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DelegateClassAdapter.javaAPI DocAndroid 5.1 API5207Thu Mar 12 22:22:44 GMT 2015com.android.tools.layoutlib.create

DelegateClassAdapter

public class DelegateClassAdapter extends org.objectweb.asm.ClassVisitor
A {@link DelegateClassAdapter} can transform some methods from a class into delegates that defer the call to an associated delegate class.

This is used to override specific methods and or all native methods in classes.

Fields Summary
private static final String
ORIGINAL_SUFFIX
Suffix added to original methods.
private static final String
CONSTRUCTOR
private static final String
CLASS_INIT
public static final String
ALL_NATIVES
private final String
mClassName
private final Set
mDelegateMethods
private final Log
mLog
Constructors Summary
public DelegateClassAdapter(Log log, org.objectweb.asm.ClassVisitor cv, String className, Set delegateMethods)
Creates a new {@link DelegateClassAdapter} that can transform some methods from a class into delegates that defer the call to an associated delegate class.

This is used to override specific methods and or all native methods in classes.

param
log The logger object. Must not be null.
param
cv the class visitor to which this adapter must delegate calls.
param
className The internal class name of the class to visit, e.g. com/android/SomeClass$InnerClass.
param
delegateMethods The set of method names to modify and/or the special constant {@link #ALL_NATIVES} to convert all native methods.


                                                                                                                        
      
             
             
              
        super(Opcodes.ASM4, cv);
        mLog = log;
        mClassName = className;
        mDelegateMethods = delegateMethods;
Methods Summary
public org.objectweb.asm.MethodVisitorvisitMethod(int access, java.lang.String name, java.lang.String desc, java.lang.String signature, java.lang.String[] exceptions)


        boolean isStatic = (access & Opcodes.ACC_STATIC) != 0;
        boolean isNative = (access & Opcodes.ACC_NATIVE) != 0;

        boolean useDelegate = (isNative && mDelegateMethods.contains(ALL_NATIVES)) ||
                              mDelegateMethods.contains(name);

        if (!useDelegate) {
            // Not creating a delegate for this method, pass it as-is from the reader to the writer.
            return super.visitMethod(access, name, desc, signature, exceptions);
        }

        if (CONSTRUCTOR.equals(name) || CLASS_INIT.equals(name)) {
            // We don't currently support generating delegates for constructors.
            throw new UnsupportedOperationException(
                String.format(
                    "Delegate doesn't support overriding constructor %1$s:%2$s(%3$s)",  //$NON-NLS-1$
                    mClassName, name, desc));
        }

        if (isNative) {
            // Remove native flag
            access = access & ~Opcodes.ACC_NATIVE;
            MethodVisitor mwDelegate = super.visitMethod(access, name, desc, signature, exceptions);

            DelegateMethodAdapter a = new DelegateMethodAdapter(
                    mLog, null, mwDelegate, mClassName, name, desc, isStatic);

            // A native has no code to visit, so we need to generate it directly.
            a.generateDelegateCode();

            return mwDelegate;
        }

        // Given a non-native SomeClass.MethodName(), we want to generate 2 methods:
        // - A copy of the original method named SomeClass.MethodName_Original().
        //   The content is the original method as-is from the reader.
        // - A brand new implementation of SomeClass.MethodName() which calls to a
        //   non-existing method named SomeClass_Delegate.MethodName().
        //   The implementation of this 'delegate' method is done in layoutlib_bridge.

        int accessDelegate = access;
        access = access & ~Opcodes.ACC_PRIVATE;  // If private, make it package protected.

        MethodVisitor mwOriginal = super.visitMethod(access, name + ORIGINAL_SUFFIX,
                                                     desc, signature, exceptions);
        MethodVisitor mwDelegate = super.visitMethod(accessDelegate, name,
                                                     desc, signature, exceptions);

        return new DelegateMethodAdapter(
                mLog, mwOriginal, mwDelegate, mClassName, name, desc, isStatic);