Develop Reference

Average calculator Fatal Exception

I am really new at programming. I am trying to run a simple average calculator and getting a force close, this is what the logcat is showing. I am running android studio version 2.3.3
FATAL EXCEPTION: main
Process: com.vu.gradingapp, PID: 6312
java.lang.NumberFormatException: For input string: ""
at java.lang.Integer.parseInt(Integer.java:620)
at java.lang.Integer.valueOf(Integer.java:794)
at com.vu.gradingapp.AverageActivity$1.onClick(AverageActivity.java:37)
at android.view.View.performClick(View.java:6219)
at android.view.View$PerformClick.run(View.java:24482)
at android.os.Handler.handleCallback(Handler.java:769)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6540)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
The code i am using is as follow
public class AverageActivity extends AppCompatActivity {
EditText editmanner, editinstances, editshortstance, editstrikes, editboxingskills, editknocks, editkicks, editResults;
Button btnResults;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.average_page);
editmanner =(EditText)findViewById(R.id.editText8);
editinstances = (EditText)findViewById(R.id.editText9);
editshortstance = (EditText)findViewById(R.id.editText10);
editstrikes = (EditText)findViewById(R.id.editText11);
editboxingskills = (EditText)findViewById(R.id.editText12);
editknocks = (EditText)findViewById(R.id.editText13);
editkicks = (EditText)findViewById(R.id.editText14);
editResults = (EditText)findViewById(R.id.editText15);
btnResults = (Button) findViewById(R.id.button10);
btnResults.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
int first, second, third, fourth, fifth, sixth, seventh, results;
first=Integer.valueOf(editmanner.getText().toString());
second=Integer.valueOf(editinstances.getText().toString());
third=Integer.valueOf(editshortstance.getText().toString());
fourth=Integer.valueOf(editstrikes.getText().toString());
fifth=Integer.valueOf(editboxingskills.getText().toString());
sixth=Integer.valueOf(editknocks.getText().toString());
seventh=Integer.valueOf(editkicks.getText().toString());
results=(first+second+third+fourth+fifth+sixth+seventh)/7;
editResults.setText(String.valueOf(results));
}
});
}
public void knowtheresults (View view) {
String button_text;
button_text = ((Button) view).getText().toString();
if (button_text.equals("Summary")) {
Intent intent = new Intent(this, ResultActivity.class);
startActivity(intent);
} else if (button_text.equals("Back")) {
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
WHat am I doing wrong :D
Thanks Guys

Error says you cannot convert "" value to number Its a java.lang.NumberFormatException. So use 0 instead of number is blank first check if edittext is blank than set its value to 0
int first;
if(editmanner.getText().toString().equals("")){
first = 0
}else{
first = Integer.valueOf(editmanner.getText().toString());
}
do this for your all int variables.

Update your code with such verification for each int variable:
if (editmanner().toString().isEmpty())
first = 0;
else
first = Integer.parseInt(editmanner().toString());
Since you have int variables (not Integer) it is preferable to use parseInt instead valueOf

Thanks guys, I just filled in the textedits with (0) and now is working. Please apologize for my silly questions.
Is there any way to hide this zeros on the textview so it shows blanks.

java.lang.NumberFormatException
Thrown to indicate that the application has attempted to convert a string to one of the numeric types, but that the string does not have the appropriate format.
The logcat already stated what is the cause of the crash. One or all of your EditText has empty string. To convert string to Integer, the string must be numeric(0,1,2 etc). You need to set EditText with numeric value (eg: 0).

Using and updating a variable across different intents

this is my first question being asked on stackoverflow. My question is regarding variable use across different recyclable intents.
e is declared like this.
final Bundle e=getIntent().getExtras();
Here i am creating new intents for different setOnClickListener() and passing a different variable for each intent.
Intent info = new Intent(EItemListView.this, ItemInfo.class);
Bundle extras = new Bundle();
int[] a=new int[listview.getAdapter().getCount()];
if (i == 0) {
extras.putIntArray("img", n5x_images);
extras.putString("info", n5x_info);
extras.putInt("pc",a[0]);
} else if (i == 1) {
extras.putIntArray("img", op3_images);
extras.putString("info", op3_info);
extras.putInt("pc",a[1]);
}
info.putExtras(extras);
startActivity(info);
Now this is the OnClickListener() where i am trying to update the variables which i passed through the intent extras, but am unable to update those variables.
addtc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
int c=e.getInt("pc");
c=c+1;
Log.i("Log","value "+c);
}
The log message which i get from the above method is always 1, i think the variable in c is always set to 0 and then increments by 1 and hence the log message shows 1.
I need the variables a[0],a[1],a[2], etc to pertain its increment operation.
To make it more clear, this is the java file i am using. The error is in the OnClickListener of addtc button at the bottom of this code.
public class ItemInfo extends AppCompatActivity {
private ViewAnimator viewanimator;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_item_info);
Button next=(Button)findViewById(R.id.bnext);
Button prev=(Button)findViewById(R.id.bprev);
viewanimator=(ViewAnimator)findViewById(R.id.viewAnimator);
TextView info=(TextView)findViewById(R.id.item_info);
Button addtc=(Button)findViewById(R.id.badd);
Button test=(Button)findViewById(R.id.button);
Bundle e=getIntent().getExtras();
int img[]=e.getIntArray("img");
for(int i=0;i<img.length;i++)
{
ImageView imgview = new ImageView(getApplicationContext());
imgview.setImageResource(img[i]);
viewanimator.addView(imgview);
}
info.setText(e.getString("info"));
next.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
viewanimator.showNext();
}
});
prev.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
viewanimator.showPrevious();
}
});
addtc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
int c=e.getInt("pc");
c=c++;
Log.i("Log","value "+c);
}
});
}
}
Thanks in advance!!!

Your approach is wrong. You cannot do this in this way. Your understanding of what an "extra" in an Intent is incorrect.
When you do this:
extras.putInt("pc",a[1]);
This adds an "extra" to the extras Bundle. The Bundle is simply a key/value pair map and you have added an entry that contains the key "pc" and the value is whatever a[1] is. It puts a copy of the value of a[1] into the Bundle, it does not put a reference to a[1] in the Bundle.
Therefore, if a[1] is 5 when you add it to the extras Bundle, a[1] will always be 5 and will never be changed to anything else.
You can't do this in this way.
Alternative: Depending on your application architecture and what you are trying to do, you can use one of the following methods:
1) Use startActivityForResult(), pass the data from one Activity to another, have the second Activity update the data and put it back into the Intent which is then returned to the "calling" Activity by using setResult().
2) Use a static variable (basically a "global" variable) to contain the data. Both activities can then access the data directly (you don't need to put the data in the Intent.
3) Put the data in a database. Both activities can then read/write from/to the database.

First advice I can give you is debugging and posting debug result. for example, are you sure that a[0] and a[1] aren't 0?
Assuming they are not, why are you declaring the bundle as final? referring to this probably final is not what you were looking for. Try removing it or replacing with private
Another suggestion is more for readable purpose, replace c = c+1; with c++; but this doesn't change the result, it just make it more linear and easier for reading.
Now after this fix (the final keyword one) tell me if something changed please :)

How can I set a button to invisible from one activity to another?

I am a android developer beginner, and I need some help please.
I have one activity (activity 1) with a button named "MORE", which when clicked takes me to another activity. This works well.
And I have another activity (activity 2). When I click on one checkbox, I need to make the button "MORE" invisible in the activity 1.
I found other similar questions, but it is throwing an error and I couldn't figure it out.
I made the button static in the activity 1
public static Button btn2;
In the activity 2 I set it to invisible
public void onClick(View view) {
Intent i;
switch (view.getId()) {
case R.id.checkBox2:
// set invisible button more in stock quotes
StockDetail.btn2.setVisibility(View.INVISIBLE);
break;
default:
break;
}
}
It is throwing this error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button
I found a similar question in this link:
Android: Hide button from another activity
I did exactly like that, but it still does not. I appreciate if someone can help me. Thank you

I think you should save a variable such as isShow (boolean) by SharePreference file. When you open activity1, you will get value at the sharepreference file.
Such as: If it is true --> you will set visible for button.

DO NOT make any variable static that may use context (like your button) as it may be highly susceptible to memory leaks. Usually there are various design patterns in place to avoid these.
A simple solution for your case can be starting your Activity2 from Activity1 using startActvityForResult(). In this setup the Activity1 expects some kind of result from Activity2. In your case it would be the state of your button. To learn more about it visit this [very small] official training doc: Getting a Result from an Activity.
Let us know if you tun intoo any issues.

you can apply a null point check like this
if(StockDetails.btn2 != null)
{
StockDetails.btn2.setVisiblity(View.Gone);
}

This will not work until StockDetail will be created. Alternatively for that you can do make a static variable inside StockDetail class like below:-
public class StockDetail extends Activity{
public static int buttonVisibility=View.VISIBLE;
#override
public void onCreate(Bundle savedInstanceState){
setContentView(R.layout.act2);
Button btn=(Button)findViewById(R.id.btn);
btn.setVisibilty(buttonVisibility);
}
and from Activity1
public void onClick(View view) {
Intent i;
switch (view.getId()) {
case R.id.checkBox2:
// set invisible button more in stock quotes
StockDetail.buttonVisibility=View.INVISIBLE;
break;
default:
break;
}
}
try the above it may help you.

Android (student cw) in need of direction

public class Menu extends Activity {
/** Called when the activity is first created. */
public void onCreate(Bundle icicle) {
//myIntent.setClassName("hello.World", "hello.World.mybuttonclick");
// myIntent.putExtra("com.android.samples.SpecialValue", "Hello, Joe!"); // key/value pair, where key needs current package prefix.
//startActivity(myIntent);
//Button myButton = (Button) findViewById(R.id.my_button);
super.onCreate(icicle);
setContentView(R.layout.main);
}
public void updateLayout(){
Intent myIntent = new Intent(Menu.this, mybuttonclick.class);
startActivity(myIntent);
// TextView sayHello = (TextView) findViewById(R.id.Hello);
}
}
Hey guys, I am a new android java student and we have to develop a simple hello world app.. I am finding some difficulty getting my onClick() activity to work, using android:Onclick in xml.. what i am trying to do is change the content view do display a simply a different layout and saying hello.. i am using setContentLayout to do this, every time i click said button tho the android app crashes out.. am i doing something wrong?
regards,
Stefan

When you set a click listener in xml you must have the method defined inside the activity you are clicking in. Lets say you set the onClick in xml to be "buttonClicked", you must create a method looking exactly like the one below.
public void buttonClicked(View view)
{
//Your code here
}
The thing to notice is that the method is a public void with only a single parameter of type View. XML defined click listeners must be like this to work. The view object in the example above is the view that was clicked.

You update layout function needs to read
public void updateLayout(View view)

In response to your question, there are a number of things that are issues causing the complication that you described. Let it first be said, that you don't have to do anything any particular way, provided that you make concessions for certain things. Android is a very flexible platform and Java, as an OOP language allows you to do things that many non OOP languages do not.
Whenever you create a "clickable" item, like a Button, if you want to have your program respond, you must have something "listen" to it. This is known as a Listener. In your case, you are looking for an OnClickListener. The OnClickListener does not have to be a part of the Activity necessarily. It just has to be a class that implements View.OnClickListener. Then, you have tell the setOnClickListener() method of the Button who its listener is. The following example shows what is necessary without your declaration in XML (but it is important).
class Menu extends Activity implements View.OnClickListener
{
public void onCreate(Bundle icicle)
{ setContentView(R.layout.main);
Button btn = (Button)findViewById(R.id.BUTTON_ID_AS_DEFINED_BY_YOUR_XML);
btn.setOnClickListener(this);
}
public void onClick(View view)
{ int id = view.getId();
if (id == R.id.BUTTON_ID_AS_DEFINED_BY_YOUR_XML)
updateLayout()//Do your Click event here
}
public void updateLayout()
{ //updateLayout code...
}
}
Something that needs to be noted is the OnClick() above. Every OnClickListener must use the same signature as theOnClick() That means itmust have the same return and same arguments even if it has a different name. For what you are trying to do (in XML), you have set your android:OnClick to updateLayout. This means that `updateLayout() must be declared as follows:
public void updateLayout(View view)
Now, getting the update method to actually work: While you provide your code, we don't actually know what errors you are getting. It is always much easier to solve a problem if we have a copy of the Logcat output that includes the error you are receiving. Once, we have that we can target your error specifically and I can edit my answer to include what you may additionally need.
FuzzicalLogic

Where is the memory leak?

my dear friends. Could you help me to figure out where do I have memory leak in my application.
There are two activities.
In first activity I'v got a rather big static ArrayList consists of bitmaps and another needed information. I made it static, because I need to take it from another activity, and It's loading takes to much time.
In another activity, I also have one static field, using as a key for getting data which present in an Intent from previous activity.
If I try to start one activity from another and go back several times, I get shutting down VM.
To be more clear, here is a snippet of my code:
public class MoviesGallery extends Activity
{
...
private static ArrayList<Movie> films = new ArrayList<Movie>();
...
public void contextButtonsClickHandler(View v)
{
switch(v.getId())
{
case R.id.play_button:
Log.d("Context Button", "Play button has clicked");
mContextButtonHasPressed = true;
Intent filmData = new Intent(MoviesGallery.this, MovieInfo.class);
filmData.putExtra(MovieInfo.mPOS,mPOSITION_OF_CLICKED_ITEM);
startActivityForResult(filmData, 1);
break;
...
}
And this is another activity:
public class FilmInfo extends Activity
{
public static String mPOS = "pos";
private int mNumOfFilm = -1;
private LinearLayout mWall;
...
protected void onCreate(Bundle savedInstanceState)
{
Bundle extra = getIntent().getExtras();
mNumOfFilm=extra.getInt(mPOS);
...
Drawable d = new BitmapDrawable(MoviesGallery.getMoviesArray().get(mNumOfFilm).getWall()));
mWall = (LinearLayout) findViewById(R.id.Wall);
mWall.setBackgroundDrawable(d);
...
setResult(0);
}

I would suggest that potentially memory-leak point is in FilmInfo class member:
private LinearLayout mWall;
Layout has reference to Activity, which each time changes.
So to avoid keeping reference to dead Activity just use in FilmInfo class
#Override
public boolean onContextItemSelected(MenuItem item)
{
//blah-blah
mWall=null;
}
Anyway recipe is simple - try to avoid keeping objects which might contain references to Activity/Context objects.