我正在制作一个Android应用程序，我在其中制作了一个自定义库。当我在网格中显示图像时它工作正常，但当我滚动gridview下来获取空指针异常 我正在使用Holderview类，而不是在使用Activity。我正在研究碎片
这是我的getview功能
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
View rootview=convertView;
if (convertView == null) {
holder = new ViewHolder();
rootview = mInflater.inflate(
R.layout.gallery_item, null);
holder.imageview = (ImageView) rootview.findViewById(R.id.thumbImage);
rootview.setTag(holder);
}
else {
holder = (ViewHolder) rootview.getTag();
}
holder.imageview.setId(position);
holder.imageview.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
int id = v.getId();
Intent intent = new Intent();
intent.setAction(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.parse("file://" + arrPath[id]), "image/*");
startActivity(intent);
}
});
holder.imageview.setImageBitmap(thumbnails[position]);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
thumbnails[position].compress(Bitmap.CompressFormat.JPEG, 100, baos); //here is the error Null Pointer Exception
byte[] b = baos.toByteArray();
String encodedImage = Base64.encodeToString(b, Base64.DEFAULT);
holder.id = position;
return rootview;
}
}
static class ViewHolder {
ImageView imageview;
static int id;
}
这是我的LOGCAT
java.lang.NullPointerException
at com.tabdemo.Tab1Fragment$ImageAdapter.getView(Tab1Fragment.java:117)
at android.widget.AbsListView.obtainView(AbsListView.java:2186)
at android.widget.GridView.makeAndAddView(GridView.java:1341)
at android.widget.GridView.makeRow(GridView.java:341)
at android.widget.GridView.fillDown(GridView.java:283)
at android.widget.GridView.fillGap(GridView.java:243)
at android.widget.AbsListView.trackMotionScroll(AbsListView.java:5257)
at android.widget.AbsListView.scrollIfNeeded(AbsListView.java:3179)
at android.widget.AbsListView.onTouchEvent(AbsListView.java:3506)
at android.view.View.dispatchTouchEvent(View.java:7263)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2235)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1932)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2241)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1946)
at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1977)
at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1427)
at android.app.Activity.dispatchTouchEvent(Activity.java:2428)
at android.support.v7.internal.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:59)
at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1925)
at android.view.View.dispatchPointerEvent(View.java:7443)
at android.view.ViewRootImpl.deliverPointerEvent(ViewRootImpl.java:3603)
at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:3531)
at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:4783)
at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:4743)
at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:4895)
at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:179)
at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:171)
at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:4863)
at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:4917)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:776)
at android.view.Choreographer.doCallbacks(Choreographer.java:579)
at android.view.Choreographer.doFrame(Choreographer.java:546)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:762)
at android.os.Handler.handleCallback(Handler.java:800)
at android.os.Handler.dispatchMessage(Handler.java:100)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5371)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
确保阵列中有足够的缩略图。如果它在这里崩溃：
thumbnails[position].compress(Bitmap.CompressFormat.JPEG, 100, baos); //here is the error Null Pointer Exception
这意味着thumbnails[position]为null。确保您的数组不为空，并且每个项目位置都有值。
答案 1 :(得分：-1)
检查thumbnails的值，然后从thumbnails获取值是否为空
if(thumbnails[position]!=null)
{
holder.imageview.setImageBitmap(thumbnails[position]);
ByteArrayOutputStream baos = new ByteArrayOutputStream();
thumbnails[position].compress(Bitmap.CompressFormat.JPEG, 100,baos);
byte[] b = baos.toByteArray();
String encodedImage = Base64.encodeToString(b, Base64.DEFAULT);
}