Question

I am a beginner at writing android apps. Can you please help me how to deal with this problem. i have included the logcat entry and activity class.

log:

11-07 12:46:28.245: D/AndroidRuntime(579): Shutting down VM
11-07 12:46:28.245: W/dalvikvm(579): threadid=1: thread exiting with uncaught exception (group=0x40015560)
11-07 12:46:28.285: E/AndroidRuntime(579): FATAL EXCEPTION: main
11-07 12:46:28.285: E/AndroidRuntime(579): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.trial.login/com.trial.login.Login1Activity}: java.lang.NullPointerException
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.os.Handler.dispatchMessage(Handler.java:99)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.os.Looper.loop(Looper.java:123)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.ActivityThread.main(ActivityThread.java:3683)
11-07 12:46:28.285: E/AndroidRuntime(579):  at java.lang.reflect.Method.invokeNative(Native Method)
11-07 12:46:28.285: E/AndroidRuntime(579):  at java.lang.reflect.Method.invoke(Method.java:507)
11-07 12:46:28.285: E/AndroidRuntime(579):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-07 12:46:28.285: E/AndroidRuntime(579):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-07 12:46:28.285: E/AndroidRuntime(579):  at dalvik.system.NativeStart.main(Native Method)
11-07 12:46:28.285: E/AndroidRuntime(579): Caused by: java.lang.NullPointerException
11-07 12:46:28.285: E/AndroidRuntime(579):  at com.trial.login.Login1Activity.onCreate(Login1Activity.java:28)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-07 12:46:28.285: E/AndroidRuntime(579):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
11-07 12:46:28.285: E/AndroidRuntime(579):  ... 11 more

LoginActivity.class:

    package com.trial.login;
    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    public class Login1Activity extends Activity {

            TextView username, password;
            EditText user_edit, pwd_edit;
            Button login, cancel;

                @Override
            public void onCreate(Bundle savedInstanceState) {

                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);
                login = (Button) findViewById(R.id.bt1);
                cancel = (Button) findViewById(R.id.bt2);
                username = (TextView) findViewById(R.id.tv1);
                password = (TextView) findViewById(R.id.tv2);
                user_edit = (EditText) findViewById(R.id.txtUname);
                pwd_edit = (EditText) findViewById(R.id.txtPwd);

                login.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View arg0) {
                        display();
                    }
                });
            }
            cancel.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {

                            user_edit.clearComposingText();
                    pwd_edit.clearComposingText();

                }
            }); 

            public void display(){

                String user_temp, pwd_temp;
            user_temp = user_edit.getText().toString();
            pwd_temp = pwd_edit.getText().toString();
            username.setText(user_temp);
            password.setText(pwd_temp);
            }
}

Answer 1

Try this:

package com.trial.login;
    import android.app.Activity;
    import android.os.Bundle;
    import android.view.View;
    import android.view.View.OnClickListener;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    public class Login1Activity extends Activity {

            TextView username, password;
            EditText user_edit, pwd_edit;
            Button login, cancel;

            @Override
            public void onCreate(Bundle savedInstanceState) {

                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);
                login = (Button) findViewById(R.id.bt1);
                cancel = (Button) findViewById(R.id.bt2);
                username = (TextView) findViewById(R.id.tv1);
                password = (TextView) findViewById(R.id.tv2);
                user_edit = (EditText) findViewById(R.id.txtUname);
                pwd_edit = (EditText) findViewById(R.id.txtPwd);

                login.setOnClickListener(new OnClickListener() {
                    @Override
                    public void onClick(View arg0) {
                        display();
                    }
                });

                 cancel.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View arg0) {

                        user_edit.clearComposingText();
                        pwd_edit.clearComposingText();

                   }
                }); 
            }


            public void display(){

                String user_temp, pwd_temp;
            user_temp = user_edit.getText().toString();
            pwd_temp = pwd_edit.getText().toString();
            username.setText(user_temp);
            password.setText(pwd_temp);
            }
}