以编程方式更改 GridView 中的 ImageView [英] Change ImageView in a GridView Programmatically

问题描述

我已经设置了一个带有 TextView 叠加层的 ImageView 网格.我的ImageAdapter代码如下:

I've set up a grid of ImageViews with TextView overlays. My ImageAdapter code is as follows:

    public View getView(int position, View convertView, ViewGroup parent) {
    ImageView imageView;
    View grid;
    LayoutInflater inflater = (LayoutInflater) mContext
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    if (convertView == null) {
        grid = new View(mContext);
        grid = inflater.inflate(R.layout.image, null);
        TextView textView = (TextView)grid.findViewById(R.id.mastery_text);

        imageView = (ImageView)grid.findViewById(R.id.mastery_image);
        grid.setLayoutParams(new GridView.LayoutParams(150, 150));
        imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
        grid.setPadding(8, 8, 8, 8);
        grid.setBackgroundResource(R.color.orange);

        imageView.setImageResource(mThumbIds[position]);            

    } else {
        grid = (View) convertView;
    }

    return grid;
}

我的 ImageAdapter 对应的 XML 布局是这样的:

The corresponding XML layout for my ImageAdapter is this:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layout_practitioner" 
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ImageView 
        android:id="@+id/mastery_image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"
    />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_gravity="bottom"
        android:background="#bbffffff"
        android:focusable="false"
        android:focusableInTouchMode="false" >

        <TextView android:id="@+id/mastery_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="0dp"
            android:textColor="@color/black"
            android:gravity="bottom|center"
            android:textSize="12sp"
            android:textAllCaps="true"
            android:paddingBottom="0dp"
            android:text="3/3"
            />

    </LinearLayout>
</FrameLayout>

我的 GridView(活动类)的 XML 代码:

XML code for my GridView (activity class):

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

    <GridView xmlns:android="http://schemas.android.com/apk/res/android"
        android:paddingTop="@dimen/activity_vertical_margin"
        android:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:id="@+id/gridview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:numColumns="4"
        android:verticalSpacing="10dp"
        android:horizontalSpacing="10dp"
        android:stretchMode="columnWidth"
        android:gravity="center" />

</LinearLayout>

这是我的主要活动的 onCreate 方法:

Here is the onCreate method of my main activity:

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_masteries);

    GridView gridview = (GridView) findViewById(R.id.gridview);

    ImageAdapter adapter = new ImageAdapter(this);
    gridview.setAdapter(adapter);

    gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v,
                                int position, long id) {
            Toast.makeText(Masteries.this, "" + position,
                    Toast.LENGTH_SHORT).show();
        }
    });
}

我想在用图像初始化网格后，根据其在网格上的位置，更改我的活动类中的 ImageViews 之一.我该怎么做?

I want to, after initializing the grid with the images, change one of the ImageViews from my activity class, given its position on the grid. How would I do that?

我不要求更改图像以响应 onItemClick.提前致谢！

I'm not asking to change the image in response to an onItemClick. Thanks in advance!

我正在考虑在我的适配器中创建一个 changeImage(int position, int imageId) 方法并从我的活动类中调用它.这是正确的方法吗?

I'm thinking of creating a changeImage(int position, int imageId) method in my Adapter and calling that from my activity class. Is that the right approach?

推荐答案

在你的适配器中:

public void updateImage(int position, int resourceId)
{
    mThumbIds[position] = resourceId;
    notifyDataSetChanged();
}

在您的活动中:

mAdapter.updateImage(<position>, <image_resource_id>);

注意事项

1. 您必须使适配器成为您的活动的成员
2. 主要思想是你修改后备数据并通知GridView这已经改变了，是时候重新绘制了
3. 您的 getView() 方法实现需要大量改进.一旦系统开始回收视图(convertView 参数进来 != null 的位置与上次使用的位置不同)，它会导致很多错误

1. You will have to make the adapter a member of your activity
2. The main idea is that you modify the backing data and and notify the GridView that this has changed and it is time to be redrawn
3. Your getView() method implementation needs a lot of improvement. It will cause lots of bugs once the system starts recycling the views (the convertView parameter comes in != null for a position different than it was used for last time)

下面是你的 getView() 应该是什么样子的草图:

Here's a sketch of how your getView() should look like:

@Override
public View getView(int position, View convertView, ViewGroup parent)
{
    ViewHolder viewHolder;
    LayoutInflater inflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    if (convertView == null) {
        convertView = inflater.inflate(R.layout.image, parent, false);
        // next three lines would not be necessary if:
        //  a) it is the same for every item;
        //  b) you inflate properly (using the parent);
        //  c) you specify this in the item's xml (R.layout.image)
        convertView.setLayoutParams(new GridView.LayoutParams(150, 150));
        convertView.setPadding(8, 8, 8, 8);
        convertView.setBackgroundResource(android.R.color.holo_red_light);

        viewHolder = new ViewHolder();
        viewHolder.mTextView = (TextView)convertView.findViewById(R.id.mastery_text);
        viewHolder.mImageView = (ImageView)convertView.findViewById(R.id.mastery_image);
        // this could also be set in xml perhaps
        viewHolder.mImageView.setScaleType(ImageView.ScaleType.CENTER_CROP);

        convertView.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder)convertView.getTag();
    }

    // update the values every time we are being asked to update the item,
    // because the item might have been reused from a different position
    viewHolder.mImageView.setImageResource(mThumbIds[position]);
    //viewHolder.mTextView.setText("myText");

    return convertView;
}


public static class ViewHolder
{
    TextView mTextView;
    ImageView mImageView;
}

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