Question

我有一个ArtistResourceImageAdapter类，它扩展了ArtistCoverFlowAdapter 我得到一个零点异常在其中一个字符串中（应该保存图像的路径）字符串是“res” 当我在构造函数中检查它似乎不是null（我使用logcat检查）但这个方法似乎是空的

@override 
protected Bitmap createBitmap(  int position) {
 if(res[position]==null)
        ..........
..............
..................          
}

现在，方法createBitmap已在ArtistResourceImageAdapter中重写，并在ArtistCoverFlowAdapter类中声明。

ArtistResourceImageAdapter的代码是（此代码中的最后一个方法（createBitmap），我得到字符串的空点异常）

package source.justanothermusicplayer.coverflw;

import java.io.File;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import source.justanothermusicplayer.R;
import source.justanothermusicplayer.R.drawable;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.util.Log;
import android.util.TypedValue;

/**
 * This class is an adapter that provides images from a fixed set of resource
 * ids. Bitmaps and ImageViews are kept as weak references so that they can be
 * cleared by garbage collection when not needed.
 * 
 */
public class ArtistResourceImageAdapter extends ArtistCoverFlowAdapter {

    /** The Constant TAG. */
    private static final String TAG = ArtistResourceImageAdapter.class.getSimpleName();
    float ht_px;float wt_px;
    /** The Constant DEFAULT_LIST_SIZE. */
    private static final int DEFAULT_LIST_SIZE = 40;

    /** The Constant IMAGE_RESOURCE_IDS. */
    private static final List<Integer> IMAGE_RESOURCE_IDS = new ArrayList<Integer>(DEFAULT_LIST_SIZE);

    /** The Constant DEFAULT_RESOURCE_LIST. */
  String[] res=new String[20];
    /** The bitmap map. */
    private final Map<Integer, WeakReference<Bitmap>> bitmapMap = new HashMap<Integer, WeakReference<Bitmap>>();

    private final Context context;

    /**
     * Creates the adapter with default set of resource images.
     * 
     * @param context
     *            context
     */

    public ArtistResourceImageAdapter(final Context context,String [] resources) { 
        super();
        this.context = context;
      ht_px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 130,context. getResources().getDisplayMetrics());
      wt_px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 115,context. getResources().getDisplayMetrics());

           setResources(resources);
    }



    public final synchronized void setResources(String[] resources) {
        IMAGE_RESOURCE_IDS.clear();res=resources;
            for ( int Id =1; Id<=resources.length;Id++) {
            IMAGE_RESOURCE_IDS.add(Id);
        }
        notifyDataSetChanged();
   }

    /**
     * Replaces resources with those specified.
     * 
     * @param resourceIds
     *            array of ids of resources.
     */

    /*
     * (non-Javadoc)
     * 
     * @see android.widget.Adapter#getCount()
     */
    @Override
    public synchronized int getCount() {
        return IMAGE_RESOURCE_IDS.size();
    }

    /*
     * (non-Javadoc)
     * 
     * @see pl.polidea.coverflow.AbstractCoverFlowImageAdapter#createBitmap(int)
     */
    @Override
    protected Bitmap createBitmap(  int position) {
        Log.v(TAG, "creating item " + position);
        String url=new String();
        if(res[position]==null)
            Log.i("holalala  jhingallaa ", "res[position] is null");
        url=res[position];
        Bitmap  b = BitmapFactory.decodeFile(url);
         b = Bitmap.createScaledBitmap(b, (int) ht_px, (int) wt_px, true);
        bitmapMap.put(position, new WeakReference<Bitmap>(b));
        return b;
    }


}

logcat：

12-12 14:16:58.876: E/AndroidRuntime(24293): FATAL EXCEPTION: main
12-12 14:16:58.876: E/AndroidRuntime(24293): java.lang.NullPointerException
12-12 14:16:58.876: E/AndroidRuntime(24293):    at java.io.File.fixSlashes(File.java:185)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at java.io.File.<init>(File.java:134)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistResourceImageAdapter.createBitmap(ArtistResourceImageAdapter.java:99)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistCoverFlowAdapter.getItem(ArtistCoverFlowAdapter.java:73)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistReflectingAdapter.createBitmap(ArtistReflectingAdapter.java:79)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistCoverFlowAdapter.getItem(ArtistCoverFlowAdapter.java:73)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistReflectingAdapter.createBitmap(ArtistReflectingAdapter.java:79)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistCoverFlowAdapter.getItem(ArtistCoverFlowAdapter.java:73)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistCoverFlowAdapter.getView(ArtistCoverFlowAdapter.java:117)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at source.justanothermusicplayer.coverflw.ArtistCoverFlowAdapter.getView(ArtistCoverFlowAdapter.java:1)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:193)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.View.measure(View.java:15401)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4950)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1426)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:703)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:578)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.View.measure(View.java:15401)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4950)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:314)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.View.measure(View.java:15401)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:855)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:578)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.View.measure(View.java:15401)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4950)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:314)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2154)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.View.measure(View.java:15401)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1856)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1104)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1279)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1002)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4294)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.Choreographer.doCallbacks(Choreographer.java:555)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.Choreographer.doFrame(Choreographer.java:525)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.os.Handler.handleCallback(Handler.java:643)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.os.Handler.dispatchMessage(Handler.java:92)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.os.Looper.loop(Looper.java:137)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at android.app.ActivityThread.main(ActivityThread.java:4803)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at java.lang.reflect.Method.invokeNative(Native Method)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at java.lang.reflect.Method.invoke(Method.java:511)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
12-12 14:16:58.876: E/AndroidRuntime(24293):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

看起来在res [position]返回null的情况下，你继续处理剩下的代码，我相信这就是给你空指针，因为你正在使用那个空值来处理其余的逻辑。尝试为条件检查添加括号并返回null。使用createBitmap的方法需要处理空位图，因为它不可用。

protected Bitmap createBitmap(  int position) {
    Log.v(TAG, "creating item " + position);
    String url=new String();
    if(res[position]==null) {
        Log.i("holalala  jhingallaa ", "res[position] is null");
        return null;
    }
    url=res[position];
    File f=new File(url);
    Bitmap  b = BitmapFactory.decodeFile(url);
    b = Bitmap.createScaledBitmap(b, (int) ht_px, (int) wt_px, true);
    bitmapMap.put(position, new WeakReference<Bitmap>(b));
    return b;
}

尝试在适配器中使用图像时出现空点异常？

1 个答案: