Question

I know that similar questions have been asked, but having read through them it seems a wide array of things can be done wrong to cause this issue. And with this being my first real Android (and Java) application, I’ve probably done most of them. Thanks in advance for your help!

Stack (Logcat decided to randomly stop working in eclipse for some reason)

Thread [<1> main] (Suspended (exception NullPointerException))  
GMSerial_CleanActivity(Activity).startActivityForResult(Intent, int) line: 3190 
GMSerial_CleanActivity(Activity).startActivity(Intent) line: 3297   
GMSerial_CleanActivity.output(String, String, String, TextView) line: 49    
GMSerial_CleanActivity$1.onCheckedChanged(CompoundButton, boolean) line: 35 
ToggleButton(CompoundButton).setChecked(boolean) line: 125  
ToggleButton.setChecked(boolean) line: 72   
ToggleButton(CompoundButton).toggle() line: 87  
ToggleButton(CompoundButton).performClick() line: 99    
View$PerformClick.run() line: 14105 
ViewRootImpl(Handler).handleCallback(Message) line: 605 
ViewRootImpl(Handler).dispatchMessage(Message) line: 92 
Looper.loop() line: 137 
ActivityThread.main(String[]) line: 4424    
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
Method.invoke(Object, Object...) line: 511  
ZygoteInit$MethodAndArgsCaller.run() line: 784  
ZygoteInit.main(String[]) line: 551 
NativeStart.main(String[]) line: not available [native method]  

Main Code

package com.greymatterrobotics.gmserial;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.ToggleButton;
import android.widget.TextView;
import android.widget.EditText;
import android.widget.CheckBox;
import android.widget.CompoundButton;



public class GMSerial_CleanActivity extends Activity {

    static public final char cr = (char) 13;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        final GMSerial_CleanActivity GMSerial = new GMSerial_CleanActivity();
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        ToggleButton toggleSend = (ToggleButton) findViewById(R.id.toggleSend);
        final TextView textLog = (TextView) findViewById(R.id.textLog);
        final EditText editBaud = (EditText) findViewById(R.id.editBaud);
        final EditText editDelay = (EditText) findViewById(R.id.editDelay);
        //final CheckBox checkInvert = (CheckBox) findViewById(R.id.checkInvert);

        toggleSend.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                if(isChecked){
                    GMSerial.output(editBaud.getText().toString(), "Hello World", editDelay.getText().toString(), textLog);
                }

            }
        });

    }

    public void output(String baud, String data, String delay, TextView log) {
        Intent serialout = new Intent();
        serialout.setClassName("com.greymatterrobotics.gmserial", "com.greymatterrobotics.gmserial.Output");
        serialout.putExtra("BAUD", baud);
        serialout.putExtra("DATA", data);
        serialout.putExtra("CHD", delay);
        startActivity(serialout);
        log.setText(log.getText().toString() + cr + data);
    }
}

Output Code (By spiritplumber[at]gmail.com)

package com.greymatterrobotics.gmserial;

import android.app.Activity;
import android.os.Bundle;
import android.os.SystemClock;

public class Output extends Activity {

    static public final char cr = (char) 13; // because i don't want to type that in every time
    static public final char lf = (char) 10; // because i don't want to type that in every time
    public String datatosend = "";


    @Override
    public void onCreate(Bundle savedInstanceState) {
        AudioSerialOutMono.activate();
        try{
            Bundle bundle = getIntent().getExtras();
            if (bundle.containsKey("BAUD"))
                AudioSerialOutMono.new_baudRate = Integer.parseInt(bundle.getString("BAUD"));
            if (bundle.containsKey("CHD"))
                AudioSerialOutMono.new_characterdelay = Integer.parseInt(bundle.getString("CHD"));
            if (bundle.containsKey("DATA"))
                datatosend = (bundle.getString("DATA"));
            AudioSerialOutMono.UpdateParameters(true);
            AudioSerialOutMono.output(datatosend+cr+lf);

            while (AudioSerialOutMono.isPlaying())
            {
                SystemClock.sleep(50);
            }
        }catch(Exception e){e.printStackTrace();}


//      android.os.Process.killProcess(android.os.Process.myPid()); // NUKE
        super.onCreate(savedInstanceState);
        this.finish();
    }
}

AndroidManifest.xml

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

    <uses-sdk android:minSdkVersion="3" />
    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".GMSerial_CleanActivity"
            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=".Output"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
            </intent-filter>
        </activity>
    </application>

</manifest>

Answer 1

The life cycle of an Activity in Android is handled automatically by the system. I mean ,you should not create a new instance of the GMSerial_CleanActivity Activity. You should call the output method directly. Don’t call GMSerial.output.

Also, in the output method, I prefer to using the code below to start a new activity(your code snippet may be right. I dont’ have Eclipse on hand and thus can’t test it).

Intent serialout = new Intent();
    serialout.setClass(this, Output.Class);