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);
    }
}