java - 登录成功后如何显示另一个布局

Question

我是 Android 新手，我有两个问题。

1. 我想在登录成功时显示另一个布局。

2. 其他部分在 onsuccess() 方法中不起作用。如果用户给出错误的用户名和密码意味着抛出错误消息，但是我收到错误:

   应用程序不幸停止

这是我的代码:

LoginFragment.java

public void onSuccess(int statusCode, Header[] headers, byte[] response) {

                // Hide Progress Dialog

                prgDialog.hide();
                try {
                    // JSON Object
                    JSONObject obj = new JSONObject(new String(response));
                    // When the JSON response has status boolean value assigned with true
                    if (obj.getBoolean("status")) {
                        Toast.makeText(getActivity().getApplicationContext(), "You are successfully logged in!", Toast.LENGTH_LONG).show();
                        // Navigate to Home screen
                        navigatetoSearchActivity();
                    }
                    // Else display error message
                    else {
                        errorMsg.setText(obj.getString("error_msg"));
                        Toast.makeText(getActivity().getApplicationContext(), obj.getString("error_msg"), Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    Toast.makeText(getActivity().getApplicationContext(), "Error Occured [Server's JSON response might be invalid]!", Toast.LENGTH_LONG).show();
                    e.printStackTrace();

                }
            }


            // When the response returned by REST has Http response code other than '200'
            @Override
            public void onFailure(int statusCode, Header[] headers, byte[] responsebody, Throwable error) {
                // Hide Progress Dialog
                prgDialog.hide();
                // When Http response code is '404'
                if (statusCode == 404) {
                    Toast.makeText(getActivity().getApplicationContext(), "Requested resource not found", Toast.LENGTH_LONG).show();
                }
                // When Http response code is '500'
                else if (statusCode == 500) {
                    Toast.makeText(getActivity().getApplicationContext(), "Something went wrong at server end", Toast.LENGTH_LONG).show();
                }
                // When Http response code other than 404, 500
                else {
                    Toast.makeText(getActivity().getApplicationContext(), "Unexpected Error occcured! [Most common Error: Device might not be connected to Internet or remote server is not up and running]", Toast.LENGTH_LONG).show();
                }

            }
        });
    }
    /**
     * Method which navigates from Login Activity to Search Activity
     */
    public void navigatetoSearchActivity(){
        Intent searchIntent = new Intent(getActivity().getApplicationContext(),Search.class);
        //searchIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        startActivity(searchIntent);
    }

Search.java

import android.app.Activity;
import android.os.Bundle;
public class Search extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //Displays Search Screen
        setContentView(R.layout.search);
    }
}

第一个问题logcat:

 java.lang.RuntimeException: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.h2o/com.h2o.Search}; have you declared this activity in your AndroidManifest.xml?
            at com.loopj.android.http.AsyncHttpResponseHandler.onUserException(AsyncHttpResponseHandler.java:313)
            at com.loopj.android.http.AsyncHttpResponseHandler.handleMessage(AsyncHttpResponseHandler.java:404)
            at com.loopj.android.http.AsyncHttpResponseHandler$ResponderHandler.handleMessage(AsyncHttpResponseHandler.java:184)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.h2o/com.h2o.Search}; have you declared this activity in your AndroidManifest.xml?
            at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1761)
            at android.app.Instrumentation.execStartActivity(Instrumentation.java:1485)
            at android.app.Activity.startActivityForResult(Activity.java:3736)
            at android.app.Activity.startActivityForResult(Activity.java:3697)
            at android.support.v4.app.FragmentActivity.startActivityFromFragment(FragmentActivity.java:829)
            at android.support.v4.app.Fragment.startActivity(Fragment.java:897)
            at com.h2o.LoginFragment$TabsAdapter.navigatetoSearchActivity(LoginFragment.java:278)
            at com.h2o.LoginFragment$TabsAdapter$3.onSuccess(LoginFragment.java:235)
            at com.loopj.android.http.AsyncHttpResponseHandler.handleMessage(AsyncHttpResponseHandler.java:360)
            at com.loopj.android.http.AsyncHttpResponseHandler$ResponderHandler.handleMessage(AsyncHttpResponseHandler.java:184)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

第二个问题logcat:

java.lang.RuntimeException: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at com.loopj.android.http.AsyncHttpResponseHandler.onUserException(AsyncHttpResponseHandler.java:313)
        at com.loopj.android.http.AsyncHttpResponseHandler.handleMessage(AsyncHttpResponseHandler.java:404)
        at com.loopj.android.http.AsyncHttpResponseHandler$ResponderHandler.handleMessage(AsyncHttpResponseHandler.java:184)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
        at com.h2o.LoginFragment$TabsAdapter$3.onSuccess(LoginFragment.java:239)
        at com.loopj.android.http.AsyncHttpResponseHandler.handleMessage(AsyncHttpResponseHandler.java:360)
        at com.loopj.android.http.AsyncHttpResponseHandler$ResponderHandler.handleMessage(AsyncHttpResponseHandler.java:184)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

错误在提供的 logcat 中清晰显示。
1) Activity 未在 Manifest 中声明。在 Activity 标签中声明它。
2) 您在 TextView 上设置文本而不对其进行初始化。
例如:TextView tv=(TextView)fingViewById(R.id.tv1);