Unfortunately, Simple app is stopped

Question

I'm new to android development and im making a simple calculator app... Whenever i'm running the code in the android emulator it's showing me Unfortunately, SimpleApp has Stopped.... I'm Using Android Studio to write the code Please help me... Following is my code....

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.myapp.simpleapp.MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="337dp"
        android:layout_height="58dp"
        android:contextClickable="false"
        android:cursorVisible="false"
        android:fontFamily="serif"
        android:longClickable="true"
        android:text="Calculator"
        android:textAlignment="center"
        android:textAllCaps="true"
        android:textColor="@android:color/holo_red_dark"
        android:textSize="36sp"
        android:visibility="visible"
        tools:layout_editor_absoluteX="24dp"
        tools:layout_editor_absoluteY="31dp" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="194dp"
        android:layout_height="43dp"
        android:text="Number 1: "
        android:textColor="@android:color/black"
        android:textSize="25sp"
        tools:layout_editor_absoluteX="24dp"
        tools:layout_editor_absoluteY="140dp" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="194dp"
        android:layout_height="44dp"
        android:text="Number 2: "
        android:textColor="@android:color/black"
        android:textSize="25sp"
        tools:layout_editor_absoluteX="24dp"
        tools:layout_editor_absoluteY="217dp" />

    <EditText
        android:id="@+id/number2"
        android:layout_width="99dp"
        android:layout_height="43dp"
        android:ems="10"
        android:hint="Number 2"
        android:inputType="number|numberSigned|numberDecimal"
        android:singleLine="true"
        android:textAlignment="center"
        android:textColor="@android:color/black"
        android:textIsSelectable="true"
        android:textSize="20sp"
        tools:layout_editor_absoluteX="262dp"
        tools:layout_editor_absoluteY="217dp" />

    <EditText
        android:id="@+id/number1"
        android:layout_width="99dp"
        android:layout_height="43dp"
        android:ems="10"
        android:hint="Number 1"
        android:inputType="number|numberSigned|numberDecimal"
        android:linksClickable="false"
        android:longClickable="true"
        android:textAlignment="center"
        android:textColor="@android:color/black"
        android:textSize="20sp"
        tools:layout_editor_absoluteX="262dp"
        tools:layout_editor_absoluteY="140dp" />

    <TextView
        android:id="@+id/result"
        android:layout_width="175dp"
        android:layout_height="40dp"
        tools:layout_editor_absoluteX="176dp"
        tools:layout_editor_absoluteY="430dp" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="103dp"
        android:layout_height="40dp"
        android:text="Result: "
        android:textColor="@android:color/black"
        android:textSize="25sp"
        tools:layout_editor_absoluteX="59dp"
        tools:layout_editor_absoluteY="433dp" />

    <Button
        android:id="@+id/btnAdd"
        android:layout_width="152dp"
        android:layout_height="49dp"
        android:text="+"
        android:textColor="@android:color/black"
        android:textSize="30sp"
        tools:layout_editor_absoluteX="24dp"
        tools:layout_editor_absoluteY="292dp" />

    <Button
        android:id="@+id/btnSub"
        android:layout_width="152dp"
        android:layout_height="49dp"
        android:text="-"
        android:textColor="@android:color/black"
        android:textIsSelectable="false"
        android:textSize="30sp"
        tools:layout_editor_absoluteX="216dp"
        tools:layout_editor_absoluteY="292dp" />

    <Button
        android:id="@+id/btnDiv"
        android:layout_width="152dp"
        android:layout_height="49dp"
        android:text="/"
        android:textColor="@android:color/black"
        android:textSize="25sp"
        tools:layout_editor_absoluteX="24dp"
        tools:layout_editor_absoluteY="362dp" />

    <Button
        android:id="@+id/btnMul"
        android:layout_width="152dp"
        android:layout_height="49dp"
        android:text="*"
        android:textAlignment="center"
        android:textColor="@android:color/black"
        android:textSize="25sp"
        tools:layout_editor_absoluteX="216dp"
        tools:layout_editor_absoluteY="362dp" />
</android.support.constraint.ConstraintLayout>

MainActivity.java

package com.myapp.simpleapp;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    EditText number1= (EditText) findViewById(R.id.number1);
    EditText number2= (EditText) findViewById(R.id.number2);

    Button add= (Button) findViewById(R.id.btnAdd);
    Button sub= (Button) findViewById(R.id.btnSub);
    Button div= (Button) findViewById(R.id.btnDiv);
    Button mul= (Button) findViewById(R.id.btnMul);


    TextView txtresult= (TextView) findViewById(R.id.result);

    double num1,num2,result;

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

        num1=Double.parseDouble(number1.getText().toString());
        num2=Double.parseDouble(number2.getText().toString());

        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                result=num1+num2;

                txtresult.setText(Double.toString(result));
            }
        });

        sub.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                result=num1-num2;

                txtresult.setText(Double.toString(result));
            }
        });

        div.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                result=num1/num2;

                txtresult.setText(Double.toString(result));
            }
        });

        mul.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                result=num1*num2;

                txtresult.setText(Double.toString(result));
            }
        });

