java - 当我更改 minSDKVersion 时发生 NetworkOnMainThreadException 错误

Question

我开发了一个登录和注册系统，当 minSDKVersion 设置为 8 时，代码工作正常，但是当我将 minSDkVersion 更改为更高版本(例如 11 或 12)时，当我尝试登录或注册时，应用程序崩溃。发生了什么变化我应该在代码中编写以便我可以在更高版本中运行。LoginActivity.java 文件如下:

   package com.example.trial;

   import java.util.HashMap;

   import org.json.JSONException;
   import org.json.JSONObject;

   import android.app.Activity;
   import android.content.Intent;
   import android.os.Bundle;
   import android.util.Log;
   import android.view.View;
   import android.widget.Button;
   import android.widget.EditText;
   import android.widget.TextView;

   import com.example.trial.library.DatabaseHandler;
   import com.example.trial.library.UserFunctions;

    public class LoginActivity extends Activity {
Button btnLogin;
Button btnLinkToRegister;
EditText inputEmail;
EditText inputPassword;
TextView loginErrorMsg;

// JSON Response node names
private static String KEY_SUCCESS = "success";
private static String KEY_ERROR = "error";
private static String KEY_ERROR_MSG = "error_msg";
private static String KEY_UID = "uid";
private static String KEY_NAME = "name";
private static String KEY_EMAIL = "email";
private static String KEY_CREATED_AT = "created_at";

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

    // Importing all assets like buttons, text fields
    inputEmail = (EditText) findViewById(R.id.loginEmail);
    inputPassword = (EditText) findViewById(R.id.loginPassword);
    btnLogin = (Button) findViewById(R.id.btnLogin);
    btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegisterScreen);
    loginErrorMsg = (TextView) findViewById(R.id.login_error);

    // Login button Click Event
    btnLogin.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            String email = inputEmail.getText().toString();
            String password = inputPassword.getText().toString();
            UserFunctions userFunction = new UserFunctions();
            Log.d("Button", "Login");
            JSONObject json = userFunction.loginUser(email, password);

            // check for login response
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    loginErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS); 
                    if(Integer.parseInt(res) == 1){
                        // user successfully logged in
                        // Store user details in SQLite Database
                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        // Clear all previous data in  database
                         userFunction.logoutUser(getApplicationContext());
                         db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL),  json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                      

                        // Launch Dashboard Screen
                        Intent dashboard = new  Intent(getApplicationContext(), DashboardActivity.class);

                        // Close all views before launching Dashboard
                        dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        startActivity(dashboard);

                        // Close Login Screen
                        finish();
                    }else{
                        // Error in login
                        loginErrorMsg.setText("Incorrect username/password");
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    });

    // Link to Register Screen
    btnLinkToRegister.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            Intent i = new Intent(getApplicationContext(),
                    RegisterActivity.class);
            startActivity(i);
            finish();
        }
    });
     }
     }

RegisterActivity.java 文件是:

    package com.example.trial;

    import org.json.JSONException;
    import org.json.JSONObject;

    import com.example.trial.library.DatabaseHandler;
    import com.example.trial.library.UserFunctions;

    import android.app.Activity;
    import android.content.Intent;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    public class RegisterActivity extends Activity {
Button btnRegister;
Button btnLinkToLogin;
EditText inputFullName;
EditText inputEmail;
EditText inputPassword;
TextView registerErrorMsg;

// JSON Response node names
private static String KEY_SUCCESS = "success";
private static String KEY_ERROR = "error";
private static String KEY_ERROR_MSG = "error_msg";
private static String KEY_UID = "uid";
private static String KEY_NAME = "name";
private static String KEY_EMAIL = "email";
private static String KEY_CREATED_AT = "created_at";

