Question

我的Android项目上有这个界面：

package com.kkoci.shairlook;

/**
* Created by kristian on 07/07/2015.
*/
public interface OnTaskFinishListener{

void onFinish();

}

我正在使用它，在我的AsyncTask类上调用onPostExecute：

package com.kkoci.shairlook;

import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.Toast;

import com.appspot.shairlook1.userEndpoint.UserEndpoint;
import com.appspot.shairlook1.userEndpoint.model.User;
import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.extensions.android.json.AndroidJsonFactory;
import com.google.api.client.googleapis.services.AbstractGoogleClientRequest;
import com.google.api.client.googleapis.services.GoogleClientRequestInitializer;

import java.io.IOException;
import java.util.Collections;
import java.util.List;

/**
* Created by kristian on 04/07/2015.
*/

public class EndpointsAsyncTaskInsert extends AsyncTask<String, Void, User> implements GoogleClientRequestInitializer {
private static UserEndpoint myApiService = null;
private Context context;
private OnTaskFinishListener listener;
EndpointsAsyncTaskInsert(Context context) {
    this.context = context;
}

public EndpointsAsyncTaskInsert(OnTaskFinishListener listener){
    this.listener = listener;
}
@Override
public void initialize(AbstractGoogleClientRequest<?> abstractGoogleClientRequest) throws IOException {
    // put it here no in MyClass
    abstractGoogleClientRequest.setDisableGZipContent(true);
}

@Override
protected User doInBackground(String... params) {
    User response = null;
    if (myApiService == null) { // Only do this once
        UserEndpoint.Builder builder = new UserEndpoint.Builder(AndroidHttp.newCompatibleTransport(),
                new AndroidJsonFactory(), null)
// options for running against local devappserver
// - 10.0.2.2 is localhost's IP address in Android emulator
// - turn off compression when running against local devappserver
                .setRootUrl("https://shairlook1.appspot.com/_ah/api/")
                .setGoogleClientRequestInitializer(this);
// end options for devappserver

        myApiService = builder.build();
    }

    try {
        User users = new User();
        users.setEmail(params[0]);
        users.setPassword(params[1]);
        users.setName(params[2]);
        response = myApiService.insertUser(users).execute();
    } catch (Exception e) {
        Log.d("Could not Add User", e.getMessage(), e);
    }
    return response;
}
protected void onPostExecute(User user){
    listener.onFinish();
}

}

但是这给了我java.lang.NoCalssDefFound错误，我在我的活动中初始化它是这样的：

public class LoginMember extends Activity implements OnTaskFinishListener    {
public void onFinish(){
    Intent intent = new Intent(LoginMember.this, WelcomeScreen.class);
    startActivity(intent);
}

然后执行：

btnLogin.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {

                InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(txtEmail.getWindowToken(), 0);
                imm.hideSoftInputFromWindow(txtPassword.getWindowToken(), 0);
                String password = txtPassword.getText().toString();
                String email = txtEmail.getText().toString();
                if ((txtEmail.length() == 0) || (txtPassword.length() == 0)) {
                    Toast.makeText(LoginMember.this, "You need to provide values for Email and Password", Toast.LENGTH_SHORT).show();
                    return;
                }

                //Go ahead and perform the transaction
                String[] params = {email, password};
                new EndpointsAsyncTaskInsert(currentActivity.getApplicationContext()).execute(params);
            }
        });

因此，执行EndpointAsyncTaskInsert方法listener.OnFinish();

时会出现问题

这是完整的logcat：

7752-7752/com.kkoci.shairlook E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at com.kkoci.shairlook.EndpointsAsyncTaskInsert.onPostExecute(EndpointsAsyncTaskInsert.java:74)
        at com.kkoci.shairlook.EndpointsAsyncTaskInsert.onPostExecute(EndpointsAsyncTaskInsert.java:24)
        at android.os.AsyncTask.finish(AsyncTask.java:631)
        at android.os.AsyncTask.access$600(AsyncTask.java:177)
        at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:175)
        at android.app.ActivityThread.main(ActivityThread.java:5279)
        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:1102)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
        at dalvik.system.NativeStart.main(Native Method)

我在这里看到这个question似乎是同一类问题，但我对此解决方案并不十分确定。

请问任何想法？

提前致谢！

Answer 1

日志说错误是java.lang.NullPointerException ...而且它是因为您使用EndpointsAsyncTaskInsert构造函数创建了Context，因此{{1} }在其内部null ...并且在不listener

中检查null的情况下取消引用它

从侦听器触发AsyncTask - AndroidStudio 1.2.2 - java.lang.NoClassDefFound

1 个答案: