Android-Activity使用（2） -传值

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //强制转换为Button,必然放在setContentView之后
        btnSatrtAty1=(Button)findViewById(R.id.btnStartAty1);
        //给按钮设定事件监听器
        btnSatrtAty1.setOnClickListener(
            //实现OnClickListener接口的了匿名类
            new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    //事件中启动Aty1
                    //参数一：MainActivity 的实例
                    //参数二：要启动的Activity的类的定义为Class类型
                    //this 指实现OnClickListener的内部类
                    Intent i=new Intent(MainActivity.this,Aty1.class);
                    i.putExtra("txt","Hello Aty1");

                    startActivity(i);
                }
        });
        System.out.print("onCreate");
    }

tvOut=(TextView)findViewById(R.id.tvOut);
tvOut.setText(getIntent().getStringExtra("txt"));

Intent i=new Intent(MainActivity.this,Aty1.class);
Bundle data=new Bundle();
data.putString("","Hello Aty1");
i.putExtras(data);

startActivity(i);

tvOut=(TextView)findViewById(R.id.tvOut);
Bundle data=getIntent().getExtras();
String txt=data.getString("txt");
tvOut.setText(txt);

        btnClose=(Button)findViewById(R.id.btnStartAty1);
        btnClose.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent i=new Intent();
                i.putExtra("result","Hello MainActivity");
                setResult(0, i);
                finish();
            }
        });

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        String result=data.getStringExtra("result");
        tvOut.setText(result);
        super.onActivityResult(requestCode, resultCode, data);
    }