空指針異常使用的ImageView

Question

時，我在這裏有一個ImageView的在我的GridViewAdapter類：

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    // Try to reuse the views 
    ImageView view = (ImageView) convertView; 
    boolean checked = (mCheckBox==null)?false:(((CheckBox) mCheckBox).isChecked()); 
    // if convert view is null then create a new instance else reuse it 
    if (view == null) { 
     view = new ImageView(Context); 
     view.setId(1); 
     Log.d("GridViewAdapter", "new imageView added"); 
    } 

，然後我試圖位圖設置爲另一類ImageView的（view）位置：

@Override 
       public void onClick(View v) { 
        if (addCheckbox.isChecked()) { 
         System.out.println("Checked"); 

         PackageManager pm = mContext.getPackageManager(); 
         final int DEST_IMAGE_WIDTH = 100; 
         final int DEST_IMAGE_HEIGHT = 100; 
         ApplicationInfo appInfo = mContext.getApplicationInfo(); 
         Drawable appIcon = pm.getApplicationIcon(appInfo); 
         Bitmap appBmp = Bitmap.createBitmap(DEST_IMAGE_WIDTH, DEST_IMAGE_HEIGHT, Config.ARGB_8888); 

         // Creates a new canvas based on the image specification 
         // created just above. 
         Canvas canvas = new Canvas(appBmp); 
         // (optional) Fills the entire canvas 
         canvas.drawColor(Color.WHITE); 
         // You need to set bounds otherwise a 0,0 sized image would be drawn. 
         appIcon.setBounds(0, 0, DEST_IMAGE_WIDTH, DEST_IMAGE_HEIGHT); 
         appIcon.draw(canvas); 

         /// Let's save to a .jpg file ... 
         File file = new File(mContext.getFilesDir().getAbsolutePath() + "/test2.jpg"); 
         FileOutputStream out; 
         try 
         { 
          file.createNewFile(); 
          out = new FileOutputStream(file); 
          appBmp.compress(Bitmap.CompressFormat.JPEG, 80, out); 
          out.close(); 

          // Load back the image file to confirms it works 
          Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath()); 
          ImageView imageView1 = (ImageView)v.findViewById(1); 
          imageView1.setImageBitmap(bitmap);    
         } 

，但我得到這個NPE：

12-22 15:58:45.782: E/AndroidRuntime(28793): FATAL EXCEPTION: main 
12-22 15:58:45.782: E/AndroidRuntime(28793): java.lang.NullPointerException 
12-22 15:58:45.782: E/AndroidRuntime(28793): at com.example.awesomefilebuilderwidget.AppInfoAdapter$1.onClick(AppInfoAdapter.java:200) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.view.View.performClick(View.java:2532) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.widget.CompoundButton.performClick(CompoundButton.java:99) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.view.View$PerformClick.run(View.java:9308) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.os.Handler.handleCallback(Handler.java:587) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.os.Handler.dispatchMessage (Handler.java:92) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.os.Looper.loop(Looper.java:150) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at android.app.ActivityThread.main(ActivityThread.java:4333) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at java.lang.reflect.Method.invokeNative(Native Method) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at java.lang.reflect.Method.invoke(Method.java:507) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 
12-22 15:58:45.782: E/AndroidRuntime(28793): at dalvik.system.NativeStart.main(Native Method) 

下面是一行200：

imageView1.setImageBitmap(bitmap); 

所以顯然我的ImageView被返回null

我猜，我沒有正確設置ID和/或不正確地使用它是誰？

我該如何解決這個問題NPE？

增加：

這裏是我的全部適配器類（GridViewAdapter）：

package com.example.awesomefilebuilderwidget; 

    IMPORTS 

    public class GridViewAdapter extends BaseAdapter { 
    private Context Context; 

    // Keep all Images in array list 
    public ArrayList<Integer> drawables = new ArrayList<Integer>(); 

    CheckBox mCheckBox=null; 

    // Constructor 
    public GridViewAdapter(Context c){ 
     Context = c; 
     Log.d("GridViewAdapter", "Constructor is set"); 

     drawables.add(R.drawable.pattern1); 
     Log.d("GridViewAdapter", "pattern1 added"); 

     drawables.add(R.drawable.pattern2); 
     Log.d("GridViewAdapter", "pattern2 added"); 

     drawables.add(R.drawable.trashcan); 
     Log.d("GridViewAdapter", "trashcan added"); 

     drawables.add(R.drawable.ic_launcher); 
     Log.d("GridViewAdapter", "ic_launcher added"); 
    } 

    public void setCheckBox(CheckBox checkbox){ 
     mCheckBox=checkbox; 
    } 

    @Override 
    // How many items are in the data set represented by this Adapter 
    public int getCount() { 
     return drawables.size(); 
    } 

    @Override 
    // Get the data item associated with the specified position in the 
    // data set 
    public Object getItem(int position) { 
     return drawables.get(position); 
    } 

    @Override 
    public long getItemId(int position) { 
     return position; 
    } 

    public boolean isSdReadable() { 

     boolean mExternalStorageAvailable = false; 
     String state = Environment.getExternalStorageState(); 

     if (Environment.MEDIA_MOUNTED.equals(state)) { 
     // We can read and write the media 
     mExternalStorageAvailable = true; 
     Log.i("isSdReadable", "External storage card is readable."); 
     } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { 
     // We can only read the media 
     Log.i("isSdReadable", "External storage card is readable."); 
     mExternalStorageAvailable = true; 
     } else { 
     // Something else is wrong. It may be one of many other 
     // states, but all we need to know is we can neither read nor write 
     mExternalStorageAvailable = false; 
     } 

     return mExternalStorageAvailable; 
     } 

    public Bitmap getThumbnail() { 

     final String APP_PATH_SD_CARD = "/TEST/"; 
     final String APP_THUMBNAIL_PATH_SD_CARD = "thumbnails"; 
     String filename = "AFBWIcon.png"; 

     String fullPath = Environment.getExternalStorageDirectory().getAbsolutePath() + APP_PATH_SD_CARD + APP_THUMBNAIL_PATH_SD_CARD; 
     Bitmap thumbnail = null; 

     // Look for the file on the external storage 
     try { 
     if (isSdReadable() == true) { 
     thumbnail = BitmapFactory.decodeFile(fullPath + "/" + filename); 
     } 
     } catch (Exception e) { 
     Log.e("getThumbnail() on external storage", e.getMessage()); 
     } 

     // If no file on external storage, look in internal storage 
     if (thumbnail == null) { 
     try { 
     File filePath = Context.getFileStreamPath(filename); 
     FileInputStream fi = new FileInputStream(filePath); 
     thumbnail = BitmapFactory.decodeStream(fi); 
     } catch (Exception ex) { 
     Log.e("getThumbnail() on internal storage", ex.getMessage()); 
     } 
     } 
     return thumbnail; 
     } 



    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // Try to reuse the views 
     ImageView view = (ImageView) convertView; 
     boolean checked = (mCheckBox==null)?false:(((CheckBox) mCheckBox).isChecked()); 
     // if convert view is null then create a new instance else reuse it 
     if (view == null) { 
      view = new ImageView(Context); 
      //view.setTag(ViewId(), "imageViewGRID"); 
      view.setId(1); 
      Log.d("GridViewAdapter", "new imageView added"); 
     } 
     if(checked == true){ 
      isSdReadable(); 
      Log.i("GridViewAdapter", "checkbox is checked"); 
     } else { 
      Log.i("GridView", "Icons not for use/checkbox not checked"); 
     } 
     view.setImageResource(drawables.get(position)); 
     view.setScaleType(ImageView.ScaleType.CENTER_CROP); 
     view.setLayoutParams(new android.widget.GridView.LayoutParams(70, 70)); 
     view.setTag(String.valueOf(position)); 
     return view; 
    } 

} 

Answer 1

ImageView imageView1 = (ImageView)v.findViewById(1); 

如何運作的？ 你不應該有這樣的事情，它的工作：

ImageView imageView1 = (ImageView)v.findViewById(R.id.example);

您需要提供一個ID不是整數的findViewById