Question

我在使这段代码工作时遇到了很多问题。我的主要活动是使用ZXing扫描条形码，然后我想获取该扫描的结果并用它查询我的API。我知道我必须使用AsyncTask来做到这一点，但我之前从未使用过，而且我遇到了很多麻烦。我的目标是在AsyncTask中查询API，然后使用生成的JSON字符串更新我的upcTxt TextView元素。我在ReadJSON代码中接下来要做什么？

这是我的主要活动代码：

public class Barcode extends Activity implements OnClickListener {

private Button scanBtn;
private TextView formatTxt, contentTxt, upcTxt;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_barcode);
    scanBtn = (Button)findViewById(R.id.scan_button);
    formatTxt = (TextView)findViewById(R.id.scan_format);
    contentTxt = (TextView)findViewById(R.id.scan_content);
    upcTxt = (TextView)findViewById(R.id.upc);
    scanBtn.setOnClickListener(this);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.barcode, menu);
    return true;
}

public void onClick(View v){
    //respond to clicks
    if(v.getId()==R.id.scan_button){
        //scan
        IntentIntegrator scanIntegrator = new IntentIntegrator(this);
        scanIntegrator.initiateScan();
    }
}

public void onActivityResult(int requestCode, int resultCode, Intent intent) {
    //retrieve scan result
    IntentResult scanningResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, intent);
    if (scanningResult != null) {
        //we have a result
        String scanResult = scanningResult.getContents();
        String scanFormat = scanningResult.getFormatName();
        formatTxt.setText("FORMAT: " + scanFormat);
        contentTxt.setText("CONTENT: " + scanResult);
        new ReadJSON().execute(new String[] {scanResult});
    } else {
        Toast toast = Toast.makeText(getApplicationContext(), "No scan data received!", Toast.LENGTH_LONG);
        toast.show();
    }
}}

这是我的ReadJSON代码：

public class ReadJSON extends AsyncTask<String, Void, Void> {

private String content;
private TextView upcTxt;
private String url;

@Override
protected Void doInBackground(String... scanResult) {
    url = "REDACTED";
    content = "";
    HttpClient Client = new DefaultHttpClient();
    HttpGet httpget = new HttpGet(url + scanResult[0]);
    ResponseHandler<String> responseHandler = new BasicResponseHandler();
    try {
        content = Client.execute(httpget, responseHandler);
        // Update upcTxt here
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}
}

提前谢谢。

更新：每当我尝试在手机上运行代码时，我都可以正常扫描条形码，但一旦尝试访问该URL，程序就会崩溃。

logcat的：

01-18 17:26:44.731: E/AndroidRuntime(24876): at com.peter.barcodetest.ReadJSON.doInBackground(ReadJSON.java:30)
01-18 17:26:44.731: E/AndroidRuntime(24876):    at com.peter.barcodetest.ReadJSON.doInBackground(ReadJSON.java:1)
01-18 17:26:46.473: D/CrashAnrDetector(376): processName: com.peter.barcodetest
01-18 17:26:46.473: D/CrashAnrDetector(376): broadcastEvent : com.peter.barcodetest data_app_crash
01-18 17:26:46.913: D/PackageBroadcastService(26662): Received broadcast action=android.intent.action.PACKAGE_REPLACED and uri=com.peter.barcodetest
01-18 17:26:55.122: I/ActivityManager(376): Process com.peter.barcodetest (pid 24876) (adj 13) has died.

Answer 1

我将您的代码更改为：

仅编辑ReadJSON

AsyncTask（已编辑）

public class ReadJSON extends AsyncTask<String, Integer, String> {

private String content;
private TextView upcTxt;
private String url;

private static final String TAG = "ReadJSON";
    String s = "";
    Context context;
    ReadJSONCallBack callback;

    public ReadJSONTask (Context context, ReadJSONCallBack cb) {
        super();
        this.callback = cb;
        this.context = context;
    }

@Override
protected String doInBackground(String... scanResult) {
    url = "REDACTED";
    HttpClient Client = new DefaultHttpClient();
    HttpGet httpget = new HttpGet(url + scanResult[0]);

    try {
        HttpResponse response = Client.execute(httpget);

        if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {

                InputStream in = response.getEntity().getContent();

                Log.d(TAG, "Got response");

                InputStreamReader inputStreamReader = new InputStreamReader(in);

                BufferedReader bufferedReader = new BufferedReader(
                        inputStreamReader);

                StringBuilder stringBuilder = new StringBuilder();
                String bufferedStrChunk = null;

                while ((bufferedStrChunk = bufferedReader.readLine()) != null) {
                    stringBuilder.append(bufferedStrChunk);
                }

                Log.d(TAG, "Content: " + stringBuilder.toString());

                return stringBuilder.toString();
        // Update upcTxt here
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}
}

protected void onPostExecute(String result) {
        callback.setString(s);
    }


    // method for parsing JSON object
    public String parseJSONObject(String output) {


        try {
            JSONArray jArray = new JSONArray(output);

            for (int i = 0; i < jArray.length(); i++) {
                JSONObject jObject = jArray.getJSONObject(i);

                String id = jObject.getString("id");
                String customer = jObject.getString("name");
                String description = jObject.getString("description");
                Long time = (Long) jObject.get("timeAsDate");

                // do something
            }
        } catch (JSONException e) {

        }
        return description;
    }

}

AsyncTask从URL读取和返回数据

1 个答案: