Android:动态更改Listview中的图像 [英] Android: Dynamically change Image in Listview

问题描述

我有一个由以下xml定义的列表视图.当用户单击任意行时，我需要在运行时切换图像.我怎样才能做到这一点?任何帮助都将受到高度赞赏.谢谢

I have a listview defined by the following xml. I need to toggle the image in the list during runtime when the user clicks on any row. How can I achieve this? Any help is highly appreciated. Thanks

//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>

推荐答案

您可以通过调用img视图.html#findViewById％28int％29"rel =" noreferrer> findViewById 在 onItemClick 处理程序:

You can locate the item's img view by calling findViewById on the second parameter (which is the View of the clicked item) within the onItemClick handler:

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重用列表项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备后用.每当列表项目视图绑定到列表项目以进行显示时，都需要访问每个项目的切换状态.

Be aware that Android reuses list item View objects (also called view recycling), so the toggle state of each item needs to be stored for later use. The toggle state of each item needs to be accessed whenever a list item view is bound to a list item for display.

例如，这是一个活动示例，可以在点击时切换每个项目的图像:

For example, here is working example of an activity that toggles the image of each item on click:

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MyArrayAdapter中的getView覆盖.

The important parts to study are the onItemClick callback and the override of getView in MyArrayAdapter.

Adapter类的="noreferrer"> getView 方法负责扩大项目的布局.在此示例中，我调用超类的getView方法来初始准备项目视图，但随后确保确保正确设置项目的img视图的资源ID:

The getView method of the Adapter class is responsible for inflating the item layout. In this example, I call the getView method of the superclass to initially prepare the item view, but then I make sure to appropriately set the resource ID of the item's img view:

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

另请参见:开发应用程序Android版– Gotchas和Quirks

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