How to handle onClickListener in android?

Question

I am trying to write a simple android application to help interpret some lab results.

package org.android.bloodgas;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Button;

public class pinit extends Activity {


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

        Button interpretButton = (Button) findViewById(R.id.Interpret);

        //interpretButton.setOnClickListener(this);
        View.OnClickListener myhandler = new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    float inpPH, inpPO2, inpPCO2, inpHCO3, inpBE;
                    inpPH = Float.valueOf(findViewById(R.id.InpPH).toString()).floatValue();
                    inpPO2 = Float.valueOf(findViewById(R.id.InpO2).toString()).floatValue();
                    inpPCO2 = Float.valueOf(findViewById(R.id.InpCO2).toString()).floatValue();
                    inpHCO3 = Float.valueOf(findViewById(R.id.InpHCO3).toString()).floatValue();
                    inpBE = Float.valueOf(findViewById(R.id.InpBE).toString()).floatValue();

                    TextView interpretation;
                    interpretation = (TextView) findViewById(R.id.Interpretation);

                    String sResult = null;
                    if (inpPH < 7.35) {
                        // Acidosis
                        sResult.concat("Acidosis. ");
                    } else {
                        if (inpPH > 7.45) {
                            // Alkalosis
                            sResult.concat("Alkalosis. ");
                        } else {
                            // Normal acidity, 7.35-7.45
                            sResult.concat("Normal pH. ");
                        }
                    }
                    interpretation.setText(sResult);
            }
        };

        interpretButton.setOnClickListener(myhandler);

    }

}

It does compile and run but when I press on the "interpret" button it simply says The application ... has stopped unexpectedly. Please try again. (Force Close).

I am totally new to android programming... So I guess this would be some very stupid mistake I have made but please help. Thanks.

update: changed the code to this (minus the logic portion while i will complete later) but still hangs when press on the button.

package org.android.bloodgas;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Button;

public class Pinit extends Activity {

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

        Button interpretButton = (Button) findViewById(R.id.Interpret);

        View.OnClickListener myhandler = new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    float inpPH, inpPO2, inpPCO2, inpHCO3, inpBE;
                    inpPH = Float.valueOf(((EditText) Pinit.this.findViewById(R.id.InpPH)).toString()).floatValue();
                    inpPO2 = Float.valueOf(((EditText) Pinit.this.findViewById(R.id.InpO2)).toString()).floatValue();
                    inpPCO2 = Float.valueOf(((EditText) Pinit.this.findViewById(R.id.InpCO2)).toString()).floatValue();
                    inpHCO3 = Float.valueOf(((EditText) Pinit.this.findViewById(R.id.InpHCO3)).toString()).floatValue();
                    inpBE = Float.valueOf(((EditText) Pinit.this.findViewById(R.id.InpBE)).toString()).floatValue();
                    // ...
            }
        };

        interpretButton.setOnClickListener(myhandler);

    }

}

logcat:

12-07 03:37:02.231: WARN/dalvikvm(1074): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074): FATAL EXCEPTION: main
12-07 03:37:02.332: ERROR/AndroidRuntime(1074): java.lang.NumberFormatException: android.widget.EditText@44f47e60
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at org.apache.harmony.luni.util.FloatingPointParser.initialParse(FloatingPointParser.java:130)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at org.apache.harmony.luni.util.FloatingPointParser.parseFloat(FloatingPointParser.java:319)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at java.lang.Float.parseFloat(Float.java:291)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at java.lang.Float.valueOf(Float.java:330)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at org.android.bloodgas.Pinit$1.onClick(Pinit.java:22)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at android.view.View.performClick(View.java:2408)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at android.view.View$PerformClick.run(View.java:8816)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at android.os.Handler.handleCallback(Handler.java:587)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at android.os.Handler.dispatchMessage(Handler.java:92)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at android.os.Looper.loop(Looper.java:123)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at android.app.ActivityThread.main(ActivityThread.java:4627)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at java.lang.reflect.Method.invokeNative(Native Method)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at java.lang.reflect.Method.invoke(Method.java:521)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-07 03:37:02.332: ERROR/AndroidRuntime(1074):     at dalvik.system.NativeStart.main(Native Method)
12-07 03:37:02.382: WARN/ActivityManager(68):   Force finishing activity org.android.bloodgas/.Pinit
12-07 03:37:02.952: WARN/ActivityManager(68): Activity pause timeout for HistoryRecord{44fbfc90 org.android.bloodgas/.Pinit}
12-07 03:37:07.761: INFO/Process(1074): Sending signal. PID: 1074 SIG: 9
12-07 03:37:09.852: INFO/ActivityManager(68): Process org.android.bloodgas (pid 1074) has died.
12-07 03:37:09.862: INFO/WindowManager(68): WIN DEATH: Window{44fa71e0 org.android.bloodgas/org.android.bloodgas.Pinit paused=false}
12-07 03:37:15.931: WARN/ActivityManager(68): Activity destroy timeout for HistoryRecord{44fbfc90 org.android.bloodgas/.Pinit}

Answer 1

First thing I see is that you have to cast this to the type of view that it is

inpPH = Float.valueOf(findViewById(R.id.InpPH).toString()).floatValue();

Second, you're calling this from within the onclickListener. So findViewById() really shouldn't even compile. You need

inpPH = Float.valueOf((TypeOfView) pinit.this.findViewById(R.id.InpPH).toString()).floatValue();

And also in java, classes should start with capital lettors, so it should be

public class Pinit extends Activity{

Update:

findViewById(R.id.InpPH) resolves to EditTex

No it doesn't. It resolves to a View. Calling .toString() on a view is not what you want. You want to do

((EditText) pinit.this.findViewById(R.id.InpPH)).getText().toString()

Answer 2

I guess you get NumberFormatException at one of the calls like this:

Float.valueOf(findViewById(R.id.InpPH).toString())

As to the doc the NumberFormatException is got if string is null, has a length of zero or can not be parsed as a float value.

However, checking the logCat trace for this would give a clean answer.