JAR文件中的startActivity时发生NullPointerException

Question

I have a child project that must be included in parent project. What I did:

1. Mark child as library and compile
2. Took resulted .jar and put it in \\libs folder from a parent project.
3. Copied all res used in child project in parent \\res folder.
4. Add .JAR file in Properties->Java Build Path->libraries.
5. Call StartActivity from parent project to an activity from child project.

After running parent project it crashes. Callstack says that is NullPointerException on:

final LinearLayout layout = (LinearLayout)findViewById(R.id.layout);
layout .setOnClickListener(this);

This means that layout is null.

I should mention that running a child project as a single project works perfectly.

What did I do wrong?

Answer 1

You can not use a .jar file if you "child" project depends on resources files. You need to import your project as a library (with source code) instead.

1. Copy your child project (all source code + resources) into your parent project libs/your_child_project_name/ directory
2. Setup your build system (Gradle or Ant) to use the third party library
3. Check for dependencies conflicts (ie both child and parent use the android support .Jar file, in that case remove the one in the child project and use the one in the parent project)
4. Rebuild your parent project
5. Now you can import from the child project