Android，从导入的 jar 文件中找不到类

问题描述

我在我的 Android 项目中包含了一个 jar 文件，如 .

更新:我现在已经尝试了您的代码.它适用于我的情况.我所做的唯一区别是在导出 Jar 期间我检查了导出 Java 源文件和资源.希望这会帮助你.试试吧！

I included a jar file in my Android project as explained in How can I use external JARs in an Android project?. With both methods described by MannyNS and Vinayak B. in this post I get the error "Could not find class 'test.libraryCalc.Calc" which is the class provided by the library. The following code illustrates the problem:

Example class provided via library: Calc.java

package test.libraryCalc;

public class Calc {
    public int add(int a, int b){
        return a + b;
    }
}

LibraryTestActivity.java

package test.library;

import test.libraryCalc.Calc;
import android.app.Activity;
import android.os.Bundle;

public class LibraryTestActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Calc calc = new Calc();
        int c = calc.add(3, 4);
    }
}

I exported the jar file containing Calc.java to LibraryTestlibscalc.jar

and added a reference to it using the "Add JARs..." button in the Java Build Path of LibraryTest

The library shows up in the Referenced libraries in LibraryTest

LibraryTest has no build problems but when running it on the emulator the following is shown in LogCat:

12-27 14:01:33.965: E/dalvikvm(747): Could not find class 'test.libraryCalc.Calc',               referenced from method test.library.LibraryTestActivity.onCreate
12-27 14:01:33.965: W/dalvikvm(747): VFY: unable to resolve new-instance 13   (Ltest/libraryCalc/Calc;) in Ltest/library/LibraryTestActivity;
12-27 14:01:33.995: D/dalvikvm(747): VFY: replacing opcode 0x22 at 0x0008
12-27 14:01:33.995: D/dalvikvm(747): VFY: dead code 0x000a-0013 in Ltest/library/LibraryTestActivity;.onCreate (Landroid/os/Bundle;)V
12-27 14:01:34.065: D/AndroidRuntime(747): Shutting down VM
12-27 14:01:34.065: W/dalvikvm(747): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
12-27 14:01:34.075: E/AndroidRuntime(747): FATAL EXCEPTION: main
12-27 14:01:34.075: E/AndroidRuntime(747): java.lang.NoClassDefFoundError: test.libraryCalc.Calc
12-27 14:01:34.075: E/AndroidRuntime(747):  at     test.library.LibraryTestActivity.onCreate(LibraryTestActivity.java:14)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.os.Handler.dispatchMessage(Handler.java:99)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.os.Looper.loop(Looper.java:123)
12-27 14:01:34.075: E/AndroidRuntime(747):  at android.app.ActivityThread.main(ActivityThread.java:4627)
12-27 14:01:34.075: E/AndroidRuntime(747):  at java.lang.reflect.Method.invokeNative(Native Method)
12-27 14:01:34.075: E/AndroidRuntime(747):  at java.lang.reflect.Method.invoke(Method.java:521)
12-27 14:01:34.075: E/AndroidRuntime(747):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
12-27 14:01:34.075: E/AndroidRuntime(747):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
12-27 14:01:34.075: E/AndroidRuntime(747):  at dalvik.system.NativeStart.main(Native Method)
12-27 14:06:34.170: I/Process(747): Sending signal. PID: 747 SIG: 9

What needs to be done to get this working? Thanks for all suggestions.

解决方案

I think that the problem is that you try to add jar that contains Android code. You cannot do this. To include Android code you should create Android library. Simply create an Android project and in the project-properties Android section set that this is library project. After that you'll be able to add this library to your projects. For more about Android libraries you can read here.

Update: I've tried your code now. It works in my case. The only difference that I've made is during export of Jar I've checked Export Java source files and resources. Hope this will help you. Try it!

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