Android onActivityResult is always 0

Android onActivityResult Always 0: Troubleshooting and Solutions

The onActivityResult() method in Android is a crucial part of handling results from activities launched with startActivityForResult(). When you encounter onActivityResult() always returning 0, it signifies a breakdown in the expected result communication. This article delves into common reasons behind this issue and offers solutions for resolving it.

Understanding onActivityResult

onActivityResult() is triggered in the originating activity (the one that launched another activity) when the launched activity finishes. It provides a mechanism for receiving data or status updates back from the child activity.

Key Parameters

• requestCode: An integer value you specify when launching the child activity using startActivityForResult().
• resultCode: An integer indicating the outcome of the child activity (e.g., RESULT_OK for successful completion, RESULT_CANCELED for cancellation).
• data: An Intent object containing the data returned by the child activity.

Common Causes of onActivityResult Returning 0

1. Incorrect Request Code

The requestCode you use when calling startActivityForResult() must match the requestCode used in onActivityResult(). If they differ, onActivityResult() won’t be triggered.

2. Missing or Incorrect Result Code Setting

In the child activity, you need to explicitly set the resultCode before calling finish() using setResult(). Failing to do so will result in a resultCode of 0.

3. Launch Mode Issues

The launch mode of the child activity can influence result handling. If the child activity uses a launch mode that prevents it from being the top activity when returning, the result might not be received correctly.

4. Activity Stack Management

If the child activity is finished before onActivityResult() is called, the result might be lost.

5. Memory Leak

In rare cases, memory leaks within the parent or child activity can interfere with result communication.

Troubleshooting Steps

1. Verify Request Code Consistency

// Parent Activity
startActivityForResult(intent, REQUEST_CODE); // Use a constant

// Child Activity
setResult(RESULT_OK, data); 
finish();

2. Ensure Result Code Setting

// Child Activity
if (conditionForSuccess) {
  setResult(RESULT_OK, data);
} else {
  setResult(RESULT_CANCELED);
}
finish();

3. Check Launch Mode

Use the standard launch mode for the child activity if you need result handling.

4. Debug Activity Stack Behavior

Use logging or debugging tools to track activity lifecycle events and ensure proper stacking.

5. Consider Memory Leaks

Perform memory leak analysis using profiling tools if needed.

Example Scenario: Choosing a Picture

Parent Activity

private static final int PICK_IMAGE_REQUEST = 1;

// ...
Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.setType("image/*");
startActivityForResult(intent, PICK_IMAGE_REQUEST);

Child Activity (Image Selection)

// ...
if (resultCode == RESULT_OK && data != null) {
  Uri selectedImageUri = data.getData();
  // ... Process the selected image 
  setResult(RESULT_OK, data); 
} else {
  setResult(RESULT_CANCELED);
}
finish();

Parent Activity (onActivityResult)

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

  if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK && data != null) {
    Uri imageUri = data.getData();
    // ... Handle the selected image
  }
}

Conclusion

By understanding common causes and implementing proper troubleshooting techniques, you can effectively debug the issue of onActivityResult() returning 0 in your Android application and achieve robust result handling. Always review request codes, result code setting, and launch modes for accurate result communication.