title: view.onclicklistener cannot be implemented
body: <p>I am new with android studio, I tried to do a test like, push two different button show different text in Textview.
   And my .java code is</p>
  
  <pre><code> import android.os.Bundle;
   import android.support.design.widget.FloatingActionButton;
   import android.support.design.widget.Snackbar;
   import android.support.v7.app.AppCompatActivity;
   import android.support.v7.widget.Toolbar;
   import android.view.View;
   import android.view.Menu;
   import android.view.MenuItem;
   import android.widget.TextView;
   import android.view.View.OnClickListener;
    public class MainActivity extends AppCompatActivity implements View.OnClickListener{
      @Override
      protected void onCreate (Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
          TextView t1;
          t1 = (TextView) findViewById(R.id.editText);
  
          t1.setOnClickListener(this);
      }
     @Override
      public void onClick (View v) {
         if (v.getId() == R.id.button)
             t1.setText("Customer1");
         if (v.getId() == R.id.button2)
             t1.setText("Custom2");
         }
     }
  </code></pre>
  
  <p>Symbol 't1' cannot be resolved in</p>
  
  <pre><code> t1.setText("Customer1");
  
   import android.view.View.OnClickListener;
  </code></pre>
  
  <p>shows unused import statement.
  I want to know which part is wrong with code, and how to fix it.</p>
  
  <p>Thx</p>