### 安卓app操作文档

#### 一、实现目标

1.  实现页面按钮跳转页面
2.  点击按钮后，页面显示来自JNI的字符串

#### 二、环境搭建

   2.1 jdk安装

![jdk](C:\Users\xieshuhui\Desktop\jdk.png)

   2.2 andriod studio 安装

![image-20241224104420533](C:\Users\xieshuhui\AppData\Roaming\Typora\typora-user-images\image-20241224104420533.png)

#### 三、具体实现

3.1 设置页面跳转

为了实现跳转页面，首先需要创建两个活动：（`MainActivity`主页面）和`SecondActivity`（跳转后的页面）

3.11 MainActivity

```
package com.example.myapplication;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

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

        Button btnNavigate = findViewById(R.id.btnNavigate);

        // 设置按钮点击事件，跳转到SecondActivity
        btnNavigate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                startActivity(intent);
            }
        });
    }
}
```

3.12 SecondActivity

```
package com.example.myapplication;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class SecondActivity extends AppCompatActivity {

    static {
        System.loadLibrary("native-lib");  // 加载JNI库
    }

    // 声明JNI方法
    private native String getJNIString();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);

        Button btnShowJNI = findViewById(R.id.btnShowJNI);
        TextView textViewFromJNI = findViewById(R.id.jniTextView);

        // 设置按钮点击事件，获取并显示JNI字符串
        btnShowJNI.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // 调用JNI方法并显示结果
                textViewFromJNI.setText(getJNIString());
            }
        });
    }
}
```

3.2 集成JNI

3.21 在`native-lib.cpp`中，编写JNI方法以返回字符串

```
#include <jni.h>
#include <string>

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_myapplication_SecondActivity_getJNIString(JNIEnv* env, jobject /* this */) {
    std::string hello = "Hello from JNI!";
    return env->NewStringUTF(hello.c_str());
}


```

3.22 CMakeLists.txt编写

```
cmake_minimum_required(VERSION 3.10.2)

# Set project name
project("myapplication")

# Set the path for the source file (make sure the path is correct)
add_library(native-lib SHARED E:/CodeProject/AndroidProjects/MyApplication/app/src/main/cpp/native-lib.cpp)

# Find the log library (important for Android projects)
find_library( log-lib
        log )

# Link the native library with the log library
target_link_libraries( native-lib
        ${log-lib} )
```

#### 四、运行结果

4.1 初始运行界面

![image-20241224113159992](C:\Users\xieshuhui\AppData\Roaming\Typora\typora-user-images\image-20241224113159992.png)

点击Page Jump跳转到第二页面

![3](C:\Users\xieshuhui\Desktop\3.png)

4.2 验证跳转功能

点击Show JNI String 按钮，成功显示“Hello from JNI!”

![4](C:\Users\xieshuhui\Desktop\4.png)