Simple hello world for Android app won't display text

I recently bought an Android phone and am trying to learn to code my own apps. Unfortunately after the first ten seconds I ran into the problem where I can't even get the "hello world" tutorial to display "hello world."

I've read similar posts and I can't seem to find a fix. Since the Android loading logo is displaying I've waited for about ten minutes thinking it was just taking a while for the emulator to boot, but no luck.

package multivax.random;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class RandomNumbersActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstan开发者_开发百科ceState) {
        super.onCreate(savedInstanceState);
        TextView tv = new TextView(this);
        tv.setText("Hello World");
        this.setContentView(tv);
    }
}

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do not close the emulator once you have turned it on. just recompile it and send it to the already open emulator.

why are you saying this.setContentView(tv); instead of just setContentView(tv); ?

and by the way check you xml file to make sure that this is the main activity (i.e. the activity that starts when your application starts)

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this.setContentView(tv) is also equals setContentView(tv), there have no problem. also right Android code. You only can find something by adb logcat,you will find some usable information.