Question

我将图像从mysql数据库填充到gridView，用户使用复选框从中选择匹配症状的图像。当图像小于10时，一切正常，但当gridview有超过10个图像时，当用户按下继续按钮时问题出现它在Logcat中给出了一个空指针引用

 java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.widget.LinearLayout.findViewById(int)' on a null object reference
                                                   at com.banmart.www.intergratedpestmanagement.ImageTest.CustomAdapterTwo$3.onClick(CustomAdapterTwo.java:120)

这是我的 CustomAdapterTwo.java

images = new ArrayList<>();

        mAdapter = new ImageAdapter(this, images);
        gridView.setAdapter(mAdapter);
proceed.setOnClickListener(new View.OnClickListener() {
            String outputStrArr;
            @Override
            public void onClick(View v) {


                int count = gridView.getAdapter().getCount();

                ArrayList<String> selectedItems = new ArrayList<String>();
                for(int i = 0; i < count; i++) {

                    LinearLayout linearLayout = (LinearLayout) gridView.getChildAt(i);
                    checkbox = (CheckBox) linearLayout.findViewById(R.id.checkBox1);

                    if(checkbox.isChecked()){
                        outputStrArr =checkbox.getTag().toString();
                        selectedItems.add(outputStrArr);

                        String [] strArr = new String[selectedItems.size()];
                        for (int j= 0; j < selectedItems.size(); j++) {
                            strArr[j] = selectedItems.get(j);
                        }
                        Intent intent = new Intent(getApplicationContext(),
                                ResultActivity.class);

                        // Create a bundle object
                        Bundle b = new Bundle();
                        b.putStringArray("selectedItems", strArr);

                        // Add the bundle to the intent.
                        intent.putExtras(b);

                        // start the ResultActivity
                        startActivity(intent);

                        finish();
                        Log.d("Item "+String.valueOf(i), checkbox.getTag().toString());
                        //  Toast.makeText(CustomAdapterTwo.this,checkbox.getTag().toString() ,Toast.LENGTH_LONG).show();
//selectedItems.add(checkbox.getTag());
                    }
                }

            }

        });

ImageAdapter

public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = null;
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.gridtwo, null);
            viewHolder = new ViewHolder();

            viewHolder.textView = (TextView) convertView.findViewById(R.id.textView1);
            viewHolder.imageView = (ImageView) convertView.findViewById(R.id.imageView1);
            viewHolder.Chkbox = (CheckBox) convertView.findViewById(R.id.checkBox1);
            viewHolder.Chkbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                @Override
                public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                    int getPosition = (Integer) buttonView.getTag();
                    images.get(getPosition).setSelected(buttonView.isChecked());
                }
            });
            convertView.setTag(viewHolder);
            convertView.setTag(R.id.textView1, viewHolder.textView);
            convertView.setTag(R.id.imageView1, viewHolder.imageView);
            convertView.setTag(R.id.checkBox1, viewHolder.Chkbox);
        }
        else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        ImagesLib image = images.get(position);
       viewHolder.textView.setText(image.getAltText());


        Glide.with(mContext).load(image.getImageUrl())
                .thumbnail(0.5f)
                .crossFade()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .into(viewHolder.imageView);

        viewHolder.Chkbox.setTag(image.getId());
viewHolder.Chkbox.setTag(position);
viewHolder.Chkbox.setChecked(images.get(position).isSelected());
        return convertView;
    }

grid.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="5dp" >

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="150dp"
        android:layout_height="150dp"
        android:layout_marginRight="10px"
         >
    </ImageView>

    <CheckBox
        android:id="@+id/checkBox1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true" />


</LinearLayout>

grid_gallery.xml

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/tableLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <TableRow
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" >

        <TextView
            android:id="@+id/textView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center"
            android:layout_gravity="center"
            android:textColor="#050"
            android:textStyle="bold"
            android:layout_marginLeft="5dp"
            android:text="Check the symptoms on the Banana Plant "
            android:layout_span="1"
            android:textAppearance="?android:attr/textAppearanceMedium" />

    </TableRow>


    <View
        android:layout_height="1dip"
        android:background="#CCCCCC" />



    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0.1">

        <GridView
            android:id="@+id/gridView1"
            android:layout_marginLeft="5dp"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:numColumns="auto_fit" >
        </GridView>

    </LinearLayout>



    <View
        android:layout_height="1dip"
        android:background="#CCCCCC" />


    <LinearLayout
        android:id="@+id/LinearLayout1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:padding="5dip"
        android:weightSum="3">

        <Button
            android:id="@+id/btnCheckAll"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:text="Check All" />
        <Button
            android:id="@+id/btnClearAll"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:text="Clear All" />
        <Button
            android:id="@+id/btnGetItem"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="#070"
            android:textColor="#fff"
            android:layout_alignParentTop="true"
            android:layout_centerHorizontal="true"
            android:text="Continue >>" />

    </LinearLayout>

</TableLayout>

Answer 1

此调用的linearlayout为空

LinearLayout linearLayout = (LinearLayout) gridView.getChildAt(i);

而不是调用getChildAt，而是必须使用此方法

public View getViewByPosition(int pos, GridView mGridView) {
    final int firstListItemPosition = mGridView.getFirstVisiblePosition();
    final int lastListItemPosition = firstListItemPosition + mGridView.getChildCount() - 1;

    if (pos < firstListItemPosition || pos > lastListItemPosition ) {
        return mGridView.getAdapter().getView(pos, null, listView);
    } else {
        final int childIndex = pos - firstListItemPosition;
        return mGridView.getChildAt(childIndex);
    }
}

Gridview with checkbox返回NullPointerException

1 个答案: