java - 使用 GoogleDriveApi for android 和 Groovy 时出现奇怪的 ClassCastException 错误

Question

我正在尝试使用适用于 Android 和 Groovy 的 GoogleDriveApi 从 Android 访问 Google Drive 帐户内容。但是我在 logcat 中收到一个关于 DriveApi 类的 ClassCastException 的奇怪错误，尽管我遵循了 Google 官方教程，但使用的是 Groovy 语言。 (为了简化问题，我创建了一个小项目，它重现了与原始项目中相同的错误。)

这是构建 gradle(该项目是从命令行生成的:有一个唯一的 gradle.build 文件。提交此 gradle 构建是我以简单的方式为您提供依赖项的一种方式)

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.5.0'
        classpath 'org.codehaus.groovy:gradle-groovy-android-plugin:0.3.10'
    }
}

apply plugin: 'android'
apply plugin: 'groovyx.grooid.groovy-android'

android {
    compileSdkVersion 'Google Inc.:Google APIs:23'
    buildToolsVersion '23.0.2'

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 23
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFile getDefaultProguardFile('proguard-android.txt')
        }
    }
}

repositories {
   jcenter()
}

project.androidGroovy {
    options {
        sourceCompatibility = '1.7'
        targetCompatibility = '1.7'
    }
}

dependencies {
    compile 'org.codehaus.groovy:groovy:2.4.6:grooid'
    compile 'com.arasthel:swissknife:1.4.0'
    compile 'com.google.android.gms:play-services-drive:8.4.0'
}

这是 GoogleApiGroovyTest.groovy

package com.loloof64.android.google_api_test

import android.app.Activity
import android.os.Bundle
import android.content.IntentSender 
import android.widget.Toast
import android.content.Context
import android.util.Log

import groovy.transform.CompileStatic

import com.arasthel.swissknife.dsl.components.GAsyncTask

import com.google.android.gms.common.api.GoogleApiClient
import com.google.android.gms.common.api.GoogleApiClient.Builder
import com.google.android.gms.drive.Drive
import com.google.android.gms.common.ConnectionResult
import com.google.android.gms.common.GooglePlayServicesUtil
import com.google.android.gms.common.api.GoogleApiClient.ConnectionCallbacks
import com.google.android.gms.common.api.GoogleApiClient.OnConnectionFailedListener

import com.google.android.gms.drive.DriveFolder
import com.google.android.gms.drive.DriveApi
import com.google.android.gms.common.api.PendingResult

@CompileStatic
public class GoogleApiGroovyTest extends Activity
implements GoogleApiClient.ConnectionCallbacks,     GoogleApiClient.OnConnectionFailedListener
{

    private GoogleApiClient googleApiClient
    private final static int RESOLVE_CONNECTION_REQUEST_CODE = 4
    private final static String APP_LOGGER_REF = "GoogleApiGroovyTest"

    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.main)

        googleApiClient = new     GoogleApiClient.Builder(this).addApi(Drive.API).addScope(Drive.SCOPE_APPFOLDER).addConnectionCallbacks(this).addOnConnectionFailedListener(this).build()
        googleApiClient.connect()
    }

    @Override
    public void onConnected(Bundle connectionHint){
        Toast.makeText(this, "Connected to Google Drive", Toast.LENGTH_SHORT).show()
        Context myThis = this
        async { context, GAsyncTask task ->
            task.after {
                Toast.makeText(myThis, "Finally printed items into screen", Toast.LENGTH_SHORT).show()
            }

            task.error { err ->
                Toast.makeText(this, "Error updating list files !", Toast.LENGTH_SHORT).show()
                Log.e(APP_LOGGER_REF, err.message)
                err.stackTrace.each { element ->
                    Log.e(APP_LOGGER_REF, element.toString())
                }
            } 

            loadExplorerItems()

            true // Seem as returning a value is needed for the async task code to be executed
        }
    }

    @Override
    public void onConnectionSuspended(int cause) {
        //TODO
    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult)     {
        // This block section is mandatory for GoogleApiClient to recover connection failure
        if (connectionResult.hasResolution()) {
            try {
                connectionResult.startResolutionForResult(this, RESOLVE_CONNECTION_REQUEST_CODE)
            } catch (IntentSender.SendIntentException e) {
                // Unable to resolve
                Toast.makeText(this, "Failed to connect to Google account !", Toast.LENGTH_SHORT).show()
            }
        } else {
                GooglePlayServicesUtil.getErrorDialog(connectionResult.getErrorCode(), this, 0).show()
        }
        // End of block section
    }

    private void loadExplorerItems(){
        Context myThis = this
        DriveFolder appFolder = DriveApi.getAppFolder(googleApiClient)
        PendingResult<DriveApi.MetadataBufferResult> pendingChildren = appFolder.listChildren(googleApiClient)
        pendingChildren.setResultCallback     {DriveApi.MetadataBufferResult result -> processResult:{
            if (result.getStatus().isSuccess()){
                Toast.makeText(myThis, "Retrieved root content", Toast.LENGTH_SHORT).show()
            }
            else {
               Toast.makeText(myThis, "Failed to get root content", Toast.LENGTH_SHORT).show() 
            }
        }}
    }
}

这是错误堆栈跟踪:

04-08 16:58:53.549  3261  3261 E GoogleApiGroovyTest: Cannot cast object 'interface com.google.android.gms.drive.DriveApi' with class 'java.lang.Class' to class 'com.google.android.gms.drive.DriveApi'
04-08 16:58:53.575  3261  3261 E GoogleApiGroovyTest: org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnSAM(DefaultTypeTransformation.java:405)
04-08 16:58:53.575  3261  3261 E GoogleApiGroovyTest: org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnNumber(DefaultTypeTransformation.java:319)
04-08 16:58:53.575  3261  3261 E GoogleApiGroovyTest: org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:232)
04-08 16:58:53.575  3261  3261 E GoogleApiGroovyTest: org.codehaus.groovy.runtime.ScriptBytecodeAdapter.castToType(ScriptBytecodeAdapter.java:603)
04-08 16:58:53.575  3261  3261 E GoogleApiGroovyTest: com.loloof64.android.google_api_test.GoogleApiGroovyTest.loadExplorerItems(GoogleApiGroovyTest.groovy:91)
04-08 16:58:53.575  3261  3261 E GoogleApiGroovyTest: com.loloof64.android.google_api_test.GoogleApiGroovyTest.access$0(GoogleApiGroovyTest.groovy)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: com.loloof64.android.google_api_test.GoogleApiGroovyTest$_onConnected_closure1.doCall(GoogleApiGroovyTest.groovy:62)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: java.lang.reflect.Method.invoke(Native Method)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:294)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1021)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: groovy.lang.Closure.call(Closure.java:426)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: com.arasthel.swissknife.dsl.components.GAsyncTask.doInBackground(GAsyncTask.groovy:49)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: android.os.AsyncTask$2.call(AsyncTask.java:295)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:234)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
04-08 16:58:53.576  3261  3261 E GoogleApiGroovyTest: java.lang.Thread.run(Thread.java:818)

同时，DriveApi.getAppFolder 方法具有以下签名:

abstract DriveFolder getAppFolder(GoogleApiClient apiClient)

DriveApi 类和 DriveFolder 类均不采用类参数。所以我无法理解 Stacktrace 错误的真正含义。

参见Drive API Android reference

Answer 1

嗯，我也不明白这个错误是从哪里来的，但事实上，您尝试在接口(interface)上调用方法，就像在类上调用静态方法一样，可能需要做一些事情有了它:

DriveFolder appFolder = DriveApi.getAppFolder(googleApiClient)

DriveApi 是一个接口(interface)，因此它没有任何方法实现。并且，getAppFolder() 是一个实例方法，而不是静态方法。因此，您需要的是 DriveApi 的实现，您可以从 Drive 获取它:

DriveFolder appFolder = Drive.DriveApi.getAppFolder(googleApiClient)