Question

我使用的是Android Studio，在更新'Android Support Libary'后，我有问题要连接到Parse.com。 22。之前工作的项目现在不起作用。经过几个小时的搜索和测试，我决定只为此打开一个清晰的项目，但问题仍然存在。

MainActivity Class

public class MainActivity extends Activity {
   List<ParseObject> data;
   List<String> nameList;
   String[] name;

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

    String appId = " ********* ";
    String clientId = " ********* ";
    Parse.initialize(getApplicationContext(), appId, clientId);

    ParseQuery<ParseObject> query = ParseQuery.getQuery("test");
    try {
        data = query.find();

    }catch (ParseException e){
        Log.i("myParseExceptionLog", "Can't connect to test table at parse");
    }

    nameList = new ArrayList<String>();
    for (int i=0 ; i < data.size(); i++){
        nameList.add(data.get(i).getString("name"));
    }
    name = nameList.toArray(new String[nameList.size()]);

    TextView myTV = (TextView)findViewById(R.id.test);
    myTV.setText(name[0]);
}
}

activity_main.xml中

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MainActivity">

<TextView
    android:id="@+id/test"
    android:text="@string/hello_world"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" />

</RelativeLayout>

AndroidManifast.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="shachar.com.parsetest" >
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

的build.gradle

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.0.0'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}
allprojects {
    repositories {
        jcenter()
    }
    }

我知道我需要在build.gradle中依赖我的jar，但请查看注释。无论如何，它出现在Project Structure中，我可以在我的类中从parse导入libs。当我尝试在build.gradle中依赖并同步Manifat时。

Project Current Libs Project Structure 在黑屏2分钟后，应用程序记住崩溃并带给我NullPointerExpiton（因为'数据'为空）。

LogCat错误

03-17 16:46:17.686  18427-18427/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: shachar.com.parsetest, PID: 18427
java.lang.RuntimeException: Unable to start activity ComponentInfo{shachar.com.parsetest/shachar.com.parsetest.MainActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2338)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
        at android.app.ActivityThread.access$800(ActivityThread.java:151)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
        at android.os.Handler.dispatchMessage(Handler.java:110)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:5292)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at shachar.com.parsetest.MainActivity.onCreate(MainActivity.java:39)
        at android.app.Activity.performCreate(Activity.java:5264)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2302)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)

at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1321)
at android.os.Handler.dispatchMessage(Handler.java:110)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5292)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
at dalvik.system.NativeStart.main(Native Method)
03-17 16:46:18.212      672-695/? E/﹕ Could not open '/data/data/hotplug/cmd'
03-17 16:46:18.212      672-695/? E/﹕ error : 2, No such file or directory
03-17 16:46:18.245     672-3024/? E/Sensors﹕ new acc setDelay handle(0),ns(20000000) err! go to hwmsen
03-17 16:46:18.323     672-3023/? E/﹕ Could not open '/data/data/hotplug/cmd'
03-17 16:46:18.323     672-3023/? E/﹕ error : 2, No such file or directory

我想知道什么？
我错过了什么？
新的“Android支持Libary”版本会出现什么变化？

修改我刚刚做了另一个测试，我从他们的网站上下载了一个complet exmple od解析器，其中包含所有设置和最后一个解析版本。我重新安装Android支持Libary但仍无法正常工作

Answer 1

是的，看起来你在第39行有空值，你可以在这里添加行号，以便我们可以看到这个空值被抛出的位置吗？

Answer 2

好的，如果for (int i=0 ; i < data.size(); i++)产生NullPointerException，那肯定是因为data为空，所以你必须检查data是否为空。

更新'Android Support Libary'v22后无法连接到Parse.com

2 个答案: