安卓：传递数据来回使用意图setResults [英] Android: passing data back and forth using intent setResults

问题描述

我创建为Android基于GPS的应用程序，并有2个主要活动和LocNames。主要展示我的地图和LocNames是获得源和用户想要的目的地。我想开始LocNames当用户从菜单中选择它，用户在输入框的名字，我想结果被发送回主。但我得到的例外这样做。

I am creating a GPS based app for Android and there are 2 activities Main and LocNames. Main shows my map and LocNames is to get source and destination that user wants. I want to start LocNames when user selected it from menu, user enters names in boxes and I want result to be send back to Main. But I am getting exceptions in doing so.

下面是我的主要是如何调用LocNames：

Here is how my Main calls LocNames:

    public boolean onOptionsItemSelected(MenuItem item) 
{
    switch (item.getItemId()) 
    {
        case R.id.showMyLocation:
            showCurrentLocation();
            break;
        case R.id.showRoute:
            Intent getLocationsIntent = new Intent(Main.this, LocNames.class);
            startActivityForResult(getLocationsIntent, 1);
            break;
    }

下面是如何，我想在LocNames的的onClick设置的结果：

Here is how I am trying to set results in onClick of LocNames:

public void onClick(View v) 
{
    // TODO Auto-generated method stub
    source = sourceText.getText().toString();
    destination = destinationText.getText().toString();     
    Intent result = new Intent(LocNames.this, Main.class);
    result.putExtra("src", source);
    result.putExtra("dest", destination);
    setResult(RESULT_OK, result);
}

但我的应用程序崩溃，当我尝试使用由LocNames返回的结果。

But my application crashed when I try to use result returned by LocNames

protected void onActivityResult(int requestCode, int resultCode, Intent data) 
{
 if(requestCode == 1 && resultCode == RESULT_OK)
    {
        source = data.getStringExtra("src");
        destination = data.getStringExtra("destination");           
    }
}

我在使用setResults没有现成的经验，但文件说，它需要一个int和意图作为参数，所以我创造为目的，但我在LocNames的的OnClick得到NullPointerException异常。

I have no prior experience in using setResults but documentation says it takes an int and an intent as argument so I am creating intent for that but I get NullPointerException in OnClick of LocNames.

问候

推荐答案

您不需要特定组件的意图。你只需要一个空的意图。因此，替换

You do not need an intent for a specific component. You only need an empty intent. So replace

Intent result = new Intent(LocNames.this, Main.class);

与

Intent intent = new Intent();

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