Question

您好我已经创建了一个应用程序，只需单击一个按钮就可以将字符串发送到下一个活动，而在第二个活动中，我使用该值来从数据库中检索数据。

我正在做以下事情。

    Intent myIntent = getIntent(); // getting the value from the previous activity
    myIntent.getStringExtra("lbl_name");
    postParameters = new ArrayList<NameValuePair>();
    postParameters.add(new BasicNameValuePair("product", lbl_name//passing the name to the database .getText().toString()));

问题是它无法识别lbl_name。

我搜索了互联网，但找不到解决方案。请告诉我我是否做得对。

传递值的代码。

Intent myIntent = new Intent(SinglePlaceActivity.this,RecoProd.class);
                                        myIntent.putExtra("lbl_name", "lbl_name");
                                        SinglePlaceActivity.this.startActivity(myIntent);

访问数据库的代码。

public class RecoProd extends Activity {
    EditText pd;
    TextView error;

    ArrayList<NameValuePair> postParameters;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        try {
            Class<?> strictModeClass = Class.forName("android.os.StrictMode", true, Thread.currentThread()
                    .getContextClassLoader());

            Class<?> threadPolicyClass = Class.forName("android.os.StrictMode$ThreadPolicy", true, Thread
                    .currentThread().getContextClassLoader());

            Class<?> threadPolicyBuilderClass = Class.forName("android.os.StrictMode$ThreadPolicy$Builder", true,
                    Thread.currentThread().getContextClassLoader());

            Method setThreadPolicyMethod = strictModeClass.getMethod("setThreadPolicy", threadPolicyClass);

            Method detectAllMethod = threadPolicyBuilderClass.getMethod("detectAll");
            Method penaltyMethod = threadPolicyBuilderClass.getMethod("penaltyLog");
            Method buildMethod = threadPolicyBuilderClass.getMethod("build");

            Constructor<?> threadPolicyBuilderConstructor = threadPolicyBuilderClass.getConstructor();
            Object threadPolicyBuilderObject = threadPolicyBuilderConstructor.newInstance();

            Object obj = detectAllMethod.invoke(threadPolicyBuilderObject);

            obj = penaltyMethod.invoke(obj);
            Object threadPolicyObject = buildMethod.invoke(obj);
            setThreadPolicyMethod.invoke(strictModeClass, threadPolicyObject);

        } catch (Exception ex) {
            String TAG = null;
            Log.w(TAG, ex);
        }
        super.onCreate(savedInstanceState);
        setContentView(R.layout.recomain);
        Intent myIntent = getIntent(); // getting the value from the previous activity
        String lbl_name= myIntent.getStringExtra("lbl_name");//< get lbl_name from Intent
        pd = (EditText) findViewById(R.id.name);

        error = (TextView) findViewById(R.id.showresult);


                postParameters = new ArrayList<NameValuePair>();
                postParameters.add(new BasicNameValuePair("product", lbl_name
                        ));


                // String valid = "1";

                DownloadWebPageTask dw = new DownloadWebPageTask();
                dw.execute("");

    }

    private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... urls) {
            String response = null;
            for (String url : urls) {
                try {
                    response = CustomHttpClient.executeHttpPost("http://192.168.1.7/abc/check2.php", postParameters);  
                    String res = response.toString();
                    // res = res.trim();
                    res = res.replaceAll("\\s+", "");
                    // error.setText(res);
                    try{
                        res = "";
                  JSONArray jArray = new JSONArray(res);
                        for(int i=0;i<jArray.length();i++){
                                JSONObject json_data = jArray.getJSONObject(i);
                                Log.i("prod_id","id: "+json_data.getInt("prod_id")+
                                        ", prod_name: "+json_data.getString("prod_name")+
                                        ", prod_category: "+json_data.getString("prod_category")+
                                        ", prod_cost: "+json_data.getDouble("prod_cost")
                                );
                                //Get an output to the screen
                                res += "\n" + json_data.getInt("prod_id") + " -> "+ json_data.getString("prod_name");
                        }
                }
                catch(JSONException e){
                        Log.e("log_tag", "Error parsing data "+e.toString());
                }

                try{
                 error.setText(res);
                }
                catch(Exception e){
                 Log.e("log_tag","Error in Display!" + e.toString());;          
                }   
           }
                 catch (Exception e) {
            Log.e("log_tag","Error in http connection!!" + e.toString());     
           }
            }
            return response;

               }
        @Override
        protected void onPostExecute(String result) {
        }
    }
}

Answer 1

您需要从Intent中提取lbl_name值：

Intent myIntent = getIntent(); // getting the value from the previous activity
 String lbl_name= myIntent.getStringExtra("lbl_name");//< get lbl_name from Intent
 postParameters = new ArrayList<NameValuePair>();
 postParameters.add(new BasicNameValuePair("product",lbl_name));

或者如果lbl_name在prev Activity中是静态的，那么您可以将其作为：

访问它

postParameters.add(new BasicNameValuePair("product",
                              Your_prev_Activity_Name.lbl_name));

Answer 2

尝试传递Intent中的字符串值，如下所示：

     Intent myIntent = new Intent(SinglePlaceActivity.this,RecoProd.class);
       myIntent.putExtra("lbl_name", "lbl_name");
       SinglePlaceActivity.this.startActivity(myIntent);

使用getString();

访问以下值

Intent myIntent = getIntent(); // getting the value from the previous activity
String lbl_name=myIntent.getString("lbl_name");
postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("product", lbl_name//passing the name to the database .getText().toString()));

后参数给出错误

2 个答案: