Question

我正在尝试在gridView上显示图像，但却出现以下错误： -

 java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to android.widget.ImageView
 at com.hubdatasolutions.receiptcloud.ReceiptTabActivity$ReceiptAdapter.getView(ReceiptTabActivity.java:128)

row_grid.xml

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="5dp" >
    <RelativeLayout 
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <ImageView
            android:id="@+id/item_image"
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:layout_marginRight="10dp"
            android:contentDescription="clickedImage"
            android:src="#ffffff" />

        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="right"
             android:layout_alignParentRight="true"
             android:src="@drawable/close"
           />
    </RelativeLayout>
        <TextView
            android:id="@+id/item_text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="5dp"
            android:textSize="15sp" >
        </TextView>

    </LinearLayout>

activity_receipt_tab.xml

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:tools="http://schemas.android.com/tools"
         android:id="@+id/mainLayout"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:background="@drawable/menu_bg"
         tools:context=".ReceiptTabActivity" >
         <LinearLayout
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:orientation="vertical" >
             <ImageView
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
                 android:background="@drawable/logo" />
             <GridView
                 android:id="@+id/gridView"
                 android:layout_width="match_parent"
                android:layout_height="0dp"
                 android:layout_weight="1"
                 android:columnWidth="90dp"
                 android:gravity="center"
                 android:horizontalSpacing="10dp"
                 android:numColumns="auto_fit"
                 android:stretchMode="columnWidth"
                android:verticalSpacing="10dp" >
             </GridView>
             <include layout="@layout/tab_footer" />
         </LinearLayout>
     </RelativeLayout>

ReceptTabActivity.java

这是java文件，我收到错误。这是我试图开发两个类的文件。我在同一个文件中膨胀gridView。

    public class ReceiptTabActivity extends BaseTabActivity {

    GridView mGrid;
    ReceiptAdapter mAdapter;
    ArrayList<ReceiptData> mReceiptList = new ArrayList<ReceiptData>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_receipt_tab);

        mReceiptList = APICaller.getInstance().getReceiptList();


        mGrid = (GridView) findViewById(R.id.gridView);
    //  mAdapter = new ReceiptAdapter(this, R.layout.receipt_grid_item);
        //mGrid.setAdapter(mAdapter);
        mAdapter = new ReceiptAdapter(this,R.layout.row_grid);
        mGrid.setAdapter(mAdapter);
        APICaller.getInstance().downloadPicData();
    }

    @Override
    public void onRefreshData(Refreshable refreshable, int requestCode) {
        if (requestCode == APICaller.DOWNLOAD_PIC_REQUEST_CODE) {
            for (ReceiptData receipt : mReceiptList) {
                String filePath = receipt.getFilePath();
                if (filePath != null && !filePath.isEmpty()) {
                    File file = new File(filePath);
                    Bitmap bitmap = decodeFile(file);
                    if (bitmap != null)
                        receipt.setImage(bitmap);
                    else
                        Log.i("Bitmap", "Still null");
                } else {
                    Log.i("String", "Still null");
                }
            }
            mAdapter.notifyDataSetChanged();
        }
    }

    // decodes image and scales it to reduce memory consumption
    private Bitmap decodeFile(File f) {
        try {
            // Decode image size
            BitmapFactory.Options o = new BitmapFactory.Options();
            o.inJustDecodeBounds = true;
            BitmapFactory.decodeStream(new FileInputStream(f), null, o);

            // The new size we want to scale to
            final int REQUIRED_SIZE = 70;

            // Find the correct scale value. It should be the power of 2.
            int scale = 1;
            while (o.outWidth / scale / 2 >= REQUIRED_SIZE
                    && o.outHeight / scale / 2 >= REQUIRED_SIZE)
                scale *= 2;

            // Decode with inSampleSize
            BitmapFactory.Options o2 = new BitmapFactory.Options();
            o2.inSampleSize = scale;
            return BitmapFactory.decodeStream(new FileInputStream(f), null, o2);
        } catch (FileNotFoundException e) {
        }
        return null;
    }

    private Bitmap decodeOriginalFile(File f) {
        try {

            return BitmapFactory.decodeStream(new FileInputStream(f));
        } catch (FileNotFoundException e) {
        }
        return null;
    }

    class ReceiptAdapter extends ArrayAdapter<View> {
        Context mContext;
        int mResource;
        ArrayList<ReceiptData> data = new ArrayList<ReceiptData>();
        public ReceiptAdapter(Context context, int resource) {
            super(context, resource);
            mContext = context;
            mResource = resource;
        }

        @Override
        public int getCount() {
            return mReceiptList.size();
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            //ImageButton mainView;
            ImageView mainView;
            //View row = convertView;
            //RecordHolder holder = null;

            mainView = (ImageView) findViewById(R.id.item_image);
            //String info = ImageView.getText().toString();
            LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
            mainView = (ImageView) inflater.inflate(mResource, parent, false);


            Bitmap bitmap = mReceiptList.get(position).getImage();
            if (bitmap != null)
                mainView.setImageBitmap(bitmap);

            return mainView;
        }

    }
}

Answer 1

在适配器类的构造函数中初始化inflater

LayoutInaflater inflater;
public ReceiptAdapter(Context context, int resource) {
            super(context, resource);
            mContext = context;
            mResource = resource;
            infalter= LayoutInflater.from(context);
        }

将getView更改为

public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder viewHolder;
        if(convertView==null)
        { 
        viewHolder = new ViewHolder();
        convertView = inflater.inflate(R.layout.row_grid, null);
        // inflate row_grid.xml  

        viewHolder.mainView= (ImageView)convertView.findViewById(R.id.item_image);
        //initialize imageview
        convertView.setTag(viewHolder);
        }else{
         viewHolder = (ViewHolderItem) convertView.getTag();

        }
        Bitmap bitmap = mReceiptList.get(position).getImage();
        if (bitmap != null)
           holder.mainView.setImageBitmap(bitmap); 
           // set bitmap to imageview

        return convertView;
    }

使用ViewHolder

http://developer.android.com/training/improving-layouts/smooth-scrolling.html

static ViewHolder
{
     ImageView mainView;
}

Answer 2

对于这两行：

    mainView = (ImageView) findViewById(R.id.item_image);
...
    mainView = (ImageView) inflater.inflate(mResource, parent, false);

似乎你做了一个复制粘贴错误。是的，你希望第一个被转换为ImageView，但我认为第二个mainView被夸大应该是你在那里写的第一个xml片段中的LinearLayout？

Answer 3

在你的适配器的getView中，首先给row_grid充气，然后用它来寻找你的ImageView

  View rowview = (View) inflater.inflate(mResource, parent, false);
  mainView = (ImageView) rowview.findViewById(R.id.item_image);

进行所需的任何自定义，然后返回row_grid（上面代码中的rowview）

android.widget.LinearLayout无法强制转换为android.widget.ImageView？

3 个答案: