当A页面跳往B页面做一些操作后，再从B页面回到A页面时，A页面想要回去一些B页面操作的数据时，我们一般会使用回调。
1 public class MainActivity extends Activity {
2
3 TextView tv_text1;
4 @Override
5 protected void onCreate(Bundle savedInstanceState) {
6 super.onCreate(savedInstanceState);
7 setContentView(R.layout.activity_main);
8 tv_text1 = (TextView)findViewById(R.id.tv_text1);
9 }
10
11 public void onclick(View v){
12 startActivityForResult(new Intent(MainActivity.this,Main2Activity.class),1);
13 }
14
15 @Override
16 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
17 if(requestCode==1&&resultCode==2){
18
19 String str = data.getStringExtra("key");
20 tv_text1.setText(str);
21 }
22 }
23 }
1 public class Main2Activity extends AppCompatActivity {
2
3 @Override
4 protected void onCreate(Bundle savedInstanceState) {
5 super.onCreate(savedInstanceState);
6 setContentView(R.layout.activity_main2);
7 }
8
9 public void click1(View v){
10
11 Intent intent = new Intent();
12 intent.putExtra("key","this is result");
13 Main2Activity.this.setResult(2,intent);
14 Main2Activity.this.finish();
15 }
16 }
较为简单，所以直接上代码了。