java - Android DexClassLoader 错误， 'optimized data directory .. not owned by current user'

Question

我正在尝试制作一个简单的 android 应用程序，它可以在运行时从 SD 卡加载 DEX 文件。

该应用程序有两个 Activity 。第一个 Activity 是一个带有按钮的简单屏幕。按下按钮时，将启动第二个 Activity ，从而调用 loadDex() 方法。 loadDex() 方法尝试在 SD 卡上找到一个 jar 文件并将其加载到当前应用程序中。

这是我第一个 Activity 的代码:

package poc.example.del.customclass;

import android.content.Intent;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;


public class MainActivity extends ActionBarActivity {

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void launchLoadClass(View view) {
        Intent intent = new Intent(MainActivity.this, LoadClass.class);
        startActivity(intent);
    }
}

这是我的第二个 Activity (加载 DEX 文件的那个)的代码:

package poc.example.del.customclass;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;

import java.io.File;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import dalvik.system.DexClassLoader;


public class LoadClass extends ActionBarActivity {

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_load_class, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void loadDex() {
        String dexFile = "/sdcard/output.jar";
        File jarFile = new File(dexFile);
        if (jarFile.exists()) {
            // Toast.makeText(getApplicationContext(), "It Worked!", Toast.LENGTH_LONG).show();
            DexClassLoader cl = new DexClassLoader (jarFile.toString (), "/data/test", null, ClassLoader.getSystemClassLoader());

        }
    }
}

调用 DexClassLoader 构造函数时会出现问题。在日志中可以发现如下错误:

03-25 10:15:48.441    1934-1934/poc.example.del.customclass E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{poc.example.del.customclass/poc.example.del.customclass.LoadClass}: java.lang.IllegalArgumentException: Optimized data directory /data/test is not owned by the current user. Shared storage cannot protect your application from code injection attacks.
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5039)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.IllegalArgumentException: Optimized data directory /data/test is not owned by the current user. Shared storage cannot protect your application from code injection attacks.
            at dalvik.system.DexFile.<init>(DexFile.java:100)
            at dalvik.system.DexFile.loadDex(DexFile.java:149)
            at dalvik.system.DexPathList.loadDexFile(DexPathList.java:261)
            at dalvik.system.DexPathList.makeDexElements(DexPathList.java:229)
            at dalvik.system.DexPathList.<init>(DexPathList.java:96)
            at dalvik.system.BaseDexClassLoader.<init>(BaseDexClassLoader.java:56)
            at dalvik.system.DexClassLoader.<init>(DexClassLoader.java:57)
            at poc.example.del.customclass.LoadClass.loadDex(LoadClass.java:54)
            at poc.example.del.customclass.LoadClass.onCreate(LoadClass.java:23)
            at android.app.Activity.performCreate(Activity.java:5104)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
            at android.app.ActivityThread.access$600(ActivityThread.java:141)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5039)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
            at dalvik.system.NativeStart.main(Native Method)

这是日志中我认为代表问题的行:

java.lang.IllegalArgumentException: Optimized data directory /data/test is not owned by the current user. Shared storage cannot protect your application from code injection attacks.

任何帮助将不胜感激，因为我在网上发现的有关此问题的信息很少。我正在为 Android 4.2、Api 17 开发应用程序。

提前致谢。

Answer 1

在学习了各种教程几天后，我找到了答案。我想我会在这里发布解决方案，以防其他人遇到类似问题。

出于安全原因，Android 不允许应用程序将文件加载到任何随机文件夹。相反，它应该加载到应用程序环境中。这是允许我继续该项目的修改后的代码。显示的代码用于“loadDex()”方法:

public void loadDex() {
    // Toast the show the method has been invoked correctly
    // Toast.makeText(getApplicationContext(), "loadDex() Method invoked", Toast.LENGTH_LONG).show();

    // name of the DEX file
    String dexFile = "/output.jar";

    // Get the path to the SD card
    File f = new File(Environment.getExternalStorageDirectory().toString() + dexFile);

    // optimized directory, the applciation and package directory
    final File optimizedDexOutputPath = getDir("outdex", 0);

    // DexClassLoader to get the file and write it to the optimised directory
    DexClassLoader classLoader = new DexClassLoader(f.getAbsolutePath(),
    optimizedDexOutputPath.getAbsolutePath(),null, getClassLoader());

    // The classpath is created for the new class
    String completeClassName = "poc.example.del.mylibrary.name";
    String methodToInvoke = "display";

    try {
        Class<?> myClass = classLoader.loadClass(completeClassName);
        Object obj = (Object)myClass.newInstance();
        Method m = myClass.getMethod(methodToInvoke);
        String s = ""+m.invoke(obj);
        makeToast(s);
    }
    catch (Exception e) {
        e.printStackTrace();
        makeToast("Something went wrong!");
    }


}

解决问题的具体代码行是:

// DexClassLoader to get the file and write it to the optimized directory
DexClassLoader classLoader = new DexClassLoader(f.getAbsolutePath(),
optimizedDexOutputPath.getAbsolutePath(),null, getClassLoader());

如您所见，optimizedDexOutputPath,getAbsolutePath() 方法返回应用程序可用于写入文件的目录。

希望这对遇到类似问题的其他人有所帮助!