Crashes in Android apps are a significant issue, with 62% of users uninstalling an app if they experience a crash. The most common cause of crashes is the `java.lang.NullPointerException`, which occurs when data is referenced after going out of scope or being garbage collected. Other common causes include mismanagement of Activity states (`java.lang.IllegalStateException`), index out of range errors (`java.lang.IndexOutOfBoundsException`), and arguments that are illegal (`java.lang.IllegalArgumentException`). Memory leaks, particularly with bitmaps, can also lead to `java.lang.OutOfMemoryError`. To mitigate these issues, developers should focus on making sure castings are always correct, canceling background threads when pausing or stopping fragments, and recycling objects whenever necessary. Additionally, requesting more heap memory from the OS is an option, but it's not advised unless absolutely necessary.