Android app unable to start activity componentinfo

Your null pointer exception seems to be on this line: String url = intent.getExtras().getString(“userurl”); because intent.getExtras() returns null when the intent doesn’t have any extras. You have to realize that this piece of code: Intent Main = new Intent(this, ToClass.class); Main.putExtra(“userurl”, url); startActivity(Main); doesn’t start the activity you wrote in Main.java, it will attempt to … Read more

“Error: Main method not found in class MyClass, please define the main method as…”

When you use the java command to run a Java application from the command line, e.g., java some.AppName arg1 arg2 … the command loads the class that you nominated and then looks for the entry point method called main. More specifically, it is looking for a method that is declared as follows: package some; public … Read more

what does Error “Thread 1:EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)” mean?

This line secondNumber = Screen.text!.toInt()! means: Get the Screen object, get the text property and please crash if it doesn’t exist, then get the text converted to an integer, and please crash if it doesn’t exist. That’s what the ! means: “I am sure this thing exists, so please crash if it doesn’t”. And crash … Read more

Definitive List of Common Reasons for Segmentation Faults

WARNING! The following are potential reasons for a segmentation fault. It is virtually impossible to list all reasons. The purpose of this list is to help diagnose an existing segfault. The relationship between segmentation faults and undefined behavior cannot be stressed enough! All of the below situations that can create a segmentation fault are technically … Read more