Android:动态更改Listview中的图像

Question

我有一个由以下xml定义的列表视图.当用户点击任何行时,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？任何帮助都非常感谢.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img通过调用findViewById处理程序中的第二个参数(即View所单击项目的参数)来找到项目的视图onItemClick:

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供以后使用.只要将列表项视图绑定到列表项以进行显示,就需要访问每个项的切换状态.

例如,以下是在点击时切换每个项目的图像的活动的工作示例:

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);
            }
        });
    }
}

研究的重要部分是onItemClick回调的覆盖getView在MyArrayAdapter.

该类的getView方法Adapter负责膨胀项目布局.在这个例子中,我所说的getView超最初编写项目视图的方法,但我一定要正确设置项目的的资源ID img的看法:

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

另请参阅:开发Android应用程序 - 陷阱和怪癖

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);

        }

    });