java - 从 URL 异步获取数据

Question

嗨，我正在编写一个 android 应用程序以从 url 获取信息并将其显示在 ListView 中。一切都运作良好。但是显示视图需要很长时间，因为我从onCreate()方法上的 url 读取文件。

我想从 URL 异步读取，所以视图响应时间不会受到损害。

我正确使用 ProgressBar 吗？

public class cseWatch extends Activity  {
    TextView txt1 ;
    Button btnBack;
    ListView listView1;
    /** Called when the activity is first created. */
    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.searchresult);

        Button btnBack=(Button) findViewById(R.id.btn_bck);
        btnBack.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent MyIntent1 = new Intent(v.getContext(),cseWatchMain.class);
                startActivity(MyIntent1);
            }
        });

        ArrayList<SearchResults> searchResults = GetSearchResults();

        //after loaded result hide progress bar
        ProgressBar pb = (ProgressBar) findViewById(R.id.progressBar1);
        pb.setVisibility(View.INVISIBLE);

        final ListView lv = (ListView) findViewById(R.id.listView1);
        lv.setAdapter(new MyCustomBaseAdapter(cseWatch.this, searchResults));

        lv.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> a, View v, int position, long id) {
                Object o = lv.getItemAtPosition(position);
                SearchResults fullObject = (SearchResults)o;
                Toast.makeText(cseWatch.this, "You have chosen: " + " " + fullObject.getName(), Toast.LENGTH_LONG).show();
            }
        });


    }//end of onCreate


private ArrayList<SearchResults> GetSearchResults(){
    ArrayList<SearchResults> results = new ArrayList<SearchResults>();

    SearchResults sr;
    InputStream in;
    try{
        txt1 = (TextView) findViewById(R.id.txtDisplay);
        txt1.setText("Sending request...");
        DefaultHttpClient httpclient = new DefaultHttpClient();
        HttpGet httpget = new HttpGet("http://www.myurl?reportType=CSV");
        HttpResponse response = httpclient.execute(httpget);
        in = response.getEntity().getContent();

        txt1.setText("parsing CSV...");


        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            try {
                String line;
                reader.readLine(); //IGNORE FIRST LINE

                while ((line = reader.readLine()) != null) {
                     String[] RowData = line.split(",");
                     sr = new SearchResults();

                     String precent = String.format("%.2g%n",Double.parseDouble(RowData[12])).trim();

                     double chng=Double.parseDouble(RowData[11]);
                     String c;
                     if(chng > 0){
                         sr.setLine2Color(Color.GREEN);
                         c="▲";
                     }else if(chng < 0){
                         sr.setLine2Color(Color.rgb(255, 0, 14));
                         c="▼";
                     }else{
                         sr.setLine2Color(Color.rgb(2, 159, 223));
                         c="-";
                     }

                     sr.setName(c+RowData[2]+"-"+RowData[1]);


                     DecimalFormat fmt = new DecimalFormat("###,###,###,###.##");
                     String price = fmt.format(Double.parseDouble(RowData[6])).trim();
                     String tradevol = fmt.format(Double.parseDouble(RowData[8])).trim();

                     sr.setLine1("PRICE: Rs."+price+" TRADE VOL:"+tradevol);
                     sr.setLine2("CHANGE:"+c+RowData[11]+" ("+precent+"%)");
                     results.add(sr);
                     txt1.setText("Loaded...");
                    // do something with "data" and "value"
                }
            }
            catch (IOException ex) {
                Log.i("Error:IO",ex.getMessage());
            }
            finally {
                try {
                    in.close();
                }
                catch (IOException e) {
                    Log.i("Error:Close",e.getMessage());
                }
            }
    }catch(Exception e){
        Log.i("Error:",e.getMessage());
        new AlertDialog.Builder(cseWatch.this).setTitle("Watch out!").setMessage(e.getMessage()).setNeutralButton("Close", null).show();  
    }

    return results;
   }

}

score 2 · Accepted Answer

应该使用 AsyncTask 将繁重的工作从 UI 线程中移开。http://developer.android.com/reference/android/os/AsyncTask.html

score 0 · Accepted Answer

我认为您应该使用可运行的。演示代码：

final ListView lv = (ListView) findViewById(R.id.listView1);
Handler handler = new Handler(app.getMainLooper());
handler.postDelayed(new Runnable() {
    @Override
    public void run() {
        lv.setAdapter(new MyCustomBaseAdapter(cseWatch.this, searchResults));
        lv.setOnItemClickListener(new OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> a, View v, int position, long id) {
                Object o = lv.getItemAtPosition(position);
                SearchResults fullObject = (SearchResults)o;
                Toast.makeText(cseWatch.this, "You have chosen: " + " " + fullObject.getName(), Toast.LENGTH_LONG).show();
            }
        });
    }
    }, 1000);

试试看。^-^

java - 从 URL 异步获取数据

2 回答 2

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