Trying to hide the menu item when there are no views
Question
I'm trying to build an app that generates buttons dynamically per floatActionButton click. This aspect works fine. But if there are no views, there shouldn't be a delete menu item on the action bar. At the start of the app, since there are no items, there is no menu item but I need the menu item to show up once I start adding views. I tried to work it with if statements but it still did not work.
This is my code:
public class MainActivity extends AppCompatActivity {
int counter = 0;
FloatingActionButton addingSemester;
Button semesterButton;
LinearLayout semesterLayout;
GridLayout semesterGridLayout;
RelativeLayout relativeLayout;
LinearLayout.LayoutParams portraitLayoutParams = new LinearLayout.LayoutParams(
AppBarLayout.LayoutParams.MATCH_PARENT,
AppBarLayout.LayoutParams.WRAP_CONTENT);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addingSemester = (FloatingActionButton) findViewById(R.id.addActionButton);
semesterLayout = (LinearLayout) findViewById(R.id.main_layout);
semesterGridLayout = (GridLayout)findViewById(R.id.semester_grid_layout);
GridLayout.LayoutParams params = new GridLayout.LayoutParams();
relativeLayout = (RelativeLayout)findViewById(R.id.relativeLayout);
semesterButton = new Button(MainActivity.this);
if (savedInstanceState != null) {
counter = savedInstanceState.getInt("counter");
for(int i = 0; i < counter; i++) {
addSemesterButton(i);
}
}
}
public void addSemesterButton(int id) {
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
double width = (size.x)/3;
semesterButton = new Button(MainActivity.this);
semesterButton.setId(id + 1);
semesterButton.setText("Semester " + (id + 1));
semesterButton.setBackgroundColor(getColor(R.color.colorPrimary));
semesterButton.setTextColor(Color.WHITE);
portraitLayoutParams.setMargins(24, 24, 24, 24);
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
GridLayout.LayoutParams params = new GridLayout.LayoutParams();
params.setMargins(24, 24, 24, 24);
params.width = (int) width;
params.height = GridLayout.LayoutParams.WRAP_CONTENT;
semesterButton.setLayoutParams(params);
semesterGridLayout.addView(semesterButton);
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.addView(semesterButton);
semesterButton.setLayoutParams(portraitLayoutParams);
}
setOnLongClickListenerForSemesterButton();
}
public void addTextView(int id){
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
double width = (size.x);
TextView instructionsPromptTextView = new TextView(MainActivity.this);
instructionsPromptTextView.setId(id);
instructionsPromptTextView.setText(R.string.click_the_button_to_add_semesters);
instructionsPromptTextView.setTextSize((float)width);
instructionsPromptTextView.setVisibility(View.VISIBLE);
instructionsPromptTextView.setBackgroundColor(Color.BLACK);
relativeLayout.addView(instructionsPromptTextView);
if(id == 0){
instructionsPromptTextView.setVisibility(View.INVISIBLE);
}
}
public void onFloatActionButtonClick(View view) {
if (counter < 8) {
addSemesterButton(counter);
counter++;
setOnLongClickListenerForSemesterButton();
} else if (counter == 8) {
Toast.makeText(MainActivity.this, "You cannot add more than 8 semesters", Toast.LENGTH_SHORT).show();
} else if (counter == 0){
addTextView(counter);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuItem item = menu.findItem(R.id.delete);
if(counter == 0){
item.setVisible(false);
}
if(counter > 0){
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.main, menu);
item.setVisible(true);
}
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.delete) {
new AlertDialog.Builder(MainActivity.this)
.setTitle("Delete entry")
.setMessage("Are you sure you want to delete everything?")
