NDK learning notes (V)

1.android studio After the code is generated, Mr , Avoid missing the specified class

stay android studio You may need to delete the generated code and regenerate it , The original code prompts the specified class that cannot be found at runtime , Not working properly . Can you test the code , Yes. .
edit app Of build.gradle, Add the following configuration

project.afterEvaluate {
    
    javaPreCompileDebug.dependsOn externalNativeBuildDebug
}

2. Call from native code java

（1） Create a class
A.h

extern int getuid();


class MyAsync {
    

public:
    MyAsync() {
    

    }

    virtual  ~ MyAsync() {
    

    }

    void get() {
    

        onUid(getuid());
    }

    virtual void onUid(int uid) {
    

    }
};

A.cpp

#include "A.h"

int getuid() {
    

    return 3000;
}

（2） Enable directors
SWIG use directors Features provide support for cross language polymorphism . To call... In native code java To prepare .

/* Module name see*/
%module(directors = 1) See;
/* For the class MyAsync Virtual method generation director in */
%feature("director") MyAsync;

// Include the customized code in the generated file , For example, the header file needed to compile the generated code 
%{
    
#include "A.h"
#include "A.cpp"
%}
%include "A.h"

（3） Override callback method
stay java Create classes in and inherit MyAsync

public class JavaAsync extends com.example.ndk2.jni.MyAsync {
    

    private final TextView textView;

    public JavaAsync(TextView textView) {
    
        this.textView = textView;
    }

    @Override
    public void onUid(int uid) {
    

        textView.setText(uid + "");
    }
}

（4） Use

    protected void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView tv = findViewById(R.id.sample_text);

        JavaAsync javaAsync = new JavaAsync(tv);
        javaAsync.get();


    }

（5） effect