Android: Including multiple Java Packages to Manif

问题:

The app I am developing has many activities organized into seven java packages. Originally I wrote all the coding and stuff for each group of activities in a java package as different projects.

Now I'm at the point where I want to put all the packages together into one project. When I add a new package to the src folder, I get an error for all my R.id.* values ("R cannot be resolved").

My instinct tells me that there is something fancy I have to put in the project manifest, but I can't find any resource online to tell me how.

(Note: I have read this and this and I still couldn't figure out how to add additional packages to my project.)

回答1:

Make sure that the import statement at the top of the Activity references the correct R file. Each project has its own R file, so if you copy an Activity from one project to another it will still be trying to reference the R file from the old project.

You do not need any explicit inclusion of different packages in the manifest. To include activities from two different packages, say:

com.example.package1.Activity1
com.example.package2.Activity2

you can do the following:

<manifest package="com.example" . . . >
  <application . . .>
    <activity android:name=".package1.Activity1" . . . />
    <activity android:name=".package2.Activity2" . . . />
  </application>
</manifest>

回答2:

Android automatically creates the class named "R" in the package declared in your App's manifest. When all of your classes are inside that package, you'll never have to explicitly import "R". However, if you have classes in other packages, they won't see it by default and you will have to include

 import <app-package>.R;

or

 import <app-package>.*;

(substituting the actual name for <app-package> of course).

If you include library projects in your App, then they can reference their own "R" classes, which will be generated within their home packages. If you have several independent activities which need to be bundled together into one final App, you should seriously consider using library projects instead of manually merging things. It could make life much easier for you.

回答3:

The problem may persist even if we change the manifest file. to avoid it we must Add an import com.example.R; in all our classes.

example: MainActivity.class in package2

pakage com.example.package2.Activity2
import com.example.R;

(TestActivity.class in package1)

pakage com.example.package1.Activity1
import com.example.R;

回答4:

Check that the layout -> main.xml file is correct and includes the android:id="@+id/whateverIdHasCausedYouTheError"

The R.java file will then be updated to include the id.. and bam, your error should disappear.