java - Android应用程序制作2.2版本但不兼容2.2+版本

Question

我必须做一个应用程序，它应该适用于所有 2.2+ 版本。我已经在 Android 设备和模拟器中进行了测试。但是这个应用程序可以在几个版本中工作，但不能在更高版本中工作，如果我启动我的应用程序，我会收到空​​值错误。我不知道为什么会这样。根据我的假设“如果我们为较低版本开发应用程序，该应用程序应该在所有其他较高版本中工作”，但这是行不通的。请帮助我。

这是我在 2.2、2.3 和一些更高版本中运行的代码。但不适用于 3.2 及更高版本。我得到了

的空值

@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_geotracker);

    textbox1 = (TextView) findViewById(R.id.textinname1);
    textbox2 = (TextView) findViewById(R.id.textinname2);

    ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo ni = cm.getActiveNetworkInfo();
    if (ni != null && ni.isConnected())
    {
        msg = "Please login to continue";
        login();
    }
    else
    {
        msg = "Sorry , network connection is not available.";
        message();
    }
}

//Login------------------------------------------------------------------------------------
public void login()
{
    final EditText uname = new EditText(this); 
    final EditText upassword = new EditText(this);
    DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener()
    {
        // DialogInterface called while setting the AlertDialog Buttons
        public void onClick(DialogInterface dialog, int which)
        {
            //Here you can perform functions of Alert Dialog Buttons as shown
             switch(which)
             {
                case DialogInterface.BUTTON_POSITIVE:
                    if(!uname.getText().toString().equals("") && !upassword.getText().toString().equals(""))
                    {
                        session_name = uname.getText().toString();
                        session_pwd = upassword.getText().toString();
                        try
                        {
                            uid = httppost(uname.getText().toString(), upassword.getText().toString(), "login.php"); //Here Iam getting null value.
                            Log.i("TAG", ""+uid);
                        }
                        catch(JSONException e)
                        {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }

                        if(uid == null || uid.length() == 6)
                        {
                            msg = "Either user name or password or both incorrect.";
                            login();
                        }
                        else
                        {
                            Toast.makeText(getApplicationContext(), "Hello " + uname.getText().toString() + ", You have successfully logged in..:)", Toast.LENGTH_LONG).show();
                            IDList()
                        }
                    }
                    else
                    {
                        Toast.makeText(getApplicationContext(), "Sorry, Either user name or password or both incorrect..:(", Toast.LENGTH_LONG).show();
                        msg = "Both user name and password are mandatory fields.";
                        login();
                    }
                break;

                case DialogInterface.BUTTON_NEGATIVE:
                    exit();
                break;
            }
         }
     };

     AlertDialog.Builder builder = new AlertDialog.Builder(this);
     LinearLayout orientation = new LinearLayout(this);
     orientation.setOrientation(1); //1 is for vertical orientation
     uname.setHint("Enter name");
     upassword.setHint("Enter password");
     upassword.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
     orientation.addView(uname);
     orientation.addView(upassword);
     builder.setView(orientation);
     builder.setMessage(msg);
     builder.setTitle("Login")
     .setIcon(R.drawable.ic_launcher)
     .setPositiveButton("Submit", dialogClickListener)
     .setNegativeButton("Exit App", dialogClickListener).show();
}

public String httppost(String param1, String param2, String file) throws JSONException
{   
     try 
     {
        String data = URLEncoder.encode("param1", "UTF-8") + "=" + URLEncoder.encode(param1, "UTF-8");
        data += "&" + URLEncoder.encode("param2", "UTF-8") + "=" + URLEncoder.encode(param2, "UTF-8");

        // Send data
        URL url = new URL("http://192.168.1.12/GeoTracker/android/"+file);
        URLConnection conn = url.openConnection();
        conn.setDoOutput(true);
        OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
        wr.write(data);
        wr.flush();

        // Get the response
        BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        the_string_response = rd.readLine();
        wr.close();
        rd.close();
    }
    catch (Exception e)
    {
    }
    textbox1.setText("");
    textbox2.setText("");

    return the_string_response;
}

这是我的日志猫，

`05-21 19:12:50.610: D/dalvikvm(4100): Late-enabling CheckJNI

05-21 19:12:50.850: E/PhonePolicy(4100): Could not preload class for phone policy: com.android.internal.policy.impl.PhoneWindow$ContextMenuCallback

05-21 19:12:50.970: D/TextLayoutCache(4100): Using debug level: 0 - Debug Enabled: 0

05-21 19:12:51.160: I/dalvikvm(4100): threadid=1: recursive native library load attempt (/system/lib/libwebcore.so)

05-21 19:12:51.160: D/dalvikvm(4100): No JNI_OnLoad found in /system/lib/libchromium_net.so 0x0, skipping init

05-21 19:12:51.220: D/dalvikvm(4100): GC_CONCURRENT freed 134K, 4% free 5078K/5255K, paused 1ms+1ms

05-21 19:12:51.750: D/libEGL(4100): loaded /system/lib/egl/libEGL_mali.so

05-21 19:12:51.760: D/libEGL(4100): loaded /system/lib/egl/libGLESv1_CM_mali.so

05-21 19:12:51.770: D/libEGL(4100): loaded /system/lib/egl/libGLESv2_mali.so

05-21 19:12:51.820: D/OpenGLRenderer(4100): Enabling debug mode 0

05-21 19:12:59.690: D/dalvikvm(4100): GC_CONCURRENT freed 159K, 5% free 5329K/5575K, 
paused 2ms+4ms`

05-21 19:13:11.500: I/TAG(4100): null

请帮助我，提前致谢...

Answer 1

在具有足够高 API 级别的设备上，系统会阻止您在主线程中执行网络操作(http post 等...)。如果您在 logcat 中进一步查找(将其设置为详细)，您可能会在其中找到类似 NETWORK_ON_MAIN_THREAD_EXCEPTION 的内容。

看起来这正是您正在做的事情。这在较低的 API 级别上可以正常工作，因为平台没有限制它(尽管这仍然是一个坏主意)

要解决此问题，您只需将网络操作移出主线程即可。考虑使用AsyncTask