Question

我目前是Android编程的初学者，现在我正在开发一个应用程序来与LAMP服务器建立JSON连接并显示JSON数据。该连接目前已成功完成，我可以创建产品并在数据库中查看，但应用程序每次都会意外关闭，有人可以帮助并指出我正确的方向，如果需要可以添加更多。

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
                                  List<NameValuePair> params) {

    is = null;
    jObj = null;
    json = "";

    // Making HTTP request
    try {

        Log.i("url", url);

        // check for request method
        if(method == "POST"){
            // request method is POST
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            Log.i("url", url);
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        }else if(method == "GET"){
            // request method is GET
            DefaultHttpClient httpClient = new DefaultHttpClient();
            String paramString = URLEncodedUtils.format(params, "utf-8");
            url += "?" + paramString;
            Log.i("url", url);
            HttpGet httpGet = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpGet);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();
        }
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }


    Log.i("Stage 1", "Stage 1");

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);

        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");

            Log.i("1 ", line);
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    Log.i("Stage 2", "Stage 2");

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    Log.i("Stage 3", "Stage 3");

    // return JSON String
    return jObj;

}

public class NewProductActivity extends Activity {


// Progress Dialog
private ProgressDialog pDialog;

JSONParser jsonParser = new JSONParser();
EditText inputName;
EditText inputPrice;
EditText inputDesc;

// url to create new product
private static String url_create_product = "http://192.168.1.165/wp-admin/android_connect/create_product.php";

// JSON Node names
private static final String TAG_SUCCESS = "success";

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.add_product);

    // Edit Text
    inputName = (EditText) findViewById(R.id.inputName);
    inputPrice = (EditText) findViewById(R.id.inputPrice);
    inputDesc = (EditText) findViewById(R.id.inputDesc);

    // Create button
    Button btnCreateProduct = (Button) findViewById(R.id.btnCreateProduct);

    // button click event
    btnCreateProduct.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {
            // creating new product in background thread
            new CreateNewProduct().execute();
        }
    });
}

/**
 * Background Async Task to Create new product
 * */
class CreateNewProduct extends AsyncTask<String, String, String> {

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(NewProductActivity.this);
        pDialog.setMessage("Creating Product..");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    /**
     * Creating product
     * */
    @SuppressWarnings("ResourceType")
    protected String doInBackground(String... args) {
        String name = inputName.getText().toString();
        String price = inputPrice.getText().toString();
        String description = inputDesc.getText().toString();

        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("name", name));
        params.add(new BasicNameValuePair("price", price));
        params.add(new BasicNameValuePair("description", description));

        // getting JSON Object
        // Note that create product url accepts POST method
        JSONObject json = jsonParser.makeHttpRequest(url_create_product,
                "POST", params);

        // check log cat fro response
        Log.d("Create Response", json.toString());

        // check for success tag
        try {
            int success = json.getInt(TAG_SUCCESS);

            if (success == 1) {
                // successfully created product
                Intent i = new Intent(getApplicationContext(), AllProductsActivity.class);
                startActivity(i);

                // closing this screen
                finish();
            } else {
                // failed to create product
            }

        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once done
        pDialog.dismiss();
    }

}

logcat 09-16 10:47:27.285 23440-23458 / com.example.androidhive.productjsonphp I / OpenGLRenderer：初始化的EGL，版本1.4 09-16 10：47：27.287 23440-23458 / com.example.androidhive.productjsonphp D / OpenGLRenderer：启用调试模式0 09-16 10：47：28.372 23440-23440 / com.example.androidhive.productjsonphp V / Monotype： SetAppTypeFace-尝试翻转，app = com.example.androidhive.productjsonphp 09-16 10：47：28.372 23440-23440 / com.example.androidhive.productjsonphp V / Monotype：字体getFontPathFlipFont - systemFont = default＃default 09-16 10：47：28.449 23440-23471 / com.example.androidhive.productjsonphp I /网址： http://api.androidhive.info/android_connect/get_all_products.php 09-16 10：47：28.451 23440-23471 / com.example.androidhive.productjsonphp I /网址： http://api.androidhive.info/android_connect/get_all_products.php？ 09-16 10:47:28.674 23440-23458 / com.example.androidhive.productjsonphp D / OpenGLRenderer：0xB7f62f50上的endAllStagingAnimators （RippleDrawable），句柄为0xb7f75e00 09-16 10：47：29.017 23440-23471 / com.example.androidhive.productjsonphp I / Stage 1：Stage 1 09-16 10:47:29.022 23440-23471 / com.example.androidhive.productjsonphp I / 1：未知数据库＆＃39; download_androidhive＆＃39; 09-16 10:47:29.022 23440-23471 / com.example.androidhive.productjsonphp I / Stage 2：Stage 2 09-16 10:47:29.023 23440-23471 / com.example.androidhive.productjsonphp E / JSON Parser：解析数据时出错org.json.JSONException：Value 未知类型java.lang.String无法转换为JSONObject 09-16 10:47:29.023 23440-23471 / com.example.androidhive.productjsonphp I / Stage 3：Stage 3 09-16 10:47:29.029 23440-23471 / com.example.androidhive.productjsonphp E / AndroidRuntime：致命异常：AsyncTask＃1 过程：com.example.androidhive.productjsonphp，PID：23440 java.lang.RuntimeException：执行doInBackground（）时发生错误在android.os.AsyncTask $ 3.done（AsyncTask.java:300）在java.util.concurrent.FutureTask.finishCompletion（FutureTask.java:355） at java.util.concurrent.FutureTask.setException（FutureTask.java:222）在java.util.concurrent.FutureTask.run（FutureTask.java:242）在android.os.AsyncTask $ SerialExecutor $ 1.run（AsyncTask.java:231） at java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1112） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:587）在java.lang.Thread.run（Thread.java:818）引起：java.lang.NullPointerException：尝试调用虚方法＆＃39; java.lang.String org.json.JSONObject.toString（）＆＃39;在...上 null对象引用 at com.example.androidhive.productjsonphp.AllProductsActivity $ LoadAllProducts.doInBackground（AllProductsActivity.java:130） at com.example.androidhive.productjsonphp.AllProductsActivity $ LoadAllProducts.doInBackground（AllProductsActivity.java:105）在android.os.AsyncTask $ 2.call（AsyncTask.java:288）在java.util.concurrent.FutureTask.run（FutureTask.java:237）在android.os.AsyncTask $ SerialExecutor $ 1.run（AsyncTask.java:231） at java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1112） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:587） at java.lang.Thread.run（Thread.java:818)09-16 10:47:29.528 23440-23440 / com.example.androidhive.productjsonphp E / WindowManager：android.view.WindowLeaked：Activity com.example.androidhive.productjsonphp.AllProductsActivity已泄露 window com.android.internal.policy.impl.PhoneWindow $ DecorView {78d7c4f 最初添加的V.E ..... R ...... D 0,0-479,116} 在android.view.ViewRootImpl。（ViewRootImpl.java:363）在android.view.WindowManagerGlobal.addView（WindowManagerGlobal.java:261）在android.view.WindowManagerImpl.addView（WindowManagerImpl.java:69）在android.app.Dialog.show（Dialog.java:298） at com.example.androidhive.productjsonphp.AllProductsActivity $ LoadAllProducts.onPreExecute（AllProductsActivity.java:117）在android.os.AsyncTask.executeOnExecutor（AsyncTask.java:587）在android.os.AsyncTask.execute（AsyncTask.java:535） at com.example.androidhive.productjsonphp.AllProductsActivity.onCreate（AllProductsActivity.java:57）在android.app.Activity.performCreate（Activity.java:5975）在android.app.Instrumentation.callActivityOnCreate（Instrumentation.java:1105）在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2269）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2378）在android.app.ActivityThread.access $ 800（ActivityThread.java:147）在android.app.ActivityThread $ H.handleMessage（ActivityThread.java:1281）在android.os.Handler.dispatchMessage（Handler.java:102）在android.os.Looper.loop（Looper.java:135）在android.app.ActivityThread.main（ActivityThread.java:5255） at java.lang.reflect.Method.invoke（Native Method）在java.lang.reflect.Method.invoke（Method.java:372）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:838）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:651)09-16 10：47：34.521 23440-23471 / com.example.androidhive.productjsonphp I /处理：发送信号。 PID：23440 SIG：9

Answer 1

你尝试从String＆＃34; json＆＃34;解析Json但是这个＆＃34; json＆＃34; string给出null值，如果请检查＆＃34; json＆＃34;在使用之前，string为null。

所以，试试这段代码

{{1}}

将新行添加到数据库并意外关闭应用

1 个答案: