Question

我需要在GridView中选择多个图片，然后在Gridview添加共享和删除按钮。

我的ImageAdapter课程：

private class ImageAdapter extends BaseAdapter {

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        final ImageView imageView;
        CheckableLayout checkableLayout;

        if (convertView == null) {
            imageView = new ImageView(activity);
            imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
            checkableLayout = new CheckableLayout(activity);
            imageView.setLayoutParams(new GridView.LayoutParams(imageWidth, imageWidth));
        } else {
            checkableLayout = (CheckableLayout) convertView;
            imageView = (ImageView) checkableLayout.getChildAt(0);
        }

        bitmap = decodeFile(getItem(position), imageWidth, imageWidth);
        imageView.setImageBitmap(bitmap);
        imageView.setOnClickListener(new OnImageClickListener(position));
        return imageView;

    }

    class OnImageClickListener implements View.OnClickListener {

        int position;

        public OnImageClickListener(int position) {
            this.position = position;
        }

        @Override
        public void onClick(View v) {
            Intent intent = new Intent(activity, ImageDisplayActivity.class);
            intent.putExtra("id", getPosition(position));
            activity.startActivity(intent);
        }
    }

    public class CheckableLayout extends FrameLayout implements Checkable {

        private boolean mChecked;

        public CheckableLayout(Context context) {
            super(context);
        }

        @Override
        public void setChecked(boolean checked) {
            mChecked = checked;
            setBackgroundDrawable(checked ? getResources().getDrawable(R.drawable.blue) : null);
        }

        @Override
        public boolean isChecked() {
            return mChecked;
        }

        @Override
        public void toggle() {
            setChecked(!mChecked);
        }
    }

    public class MultiChoiceModeListener implements GridView.MultiChoiceModeListener {

        @Override
        public void onItemCheckedStateChanged(ActionMode mode, int position, long id, boolean checked) {
            int selectCount = gridView.getCheckedItemCount();
            switch (selectCount) {
                case 1:
                    mode.setSubtitle("One item selected");
                    break;
                default:
                    mode.setSubtitle("" + selectCount + " items selected");
                    break;
            }
        }

        @Override
        public boolean onCreateActionMode(ActionMode mode, Menu menu) {
            mode.setTitle("Select Items");
            mode.setSubtitle("One item selected");
            return true;
        }

        @Override
        public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
            return true;
        }

        @Override
        public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
            return true;
        }

        @Override
        public void onDestroyActionMode(ActionMode mode) {

        }
    }
}

但是当我尝试打开Gridview时，它会给我一个错误。

我的Logcat详细信息

02-10 21：10：46.965 21658-21658 / com.android.example E / AndroidRuntime：致命异议：主要处理：com.android.example，PID：21658 java.lang.ClassCastException：android.widget.ImageView无法强制转换为com.android.example.GridViewActivity $ CheckableLayout 在com.android.example.GridViewActivity $ ImageAdapter.getView（GridViewActivity.java:224）在android.widget.AbsListView.obtainView（AbsListView.java:2255）在android.widget.GridView.onMeasure（GridView.java:1044）在android.view.View.measure（View.java:16540）在android.widget.RelativeLayout.measureChild（RelativeLayout.java:689）在android.widget.RelativeLayout.onMeasure（RelativeLayout.java:473）在android.view.View.measure（View.java:16540）在android.support.v4.widget.DrawerLayout.onMeasure（DrawerLayout.java:851）在android.view.View.measure（View.java:16540）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5137）在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）在android.view.View.measure（View.java:16540）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5137）在android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1404）在android.widget.LinearLayout.measureVertical（LinearLayout.java:695）在android.widget.LinearLayout.onMeasure（LinearLayout.java:588）在android.view.View.measure（View.java:16540）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5137）在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）在android.view.View.measure（View.java:16540）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5137）在android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1404）在android.widget.LinearLayout.measureVertical（LinearLayout.java:695）在android.widget.LinearLayout.onMeasure（LinearLayout.java:588）在android.view.View.measure（View.java:16540）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:5137）在android.widget.FrameLayout.onMeasure（FrameLayout.java:310）在com.android.internal.policy.impl.PhoneWindow $ DecorView.onMeasure（PhoneWindow.java:2291）在android.view.View.measure（View.java:16540）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:1942）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1132）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1321）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1019）在android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:5725）在android.view.Choreographer $ CallbackRecord.run（Choreographer.java:761）在android.view.Choreographer.doCallbacks（Choreographer.java:574）在android.view.Choreographer.doFrame（Choreographer.java:544）在android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:747）在android.os.Handler.handleCallback（Handler.java:733）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:136）在android.app.ActivityThread.main（ActivityThread.java:5086） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:785）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:601）

Answer 1

您应该从convertView方法返回getView。

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

    // code here

    convertview.addView(checkableLayout);
    return convertView;

}

Answer 2

ClassCastException：android.widget.ImageView无法强制转换为 com.android.example.GridViewActivity $ CheckableLayout

因为您从ImageView返回getView，但是尝试将其转换为此行中的CheckableLayout：

checkableLayout = (CheckableLayout) convertView;

从checkableLayout方法返回getView()：

        @Override
        public View getView(final int position, 
                            View convertView, ViewGroup parent) {
            final ImageView imageView;
            CheckableLayout checkableLayout;

            if (convertView == null) {
                imageView = new ImageView(activity); 
                // your code here ... 
                // add ImageView to checkableLayout
                checkableLayout.addView(imageView); 

            } else 
               checkableLayout = (CheckableLayout) convertView;
               imageView = (ImageView) checkableLayout.getChildAt(0);
               // your code here ... 
              return checkableLayout;

   }

在GridView Android中实现多选

2 个答案: