Question

我收到错误ERROR / AndroidRuntime（1482）：来自我的ImageAdapter类的java.lang.NullPointerException。请帮我解决这个问题。

ImageSwitcherActivity.java

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Gallery.LayoutParams;
import android.widget.ViewSwitcher.ViewFactory;

public class ImageSwitcherActivity extends Activity{
    private ImageSwitcher iSwitcher;
    private Gallery gallery;
    Integer[] images = {R.drawable.image1,R.drawable.image2,
            R.drawable.image3,R.drawable.image4,
            R.drawable.image5,R.drawable.icon,
            R.drawable.icon,R.drawable.icon,
            R.drawable.icon
    }; 
    static int counter = 0;
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        counter = images.length;
        Log.i("Image counter in onCreate", "" +counter);
        setContentView(R.layout.imageswitcher);

        gallery = (Gallery)findViewById(R.id.glry);
        gallery.setAdapter(new ImageAdapter1(this));

    }

    class ImageAdapter1 extends BaseAdapter{
        Context m;

        public ImageAdapter1(Context c){
            m = c;
        }
        public ImageAdapter1(ImageSwitcherActivity imageSwitcherActivity) {
            // TODO Auto-generated constructor stub
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            Log.i("Image Count in ImageAdapter1", ""+counter);
            return counter;
        }

        @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 View getView(int position, View convertView, ViewGroup parent) {
            // TODO Auto-generated method stub
            Log.i("Enters in GetView", "GetView");
            ImageView i = new ImageView(m);
            Log.i("After Intializing Imageview", "Init ImageView");
            i.setImageResource(images[position]);
            i.setLayoutParams(new Gallery.LayoutParams(150, 150));
            i.setScaleType(ImageView.ScaleType.FIT_XY);
            return i;

        }
    }

我的LogCat详细信息：

07-14 06:10:14.290: ERROR/AndroidRuntime(1515): FATAL EXCEPTION: main
07-14 06:10:14.290: ERROR/AndroidRuntime(1515): java.lang.NullPointerException
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.ViewConfiguration.get(ViewConfiguration.java:228)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.View.<init>(View.java:1878)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.ImageView.<init>(ImageView.java:103)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at com.myworkspace.ImageAdapter1.getView(ImageSwitcherActivity.java:107)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:192)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.View.measure(View.java:8313)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1017)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:386)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.View.measure(View.java:8313)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.View.measure(View.java:8313)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:531)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:309)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.View.measure(View.java:8313)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3138)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:250)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.View.measure(View.java:8313)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.ViewRoot.performTraversals(ViewRoot.java:839)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1859)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.os.Looper.loop(Looper.java:123)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at android.app.ActivityThread.main(ActivityThread.java:3647)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at java.lang.reflect.Method.invokeNative(Native Method)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at java.lang.reflect.Method.invoke(Method.java:507)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
07-14 06:10:14.290: ERROR/AndroidRuntime(1515):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

只需删除

行

public ImageAdapter1(ImageSwitcherActivity imageSwitcherActivity)
{
   // TODO Auto-generated constructor stub
}

因为它被称为构造函数，但未将Context m设置为ImageSwitcherActivity。由于Context为null，因此会导致NullPointerException

Answer 2

只是尝试替换此代码

Activity m;

    public ImageAdapter1(Activity c){
        m = c;
    }

取代

Context m;

    public ImageAdapter1(Context c){
        m = c;
    }

希望这有效。

从ImageAdapter类获取NullPointerException

2 个答案: