我在一个扩展到基本适配器的类中使用android小吃吧,当我点击图像时,我得到一个空指针异常。我使用此代码从sdcard中提取图像并将其显示在gridview中。
public class GridViewImageAdapter extends BaseAdapter{
private Activity _activity;
private ArrayList<String> _filePaths = new ArrayList<String>();
private int imageWidth;
private View view;
public GridViewImageAdapter(Activity activity, ArrayList<String> filePaths,
int imageWidth) {
this._activity = activity;
this._filePaths = filePaths;
this.imageWidth = imageWidth;
}
@Override
public int getCount() {
return this._filePaths.size();
}
@Override
public Object getItem(int position) {
return this._filePaths.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
public void removeitem(int position){
this._filePaths.remove(position);
notifyDataSetChanged();
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ImageView imageView;
if (convertView == null) {
imageView = new ImageView(_activity);
} else {
imageView = (ImageView) convertView;
}
// get screen dimensions
Bitmap image = decodeFile(_filePaths.get(position), imageWidth,
imageWidth);
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
imageView.setLayoutParams(new GridView.LayoutParams(imageWidth,
imageWidth));
imageView.setImageBitmap(image);
// image view click listener
imageView.setOnClickListener(new OnImageClickListener(position));
return imageView;
}
class OnImageClickListener implements OnClickListener {
int _postion;
// constructor
public OnImageClickListener(int position) {
this._postion = position;
}
@Override
public void onClick(View v) {
// on selecting grid view image
// launch full screen activity
// Intent i = new Intent(_activity, FullScreenViewActivity.class);
// i.putExtra("position", _postion);
// _activity.startActivity(i);
final String imgPath=_filePaths.get(_postion);
final Snackbar snackbar = Snackbar
.make(view, "Delete Image?", Snackbar.LENGTH_LONG)
.setAction("DELETE", new View.OnClickListener() {
@Override
public void onClick(View view) {
File file = new File(imgPath);
file.delete();
Snackbar snackbar1 = Snackbar.make(view, "Image Deleted!", Snackbar.LENGTH_SHORT);
notifyDataSetChanged();
View sbView = snackbar1.getView();
TextView textView = (TextView) sbView.findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.YELLOW);
snackbar1.show();
}
});
snackbar.setActionTextColor(Color.RED);
View sbView = snackbar.getView();
TextView textView = (TextView) sbView.findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.YELLOW);
snackbar.show();
}
}
/*
* Resizing image size
*/
public static Bitmap decodeFile(String filePath, int WIDTH, int HIGHT) {
try {
File f = new File(filePath);
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
BitmapFactory.decodeStream(new FileInputStream(f), null, o);
final int REQUIRED_WIDTH = WIDTH;
final int REQUIRED_HIGHT = HIGHT;
int scale = 1;
while (o.outWidth / scale / 2 >= REQUIRED_WIDTH
&& o.outHeight / scale / 2 >= REQUIRED_HIGHT)
scale *= 2;
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
return null;
}
}
错误:
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.view.ViewGroup.getContext()' on a null object reference
at android.support.design.widget.Snackbar.<init>(Snackbar.java:180)
at android.support.design.widget.Snackbar.make(Snackbar.java:209)
at nidhinkumar.gridcam.camerasample.adapter.GridViewImageAdapter$OnImageClickListener.onClick(GridViewImageAdapter.java:95)
at android.view.View.performClick(View.java:4848)
at android.view.View$PerformClick.run(View.java:20260)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5624)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)
答案 0 :(得分:2)
问题在于您传递的视图Snackbar snackbar1 = Snackbar.make(view, "Image Deleted!", Snackbar.LENGTH_SHORT);
您尚未初始化view
。初始化view
答案 1 :(得分:0)
public void onClick(View v) {
// on selecting grid view image
// launch full screen activity
// Intent i = new Intent(_activity, FullScreenViewActivity.class);
// i.putExtra("position", _postion);
// _activity.startActivity(i);
view=v;
final String imgPath=_filePaths.get(_postion);
final Snackbar snackbar = Snackbar
.make(view, "Delete Image?", Snackbar.LENGTH_LONG)
.setAction("DELETE", new View.OnClickListener() {
@Override
public void onClick(View view) {
File file = new File(imgPath);
file.delete();
Snackbar snackbar1 = Snackbar.make(view, "Image Deleted!", Snackbar.LENGTH_SHORT);
notifyDataSetChanged();
View sbView = snackbar1.getView();
TextView textView = (TextView) sbView.findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.YELLOW);
snackbar1.show();
}
});
snackbar.setActionTextColor(Color.RED);
View sbView = snackbar.getView();
TextView textView = (TextView) sbView.findViewById(android.support.design.R.id.snackbar_text);
textView.setTextColor(Color.YELLOW);
snackbar.show();
}
我已使用view = v andd初始化视图,现在它可以正常工作