نکات جلسه ۳ مقدماتی

 package ir.ben.hassan;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.Date;
import java.util.Random;

public class MainActivity extends AppCompatActivity {
    TextView tv;//= this.<TextView>findViewById(R.id.tv);
Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
         tv= this.<TextView>findViewById(R.id.tv);
        tv.setText(new Date().toString());
        tv.setTextColor(Color.LTGRAY);
         button= this.<Button>findViewById(R.id.button3);
/*
        tv.setVisibility(View.INVISIBLE );
*/
    }

public void button3OnClick(View v){
        if (v.getId()==R.id.button3)
    {
        tv= this.<TextView>findViewById(R.id.tv);
        tv.setTextColor(Color.LTGRAY);

        Random random=new Random();
        tv.setTextColor((Color.rgb(random.nextInt(256),random.nextInt(256),random.nextInt(256))));
    }


}


}
توی xml ش هم :

android:onClick="button3OnClick"