如何刷新GridView？

Question

我有一个与Google教程非常相似的GridView,除了我想在运行时添加ImageViews(通过子活动).结果还可以,但View的布局搞砸了:GridView没有填充其父级的内容,我需要做些什么才能正确设计它？

这里添加孩子的代码:

public void initializeWorkbench(GridView gv, Vector<String> items) {
        Prototype.workbench.setDimension(screenWidth, divider.height()+workbenchArea.height());
        Prototype.workbench.activateWorkbench();
        // this measures the workbench correctly
        Log.d(Prototype.TAG, "workbench width: "+Prototype.workbench.getMeasuredWidth());
        // 320
        Log.d(Prototype.TAG, "workbench height: "+Prototype.workbench.getMeasuredHeight());
        // 30
        ImageAdapter imgAdapter = new ImageAdapter(this.getContext(), items);
        gv.setAdapter(imgAdapter);
        gv.measure(screenWidth, screenHeight);
        gv.requestLayout();
        gv.forceLayout();
        Log.d(Prototype.TAG, "gv width: "+gv.getMeasuredWidth());
        // 22
        Log.d(Prototype.TAG, "gv height: "+gv.getMeasuredHeight());
        // 119
        Prototype.workbench.setDimension(screenWidth, divider.height()+workbenchArea.height());
    }
}

工作台中的activateWorkbench,setDimension和measure(GridView上方的LinearLayout):

public void activateWorkbench() {
    if(this.equals(Prototype.workbench)) {
        this.setOrientation(VERTICAL);
        show = true;
        measure();
    }
}

public void setDimension(int w, int h) {
    width = w;
    height = h;
    this.setLayoutParams(new LinearLayout.LayoutParams(width, height));
    this.invalidate();
}

private void measure() {
    if (this.getOrientation() == LinearLayout.VERTICAL) {
        int h = 0;
        int w = 0;
        this.measureChildren(0, 0);
        for (int i = 0; i < this.getChildCount(); i++) {
            View v = this.getChildAt(i);
            h += v.getMeasuredHeight();
            w = (w < v.getMeasuredWidth()) ? v.getMeasuredWidth() : w;
        }
        if (this.equals(Prototype.tagarea))
            height = (h < height) ? height : h;
        if (this.equals(Prototype.tagarea))
            width = (w < width) ? width : w;
    }
    this.setMeasuredDimension(width, height);
}

ImageAdapter构造函数:

public ImageAdapter(Context c, Vector<String> items) {
    mContext = c;

    boolean mExternalStorageAvailable = false;
    boolean mExternalStorageWriteable = false;
    String state = Environment.getExternalStorageState();

    if (Environment.MEDIA_MOUNTED.equals(state)) {
        // We can read and write the media
        mExternalStorageAvailable = mExternalStorageWriteable = true;
    } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
        // We can only read the media
        mExternalStorageAvailable = true;
        mExternalStorageWriteable = false;
    } else {
        // Something else is wrong. It may be one of many other states, but
        // all we need
        // to know is we can neither read nor write
        mExternalStorageAvailable = mExternalStorageWriteable = false;
    }

    if (mExternalStorageAvailable && mExternalStorageWriteable) {
        for (String item : items) {
            File f = new File(item);
            if (f.exists()) {
                try {
                    FileInputStream fis = new FileInputStream(f);
                    Bitmap b = BitmapFactory.decodeStream(fis);
                    bitmaps.add(b);
                    files.add(f);
                } catch (FileNotFoundException e) {
                    Log.e(Prototype.TAG, "", e);
                }
            }
        }
    }
}

和xml布局:

<LinearLayout   xmlns:android="http://schemas.android.com/apk/res/android" 
            android:layout_width="fill_parent" 
            android:layout_height="fill_parent"
                android:orientation="vertical"
                android:gravity="bottom"

                android:paddingLeft="0px"
                android:paddingTop="0px"
                android:paddingRight="0px">

    <com.unimelb.pt3.ui.TransparentPanel
            android:id="@+id/workbench" 
            android:layout_width="fill_parent"
            android:layout_height="10px"
            android:paddingTop="0px"
            android:paddingLeft="0px"
            android:paddingBottom="0px"
            android:paddingRight="0px">

        <GridView xmlns:android="http://schemas.android.com/apk/res/android" 
            android:id="@+id/gridview"
            android:layout_width="fill_parent" 
            android:layout_height="fill_parent"
            android:columnWidth="90dp"
            android:numColumns="auto_fit"
            android:verticalSpacing="10dp"
            android:horizontalSpacing="10dp"
            android:stretchMode="columnWidth"
            android:gravity="center" />

    </com.unimelb.pt3.ui.TransparentPanel>

</LinearLayout>

Answer 1

GridView有一个invalidateViews()方法.

当你调用这个方法时:"所有要重建和重绘的视图." http://developer.android.com/reference/android/widget/GridView.html

我想这就是你需要的:)

Answer 2

您必须首先告诉适配器通知数据已更改并再次将适配器设置为网格

adapter.notifyDataChanged();
grid.setAdapter(adapter);

Answer 3

这可能会有所帮助.在对项目执行删除后刷新书籍图像缩略图的网格视图.使用adapter.notifyDataChanged(); 如上所述对我不起作用,因为它在我的适配器中调用.

//this is a call that retrieves cached data.
//your constructor can be designed and used without it.
final Object data = getLastNonConfigurationInstance();

我基本上只是重新加载适配器并将其绑定到相同的视图.

//reload the adapter
adapter = new BooksAdapter(MyBooks.this, MyBooks.this, data, show_collection );
grid.invalidateViews();
grid.setAdapter(adapter);

Answer 4

@flyerz @snagnever

你们一起得到了它们.它应该是:

adapter.notifyDataChanged();
grid.invalidateViews();

这将标记其数据已更改的适配器,然后在调用invalidateViews()方法后将其传播到网格.

很高兴我发现了这个问题,因为我无法弄清楚如何在渲染后将项目添加到网格中.

Answer 5

这些答案中没有一个对我有用,我不得不将它们全部混合在一起.要实际让GridView更新,您需要这样做:

 adapter.notifyDataChanged();
 grid.invalidateViews();
 grid.setAdapter(adapter);

希望这可以帮助任何无法获得其他解决方案的人.

Answer 6

你不应该调用invalidateViews和setAdapter刷新grid view.保持grid view更新并不是一个好主意,如果以这种方式更新,则会花费大量时间和内存.

如果您有机会查看getView方法,您将看到convertView只创建一次.当您致电时notifyDataChanged,它将更新此视图.而如果您打电话invalidateViews,将重新创建以前创建的视图.这不是一个好的解决方案.

getView调用时会调用您的方法notifyDataChanged.所以你的getView方法看起来应该像下面的代码.

public List list;

public class SimpleItemViewHolder extends Object
{
    public TextView textView;
    public ImageView imageView;
}

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

    View itemView = convertView;
    SimpleItemViewHolder viewHolder;

    if(convertView==null)
    {
        viewHolder = (SimpleItemViewHolder)itemView.getTag();

    }else{
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        itemView = inflater.inflate(R.layout.layout_name, null);
        TextView labelField = (TextView) itemView.findViewById(R.id.label_field);
        labelField.setText(list.get(position).Name);
        //Typeface boldFont = Typeface.createFromAsset(context.getAssets(), "fonts/Font-Bold.ttf");
        //labelField.setTypeface(boldFont);

        ImageView imageView = (ImageView) itemView.findViewById(R.id.image_view);
        //Bitmap bitmap = init your bitmap here;
        //imageView.setImageBitmap(bitmap);  

        viewHolder = new SimpleItemViewHolder();
        viewHolder.imageView = imageView;
        viewHolder.textView = labelField;
        itemView.setTag(viewHolder);

    }

    //don't create new views, instead use previous ones and update them.
    viewHolder.textView.setText(list.get(position).Name);
    //viewHolder.imageView.setImageBitmap(your_bitmap);  
    return itemView;
}

Answer 7

您正在放置较高的GridView内部。com.unimelb.pt3.ui.TransparentPanel10px

• 你不应该使用px，你应该使用dp。
• 更改com.unimelb.pt3.ui.TransparentPanel为android:layout_height="10px"​android:layout_height="fill_parent"