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Android Studio not recognizing Java objects

For reference I am using Android Studio 3.1.4. My problem is that android studio isn't recognizing any of my java objects aka all of the objects names are underlined in red. Here is the code for my main activity:
package com.example.t00587599.unitconverter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.AdapterView;
public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Spinner spinner = findViewById(R.id.spinner);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(context: this, R.array.temptypes, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(this);
}
}

I donot know much about the issues that you are facing as there can be multiple reasons why that is happening. There are two things that you could be happening
- if your package is compiled then you should check if the files are in the project. Or the project where the package is included is added in the build.gradle. I do this by adding
compile ":unitconverter"
- if you are including this as a compiled dependency then you can add the following line in your build.grade for the project
compile "com.example.t00587599.unitconverter"
After that you should do a gradle sync. If after doing all this you still get the red lines then you should do a "File/Sync Project with Gradle Files" from the file menu.
All of these class of problems disappear after these steps for me.
If it still appears then you should give us the error that come when you highlight it.

build.xml:1: Premature end of file

I am new in Android development, and I wanna build some apps for myself. I have installed Android SDK last version, NetBeans IDE 7.4 and also the plugin for this. I wrote a simple code for Android to see if it works:
package com.app;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class MainActivity extends Activity
{
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
TextView tv = new TextView(this);
tv.setText("HelloWorld");
setContentView(tv);
}
}
When I try to build and run with an emulator, I get this error: [path] \AndroidApplication1\build.xml:1: Premature end of file.
When I go to the file (build.xml) I see that is empty. I should write to it? What should I do? Thanks in advance.

Red line error with correct code

image
Well i have this problem when the code is correct, but it gives me red line error!
can anybody help me.
Main.java
package com.example.sout;
import android.content.DialogInterface;
import android.graphics.drawable.AnimationDrawable;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import
~
import android.widget.ImageView;
public class Main extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
ImageView iv = (ImageView) findViewById(R.id.img1);
iv.setBackgroundResource (R.anim.animation);
~~~~~~~~~~~~~~~~
iv.setOnClickListener(new OnClickListener());
~~~~~~~~~~~~~~~ ~
}
in (note the ~ characters above):
iv.setBackgroundResource (R.anim.animation);
iv.setOnClickListener(new OnClickListener());
The setBackgroundResource and setOnClickListener are red too.

The error in iv.setBackgroundResource (R.anim.animation); comes because that method takes integer as a parameter .So change it to the following,
iv.setBackgroundResource (R.drawable.image1); //image1 is a drawable which is inside your drawable folder.
and the second error comes because you have not imported the required package and have not overridden the methods required for that. Change it to the following,
iv.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
//do your task here
}
});
after changing press ctrl+shift+p to import the required packages.

Sometimes, at least with Eclipse, it gets it into it head that there's an error and it won't let it go. But, with Eclipse, you can at least put the cursor over a marker and it will explain what the problem is (or what it thinks it is). I'd try to hover over the errant lines to see if a popup box appears telling you what it thinks.
If you're sure it's wrong, often I've found that saving the file (or all files) will fix it. Sometimes adding then deleting a space on the errant line will fix it.
However, I notice that you have an incomplete import at the top of your file and this may be preventing the syntax checker from properly analysing the source file.
My advice is to fix that first, then try those other two tricks (save then, if that doesn't work, edit and undo on the errant line). Hopefully that will make it disappear.
Of course, you may want to check, just in case, your R.java file to ensure that member exists in there somewhere. I've been bitten by my own misspellings before.

Clean deleted R. Cant run any of my codeI

I did clean project and now i cannot run any of my code. Any files that has to do with R, just says cannot be resolved as a field. I've looked at so many other stackoverflow posts with similar problems but none seems to actually help. Help please!!
I have about 15 classes but here is an example
package com.Class;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.preference.PreferenceActivity;
import android.preference.PreferenceManager;
public class NewAccount extends PreferenceActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.xml.preferences);
SharedPreferences sp = PreferenceManager
.getDefaultSharedPreferences(this);
}
}

If R.java is not being generated, chances are there are some other errors in your code than the ones referring to the R file. Find these errors, solve them, and then R will be regenerated.

Did you import the R file?
import com.example.myapp.R;
This may be useful too: R cannot be resolved - Android error

android "main cannot be resolved or is not a field"

i m new to this platform, please help me to find what is the error...
setContentView(R.layout.main); // this line shows the error.
Code:
package com.example.helloandroid;
import android.R;
import android.app.Activity;
import android.os.Bundle;
public class HelloAndroidActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}

Try deleting the line import android.R then clean your project.

Just adding more details on why the error is coming.
As there is an import of android.R so setContentView() is looking for a layout file 'android.R.layout.main' and there is no main.xml in the layout files that come along with SDK. So, using the correct R.java import will work.

clean Project then try To Run because i faced same problem before a month and remember layout/main.xml must be their and it must not contains any error.
you can Also Do this
import android.R;
or
import your.application.packagename.R; Now Clear Project and Run it.

You must have to simply change the
setContentView(R.layout.main);
... to:
setContentView(R.layout.activity_main);
... because Layout contains this .xml file.
I hope your problem will be solved.

First remove import android.R;
After any change on xml fiels you must clean project.
Build > Clean Project
after that every things corrects.