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

    // Importing all assets like buttons, text fields
    inputFullName = (EditText) findViewById(R.id.registerName);
    inputEmail = (EditText) findViewById(R.id.registerEmail);
    inputPassword = (EditText) findViewById(R.id.registerPassword);
    btnRegister = (Button) findViewById(R.id.btnRegister);
    btnLinkToLogin = (Button) findViewById(R.id.btnLinkToLoginScreen);
    registerErrorMsg = (TextView) findViewById(R.id.register_error);

    // Register Button Click event
    btnRegister.setOnClickListener(new View.OnClickListener() {         
        public void onClick(View view) {
            String name = inputFullName.getText().toString();
            String email = inputEmail.getText().toString();
            String password = inputPassword.getText().toString();
            UserFunctions userFunction = new UserFunctions();
            JSONObject json = userFunction.registerUser(name, email, password);

            // check for login response
            try {
                if (json.getString(KEY_SUCCESS) != null) {
                    registerErrorMsg.setText("");
                    String res = json.getString(KEY_SUCCESS); 
                    if(Integer.parseInt(res) == 1){
                        // user successfully registred
                        // Store user details in SQLite Database
                        DatabaseHandler db = new DatabaseHandler(getApplicationContext());
                        JSONObject json_user = json.getJSONObject("user");

                        // Clear all previous data in database
                        userFunction.logoutUser(getApplicationContext());
                        db.addUser(json_user.getString(KEY_NAME), json_user.getString(KEY_EMAIL), json.getString(KEY_UID), json_user.getString(KEY_CREATED_AT));                        
                        // Launch Dashboard Screen
                        Intent dashboard = new Intent(getApplicationContext(), DashboardActivity.class);
                        // Close all views before launching Dashboard
                        dashboard.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
                        startActivity(dashboard);
                        // Close Registration Screen
                        finish();
                    }else{
                        // Error in registration
                        registerErrorMsg.setText("Error occured in registration");
                    }
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    });

    // Link to Login Screen
    btnLinkToLogin.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            Intent i = new Intent(getApplicationContext(),
                    LoginActivity.class);
            startActivity(i);
            // Close Registration View
            finish();
        }
    });
      }
      }

logcat 看起来像这样:

   03-24 01:20:22.154: E/AndroidRuntime(1787): FATAL EXCEPTION: main
   03-24 01:20:22.154: E/AndroidRuntime(1787): android.os.NetworkOnMainThreadException
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1133)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at libcore.io.IoBridge.connect(IoBridge.java:112)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at java.net.Socket.connect(Socket.java:842)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at com.example.trial.library.JSONParser.getJSONFromUrl(JSONParser.java:47)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at com.example.trial.library.UserFunctions.loginUser(UserFunctions.java:43)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at com.example.trial.LoginActivity$1.onClick(LoginActivity.java:56)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.view.View.performClick(View.java:4240)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.view.View$PerformClick.run(View.java:17721)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.os.Handler.handleCallback(Handler.java:730)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.os.Handler.dispatchMessage(Handler.java:92)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.os.Looper.loop(Looper.java:137)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at android.app.ActivityThread.main(ActivityThread.java:5103)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at java.lang.reflect.Method.invokeNative(Native Method)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at java.lang.reflect.Method.invoke(Method.java:525)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
   03-24 01:20:22.154: E/AndroidRuntime(1787):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

从 API 级别 11 开始，您无法在 UI 线程上执行网络操作。

因此，您必须使用AsyncTask或Thread。

AsyncTask 示例。

 class DowloadTest extends AsyncTask<String, Integer, String>

 {
    @Override
    protected void onPreExecute() {
        pDialog = new ProgressDialog(YourActivityName.this);
        pDialog.setMessage("Please wait..");
        pDialog.setIndeterminate(true);
        pDialog.setCancelable(false);
        pDialog.show();
    };

    @Override
    protected String doInBackground(String... params) {
        // parse your data here
        return null;

    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);

        pDialog.dismiss();

        }

    }
}

然后在需要时执行此函数，例如，

  new DowloadTest().execute();

更多引用请访问 Here