Question

尝试使用asynctask进行延迟加载。它的75％工作正常;能够在doInBackground()中运行方法。但加载后UI未更新。我意识到内容不存储在我声明的数组中（如果我没有使用asynctask）。看到onProgressUpdate和publishUpdate但不确定如何使用它们。运行searchContent()后，数据将存储在mStrings[]和dStrings[]中，以便将其传递到我的适配器。有什么帮助吗？

HelloClass.java

public class HelloClass extends Activity {

ListView list;
LazyAdapter adapter;

ProgressDialog dialog;
private String[] mStrings = {};
private String[] dStrings = {};

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

    new TheTask().execute();        

    list=(ListView)findViewById(R.id.list);         
    adapter=new LazyAdapter(this, mStrings, dStrings);
    list.setAdapter(adapter);

}

protected class TheTask extends AsyncTask<Void, Void, Void>{

    protected void onPreExecute() {
        dialog = ProgressDialog.show(HelloClass.this, "Retrieving Information", "Please wait for few seconds...", true, false);
    }

    protected Void doInBackground(Void... params) {
        searchContent();
        return null;
    }

    protected void onPostExecute(Void result) {
        dialog.dismiss();
    }
}

public void searchContent()
{
    String imageC = "";
    String textC = "";


    try {

        URL url = new URL(targetURL);

        // Make the connection
        URLConnection conn = url.openConnection();
        BufferedReader reader = new BufferedReader(
         new InputStreamReader(conn.getInputStream()));

        String line = reader.readLine();

        while (line != null) {

            if(line.contains("../../"))
            {

                String xyz = line.substring(0,xyz.indexOf('"'));
                imageC = xyz +";";                  
                mStrings = imageC.split(";");
                line = reader.readLine();
            }

            if(line.contains("../../") == false)
            {
                line = reader.readLine();
            }

            if (line.contains("Nametag"))
            {
                int startIndex = line.indexOf("Gnametag") + 10;
                int endIndex = line.indexOf("<", startIndex + 1);
                String gname = line.substring(startIndex,endIndex);
                textC = textC.replaceAll("</span>", "");
                textC += "Name: "+gname+ "\n";
            }                   

                if (line.contains("Age"))
                {
                    textC += "Age: "+reader.readLine() + "\n" + ";";
                    textC = textC.replaceAll("                  ", "");
                dStrings = textC.split(";");
                }

            if (line.contains("Last Update"))
            {
                reader.close();
            }                               
        }           

        // Close the reader
        reader.close();

    } catch (Exception ex) {
        ex.printStackTrace();           
    }


}

Adapter.java

public class LazyAdapter extends BaseAdapter {

private Activity activity;
private String[] data;
private String[] text;
private static LayoutInflater inflater=null;
public ImageLoader imageLoader; 

public LazyAdapter(Activity a, String[] d, String[] t) {
    activity = a;
    data=d;
    text = t;
    inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    imageLoader=new ImageLoader(activity.getApplicationContext());
}

EDITTED：

protected class TheTask extends AsyncTask<Void, Void, Void>{

    protected void onPreExecute() {
        dialog = ProgressDialog.show(HelloClass.this, "Retrieving Information", "Please wait for few seconds...", true, false);
    }

    protected void doInBackground(String[]... params) {
        searchContent();
        MyResultClass result = new MyResultClass();
        result.mStrings = mStrings;
        result.dStrings = dStrings;
        return result;
    }   
    protected void onPostExecute(String[] result) {
        dialog.dismiss();
    }

}

class MyResultClass
{ 
    public String[] mStrings; 
    public String[] dStrings; 

}

Answer 1

您的适配器在内部保留自己的数据结构。这意味着如果你想改变它的状态，你必须直接操作它。

在您的情况下，您应该在工作完成后再次在适配器中设置mStrings和dStrings。

当您希望在任务运行时与UI进行交互时，例如当您想要显示进度条时，可以使用

publishUpdate和onProgressUpdate。

Answer 2

您不应该在doInBackground中使用Classvars。构建一个结果对象并将其传递给onPostExecute，它在UI-Thread中运行。在那里你可以设置你的String []或适配器或任何你想要的。

和什么gwa sais。我刚才看到，我的“解决方案”只是一个“更好的练习”，我猜...当然你必须让适配器知道这个变化。或者你要告诉它，它的基础数据结构已经改变，或者你通过使用适配器的方法来改变数据结构。

protected class TheTask extends AsyncTask<Void, Void, MyResultClass >{

protected void onPreExecute() {
    dialog = ProgressDialog.show(HelloClass.this, "Retrieving Information", "Please wait for few seconds...", true, false);
}

protected MyResultClass doInBackground(String[]... params) {
    searchContent();
    MyResultClass result = new MyResultClass();
    result.mStrings = mStrings;
    result.dStrings = dStrings;
    return result;
}   
protected void onPostExecute(MyResultClass result) {
    dialog.dismiss();
// Set new adapter-values here.  
}
}

class MyResultClass
{ 
    public String[] mStrings; 
    public String[] dStrings; 
}

我希望您了解this有关AsyncTask的网站？

Android - Asynctask不将数据传递到私有数组？

2 个答案: