Android Studio的多个onCreate方法

Question

I've been trying to make two buttong on my main layout. The buttons are supposed to open a second layout, called barcode_scanner.xml and vragen.xml

However, only the first button opens the scanner. The second button does not do anything.

This is my current code from MainActivity.java

package com.kvprasad.zbarbarcodescanner;

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

public class MainActivity extends AppCompatActivity {

    private Button scannerButton;

    //@Override
    //protected void onCreate(Bundle savedInstanceState) {
    //  super.onCreate(savedInstanceState);
    //setContentView(R.layout.activity_main);

    // scannerButton = (Button) findViewById(R.id.scannerButton);

    //scannerButton.setOnClickListener(new View.OnClickListener() {
    //  @Override
    // public void onClick(View v) {

//                Intent intent = new Intent(v.getContext(), BarcodeScanner.class);
    //              startActivity(intent);
    //        }
    //  });
    //}

    @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
    //Barcodescanner knop
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button next = (Button) findViewById(R.id.scannerButton);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), BarcodeScanner.class);
                startActivityForResult(myIntent, 0);
            }
        });
    }




//bovenbouw knop
    public class AutoBodyActivity extends MainActivity {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button next = (Button) findViewById(R.id.bovenbouw);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), Vragen.class);
                startActivityForResult(myIntent, 0);

                    }
                });
            }};
        }

This is the specific part with the onCreate methods:

@Override
    //Barcodescanner knop
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button next = (Button) findViewById(R.id.scannerButton);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), BarcodeScanner.class);
                startActivityForResult(myIntent, 0);
            }
        });
    }




//bovenbouw knop
    public class AutoBodyActivity extends MainActivity {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button next = (Button) findViewById(R.id.bovenbouw);
        next.setOnClickListener(new View.OnClickListener() {
            public void onClick(View view) {
                Intent myIntent = new Intent(view.getContext(), Vragen.class);
                startActivityForResult(myIntent, 0);

                    }
                });
            }};
        }

The button with id: 'scannerButton' works fine, but the button with id: 'bovenbouw'

I don't see any mistakes in the code. What is possibly wrong?

Answer 1

You should declare both buttons in the MainActivity.onCreate(..) method

Button b1 = (Button) findViewById(R.id.b1);
Button b2 = (Button) findViewById(R.id.b2);

and then register your onClick listeners to open a new Activity.

For your second activity you'd have an own class SecondActivity with its own onCreate method to take care of stuff.

To open the second Activity you just open a new Intent like so

Intent intent = new Intent(this, SecondActivity.class);
startActivity(intent)

hope this helps :)