Android动态加载类

布满荆棘的人生 2023-10-11 10:22 14阅读 0赞

1.把class文件打包成dex文件。

在android-sdk/build-tool下有个dx脚本工具，可以将class文件打包成dex文件。

dx --dex --no-strict --output <输出dex路径> <class文件路径>

2.将dex文件放入手机中的某个路径下。

3.使用DexClassLoader加载dex文件中的类。

Activity代码：

package com.champion.loaddexdemo;
    
    import android.Manifest;
    import android.content.Context;
    import android.content.pm.PackageManager;
    import android.os.Environment;
    import android.support.annotation.NonNull;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    
    import junit.framework.Assert;
    
    import java.io.File;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    
    import dalvik.system.DexClassLoader;
    
    public class MainActivity extends AppCompatActivity {
        int storageRequestCode = 1;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            if(PackageManager.PERMISSION_DENIED == checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE)){
                requestPermissions(new String[]{Manifest.permission.READ_EXTERNAL_STORAGE}, storageRequestCode);
            }
            findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    //本例中是将out.dex放在sdcard根目录下
                    File dexFile = new File(Environment.getExternalStorageDirectory(), "out.dex");
                    if(!dexFile.exists()){
                        System.out.println("dexFile not exists");
                        return;
                    }
                    File odexDir = getDir("odex", Context.MODE_PRIVATE);
                    if(!odexDir.exists()){
                        System.out.println("odexDir not exists");
                        odexDir.mkdir();
                    }
                    //新建一个DexClassLoader，以dex文件的路径为参数，传入一个放置odex文件的文件夹路径
                    DexClassLoader dexClassLoader = new DexClassLoader(dexFile.getAbsolutePath(),
                            odexDir.getAbsolutePath(), null, getClassLoader());
                    try {
                        //使用dexClassLoader进行加载dex文件中的类
                        Class clazz = dexClassLoader.loadClass("com.champion.loaddexdemo.dynanmicLoadedTest");
                        Object object = clazz.newInstance();
                        //调用类中的方法
                        Method method = clazz.getMethod("load");
                        method.invoke(object);
                    } catch (ClassNotFoundException e) {
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    } catch (InstantiationException e) {
                        e.printStackTrace();
                    } catch (NoSuchMethodException e) {
                        e.printStackTrace();
                    } catch (InvocationTargetException e) {
                        e.printStackTrace();
                    }
                }
            });
        }
    
        @Override
        public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
            if(requestCode == storageRequestCode){
                System.out.println("request code success!!!!!");
            }
        }
    
    }

被加载的测试类代码：

package com.champion.loaddexdemo;
    
    public class dynanmicLoadedTest {
        static {
            System.out.println("static load success!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
        }
        public void load(){
            System.out.println("load+++++++++++++++++++++++++++++++++");
        }
    }