Android全局资源访问

package com.example.metrox.l12;

import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main);
TextView tv = new TextView(this);
tv.setText("Android全局资源访问");
//setContentView(tv);

LinearLayout l = new LinearLayout(this);

final ImageView iv = new ImageView(this);
iv.setImageResource(R.mipmap.ic_launcher);

Button btn = new Button(this);
btn.setText("打开另一个Content");

btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
setContentView(iv);
}
});
l.addView(tv);
l.addView(btn);
setContentView(l);
}
}