java - putExtra() 不起作用

Question

我的问题是在 3 个 Activity 之间传递一个字符串。我解释一下我是如何做到的。

第一个名为 loginActiviy 的 Activity 是我执行此操作的地方。

  //OnCreate ecc before this
     @Override
 public void onActivityResult(int requestCode, int resultCode, Intent data) {
     data.putExtra("Name", Name);
     super.onActivityResult(requestCode, resultCode, data);
 }

 public void onResume()
 {
     super.onResume();
     finish();
 }

当 Activity 结束时调用 finish() (也许这是我不知道的问题)，然后控制权传递到第一个 Activity ，我在其中执行此操作

    //OnCreate ecc before
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
    Bundle extras = data.getExtras();
    String name = null;
    if(extras != null) {
        name = extras.getString("Name");
    }
    super.onActivityResult(requestCode, resultCode, data);
    try
    {
        Intent people = new Intent(this, MainPeopleActivity2.class);
        people.putExtra("Name", name);
        startActivity(people);
        this.finish();
    }
    catch(Exception e)
    {
        Toast.makeText(getApplicationContext(), e, Toast.LENGTH_LONG).show();
    }
}

现在开始第三个 Activity ，在哪里采取这样做的 Intent

        String name;
    if (savedInstanceState == null) {
        Bundle extras = getIntent().getExtras();
        if(extras == null) {
            name= null;
        } else {
            name= extras.getString("Name");
        }
    } else {
        name = (String) savedInstanceState.getSerializable("Name");
    }

但正如您可以想象的那样，情况并非如此，字符串是空的。

我哪里错了？提前致谢。

这是完整的登录类

                public void onSuccess(LoginResult loginResult) {
                GraphRequest.newMeRequest(
                        loginResult.getAccessToken(), new GraphRequest.GraphJSONObjectCallback() {
                            @Override
                            public void onCompleted(JSONObject user, GraphResponse response) {
                                if (response.getError() != null) {
                                } else {
                                    id = user.optString("id");
                                    firstName = user.optString("first_name");
                                    lastName = user.optString("last_name");
                                    email = user.optString("email");
                                    Log.i(TAG,"User ID "+ id);
                                    Log.i(TAG,"Email "+ email);
                                }
                                Name = firstName + " " + lastName;
                                Toast.makeText(getApplicationContext(), "Log in with " + Name, Toast.LENGTH_LONG).show();
                            }
                        }).executeAsync();
        }

Answer 1

您可以通过以下方式解决问题并让代码正常运行。

唯一需要 onActivityResult() 的地方是 Activity A(第一个 Activity)。

该过程的第一步是使用 startActivityForResult() 启动您的 LoginActivity，可能来自 onCreate():

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

    Intent i = new Intent(this, LoginActivity.class);
    startActivityForResult(i, 999);

}

然后，在此类中设置 onActivityResult() 方法，该方法将处理 LoginActivity 的结果，并将 Name 发送到 MainPeopleActivity2:

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    //check request code and result code:
    if (requestCode == 999 && resultCode == RESULT_OK) {
        //get the extras:
        Bundle extras = data.getExtras();
        String name = null;
        if (extras != null) {
            name = extras.getString("Name");
            try {
                Intent people = new Intent(this, MainPeopleActivity2.class);
                people.putExtra("Name", name);
                startActivity(people);
                //this.finish();
            } catch (Exception e) {
                e.printStackTrace();
                Toast.makeText(getApplicationContext(), e.toString(), Toast.LENGTH_LONG).show();
            }
        }
    }
}

然后您的 LoginActivity 中的 onSuccess() 方法将需要在此处添加一些代码。通过调用 setResult() 将名称发送回第一个 Activity:

public void onSuccess(LoginResult loginResult) {
    GraphRequest.newMeRequest(
            loginResult.getAccessToken(), new GraphRequest.GraphJSONObjectCallback() {
                @Override
                public void onCompleted(JSONObject user, GraphResponse response) {
                    if (response.getError() != null) {
                        //process error
                    } else {
                        id = user.optString("id");
                        firstName = user.optString("first_name");
                        lastName = user.optString("last_name");
                        email = user.optString("email");
                        Log.i(TAG,"User ID "+ id);
                        Log.i(TAG, "Email " + email);

                        Name = firstName + " " + lastName;
                        Toast.makeText(getApplicationContext(), "Log in with " + Name, Toast.LENGTH_LONG).show();

                        //adding this:
                        Intent i = new Intent();
                        i.putExtra("Name", Name);
                        LoginActivity.this.setResult(RESULT_OK, i);
                        LoginActivity.this.finish();
                    }


                }
            }).executeAsync();
}

然后，您将能够在 onCreate() 中成功获取 MainPeopleActivity2 Activity 中的名称:

public class MainPeopleActivity2 extends ActionBarActivity {

    String name;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_MainPeopleActivity2);

        if (savedInstanceState == null) {
            Bundle extras = getIntent().getExtras();
            if(extras == null) {
                name= null;
            } else {
                name= extras.getString("Name");
            }
        } else {
            name = (String) savedInstanceState.getSerializable("Name");
        }

    }

  //...... rest of the code in this class