Develop Reference

FindViewById returning null EditText

I have common problem with findViewById() function, it returns null:
<EditText
android:id="#+id/nameText"
/>
<Button
android:text="Save"
android:onClick="buttonClick1"
/>
</TableRow
android:onClick="buttonClick1"
/>
Activity1.java:
public class Activity1 extends ActionBarActivity {
public void buttonClick1(View view) {
setContentView(view);
EditText nameText = (EditText) view.findViewById(R.id.nameText);
EditText lastNameText = (EditText) view.findViewById(R.id.lastNameText);
EditText indexNumberText = (EditText) view.findViewById(R.id.indexNumberText);
Log.d(">>>> ", nameText.getText().toString());
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_activity1);
}
}
}
In buttonClick1() findViewById() returns null. Please explain why?

Remove setContentView(view); from buttonClick1 method
and initialise all your textview in this manner by removing view.
EditText nameText = (EditText) findViewById(R.id.nameText);
EditText lastNameText = (EditText) findViewById(R.id.lastNameText);
EditText indexNumberText = (EditText) findViewById(R.id.indexNumberText);
Also initialize the controls in the xml properly by giving height and width to controls

Multiple problems unless you're not posting all your code.
1) In your XML you close a TableRow tag, but I don't see you opening it. Might just be lazy copy-pasting.
2) In your onCreate you seem to be missing a listener for your button. There is nothing to indicate that you have a button anywhere. You need to find the view of your button as follows:
Button button = (Button) findViewById(R.id.nameOfButton);
Then you need to set a listener for it like this:
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Here goes whatever should happen when you click the button.
}
});
3) As for your ButtonClick1 method, delete it. It looks like you were trying to create a listener, but it is pretty far from what it should look like.

Try to replace your code by this one :
public class Activity1 extends ActionBarActivity {
#
Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_activity1);
EditText nameText = (EditText) findViewById(R.id.nameText);
EditText lastNameText = (EditText) findViewById(R.id.lastNameText);
EditText indexNumberText = (EditText) findViewById(R.id.indexNumberText);
}
public void buttonClick1(View view) {
//Your stuff
Log.d(">>>> ", nameText.getText().toString());
}
}
Since now would be the normal code that have you tried, if you want to set a click on a button you'll have to declare it as :
Button button1 = (Button) findViewById(R.id.button1);
Then you can do the :
public void buttonClick1(View v) {
// Your stuff
}
EDIT
Make sure that you have on your XML all of your EditText and all of your Button for example : or , also make sure that you have an android:id="#+id/yourID in all of your stuff..., by the way instead of using an onClick method in your XML for your Button, you could use this to use an OnClickListener
The point 1 to 3 should go inside of onCreate the point 4 should go outside of onCreate.
1.- Implements View.OnClickListener in your Activity1
public class Activity1 extends ActionBarActivity implements View.OnClickListener {
2.- Declare it
Button button1 = (Button) findViewById(R.id.button1);
3.- Do the setOnClickListener like this :
button1.setOnClickListener(this);
4.- Create an OnClick method :
#Override
public void onClick(View view) {
if (View.equals(button1))
//Your stuff
}

How to Add to a textview when a button is pressed

I know this has been asked before but I cannot make this work so here is what I have so far
class Click extends Activity {
int i=0;
protected void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.activity_main);
final TextView mTextView = (TextView) findViewById(R.id.Counter);
mTextView.setText(""+i);
final Button button = (Button) findViewById(R.id.AddOne);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// Perform action on click
TextView tv= (TextView) findViewById(R.id.Counter);
i=i+1;
mTextView.setText(Integer.toString(i));
}
});
}
Every time I run the app in an emulator it crashes
java.lang.IllegalStateException: Could not find a method Click(View) in the activity class com.scouting.corbin.frc_201415_scouting.MainActivity for onClick handler on view class android.widget.Button with id 'AddOne'
I know this is probably something completely stupid but I am new to this and need help thank you in advance.

