190 lines
5.3 KiB
Markdown
190 lines
5.3 KiB
Markdown
# 安卓APP
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## 目的
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1. 实现页面按钮跳转页面
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2. 点击按钮后，页面显示来自JNI的字符串
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## 实验步骤
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### 1. 准备开发环境
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- Android Studio
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- JDK
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- NDK（创建项目时会自动部署）
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- CMake（创建项目时会自动部署）
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### 2. 创建一个原生C++安卓项目
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> 部署原生C++安卓项目时，路径中不能有空格
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>
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> 使用了API 28: Android 9.0
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### 3. 主页面添加按钮
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在`MainActivity.java`中添加一个按钮，点击后跳转到`SecondActivity`
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```
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package com.example.jnidemoapp;
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import android.content.Intent;
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import android.os.Bundle;
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import android.view.View;
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import android.widget.Button;
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import androidx.appcompat.app.AppCompatActivity;
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public class MainActivity extends AppCompatActivity {
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@Override
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protected void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
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setContentView(R.layout.activity_main);
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// 页面跳转按钮
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Button button = findViewById(R.id.button_go_to_second);
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button.setOnClickListener(new View.OnClickListener() {
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@Override
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public void onClick(View v) {
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Intent intent = new Intent(MainActivity.this, SecondActivity.class);
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startActivity(intent);
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}
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});
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}
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}
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```
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### 4. 创建SecondActivity.java
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新建`SecondActivity.java`文件，显示来自JNI的字符串
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```
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package com.example.jnidemoapp;
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import android.os.Bundle;
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import android.widget.TextView;
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import androidx.appcompat.app.AppCompatActivity;
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public class SecondActivity extends AppCompatActivity {
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// 加载本地库
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static {
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System.loadLibrary("jnidemoapp");
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}
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// 声明一个本地方法
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public native String stringFromJNI();
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@Override
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protected void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
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setContentView(R.layout.activity_second);
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// 显示 JNI 返回的字符串
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TextView textView = findViewById(R.id.text_jni_string);
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textView.setText(stringFromJNI());
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}
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}
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```
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### 5. 调整界面布局
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- 在`activity_main.xml`中添加一个按钮：
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```
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<?xml version="1.0" encoding="utf-8"?>
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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android:layout_width="match_parent"
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android:layout_height="match_parent">
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<Button
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android:id="@+id/button_go_to_second"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:text="跳转"
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android:layout_centerInParent="true"/>
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</RelativeLayout>
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```
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- 在 `activity_second.xml` 添加一个 `TextView`：
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```
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<?xml version="1.0" encoding="utf-8"?>
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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android:layout_width="match_parent"
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android:layout_height="match_parent">
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<TextView
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android:id="@+id/text_jni_string"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:text="等待JNI数据..."
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android:textSize="18sp"
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android:layout_centerInParent="true"/>
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</RelativeLayout>
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```
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### 6. 添加JNI字符串
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- 配置`CMakeLists.txt`文件
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```
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# For more information about using CMake with Android Studio, read the
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# documentation: https://d.android.com/studio/projects/add-native-code.html
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# Sets the minimum version of CMake required to build the native library.
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cmake_minimum_required(VERSION 3.22.1)
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# Declares and names the project.
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project("jnidemoapp")
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# Creates and names a library, sets it as either STATIC
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# or SHARED, and provides the relative paths to its source code.
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# You can define multiple libraries, and CMake builds them for you.
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# Gradle automatically packages shared libraries with your APK.
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add_library( # Sets the name of the library.
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jnidemoapp
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# Sets the library as a shared library.
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SHARED
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# Provides a relative path to your source file(s).
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native-lib.cpp)
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# Searches for a specified prebuilt library and stores the path as a
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# variable. Because CMake includes system libraries in the search path by
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# default, you only need to specify the name of the public NDK library
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# you want to add. CMake verifies that the library exists before
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# completing its build.
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find_library( # Sets the name of the path variable.
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log-lib
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# Specifies the name of the NDK library that
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# you want CMake to locate.
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log)
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# Specifies libraries CMake should link to your target library. You
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# can link multiple libraries, such as libraries you define in this
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# build script, prebuilt third-party libraries, or system libraries.
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target_link_libraries( # Specifies the target library.
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jnidemoapp
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# Links the target library to the log library
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# included in the NDK.
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${log-lib})
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```
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> 这里的库名称需要和SecondActivity.java中的System.loadLibrary函数中的库名称对应
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### 7. 编译运行模拟器，并测试
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- 起始页面：
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- 点击按钮后：
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 |