I would like to know how can I ask my app to check if my toggle buttons are checked or not so that when I press the play button, the app plays a sound only for the toggle buttons that are checked. (For instance, if button 1 and 3 are checked, when I press the play button it should do "Sound, silence, sound, silence" and loop until I press stop).
The problem is that right now when I press play, my app closes and I get the error "Attempt to invoke virtual method 'boolean android.widget.ToggleButton.isChecked()' on a null object reference"
.
I don't know how to resolve this problem. Here is my code :
MainActivity :
public class MainActivity extends AppCompatActivity {
public ToggleButton button1, button2, button3, button4;
public Sampler mySample;
public ImageButton playButton;
public ImageButton stopButton;
public boolean playing;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
playButton = (ImageButton) findViewById(R.id.play);
stopButton = (ImageButton) findViewById(R.id.stop);
button1 = (ToggleButton) findViewById(R.id.button1);
button2 = (ToggleButton) findViewById(R.id.button2);
button3 = (ToggleButton) findViewById(R.id.button3);
button4 = (ToggleButton) findViewById(R.id.button4);
mySample = new Sampler(this);
playButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
mySample.play();
}
});
stopButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v)
{
mySample.stop();
}
});
}
Sampler class :
public class Sampler extends Activity {
SoundPool sp;
private int snareId;
private Context mycontext;
public boolean playing;
public ToggleButton button1, button2, button3, button4;
public Sampler(Context appcontext) {
this.mycontext = appcontext;
sp = new SoundPool(10, AudioManager.STREAM_MUSIC, 0);
snareId = sp.load(mycontext, R.raw.snare, 1);
}
public void play() {
playing = true;
while (playing) {
if (button1.isChecked()) {
sp.play(snareId, 10, 10, 1, 0, 1);
try {
Thread.sleep(60000 / (120 * 4));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if (button2.isChecked()) {
sp.play(snareId, 10, 10, 1, 0, 1);
try {
Thread.sleep(60000 / (120 * 4));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if (button3.isChecked()) {
sp.play(snareId, 10, 10, 1, 0, 1);
try {
Thread.sleep(60000 / (120 * 4));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if (button4.isChecked()) {
sp.play(snareId, 10, 10, 1, 0, 1);
try {
Thread.sleep(60000 / (120 * 4));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
else {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
if(!playing){
break;
}
}
}
public void stop(){
playing = false;
}
In Sampler
class, button1
isn't initialised, resulting in null object reference
error. To link up to MainActivity's button1
, try this:
button1 = (((Activity)mycontext).findViewById(R.id.button1));