Android's lineSpacingExtra attribute, intended to add extra vertical space between lines of text within a TextView, sometimes stubbornly refuses to work as expected. Developers often encounter situations where the defined spacing simply doesn't appear on the screen, especially on older Android versions or specific devices. This can be frustrating, leading to cramped text and poor readability.

Several factors can contribute to this issue. One common culprit is the presence of conflicting attributes. For example, if lineSpacingMultiplier is also set, it can override or interfere with the lineSpacingExtra value. The Android system might prioritize one attribute over the other based on internal rules or the specific TextView implementation.

Another potential cause lies in the TextView's includeFontPadding property. By default, Android includes extra padding above and below the text based on the font metrics. This padding can sometimes negate the effect of lineSpacingExtra, especially if the font's default padding is already significant. Setting android:includeFontPadding="false" in the XML layout or programmatically using textView.setIncludeFontPadding(false) might resolve the problem.

Furthermore, the specific font being used can also influence how lineSpacingExtra behaves. Some fonts have inherent line spacing characteristics that might clash with the added space. Experimenting with different fonts or customizing the font metrics using a custom Typeface could offer a solution. Additionally, if you're using custom text rendering (e.g., drawing text directly on a Canvas), you'll need to handle line spacing manually, as the TextView attributes won't apply.

Compatibility issues across different Android versions can also play a role. While lineSpacingExtra is a standard attribute, its implementation and behavior might vary slightly between API levels. Thorough testing on different devices and Android versions is crucial to ensure consistent rendering. Consider using support libraries or compatibility code to address any discrepancies.

If you're setting lineSpacingExtra programmatically, double-check the units. The value should be specified in pixels (px). If you accidentally use density-independent pixels (dp) or scale-independent pixels (sp) without proper conversion, the spacing might appear incorrect or non-existent. Use getResources().getDimensionPixelSize() or a similar method to convert dp or sp values to pixels before applying them.

Finally, inspect the TextView's layout hierarchy for any unexpected parent views that might be influencing its rendering. Constraints or padding on parent layouts could inadvertently affect the available space for the text, making it seem like lineSpacingExtra isn't working. Carefully review the layout structure and adjust padding/margin settings as needed.

In summary, troubleshooting lineSpacingExtra requires a systematic approach. Start by checking for conflicting attributes, disabling includeFontPadding, experimenting with different fonts, considering compatibility issues, verifying unit types, and inspecting the layout hierarchy. Addressing these potential pitfalls will significantly increase the chances of achieving the desired line spacing in your Android TextViews.