Intent.FLAG_ACTIVITY_FORWARD_RESULT作用

适用情况

多个Activity的值传递。ActivityA到达ActivityB再到达ActivityC，但ActivityB为过渡页可以finish了，此时ActivityC将值透传至ActivityA。

代码实现

第一个页面：A跳到B

public class AActivity extends Activity{    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Button button=new Button(this);        button.setText("B");        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent=new Intent(v.getContext(),BActivity.class);                startActivityForResult(intent,1);            }        });        setContentView(button);    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        System.out.println("A:" + (data == null ? data : data.getStringExtra("data")));    }}

过渡页：中间有再多过渡页也是一样。B跳到C

public class BActivity extends Activity {    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Button button = new Button(this);        button.setText("C");        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent(v.getContext(), CActivity.class);                intent.setFlags(Intent.FLAG_ACTIVITY_FORWARD_RESULT);                startActivity(intent);                finish();            }        });        setContentView(button);    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        super.onActivityResult(requestCode, resultCode, data);        System.out.println("B:" + (data == null ? data : data.getStringExtra("data")));    }}

C传值然后在A的OnActivityResult中获取值

public class CActivity extends Activity{    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        Button button=new Button(this);        button.setText("result");        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent=new Intent();                intent.putExtra("data","data");                setResult(Activity.RESULT_OK,intent);                finish();            }        });        setContentView(button);    }}

输出结果：
System.out: A:data

注意：中间页面不能调用startActivityForResult方法，否则回报android.util.AndroidRuntimeException: FORWARD_RESULT_FLAG used while also requesting a result。中间页面需要finish后前面页面才能收到返回结果。