activity结束之后刷新之前的activity的内容

启动页：
btnButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                String str=txtEditText.getText().toString();
                intent.putExtra("fromMain", str);
                // startActivity(intent);
                // 启动需要监听返回值的Activity，并设置请求码：requestCode
                startActivityForResult(intent, 1);
            }

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// 当otherActivity中返回数据的时候，会响应此方法
// requestCode和resultCode必须与请求startActivityForResult()和返回setResult()的时候传入的值一致。
if (requestCode == 1 && resultCode == SecondActivity.RESULT_CODE) {
Bundle bundle=data.getExtras();
String strResult = bundle.getString("result");
Log.i(TAG,"onActivityResult: "+ strResult);
Toast.makeText(MainActivity.this, strResult, Toast.LENGTH_LONG).show();
}
}

btnBack.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                Intent intent = new Intent();
                intent.putExtra("result", txtContent.getText().toString());
                setResult(RESULT_CODE, intent);// 设置resultCode，onActivityResult()中能获取到
                finish();
            }
        });