将结果传递给另一个活动

Question

I'm writing an application for Android and I have difficulties with change the Buttons background. I have four Activities, Activity1 is a TableLayout where I have three Buttons. Every Button opens another Activity. I'd like to change the Button in Activity1 from Activity2. So I tried to do it with passing a Result. In Activity2 I set a Result like this:

@Override
public void onClick(View v) {
        setResult(Activity1.RESULT_OK);
        finish();
    }
}

In Activity1 I have this code:

          protected void onActivityResult(int requestCode, int resultCode, Intent data){
          if (resultCode == RESULT_OK)
          button1.setBackgroundResource(R.drawable.image);    
          }

So when the user click the Button in the Activity2 then in the Activity1 the Button change the background. My problem is that I can do that only once and I have to do that two more times in the other Activities. I tried to do RESULT_OK2 but it shows me error. So how can I do it more times? I tried to change the background another way. In Activity2 I used the button1 which is in Activity1 but I then I got NullPointerExeption. If anyone has an idea how to that please response!

Answer 1

You can compare the requestCode too (this is the request code you passed on startActivityForResult)

This will avoid the RESULT_OK being interpreted to every activity result.

Answer 2

I tried to do RESULT_OK2

There is no Activity constant for RESULT_OK2 so that's why you get the error

You can pass back Intent Extras . Something like

@Override
public void onClick(View v) {
    // add the intent info
    Intent i = new Intent(); // make sure to use empty constructor
    i.putExtra("image", someVar); // might want activity const for key and someVar can be String, int, or whatever you want to use 
    setResult(Activity1.RESULT_OK, i);
    finish();
}
}

then check for that var in your onActivityResult() in the data param and set the image appropriately.

Going back to previous activity

Answer 3

when you start the activity for result in android you have to pass request code and based on that request code you can make the conditions in the onActivityResultMethod.

**Button 1**
Intent i = new Intent(this, yourclass1);
startActivityForResult(i, 1);

**in yourclass1**
setResult(RESULT_OK);
finish();

**Button 2**
Intent i = new Intent(this, yourclass2);
startActivityForResult(i, 2);

**in yourclass2**
setResult(RESULT_OK);
finish();

**Button 3**
Intent i = new Intent(this, yourclass3);
startActivityForResult(i, 3);

**in yourclass3**
setResult(RESULT_OK);
finish();

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

    if (requestCode == 1 && resultCode == RESULT_OK) {
       // change background of button 1
    }else if (requestCode == 2 && resultCode == RESULT_OK) {
       // change background of button 2
    }else if (requestCode == 3 && resultCode == RESULT_OK) {
       // change background of button 3
    }
}

Answer 4

You can store a value in SharedPreference and based on the value in SharedPreference, you can change the background color of button1.

In Activity 2,

@Override
public void onClick(View v) {
    SharedPreferences.Editor editor = getSharedPreferences("RESULTS", MODE_PRIVATE).edit();
    editor.putInt("BUTTON1_bg", 1);
    editor.commit();
    finish();
}

In Activity 1

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
      SharedPreferences prefs = getSharedPreferences("RESULTS", MODE_PRIVATE); 
      int bg = prefs.getInt("BUTTON1_bg");
      // based on value of  bg, you can decide what background to use for button1
    }

Answer 5

You need to start all the three activity with different request code. Or get the intent data to distinguish. You can do something like From Activity1 start all activity with a requestCode as

startActivityForResult( <intent>,<an requestCode>);

Then you can filter the same requestCode in onActivityResult() as

if(requestCode==11){
   button1.setBackgroundResource(R.drawable.image);  
}else if(requestCode==22){
   button2.setBackgroundResource(R.drawable.image);  
}else if(requestCode==33){
   button3.setBackgroundResource(R.drawable.image);  
}