    }
}

LogCat

04-03 12:25:38.913 3927-3927/? E/memtrack: Couldn't load memtrack module (No such file or directory)
04-03 12:25:38.913 3927-3927/? E/android.os.Debug: failed to load memtrack module: -2
04-03 12:25:39.372 3952-3952/? E/memtrack: Couldn't load memtrack module (No such file or directory)
04-03 12:25:39.373 3952-3952/? E/android.os.Debug: failed to load memtrack module: -2
04-03 12:25:49.078 4097-4097/? E/memtrack: Couldn't load memtrack module (No such file or directory)
04-03 12:25:49.078 4097-4097/? E/android.os.Debug: failed to load memtrack module: -2
04-03 12:25:49.647 4122-4122/? E/memtrack: Couldn't load memtrack module (No such file or directory)
04-03 12:25:49.648 4122-4122/? E/android.os.Debug: failed to load memtrack module: -2
04-03 12:25:58.059 3666-3666/com.myapp.simpleapp E/AndroidRuntime: FATAL EXCEPTION: main
                                                                   Process: com.myapp.simpleapp, PID: 3666
                                                                   java.lang.NumberFormatException: Invalid double: ""
                                                                       at java.lang.StringToReal.invalidReal(StringToReal.java:63)
                                                                       at java.lang.StringToReal.parseDouble(StringToReal.java:267)
                                                                       at java.lang.Double.parseDouble(Double.java:301)
                                                                       at com.myapp.simpleapp.MainActivity$4.onClick(MainActivity.java:70)
                                                                       at android.view.View.performClick(View.java:4780)
                                                                       at android.view.View$PerformClick.run(View.java:19866)
                                                                       at android.os.Handler.handleCallback(Handler.java:739)
                                                                       at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                       at android.os.Looper.loop(Looper.java:135)
                                                                       at android.app.ActivityThread.main(ActivityThread.java:5254)
                                                                       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:903)
                                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
04-03 12:25:58.079 1163-1163/? E/EGL_emulation: tid 1163: eglCreateSyncKHR(1299): error 0x3004 (EGL_BAD_ATTRIBUTE)
04-03 12:26:02.452 1810-2202/system_process E/InputDispatcher: channel '21dd8534 com.myapp.simpleapp/com.myapp.simpleapp.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
04-03 12:26:02.581 1175-1175/? E/audio_hw_generic: Error opening input stream format 1, channel_mask 0010, sample_rate 16000

Don't use static initialisation for your View. Do thw `findViewById` inside `onCreate` like all of the examples — David Rawson, Apr 03 '17 at 05:54
@Samrat please insert a integer value for number1 and number2, before you click +,-,etc — Nabil, Apr 03 '17 at 07:04
done... now the problem is solved.. but when i run the app all the component are mess up with each other.... — Samrat, Apr 03 '17 at 07:31
Yes. im talking about interface.. they are mess up with each other — Samrat, Apr 03 '17 at 07:46
@Samrat please accept my answer if your initial query has been solved. Regarding your view, it do not depend upon the changes we have made in the Activity.Try using a LinearLayout/RelativeLayout as the parent view of your xml and try. — Nabil, Apr 03 '17 at 07:50

Nabil · Answer 1 · 2017-04-03T06:20:02.773

Use findViewById inside onCreate and use Double.parse only after values have been entered in the edittexts.

Try this code:

public class MainActivity extends Activity {

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

        final EditText number1 = (EditText) findViewById(R.id.number1);
        final EditText number2 = (EditText) findViewById(R.id.number2);

        Button add = (Button) findViewById(R.id.btnAdd);
        Button sub = (Button) findViewById(R.id.btnSub);
        Button div = (Button) findViewById(R.id.btnDiv);
        Button mul = (Button) findViewById(R.id.btnMul);

        final TextView txtresult = (TextView) findViewById(R.id.result);

        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                double num1, num2, result;

                num1 = Double.parseDouble(number1.getText().toString());
                num2 = Double.parseDouble(number2.getText().toString());

                result = num1 + num2;

                txtresult.setText(Double.toString(result));
            }
        });

        sub.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                double num1, num2, result;

                num1 = Double.parseDouble(number1.getText().toString());
                num2 = Double.parseDouble(number2.getText().toString());

                result = num1 - num2;

                txtresult.setText(Double.toString(result));
            }
        });

        div.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                double num1, num2, result;

                num1 = Double.parseDouble(number1.getText().toString());
                num2 = Double.parseDouble(number2.getText().toString());

                result = num1 / num2;

                txtresult.setText(Double.toString(result));
            }
        });

        mul.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                double num1, num2, result;

                num1 = Double.parseDouble(number1.getText().toString());
                num2 = Double.parseDouble(number2.getText().toString());

                result = num1 * num2;

                txtresult.setText(Double.toString(result));
            }
        });

    }
}

score 0 · Answer 2 · answered Apr 03 '17 at 06:05

The most common cause of this problem is a NullPointerException at runtime.

Steps to follow:

Observe the Stack trace on Android Studio as shown below:

You can then analyze the Stack trace, and zero in on what exactly caused the exception, and the line that caused it. Alternatively, you can post the screenshot of your stack trace so it can be easier to answer the question.

Unfortunately, Simple app is stopped

2 Answers2