在android studio中无法解析方法'findViewById'

Question

I am joining two activity through intent

package com.smartcodeone.newapp1;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;

public  class MainActivity extends ActionBarActivity  {

    public static final String STRING_VAR = "com.smartcodeone.newapp1.HELLO_WORLD";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btnMsg = (Button) findViewById(R.id.btnMsg);


        btnMsg.setOnClickListener(new View.OnClickListener(){

            //when user click's this function will be called
            public void onClick(View v){
                Intent intentvar = new Intent(getApplicationContext(),Main2Activity.class);
                intentvar.putExtra(STRING_VAR,"Hello World");   //this is used to pass data to next intent
               startActivity(intentvar);
            }
        });


    }

    private int findViewId(int btnMsg) {
            return 0;

    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;



    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public android.support.v4.app.FragmentManager getSupportFragmentManager() {
        return null;
    }
}

Answer 1

It might have to do with Android Studio. Try cleaning your project and then rebuilding. If that doesn't work go to File -> Invalidate Caches/Restart ...

I get those issues sometimes as well. Let me know if that works. I tried your code and it works fine.

Answer 2

The issue seems to be that you defined a method named: findViewById(int button) that always return 0.

Use the Activity method instead of your own:

this.findViewById(int resourceId)

Good luck!

Answer 3

It seems you are implementing your own findviewbyid(). I don't know if you intend to do so.

Try removing

private int findviewbyid(int btnMsg) {
}

The ActionBarActivity's findviewbyid should resolve your button from your layout file.

Answer 4

Assuming you meant to the original findViewById(int) and not the function you wrote there:
Try extending from Activity instead.
That means that you will have to delete the useless function you didn't use and import android.app.Activity .

In Addition, don't use the android.support.v7.* package.
From my little experience it only causes troubles, unless you know what are you doing with it.