Android：动态更改列表视图中的图像

Question

我有一个由以下 xml 定义的列表视图。当用户单击任何行时，我需要在运行时切换列表中的图像。我怎样才能做到这一点？非常感谢任何帮助。谢谢

//list_item.xml
<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/play" 
android:id="@+id/img"
/> 
<TextView 
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center_vertical"
android:id="@+id/txt"
/>
</LinearLayout>

Answer 1

您可以通过在onItemClick 处理程序中对第二个参数（即被点击项目的View）调用findViewById 来定位项目的img 视图：

public void onItemClick(AdapterView parentView, View clickedItemView, int pos, long id)
{
    ImageView imageView = (ImageView) clickedItemView.findViewById(R.id.img);
    // ...
}

编辑：请注意，Android 会重复使用列表项View 对象（也称为视图回收），因此需要存储每个项的切换状态以供以后使用。每当列表项视图绑定到列表项以进行显示时，都需要访问每个项的切换状态。

例如，这是一个在点击时切换每个项目的图像的活动示例：

import java.util.Arrays;
import java.util.List;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;

public class SO4539968TestCaseActivity extends Activity {
    private static final List<String> ITEM_TEXTS = Arrays.asList(new String[] {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13"});

    private boolean[] itemToggled;

    private class MyArrayAdapter<T> extends ArrayAdapter<T>
    {
        public MyArrayAdapter(Context context, int resource, int textViewResourceId, List<T> objects) {
            super(context, resource, textViewResourceId, objects);
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View itemView = super.getView(position, convertView, parent);
            ImageView imageView = (ImageView) itemView.findViewById(R.id.img);
            imageView.setImageResource(itemToggled[position] ? R.drawable.on : R.drawable.off);
            return itemView;
        }
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        itemToggled = new boolean[ITEM_TEXTS.size()];
        Arrays.fill(itemToggled, false);

        ListView listView = (ListView) findViewById(R.id.list_view0);
        listView.setAdapter(new MyArrayAdapter<String>(this, R.layout.list_item, R.id.txt, ITEM_TEXTS));
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            public void onItemClick(AdapterView<?> listView, View itemView, int position, long id) {
                itemToggled[position] = ! itemToggled[position];

                ImageView imageView = (ImageView) itemView.findViewById(R.id.img);
                imageView.setImageResource(itemToggled[position] ? R.drawable.on : R.drawable.off);
            }
        });
    }
}

要研究的重要部分是onItemClick 回调和getView 在MyArrayAdapter 中的覆盖。

Adapter 类的getView 方法负责膨胀项目布局。在这个例子中，我调用超类的getView 方法来初步准备项目视图，但随后我确保适当地设置项目的img 视图的资源ID：

imageView.setImageResource(itemToggled[position] ? R.drawable.on : R.drawable.off);

另请参阅：Developing Applications for Android – Gotchas and Quirks

Answer 2

    listview.setOnItemClickListener(new AdapterView.OnItemClickListener(){

        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            ImageView imageView=arg1.findViewById(R.id.img);
            imageView.setImageResource(R.drawable.new_image);

        }

    });

Answer 3

我将动态生成列表视图，然后绑定到 onclickitem 事件，以便按照“Kiril Kirilov”的说法执行 setimageresource。

Answer 4

这很容易做到，您只需要查看用户单击的列表项的位置即可。一个描述良好的完整演示代码如下_

 public class ChangeImageInListDynamically extends Activity {
/**
 * Adapter for your data. 
 */
ImageAdapter adpAR;
ArrayList<String> itemList;
ListView mListView;
ImageAdapter mAdapter;

/**
 * Indicate which item is currently selected.  
 * Its default selected item is '0' e.g., 1st item. 
 */
private int selectedPosition=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    itemList = new ArrayList<String>();
    for (int i = 0; i < 11; i++) {
        itemList.add("Item - "+i);
    }

    mListView = (ListView)findViewById(R.id.data_list);

    //Initialize your adapter
    mAdapter = new ImageAdapter(nChangeImageInListDynamically.this, itemList);

    //set adapter to your list.
    mListView.setAdapter(mAdapter);

    //set list click listener.
    mListView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> av, View view, int position, long id) {
            //your image that need to change dynamically.
            ImageView imageView = (ImageView) view.findViewById(R.id.select);

            //position of clicked item.  
            selectedPosition=position;

            //change image of respective image.
            imageView.setImageResource(R.drawable.selected);

            //notify your adapter to update your list.  
            adpAR.notifyDataSetChanged();
        }
    });

}

static class ViewHolder {
    TextView title;
    ImageView img;                  
}   

/**
 * Your ImageAdapter.
 */
public class ImageAdapter extends BaseAdapter {

    ArrayList<String> dataList;
    Context context;

    public ImageAdapter(Context context, ArrayList<String> arrayList) {
        this.context = context;
        this.dataList = arrayList;

    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return dataList.size();;
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = convertView;

        final ViewHolder holder;
        Log.d("posiiton ImageAdapater : ",""+position);
        if (row == null) { 
            LayoutInflater inflater = ChangeImageInListDynamically.this.getLayoutInflater();
            row = inflater.inflate(R.layout.listrow, null);

            holder = new ViewHolder();
            holder.title = (TextView) row.findViewById(R.id.text);
            holder.img = (ImageView) row.findViewById(R.id.select);
            row.setTag(holder);
        } else {
            holder = (ViewHolder) row.getTag();
        }

        //set titel text.
        holder.title.setText(dataList.get(position));

        //Change Image of selected item dynamically.
             if(selectedPosition == position) {
                 //Item is selected.
                 holder.img.setImageResource(R.drawable.selected);

             }else{
                 //Other non-selected items.
                 holder.img.setImageResource(R.drawable.dis_selected);

             }

        return row;

    }

 }

}

我希望这对所有人都有帮助:)

Answer 5

使用

public void setImageResource (int resId);

ImageView 类的方法。

附：我之前的答案似乎不完整，这是整个解决方案：

ImageView imageView = (ImageView) this.findViewById(R.id.img);
                ((BitmapDrawable)imageView.getDrawable()).getBitmap().recycle();
                imageView.setImageResource(R.drawable.new_image);
                imageView.invalidate();