
     private Context mContext; 
      public FavAdapter(Context c) { 
       mContext = c; 
      } 
     @Override 
     public int getCount() { 
      // TODO Auto-generated method stub 
      return imagenames.length; 
     } 

     @Override 
     public Object getItem(int position) { 
      // TODO Auto-generated method stub 
      return position; 
     } 

     @Override 
     public long getItemId(int position) { 
      // TODO Auto-generated method stub 
      return position; 
     } 


     @Override 
     public ImageView getView(int position, View convertView, ViewGroup parent) { 
      // ImageView i = new ImageView(mContext); 
      ImageView imageView; 
       imageView = new ImageView(mContext); 
       if (convertView == null) { 

        imageView.setLayoutParams(new GridView.LayoutParams(100, 100)); 
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); 

        imageView.setPadding(0, 0, 0, 0); 
       } else { 
        imageView = (ImageView) convertView; 
       } 

      Bitmap b=BitmapFactory.decodeFile(imagenames[position].toString()); 
      Log.i("CUTEWALLPAPER", "Position"+position+" "+b.getHeight()); 
      imageView.setImageBitmap(b); 

      imageView.setScaleType(ImageView.ScaleType.FIT_CENTER); 
       /* Set the Width/Height of the ImageView. */ 
       imageView.setLayoutParams(new GridView.LayoutParams(300, 300)); 
       return imageView; 
     } 

    } 

}

我的xml文件如下：

<?xml version="1.0" encoding="utf-8"?> 
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" android:weightSum="1" android:orientation="horizontal" android:layout_height="wrap_content"> 
    <GridView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/favgrid" 
    android:layout_width="fill_parent" 
    android:columnWidth="90dp" 
    android:numColumns="1" 
    android:verticalSpacing="0dp" 
    android:horizontalSpacing="10dp" 
    android:stretchMode="columnWidth" 
    android:gravity="center" android:layout_height="fill_parent"/> 
    </RelativeLayout>

的logcat的錯誤顯示空指針異常。

07-06 22:57:26.892: ERROR/AndroidRuntime(302): java.lang.NullPointerException 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at com.cutewallpaper.Favourites$FavAdapter.getView(Favourites.java:112) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at com.cutewallpaper.Favourites$FavAdapter.getView(Favourites.java:1) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.AbsListView.obtainView(AbsListView.java:1274) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.GridView.makeAndAddView(GridView.java:1218) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.GridView.makeRow(GridView.java:265) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.GridView.fillDown(GridView.java:218) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.GridView.fillFromTop(GridView.java:337) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.GridView.layoutChildren(GridView.java:1112) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.AbsListView.onLayout(AbsListView.java:1113) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.View.layout(View.java:6830) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.RelativeLayout.onLayout(RelativeLayout.java:900) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.View.layout(View.java:6830) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.View.layout(View.java:6830) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.LinearLayout.onLayout(LinearLayout.java:918) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.View.layout(View.java:6830) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.View.layout(View.java:6830) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.ViewRoot.performTraversals(ViewRoot.java:996) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1633) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.os.Handler.dispatchMessage(Handler.java:99) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.os.Looper.loop(Looper.java:123) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at android.app.ActivityThread.main(ActivityThread.java:4363) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at java.lang.reflect.Method.invokeNative(Native Method) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at java.lang.reflect.Method.invoke(Method.java:521) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 
07-06 22:57:26.892: ERROR/AndroidRuntime(302):  at dalvik.system.NativeStart.main(Native Method)

我不知道如何解決這個問題。幫我在此先感謝

來源

2012-07-06 Shalini

不能得到你..你要問哪一行 – Shalini 2012-07-06 05:34:06

位圖b = BitmapFactory.decodeFile（imagenames [position] .toString（））;.這是112 – Shalini 2012-07-06 05:37:57

中的行您需要從SDCard中檢索所有圖像嗎？ – Venky 2012-07-06 05:42:01

您使用imagenames陣列100大小，但你不知道有多少圖像存在進入「WallpaperPro」文件夾中。所以你必須使用ArrayList。
而且您的GridView大小也是100，但可能有可能imagenames數組包含少於100個圖像。這是空指針異常的主要原因。
使用這條線作爲String backupPath=Environment.getExternalStorageDirectory().getPath() + "/WallpaperPro";或String backupPath=Environment.getExternalStorageDirectory() + "/WallpaperPro";String backupPath=Environment.getExternalStorageDirectory().getAbsolutePath() + "/WallpaperPro";
確保您的文件夾名稱是WallpaperPro。

我希望這會幫助你，評論任何查詢。

來源

2012-07-06 05:46:37

[getPath和getAbolutePath的區別]（http://stackoverflow.com/questions/1099300/whats-the-difference-between-getpath-getabsolutepath-and-getcanonicalpath） – 2012-07-06 05:54:05

thnaks for清晰的答案。但是，如果我給ArrayList中的圖像名稱，我不會在gridview中聲明爲imagenames [position]。 – Shalini 2012-07-06 07:04:44

你可以使用imagenames.get（位置）如果imagenames將arraylist – 2012-07-06 07:09:38

在gridview中獲取文件夾圖像

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