.setCancelable(true)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterGridLayout.removeAllViews();
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.removeAllViews();
}
counter = 0;
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
})
.show();
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putInt("counter", counter);
super.onSaveInstanceState(savedInstanceState);
}
private void setOnLongClickListenerForSemesterButton() {
semesterButton.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
final Button b = (Button) v;
b.setTag(b.getText().toString());
b.setBackgroundColor(Color.RED);
b.setText("Delete");
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("Delete entry");
builder.setMessage("Are you sure you want to delete this entry?");
builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterGridLayout.removeView(b);
for (int i = 0; i < semesterGridLayout.getChildCount(); i++) {
((Button) semesterGridLayout.getChildAt(i)).setText("Semester " + (i + 1));
}
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.removeView(b);
for (int i = 0; i < semesterLayout.getChildCount(); i++) {
((Button) semesterLayout.getChildAt(i)).setText("Semester " + (i + 1));
}
}
counter--;
}
});
builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
b.cancelLongPress();
b.setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimary));
b.setText(b.getTag().toString());
dialog.cancel();
}
});
builder.show();
return true;
}
});
}
}
EDIT
This is the stacktrace
FATAL EXCEPTION: main
Process: myapp.onur.journeygpacalculator, PID: 22605
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.view.View$DeclaredOnClickListener.onClick(View.java:4711)
at android.view.View.performClick(View.java:5623)
at android.view.View$PerformClick.run(View.java:22433)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6247)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:872)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:762)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.view.View$DeclaredOnClickListener.onClick(View.java:4706)
at android.view.View.performClick(View.java:5623)
at android.view.View$PerformClick.run(View.java:22433)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6247)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:872)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:762)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'android.view.MenuItem android.view.Menu.add(int, int, int, java.lang.CharSequence)' on a null object reference
at android.view.MenuInflater$MenuState.addItem(MenuInflater.java:493)
at android.view.MenuInflater.parseMenu(MenuInflater.java:190)
at android.view.MenuInflater.inflate(MenuInflater.java:111)
at android.support.v7.view.SupportMenuInflater.inflate(SupportMenuInflater.java:113)
at myapp.onur.journeygpacalculator.MainActivity.inflateMenu(MainActivity.java:182)
at myapp.onur.journeygpacalculator.MainActivity.onFloatActionButtonClick(MainActivity.java:168)
2 answers
solution1
0 2017-04-24 16:34:07
Instead of setting it invisible only in onCreateOptionsMenu set it in your action button click too like below
MenuItem item;
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.main, menu);
item = menu.findItem(R.id.delete);
item.setVisible(false);
return super.onCreateOptionsMenu(menu);
}
public void onFloatActionButtonClick(View view) {
if (counter < 8) {
addSemesterButton(counter);
counter++;
setOnLongClickListenerForSemesterButton();
item.setVisible(true);
} else if (counter == 8) {
Toast.makeText(MainActivity.this, "You cannot add more than 8 semesters", Toast.LENGTH_SHORT).show();
item.setVisible(true);
} else if (counter == 0){
addTextView(counter);
item.setVisible(false);
}
}
solution2
0 2017-04-27 19:35:52
1. Update onCreateOptionsMenu() as below, to hide delete option when app starts first:
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
itemDelete = menu.findItem(R.id.delete);
// Required to hide delete option when app starts first
itemDelete.setVisible(false);
return true;
}
2. Add below method to update the state of delete option.
public void updateOptionMenu() {
if (counter > 0)
item.setVisible(true);
else
item.setVisible(false);
}
3. Call updateOptionMenu() method from all places where the counter value changes like: onFloatActionButtonClick() and AlertDialog's onClick() methods.
