java - 在 ListView 中加载多个图像

Question

我正在学习 NewBoston 教程 ( https://www.youtube.com/watch?v=nOdSARCVYic&list=PL6gx4Cwl9DGBsvRxJJOzG4r4k_zLKrnxl&index=48 )

他展示了如何将图像放入列表中，但从未展示过如何为每段文本分配不同的图像。

这是我的 MainActivity。

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);


    String[] Jobsites = {"River Park Place", "Mayfair", "Jameson House"};
    ListAdapter jobsiteAdapter = new CustomAdapter(this, Jobsites);
    ListView jobsiteListView = (ListView) findViewById(R.id.jobsiteListView);
    jobsiteListView.setAdapter(jobsiteAdapter);

    jobsiteListView.setOnItemClickListener(
            new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    String jobsite = String.valueOf(parent.getItemAtPosition(position));
                    //Toast.makeText(MainActivity.this, jobsite, Toast.LENGTH_LONG).show();
                    if (jobsite == "River Park Place"){
                        //Perform segue to the proper view where employess can sign in
                        //******************************************
                        System.out.println("*****************");
                        System.out.println("Attempting to segue");
                        System.out.println("*****************");



                        //******************************************
                    }else{
                        System.out.println("*****************");
                        System.out.println("These jobsites aren't avaliable yet!");
                        System.out.println("*****************");
                        Toast.makeText(MainActivity.this, "**These Sites aren't avaliable yet!**", Toast.LENGTH_LONG).show();
                    }
                }
            }
        );

    }
}

在视频中，我们制作了一个处理图像的自定义 View 。这是代码。

class CustomAdapter extends ArrayAdapter<String> {


public CustomAdapter(Context context, String[] jobsites) {
    super(context,R.layout.custom_row ,jobsites);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    LayoutInflater jobsiteInflater = LayoutInflater.from(getContext());
    View customView = jobsiteInflater.inflate(R.layout.custom_row, parent, false);

    String singleJobsiteItem = getItem(position);

    ImageView josbiteImage = (ImageView) customView.findViewById(R.id.josbiteImage);

    josbiteImage.setImageResource(R.drawable.riverparkplace);


    return customView;

    }
}

我还有另外两张图片要添加到列表底部的两项文本中。现在它只是为列表中的所有三行一遍又一遍地加载相同的图片。

Answer 1

让我逐步指导您完成此过程。在我们继续之前，您需要了解 ListView 的 ArrayAdapter 会使用您指定的数据填充每一行。换句话说，您希望像处理 Jobsites 字符串数组一样将图像传递给适配器。

1. 定义一个简单包装器对象，其中包含您的字符串(Jobsites)和您要分配给它的图像。

   public class SimpleObject {
   
       private String jobSite;
       private int imageID; // your R.drawable.image
   
       public SimpleObject(String jobSite, int imageID) {
           this.jobSite = jobSite;
           this.imageID = imageID;
       }
   
       public String getJobSite() {
           return jobSite;
       }
   
       public int getImageID() {
           return imageID;
       }
   }
   

2. 初始化要由适配器使用的 SimpleObject 数组。在主 Activity 的 onCreate() 中，执行以下操作:

   ArrayList<SimpleObject> objectList = new ArrayList<>();
   objectList.add(new SimpleObject("River Park Place", R.drawable.image1);
   objectList.add(new SimpleObject("Mayfair", R.drawable.image2);
   // the list goes on....
   

3. 现在，更改您的 CustomAdapter 以保存 SimpleObject 而不是 String:

   class CustomAdapter extends ArrayAdapter<SimpleObject> {
   
   
       public CustomAdapter(Context context, ArrayList<SimpleObject> objectList) {
           super(context,R.layout.custom_row ,objectList);
       }
   
       @Override
       public View getView(int position, View convertView, ViewGroup parent) {
           LayoutInflater jobsiteInflater = LayoutInflater.from(getContext());
           View customView = jobsiteInflater.inflate(R.layout.custom_row, parent, false);
   
           // Get the SimpleObject
           SimpleObject item = (SimpleObject) getItem(position);
           String singleJobsiteItem = item.getJobSite(); // get the String
   
           ImageView josbiteImage = (ImageView) customView.findViewById(R.id.josbiteImage);
   
           josbiteImage.setImageResource(item.getImageID()); // get the image ID and assign it to jobsiteImage :)
   
   
           return customView;
   
       }
   }
   

4. 现在确保使用新的 SimpleObject 列表在主 Activity 中初始化适配器:

   ListAdapter jobsiteAdapter = new CustomAdapter(this, objectList);