Question

Here are my files (Conversion.xml, Conversion.java and AndroidManifest.xml). It is a small part of a project. I am able to get to the screen where I want to convert the power in watts to decibels. But when I enter the power value and click the button “Convert”, the app crashes and goes back to the my app home screen.

conversion.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".ConvertTodB" >

    <EditText
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="Enter the power in Watts"
        android:inputType="number"
        android:text="@string/et1" />

    <Button
        android:id="@+id/bConvert"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/Convert" />

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="Result in dB"
        android:text="@string/et2" 
        android:textSize="20sp"/>

</LinearLayout>

Conversion.java

package com.example.rfconcepts;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.lang.Math;

public class Conversion extends Activity {

    EditText entered_val;
    TextView result_val;
    Button bCon;

    @Override
    protected void onCreate(Bundle convertTodB) {

        super.onCreate(convertTodB);
        setContentView(R.layout.conversion);

        entered_val = (EditText) findViewById(R.string.et1);
        bCon = (Button) findViewById(R.id.bConvert);
        result_val = (TextView) findViewById(R.string.et2);

        bCon.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub

                if(entered_val.getText() != null && entered_val.getText().length() != 0){
                    result_val.setText(String.valueOf(10 * Math.log10(Double
                            .valueOf(entered_val.getText().toString()))));
                }

            }
        });
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.rfconcepts"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.rfconcepts.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <activity
            android:name="com.example.rfconcepts.Conversion"
            android:label="@string/app_name">
        </activity>
    </application>

</manifest>

I thank you in advance for the advise.

P.S:

Here is a list of things I did after reading a lot of solutions for various questions posted here.

• Instead of using onClickListener, in conversion.xml, i added the attribute “android:onClick = “onClickConvert” and added the follwoing onClickConvert method in the Activity class.

public void onClickConvert(View v){
        if(entered_val.getText() != null && entered_val.getText().length() != 0){
            result_val.setText(String.valueOf(10 * Math.log10(Double
                    .valueOf(entered_val.getText().toString()))));
        }
    }

• Changed Double.parseDouble() to Double.valueOf() (Although, I do not think this is the issue)

• Checked if the editText itself has null, hence the if statement.

Answer 1

entered_val = (EditText) findViewById(R.string.et1);

Why are you referring to a string? It should be an ID.

You did not declare an ID for your EditTexts. Do something like this:

<EditText
        [...]
        android:id="@+id/MyEditText"
         />

Then you can refer to it like this:

entered_val = (EditText) findViewById(R.Id.MyEditText);

Also do the same with your TextView.

Second issue:
EditText.getText() returns an Editable, but you need a String. Convert it like this:

 if(entered_val.getText().toString() != null && entered_val.getText().toString().length() != 0