Here is the full code:
public class MainActivity extends AppCompatActivity {
MenuItem itemDelete;
int counter = 0;
FloatingActionButton addingSemester;
Button semesterButton;
LinearLayout semesterLayout;
GridLayout semesterGridLayout;
RelativeLayout relativeLayout;
LinearLayout.LayoutParams portraitLayoutParams = new LinearLayout.LayoutParams(
AppBarLayout.LayoutParams.MATCH_PARENT,
AppBarLayout.LayoutParams.WRAP_CONTENT);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
addingSemester = (FloatingActionButton) findViewById(R.id.addActionButton);
semesterLayout = (LinearLayout) findViewById(R.id.main_layout);
semesterGridLayout = (GridLayout)findViewById(R.id.semester_grid_layout);
GridLayout.LayoutParams params = new GridLayout.LayoutParams();
relativeLayout = (RelativeLayout)findViewById(R.id.relativeLayout);
semesterButton = new Button(MainActivity.this);
if (savedInstanceState != null) {
counter = savedInstanceState.getInt("counter");
for(int i = 0; i < counter; i++) {
addSemesterButton(i);
}
}
addTextView(counter);
}
public void addSemesterButton(int id) {
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
double width = (size.x)/3;
semesterButton = new Button(MainActivity.this);
semesterButton.setId(id + 1);
semesterButton.setText("Semester " + (id + 1));
semesterButton.setBackgroundColor(getColor(R.color.colorPrimary));
semesterButton.setTextColor(Color.WHITE);
portraitLayoutParams.setMargins(24, 24, 24, 24);
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
GridLayout.LayoutParams params = new GridLayout.LayoutParams();
params.setMargins(24, 24, 24, 24);
params.width = (int) width;
params.height = GridLayout.LayoutParams.WRAP_CONTENT;
semesterButton.setLayoutParams(params);
semesterGridLayout.addView(semesterButton);
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.addView(semesterButton);
semesterButton.setLayoutParams(portraitLayoutParams);
}
setOnLongClickListenerForSemesterButton();
}
public void addTextView(int id){
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
double width = (size.x);
TextView instructionsPromptTextView = new TextView(MainActivity.this);
instructionsPromptTextView.setId(id);
instructionsPromptTextView.setText(R.string.click_the_button_to_add_semesters);
instructionsPromptTextView.setTextSize((float)width);
instructionsPromptTextView.setVisibility(View.VISIBLE);
instructionsPromptTextView.setBackgroundColor(Color.BLACK);
relativeLayout.addView(instructionsPromptTextView);
/*
if(id == 0){
instructionsPromptTextView.setVisibility(View.INVISIBLE);
}*/
}
public void onFloatActionButtonClick(View view) {
if (counter < 8) {
addSemesterButton(counter);
counter++;
setOnLongClickListenerForSemesterButton();
// Required to show delete option
updateOptionMenu();
} else if (counter == 8) {
Toast.makeText(MainActivity.this, "You cannot add more than 8 semesters", Toast.LENGTH_SHORT).show();
}
// Will never be called because counter == 0 will be consumed by first if condition
/*
else if (counter == 0){
addTextView(counter); // Move it to onCreate()
}*/
}
public void updateOptionMenu() {
if (counter > 0)
item.setVisible(true);
else
item.setVisible(false);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
itemDelete = menu.findItem(R.id.delete);
// Required to hide delete option when app starts first
itemDelete.setVisible(false);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.delete) {
new AlertDialog.Builder(MainActivity.this)
.setTitle("Delete entry")
.setMessage("Are you sure you want to delete everything?")
.setCancelable(true)
.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterGridLayout.removeAllViews();
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.removeAllViews();
}
counter = 0;
updateOptionMenu(); // Required to hide option item when all views are removed
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
})
.show();
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putInt("counter", counter);
super.onSaveInstanceState(savedInstanceState);
}
private void setOnLongClickListenerForSemesterButton() {
semesterButton.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
final Button b = (Button) v;
b.setTag(b.getText().toString());
b.setBackgroundColor(Color.RED);
b.setText("Delete");
AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
builder.setTitle("Delete entry");
builder.setMessage("Are you sure you want to delete this entry?");
builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
if (MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterGridLayout.removeView(b);
for (int i = 0; i < semesterGridLayout.getChildCount(); i++) {
((Button) semesterGridLayout.getChildAt(i)).setText("Semester " + (i + 1));
}
} else if (!MainActivity.this.getResources().getBoolean(R.bool.is_landscape)) {
semesterLayout.removeView(b);
for (int i = 0; i < semesterLayout.getChildCount(); i++) {
((Button) semesterLayout.getChildAt(i)).setText("Semester " + (i + 1));
}
}
counter--;
updateOptionMenu(); // Required to hide delete item if this button is last button to be removed
}
});
builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
b.cancelLongPress();
b.setBackgroundColor(ContextCompat.getColor(MainActivity.this, R.color.colorPrimary));
b.setText(b.getTag().toString());
dialog.cancel();
}
});
builder.show();
return true;
}
});
}
}
Hope this will help~
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