Resume in onResume() | Android Tutorial pdf

Resume in onResume()

Now, we need to restart our thread if it is needed. It will be needed if the progress is greater than 0, indicating we were in the middle of our background work when our activity was so rudely interrupted.
So, add the following implementation of onResume():
@Override
public void onResume() {
super.onResume();
isActive.set(true);
if (progress>0) {
startWork();
}
}
This assumes we have pulled out our thread-starting logic into a startWork() method, which you should implement as follows:

private void startWork() {
setProgressBarVisibility(true);
new Thread(longTask).start();
}
And you can change our menu handler to also use startWork():
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId()==R.id.toast) {
String message="No restaurant selected";
if (current!=null) {
message=current.getNotes();
}
Toast.makeText(this, message, Toast.LENGTH_LONG).show();
return(true);
}
else if (item.getItemId()==R.id.run) {
startWork();
return(true);
}
return(super.onOptionsItemSelected(item));
}
Finally, we need to not reset and hide the progress indicator when our background thread ends if it ends because our activity is not active. Otherwise, we will never restart it, since the progress will be reset to 0 every time. So, change longTask one more time, to look like this:
private Runnable longTask=new Runnable() {
public void run() {
for (int i=progress;
i<10000 && isActive.get();
i+=200) {
doSomeLongWork(200);
}
if (isActive.get()) {
runOnUiThread(new Runnable() {
public void run() {
setProgressBarVisibility(false);
progress=0;
}
});
}
}
};
What this does is reset the progress only if we are active when the work is complete, so we are ready for the next round of work. If we are inactive, and fell out of our loop for that reason, we leave the progress as-is.
At this point, recompile and reinstall the application.T o test this feature:
1. Use the [MENU] button to run the long task.
2. While it is running, click the green phone button on the emulator (lower-left corner of the "phone"). This will bring up the call log activity and, as a result, pause our LunchList activity.
3. After a while, click the BACK button – you should see the LunchList resuming the background work from the point where it left off. 

Here is the full LunchList implementation, including the changes shown above:
package apt.tutorial;
import android.app.TabActivity;
import android.os.Bundle;
import android.os.SystemClock;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;
import android.view.Window;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.RadioGroup;
import android.widget.TabHost;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicBoolean;
public class LunchList extends TabActivity {
List<Restaurant> model=new ArrayList<Restaurant>();
RestaurantAdapter adapter=null;
EditText name=null;
EditText address=null;
EditText notes=null;
RadioGroup types=null;
Restaurant current=null;
AtomicBoolean isActive=new AtomicBoolean(true);
int progress=0;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_PROGRESS);
setContentView(R.layout.main);
name=(EditText)findViewById(R.id.name);
address=(EditText)findViewById(R.id.addr);
notes=(EditText)findViewById(R.id.notes);
types=(RadioGroup)findViewById(R.id.types);
Button save=(Button)findViewById(R.id.save);
save.setOnClickListener(onSave);
ListView list=(ListView)findViewById(R.id.restaurants);
adapter=new RestaurantAdapter();
list.setAdapter(adapter);
TabHost.TabSpec spec=getTabHost().newTabSpec("tag1");
spec.setContent(R.id.restaurants);
spec.setIndicator("List", getResources()
.getDrawable(R.drawable.list));
getTabHost().addTab(spec);
spec=getTabHost().newTabSpec("tag2");
spec.setContent(R.id.details);
spec.setIndicator("Details", getResources()
.getDrawable(R.drawable.restaurant));
getTabHost().addTab(spec);
getTabHost().setCurrentTab(0);
list.setOnItemClickListener(onListClick);
}
@Override
public void onPause() {
super.onPause();
isActive.set(false);
}
@Override
public void onResume() {
super.onResume();
isActive.set(true);
if (progress>0) {
startWork();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
new MenuInflater(this).inflate(R.menu.option, menu);
return(super.onCreateOptionsMenu(menu));
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId()==R.id.toast) {
String message="No restaurant selected";
if (current!=null) {
message=current.getNotes();
}
Toast.makeText(this, message, Toast.LENGTH_LONG).show();
return(true);
}
else if (item.getItemId()==R.id.run) {
startWork();
return(true);
}
return(super.onOptionsItemSelected(item));
}
private void startWork() {
setProgressBarVisibility(true);
new Thread(longTask).start();
}
private void doSomeLongWork(final int incr) {
runOnUiThread(new Runnable() {
public void run() {
progress+=incr;
setProgress(progress);
}
});
SystemClock.sleep(250); // should be something more useful!
}
private View.OnClickListener onSave=new View.OnClickListener() {
public void onClick(View v) {
current=new Restaurant();
current.setName(name.getText().toString());
current.setAddress(address.getText().toString());
current.setNotes(notes.getText().toString());
switch (types.getCheckedRadioButtonId()) {
case R.id.sit_down:
current.setType("sit_down");
break;
case R.id.take_out:
current.setType("take_out");
break;
case R.id.delivery:
current.setType("delivery");
break;
}
adapter.add(current);
}
};
private AdapterView.OnItemClickListener onListClick=new
AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent,
View view, int position,
long id) {
current=model.get(position);
name.setText(current.getName());
address.setText(current.getAddress());
notes.setText(current.getNotes());
if (current.getType().equals("sit_down")) {
types.check(R.id.sit_down);
}
else if (current.getType().equals("take_out")) {
types.check(R.id.take_out);
}
else {
types.check(R.id.delivery);
}
getTabHost().setCurrentTab(1);
}
};
private Runnable longTask=new Runnable() {
public void run() {
for (int i=progress;
i<10000 && isActive.get();
i+=200) {
doSomeLongWork(200);
}
if (isActive.get()) {
runOnUiThread(new Runnable() {
public void run() {
setProgressBarVisibility(false);
progress=0;
}
});
}
}
};
class RestaurantAdapter extends ArrayAdapter<Restaurant> {
RestaurantAdapter() {
super(LunchList.this, R.layout.row, model);
}
public View getView(int position, View convertView,
ViewGroup parent) {
View row=convertView;
RestaurantHolder holder=null;
if (row==null) {
LayoutInflater inflater=getLayoutInflater();
row=inflater.inflate(R.layout.row, parent, false);
holder=new RestaurantHolder(row);
row.setTag(holder);
}
else {
holder=(RestaurantHolder)row.getTag();
}
holder.populateFrom(model.get(position));
return(row);
}
}
static class RestaurantHolder {
private TextView name=null;
private TextView address=null;
private ImageView icon=null;
RestaurantHolder(View row) {
name=(TextView)row.findViewById(R.id.title);
address=(TextView)row.findViewById(R.id.address);
icon=(ImageView)row.findViewById(R.id.icon);
}
void populateFrom(Restaurant r) {
name.setText(r.getName());
address.setText(r.getAddress());
if (r.getType().equals("sit_down")) {
icon.setImageResource(R.drawable.ball_red);
}
else if (r.getType().equals("take_out")) {
icon.setImageResource(R.drawable.ball_yellow);
}
else {
icon.setImageResource(R.drawable.ball_green);
}
}
}
}