Develop Reference

why am i getting error message on MainActivity Java?

I always get an error warning anytime i want to set find view by id
public class MainActivity extends AppCompatActivity {
View pdfView = findViewById(R.id.pdfView);
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pdfView.**fromAsset**("").load();
}
The error comes from "fromAsset." It always highlighted in red.
Does anyone have a solution to this?

Please initialize View inside onCreate() Method.
View pdfView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pdfView = findViewById(R.id.pdfView);
pdfView.**fromAsset**("").load();
}

App crahing when Button declared outside onCreate method [duplicate]

This question already has answers here:
Why does my Android app crash with a NullPointerException when initializing a variable with findViewById(R.id.******) at the beginning of the class?
(9 answers)
Closed 1 year ago.
The following code crashes the app
public class SharedPreferencesActivity extends AppCompatActivity {
Button b1=(Button)findViewById(R.id.buttonSave); //**ERROR**
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shared_preferences);
}
Whereas the following code works fine
public class SharedPreferencesActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shared_preferences);
Button b1=(Button)findViewById(R.id.buttonSave);//**REPLACED BUTTON DECLARATION**
}
Why is this happening?

If you want a reference to your button globally then you should declare it outside then initialize it in onCreate
Button b1; //declare the button variable
public class SharedPreferencesActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_shared_preferences);
b1 = (Button) findViewById(R.id.buttonSave); //initialize on creation
}
You should read more into the basics of Java when learning Android

Android Intents to pass data

I don't know why, but this isn't working. Can anyone see anything wrong with my code.
I have two activities and I'm passing data from two
public class InputActivity extends AppCompatActivity {
EditText number1EditText;
EditText number2EditText;
Button addButton;
InputActivity code looks like this
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_input);
number1EditText = (EditText)findViewById(R.id.editText);
number2EditText = (EditText)findViewById(R.id.editText2);
addButton = (Button)findViewById(R.id.button);
addButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent mIntent = new Intent(getApplicationContext(), AddActivity.class);
mIntent.putExtra("number1", number1EditText.getText().toString());
mIntent.putExtra("number2", number2EditText.getText().toString());
startActivity(mIntent);
}
});
}
AddActivity code looks like this
public class AddActivity extends AppCompatActivity {
TextView answer;
double y=0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_add);
answer =(TextView)findViewById(R.id.textView);
String value1 = getIntent().getExtras().getString("number1");
String value2 = getIntent().getExtras().getString("number2");
answer.setText((int) (Double.parseDouble(value1)+Double.parseDouble(value2)));
}

Just looking quickly:
answer.setText((int) (Double.parseDouble(value1)+Double.parseDouble(value2)));
You're passing a int to the method setText() which happens to have an overload that receives a int argument for the cases when you pass the reference from a String in some xml. You may be getting a ResourceNotFoundException.
If you want to show a text with the sum between your values:
answer.setText(String.valueOf((int) (Double.parseDouble(value1)+Double.parseDouble(value2))));
Just keep in mind that there are a lot of checks you have to do first, you may get another exceptions doing this kind of parse, like NumberFormatException for instance.

What could possibly be causing this NPE in onCreate?

I am getting an NPE in onCreate of the following file (MySubActivity):
public class MySubActivity extends MySuperActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myTextView.setText(getResources().getString(R.string.myString));
}
}
MySuperActivity:
public class MySuperActivity extends Activity {
protected TextView myTextView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_layout);
myTextView = (TextView)findViewById(R.id.myTextViewid);
}
}
The strange thing is that I have never seen this crash while testing the app. The page works fine when I test it. However I got a crash report from Google notifying me of the crash. I cannot reproduce it, and I have no idea under what scenario this crash could happen. Seeing as how it works for me, the resource ids and string names etc. must be correct.
The only thing that came across my mind was that maybe the user had their phone set to a different language, so it couldn't properly pull the resources. However, there are default resources for all of them, and I tested changing the language of my emulator and it didn't crash. Any ideas?

Set your view in another method, like this:
public class MySubActivity extends MySuperActivity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
private void setView(){
myTextView.setText(getResources().getString(R.string.myString));
}
}
Edit: Don't call setView() in MySuperActivity
public class MySuperActivity extends Activity {
protected TextView myTextView;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_layout);
myTextView = (TextView)findViewById(R.id.myTextViewid);
// Or, you can do this in a method called getView() if you like
}
}

Want to Run a function without click any button when application start

I have a function named 'func()'. I want to run this function when application start without clicking any button. just when application load I want to show a massage.that massage in that function. I just want to run that function when app start what will be the code.
public class TextViewActivity extends Activity {
public static EditText etxt;
public final void func(){
etxt.setText("Massage");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
etxt= (EditText) findViewById(R.id.etxt2);
}
}

Just put a call to the function on the onCreate
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
etxt= (EditText) findViewById(R.id.etxt2);
func(); //A call to the function.
}
Hope that helps.

I don't recommend subclassing the Application in order to do this. When the application starts it will go to the main activity. So I would say just keep a SharedPreference boolean value if it has been set. If not show the message.
So keep state of the application here: http://developer.android.com/reference/android/content/SharedPreferences.html, just set a boolean. Remember when you app gets called, the activity onCreate always gets called of the main activity, so its just a matter of not calling it again.

try using below code.. you need to call ur function after you initialize edittext etxt. so it can not cause you NPE
public final void func(){
etxt.setText("Message");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
etxt= (EditText) findViewById(R.id.etxt2);
func();// here your function call.
}

Try this:
public class TextViewActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.etxt2).setText("SMTH");
}
}
In case you really need a function to be called, you can use this:
public class TextViewActivity extends Activity {
public final void func() {
findViewById(R.id.etxt2).setText("SMTH");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
func();
}
}