I have a problem in a counting program that shows how many times a method such as onCreate, onStart etc. was called and it seems to be working fine when I go from Activity1 to Activity2 and then back to Activity1 but when I switch orientation, only mResume gets increased. So for example when I start the app and switch orientation 3 times the result looks like this:
onCreate() calls:1
onStart() calls:1
onResume() calls:4
onRestart() calls:1
Another wierd thing is that when I commented out mResume,mRestart and mStart from onRestoreInstanceState, then suddenly 2 variables get updated mStart and mResume.
public void onRestoreInstanceState(Bundle savedInstanceState) {
// Always call the superclass so it can restore the view hierarchy
super.onRestoreInstanceState(savedInstanceState);
Log.i(TAG, "Entered the onRestoreInstanceState() method");
// Restore state members from saved instance
//mResume = savedInstanceState.getInt(RESUME_KEY);
//mRestart = savedInstanceState.getInt(RESTART_KEY);
//mStart = savedInstanceState.getInt(START_KEY);
mCreate = savedInstanceState.getInt(CREATE_KEY);
here is the full code
public class ActivityOne extends Activity {
// Use these as keys when you're saving state between reconfigurations
private static final String RESTART_KEY = "restart";
private static final String RESUME_KEY = "resume";
private static final String START_KEY = "start";
private static final String CREATE_KEY = "create";
// String for LogCat documentation
private final static String TAG = "Lab-ActivityOne";
// Lifecycle counters
// TODO:
// Create variables named
// mCreate, mRestart, mStart and mResume
// to count calls to onCreate(), onRestart(), onStart() and
// onResume(). These variables should not be defined as static.
// You will need to increment these variables' values when their
// corresponding lifecycle methods get called.
int mCreate;
int mRestart;
int mStart;
int mResume;
// TODO: Create variables for each of the TextViews
// named mTvCreate, mTvRestart, mTvStart, mTvResume.
// for displaying the current count of each counter variable
TextView mTvCreate;
TextView mTvRestart;
TextView mTvResume;
TextView mTvStart;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_one);
// TODO: Assign the appropriate TextViews to the TextView variables
// Hint: Access the TextView by calling Activity's findViewById()
// textView1 = (TextView) findViewById(R.id.textView1);
mTvCreate = (TextView) findViewById(R.id.create);
mTvRestart = (TextView) findViewById(R.id.restart);
mTvStart = (TextView) findViewById(R.id.start);
mTvResume = (TextView) findViewById(R.id.resume);
Button launchActivityTwoButton = (Button) findViewById(R.id.bLaunchActivityTwo);
launchActivityTwoButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO:
// Launch Activity Two
// Hint: use Context's startActivity() method
// Create an intent stating which Activity you would like to
// start
Intent intent = new Intent(v.getContext(), ActivityTwo.class);
// Launch the Activity using the intent
startActivity(intent);
}
});
// Has previous state been saved?
if (savedInstanceState != null) {
// TODO:
// Restore value of counters from saved state
// Only need 4 lines of code, one for every count variable
mCreate = savedInstanceState.getInt(CREATE_KEY);
mRestart = savedInstanceState.getInt(RESTART_KEY);
mStart = savedInstanceState.getInt(START_KEY);
mResume = savedInstanceState.getInt(RESUME_KEY);
}
// Emit LogCat message
Log.i(TAG, "Entered the onCreate() method");
// TODO:
// Update the appropriate count variable
// Update the user interface via the displayCounts() method
mCreate += 1;
displayCounts();
}
// Lifecycle callback overrides
@Override
public void onStart() {
super.onStart();
// Emit LogCat message
Log.i(TAG, "Entered the onStart() method");
// TODO:
// Update the appropriate count variable
// Update the user interface
mStart += 1;
displayCounts();
}
@Override
public void onResume() {
super.onResume();
// Emit LogCat message
Log.i(TAG, "Entered the onResume() method");
// TODO:
// Update the appropriate count variable
// Update the user interface
mResume += 1;
displayCounts();
}
@Override
public void onPause() {
super.onPause();
// Emit LogCat message
Log.i(TAG, "Entered the onPause() method");
}
@Override
public void onStop() {
super.onStop();
// Emit LogCat message
Log.i(TAG, "Entered the onStop() method");
}
@Override
public void onRestart() {
super.onRestart();
// Emit LogCat message
Log.i(TAG, "Entered the onRestart() method");
// TODO:
// Update the appropriate count variable
// Update the user interface
mRestart += 1;
displayCounts();
}
@Override
public void onDestroy() {
super.onDestroy();
// Emit LogCat message
Log.i(TAG, "Entered the onDestroy() method");
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
Log.i(TAG, "Entered the onSaveInstanceState() method");
// TODO:
// Save state information with a collection of key-value pairs
// 4 lines of code, one for every count variable
savedInstanceState.putInt(CREATE_KEY, mCreate);
savedInstanceState.putInt(RESTART_KEY, mRestart);
savedInstanceState.putInt(START_KEY, mStart);
savedInstanceState.putInt(RESUME_KEY, mResume);
}
public void onRestoreInstanceState(Bundle savedInstanceState) {
// Always call the superclass so it can restore the view hierarchy
super.onRestoreInstanceState(savedInstanceState);
Log.i(TAG, "Entered the onRestoreInstanceState() method");
// Restore state members from saved instance
mResume = savedInstanceState.getInt(RESUME_KEY);
mRestart = savedInstanceState.getInt(RESTART_KEY);
mStart = savedInstanceState.getInt(START_KEY);
mCreate = savedInstanceState.getInt(CREATE_KEY);
//displayCounts();
}
// Updates the displayed counters
// This method expects that the counters and TextView variables use the
// names
// specified above
public void displayCounts() {
mTvCreate.setText("onCreate() calls: " + mCreate);
mTvStart.setText("onStart() calls: " + mStart);
mTvResume.setText("onResume() calls: " + mResume);
mTvRestart.setText("onRestart() calls: " + mRestart);
}
}
here is the 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" >
<TextView android:id="@+id/create"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/onCreate" />
<TextView android:id="@+id/start"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/onStart" />
<TextView android:id="@+id/resume"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/onResume" />
<TextView android:id="@+id/restart"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/onRestart" />
<Button android:id="@+id/bLaunchActivityTwo"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/button" />
</LinearLayout>
You are getting the values of mCreate, mStart, mRestart and mResume from the Bundle object twice, in onCreate and in onRestoreInstanceState. This means that any changes to your counts made between retrieving the values the two times will be ignored.
If it is called at all, onRestoreInstanceState gets called after onCreate, so you should not restore the values in onRestoreInstanceState as they would already have been restored in onCreate.