content: package com.alibaba.android.playground;
  
  import android.content.Intent;
  import android.os.Bundle;
  import android.support.v7.app.AppCompatActivity;
  import android.view.View;
  
  public class MainActivity extends AppCompatActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          findViewById(R.id.btn_1).setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
                  startActivity(new Intent(MainActivity.this, Demo1Activity.class));
              }
          });
  
          findViewById(R.id.btn_2).setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
                  startActivity(new Intent(MainActivity.this, Demo2Activity.class));
              }
          });
  
          findViewById(R.id.btn_3).setOnClickListener(new View.OnClickListener() {
              @Override
              public void onClick(View v) {
                  startActivity(new Intent(MainActivity.this, Demo3Activity.class));
              }
          });
      }
  }
  