As per your logcat.
java.lang.IllegalStateException: Could not find a method Click(View)
in the activity class
com.scouting.corbin.frc_201415_scouting.MainActivity for onClick
handler on view class android.widget.Button with id 'AddOne'
I suggest you to add Click(View v) in your MainActivity
public void Click(View v)
{
}

You need to take the root element here. Depending on parent layout include this line in the activity after setContentView().
RelativeLayout layout=(RelativeLayout)findViewById(R.id.yourLayoutId);// If its some other layout change "RelativeLayout" to your opted layout.
and in onClick() method of button, add following.
layout.add(tv);

Yopu want To add one Linearlayout in xml file
and set id for your LinearLayout.
android:id="#+id/linearlayout"
And change your addTextView method to following
public void addTextView(String text){
LinearLayout layout=(LinearLayout)findViewById(R.id.linear);
TextView textView=new TextView(this);
textView.setText(text);
textView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));
layout.addView(textView);
}
and call this method from your Forloop

Perhaps consider using the android:onClick="example_method" attribute for the button in your xml file. Then create the appropriate method in the class. public void example_method(View v) {} Then place the code you have in your onClick function into the new one. It's easier than using an listener.

Ok so all of you helped I completely got rid of that code which was too comlicated for what I was trying to do. After taking bits of suggestions and some reasearch I came up with this
public void AddOne(View v) {
TextView tv= (TextView) findViewById(R.id.Counter);
i=i+1;
tv.setText(""+i);
}
As you can see much simpler than what I had before and this one works thank you all

Android - Setting an ImageView content from another class

Here's the thing:
I have two classes: Main and control.java
the Main class is an Activity class where I build my app and the control class I just use for variables controls that I must access from other classes.
The problem is: In class Main I got 2 methods, and I have an ImageView in each of them, I need to set the image view resource of the second method on a click listener of the first one. Like this:
public void first() {
final ImageView first = (ImageView) findViewById(R.id.myview);
first.setBackgroundResource(R.drawable.myimage);
}
public void second() {
final ImageView second = (ImageView) findViewById(R.id.myview2);
//And then, I want something like this: first.setBackgroundResource(first);
}
Thanks guys!

Why don't you just do something like:
public void second() {
final ImageView second = (ImageView) findViewById(R.id.myview2);
final ImageView first = (ImageView) findViewById(R.id.myview);
first.setBackgroundResource(R.drawable.myimage);
}
Otherwise, you'd have to use a private/public class variable and define it outside the method.

I admit to being a bit confused by your question but I think below is at least the start of what you're looking for
#Override
protected void onCreate(Bundle savedInstanceState) {
control.setImageView((ImageView) findViewById(R.id.myview));
second = (ImageView) findViewById(R.id.myview2);
}
public void first() {
control.getImageView().setBackgroundResource(R.drawable.myimage);
}
public void second() {
second.setBackgroundDrawable(control.getImageView().getDrawable());
}
ImageView second;

How to display a something from an EditText?

I thought making thing part of the app would be easy, however I was wrong. I wish to have a textView display whatever the user wrote in the editText. This is what I tried.
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
// TODO Auto-generated method stub
myTextView.setText(myEditText.getText().toString());
// of course I would use variables in place of the
// myTextView and myEditText
}
});
This is another way I tried to get this done.
add.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
// TODO Auto-generated method stub
//num1 is my String variable
num1 = myEditText.getText().toString();
myTextView.setText(num1);
}
});
Both times the textView comes up with nothing in it.
Thank you for any help!

onClickListener merely responds to user clicks. You need to implement a TextWatcher on your EditText. The most straightforward way of doing this is to implement TextWatcher in your class, then make a call to myEditText.addTextChangedListener(this).
I recommend adding something like the following to your onTextChanged method:
#Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
myTextView.setText(myTextView.getText()+s);//or something like this...
}

I usually use GetDlgItemText.
char Buffer[120];
GetDlgItemText(hwndDlg, (control), buffer, sizeof(buffer));
This will read it and store it in buffer.

In the EditText the getText call should you return the String, I don't believe you need to call the ToString method on it. The way you are using it in the onClickListener implies you have a button that should be calling a function to set the text into the textview. If you want it dynamically you should be able to use onTextChanged to fill in the data.

First of all check whether the control is coming to your setOnClickListener(). Put in a Log to find that out.
Next make sure that "add" is the button or item that u r using to initiate the copy process.
This statement of yours is correct.
myTextView.setText(myEditText.getText().toString());
Though you do not require the toString(). Doesnt really make a difference. I suggest you check that your textview and edittext is fine.

have you check the visibility of textview ?before clicking add button it is invisible rite?then u have to set the visibility on add button click.

From your code i understood that there is a button here too so try this should work:
public class Activity1 extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn = (Button)findViewById(R.id.mybutton);
btn.setOnClickListener(btncall);
}
private OnClickListener btncall = new OnClickListener()
{
public void onClick(View v)
{
TextView mytextView = (TextView) findViewById(R.id.MytextView);
EditText myeditText = (EditText) findViewById(R.id.MyeditText);
mytextView.setText(myeditText.getText().toString());
}
};
}

ParseInt Exception

I am creating a small calc app with EditText views and Im running into an runtime exception when the user leaves an EditText view empty causing the ParseInt to try and Parse nothing. Ive read that I need to 'Try' and 'Catch' this error before it occurs, but Im unsure of where and how to do this!
Any advice is much appreciated!
Here is my code:
public class HandlerExamples extends Activity implements OnClickListener {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button button = (Button)findViewById(R.id.testButton);
button.setOnClickListener(this);
public void onClick(View v) {
String a,b,t;
double vis;
EditText txtbox1 = (EditText)findViewById(R.id.A);
EditText txtbox2 = (EditText)findViewById(R.id.B);
EditText txtbox3 = (EditText)findViewById(R.id.t);
TextView tv = (TextView) findViewById(R.id.Answer);
a = txtbox1.getText().toString();
b = txtbox2.getText().toString();
t = txtbox3.getText().toString();
vis = ((Integer.parseInt(a)*1) + (Integer.parseInt(b)*2)) / (Double.parseDouble(t));
tv.setText(double.toString(vis));
}
}
Thanks so much!

public void onClick(View v) {
int id = v.getId();
switch(id){
case R.id.xx:
//do things xx click
break;
case R.id.yy:
//do things yy click
break;
}
}
you can get the view id to know whick widget was clicked.

Changwei Yao defined one way you can do this, but here's the way most Android programmers would do this (programmatically), since it's a little easier to read and figure out what your widgets are doing:
But first, remove the implements OnClickListener from your Activity, as it's not needed.
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// what you want your button to do when clicked
}
}
editText.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// what you want your EditText to do when clicked
// (such as editText.setText(""))
}
}
Another way to do the same thing is to define android:onClick="insert_method_name_here" for the widgets that you want perform an action when clicked. In your case, in your main.xml (since that's what you're using in your Activity), you could write something like...
<Button android:id="#+id/testButton"
(other attributes you wish to apply to the button)
android:onClick="buttonAction" />
<EditText
(other attributes)
android:onClick="textAction" />
And then, in your Activity, you define the methods buttonAction(View v) and textAction(View v). Note that these methods must be public void, and must take the sole argument View v.
(One advantage of the XML method is that you don't necessarily have to define an android:id attribute for these widgets, unless you need to be able to manipulate them or extract information from them in your code (which means you will need to define an android:id for your EditText since you'll likely want the user's input))

If you only need to exclude the empty text field then hotveryspicy's solution is probably the quickest. For a secure solution: catching the NumberFormatException will filter anything that can not be converted to an integer.
int vis;
try {
vis = Integer.parseInt(a);
}
catch(NumberFormatException nfe) {
Log.e(TAG,"trying to convert:"+a+" to integer failed");
vis = 0;
}