在 GridView Android 中实现 Multi Select

Question

我需要在 GridView 中 select 多张图片，并在 Gridview 中添加分享和删除按钮。

我的ImageAdapterclass:

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 时出现错误。

我的 Logcat 详细信息

02-10 21:10:46.965 21658-21658/com.android.example E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.android.example, PID: 21658 java.lang.ClassCastException: android.widget.ImageView cannot be cast to com.android.example.GridViewActivity$CheckableLayout at com.android.example.GridViewActivity$ImageAdapter.getView(GridViewActivity.java:224) at android.widget.AbsListView.obtainView(AbsListView.java:2255) at android.widget.GridView.onMeasure(GridView.java:1044) at android.view.View.measure(View.java:16540) at android.widget.RelativeLayout.measureChild(RelativeLayout.java:689) at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:473) at android.view.View.measure(View.java:16540) at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:851) at android.view.View.measure(View.java:16540) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5137) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:16540) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5137) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) at android.view.View.measure(View.java:16540) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5137) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:16540) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5137) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) at android.view.View.measure(View.java:16540) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5137) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291) at android.view.View.measure(View.java:16540) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1942) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1132) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1321) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1019) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5725) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761) at android.view.Choreographer.doCallbacks(Choreographer.java:574) at android.view.Choreographer.doFrame(Choreographer.java:544) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747) at android.os.Handler.handleCallback(Handler.java:733) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5086) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)

Answer 1

ClassCastException: android.widget.ImageView cannot be cast to com.android.example.GridViewActivity$CheckableLayout

因为您正在从 getView returning ImageView 但试图在这一行中将其转换为 CheckableLayout:

checkableLayout = (CheckableLayout) convertView;

return checkableLayout 来自 getView() 方法：

        @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;

   }

Answer 2

你应该 return convertView 来自 getView 方法。

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

    // code here

    convertview.addView(checkableLayout);
    return convertView;

}

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