Question

So, I have this code:

package com.example.ponto_2d;

import android.app.Activity;
import android.view.Menu;
import android.view.MotionEvent;
import android.widget.TextView;

public class MainActivity extends Activity {
pontos p1=new pontos();
pontos p2=new pontos();

            @Override
            public boolean onTouchEvent(MotionEvent event) {

                TextView tv1 = (TextView) findViewById(R.id.textView2);

                   int eventaction= event.getAction();

                   switch (eventaction){
                   case MotionEvent.ACTION_DOWN:
                       p1.x=event.getX();
                       break;   

                   }

                   tv1.setText(""+p1.x);

                   return true;
            }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

This class:

package com.example.ponto_2d;

public class pontos {
        public double x,y;


        public double distancia(pontos p2){

            return Math.sqrt((p2.x-x)*(p2.x-x) + (p2.y-y)*(p2.y-y));
        }
}

This xml layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="38dp"
        android:text="@string/titulo_app"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_marginBottom="30dp"
        android:layout_toRightOf="@+id/textView1"
        android:text="@string/valor"
        android:textAppearance="?android:attr/textAppearanceSmall" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView2"
        android:layout_alignBottom="@+id/textView2"
        android:layout_alignRight="@+id/textView1"
        android:text="@string/distancia_1"
        android:textAppearance="?android:attr/textAppearanceMedium" />


</RelativeLayout>

I think that it is all right, but when I run the emulator, I get nothing, not even a single button.
Any idea about what what could be the problem?

Answer 1

You don’t have an onCreate() method, so nothing really starts up. onCreate() is the android equivalent of main() in Java. Try using:

public class MainActivity extends Activity {
pontos p1=new pontos();
pontos p2=new pontos();


    @Override
    public void onCreate(Bundle bundle) {
        super.onCreate(bundle);
        setContentView(R.layout.<yourXMLFile>);
    }
            @Override
            public boolean onTouchEvent(MotionEvent event) {

                TextView tv1 = (TextView) findViewById(R.id.textView2);

                   int eventaction= event.getAction();

                   switch (eventaction){
                   case MotionEvent.ACTION_DOWN:
                       p1.x=event.getX();
                       break;   

                   }

                   tv1.setText(""+p1.x);

                   return true;
            }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

Replace with the name of your xml layout file, minus the extension.