Android 当我按下“onActivityResult”时出错；取消“；我的第二个活动按钮

我有以下活动：

---

活动1

//declare
private static final int SAVE_DATA_FROM_ACTIVITY = 203;

//........... not important code

//button to open second Activity
public void btn_openSecondActivity(View view)
    {

            Intent intent = new Intent(Activity2.this, Activity1.class);

            startActivityForResult(intent, SAVE_DATA_FROM_ACTIVITY);
        }
    }


 protected void onActivityResult (int requestCode, int resultCode, Intent data)
    {
      if (requestCode == SAVE_DATA_FROM_activity)
        {
            name= data.getStringExtra("Name");
        }
    }


//....... not important code

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == SAVE_DATA_FROM_activity) {
        if (resultCode == Activity.RESULT_OK) {
            name = data.getStringExtra("Name");
        } else if (resultCode == Activity.RESULT_CANCELED){
            // TODO something
        }
    }
}

活动2

在第二个活动中，我有两个按钮：

取消

拯救

//

//declare
private static final int OK_RESULT_CODE = 1;

//Cancel button
public void btn_cancel(View view)
{
    finish();
}

//Save button
public void btn_save (View view)
{

    Intent intent = new Intent();
    intent.putExtra("Name",et_name.getText().toString());

    setResult(OK_RESULT_CODE, intent);

    finish();
}

问题

当我单击“保存”按钮时，所有操作都很完美，但问题是当我单击“取消”按钮时，它会报告一个错误：

Failure delivering result ResultInfo{who=null, request=203, result=0, data=null} to activity {com.example.alvaro.project/com.alvaro.project.Activity1}: java.lang.NullPointerException

我理解问题所在，当我取消时，结果代码不相同，但我不知道如何解决它

---

有什么建议吗？

您在

onActivityResult

方法中遇到了问题。你不检查结果

将您的状况从：

if (requestCode == SAVE_DATA_FROM_activity)

致：

改变这个

if (requestCode == SAVE_DATA_FROM_activity)
    {
        name= data.getStringExtra("Name");
    }

进入

及

您的取消方法如下

public void btn_cancel(View view)
{
   setResult(RESULT_CANCELED);
    finish();
}

---

使用Android的默认OK，而不是OK\u RESULT\u CODE像活动一样。RESULT\u OK

检查是否设置了结果

protected void onActivityResult (int requestCode, int resultCode, Intent data)
{
  if (requestCode == SAVE_DATA_FROM_activity && resultCode = Activity2.OK_RESULT_CODE)
    {
        name= data.getStringExtra("Name");
    } else {
       //probably btn_cancel pressed
    }
}

---

在onActivityResult中检查结果代码

 protected void onActivityResult (int requestCode, int resultCode, Intent data)
    {
      if (resultCode == 1/*OK_RESULT_CODE from Second Activity */ && requestCode == SAVE_DATA_FROM_activity)
        {
            name= data.getStringExtra("Name");
        }
    }

---

活动1

//declare
private static final int SAVE_DATA_FROM_ACTIVITY = 203;

//........... not important code

//button to open second Activity
public void btn_openSecondActivity(View view)
    {

            Intent intent = new Intent(Activity2.this, Activity1.class);

            startActivityForResult(intent, SAVE_DATA_FROM_ACTIVITY);
        }
    }


 protected void onActivityResult (int requestCode, int resultCode, Intent data)
    {
      if (requestCode == SAVE_DATA_FROM_activity)
        {
            name= data.getStringExtra("Name");
        }
    }


//....... not important code

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == SAVE_DATA_FROM_activity) {
        if (resultCode == Activity.RESULT_OK) {
            name = data.getStringExtra("Name");
        } else if (resultCode == Activity.RESULT_CANCELED){
            // TODO something
        }
    }
}

活动2

删除字段确定\u结果\u代码

//Cancel button
public void btn_cancel(View view) {
    setResult(Activity.RESULT_CANCELED, new Intent());
    finish();
}

//Save button
public void btn_save(View view) {
    Intent intent = new Intent();
    intent.putExtra("Name", et_name.getText().toString());
    setResult(Activity.RESULT_OK, intent);

    finish();
}

---

确保您的“确定结果”代码是公开的