Error when trying to open a new Activity

Question

Well, I have the MainActivity which has two buttons, I’m trying to do something simple: When you click one, go to a Activity, when you click on another, go to another Activity.

This is the mainactivity:

public class MainActivity extends ActionBarActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    }

    public void changeActivity(View view){
            Intent it = new Intent(MainActivity.this, HomeSpanishActivity.class);
            startActivity(it);
    }


    @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);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

            public PlaceholderFragment() {
            }

            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                                             Bundle savedInstanceState) {
                    View rootView = inflater.inflate(R.layout.fragment_main, container, false);
                    return rootView;

            }
    }
}

Mainactivity.xml

<Button
    android:id="@+id/btnOptionIngles"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Ingles"
    android:layout_centerVertical="true"
    android:layout_alignLeft="@+id/txtWelcome"
    android:layout_alignStart="@+id/txtWelcome"
    android:onClick="changeActivity"/>

<Button
    android:id="@+id/btnOptionEspanhol"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Espanhol"
    android:layout_alignTop="@+id/btnOptionIngles"
    android:layout_alignRight="@+id/txtWelcome"
    android:layout_alignEnd="@+id/txtWelcome"
    android:layout_alignBottom="@+id/btnOptionIngles"
    android:onClick="changeActivity"/>

Manifest:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.edsonmarcelo.tapfun" >

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >

    <!-- Splash screen -->
    <activity
        android:name=".SplashActivity"
        android:configChanges="orientation|keyboardHidden|screenSize"
        android:label="@string/app_name"
        android:screenOrientation="portrait"
        android:theme="@style/Theme.AppCompat.NoActionBar" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:screenOrientation="portrait"
        android:theme="@style/Theme.AppCompat.Light.NoActionBar" >
    </activity>
    <activity
        android:name=".HomeEnglishAcitivity"
        android:label="@string/title_activity_home_english_acitivity" >
    </activity>
    <activity
        android:name=".HomeSpanishActivity"
        android:label="@string/title_activity_home_spanish" >
    </activity>

</application>

ERROR:

04-26 21:52:33.261: E/AndroidRuntime(6020): FATAL EXCEPTION: main
04-26 21:52:33.261: E/AndroidRuntime(6020): java.lang.RuntimeException: Unable      to start activity             ComponentInfo{com.example.edsonmarcelo.tapfun/com.example.edsonmarcelo.tapfun.Home   SpanishActivity}: java.lang.NullPointerException
04-26 21:52:33.261: E/AndroidRuntime(6020):     at    android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.ActivityThread.access$700(ActivityThread.java:159)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.os.Looper.loop(Looper.java:176)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.ActivityThread.main(ActivityThread.java:5419)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at java.lang.reflect.Method.invokeNative(Native Method)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at java.lang.reflect.Method.invoke(Method.java:525)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at dalvik.system.NativeStart.main(Native Method)
04-26 21:52:33.261: E/AndroidRuntime(6020): Caused by: java.lang.NullPointerException
04-26 21:52:33.261: E/AndroidRuntime(6020):     at com.example.edsonmarcelo.tapfun.HomeSpanishActivity.onCreate(HomeSpanishActivity.java:21)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.Activity.performCreate(Activity.java:5372)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-26 21:52:33.261: E/AndroidRuntime(6020):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)

Englishomeactivity

package com.example.edsonmarcelo.tapfun;

public class HomeEnglishAcitivity extends ActionBarActivity {

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

    GridView gridview = (GridView) findViewById(R.id.gdViewHomeEnglish);
    gridview.setAdapter(new ImageAdapter(this));

    gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v,
                                int position, long id) {
            Toast.makeText(HomeEnglishAcitivity.this, "" + position,
                    Toast.LENGTH_SHORT).show();
        }
    });
}


@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_home_english_acitivity, 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);
}
}

Spanishhomeactivity

package com.example.edsonmarcelo.tapfun;


public class HomeSpanishActivity extends ActionBarActivity {

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

    GridView gridview = (GridView) findViewById(R.id.gdViewHomeEnglish);
    gridview.setAdapter(new ImageAdapter(this));

    gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View v,
                                int position, long id) {
            Toast.makeText(HomeSpanishActivity.this, "" + position,
                    Toast.LENGTH_SHORT).show();
        }
    });
}


@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_home_spanish, 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);
}
}

Answer 1

Well, you didn’t specify which error, but what seems to be happening is opening only the Homespanishactivity and never the other, since you are using the same method changeActivity.

You can do as follows by changing this method:

public void changeActivity(View view) {
    Intent it;

    if (view.getId() == R.id.btnOptionIngles) {
        it = new Intent(this, HomeEnglishAcitivity.class);
    } else {
        it = new Intent(this, HomeSpanishActivity.class);
    }

    startActivity(it);
}

So you will check which button was pressed and select the Activity correct.