Question

所以我一直在研究这个问题，并发现这个问题似乎发生在它无法达到我在我的Activity中引用的内容时。我认为这个问题可能在于我试图达到应用课程，但我不确定。我已经尝试评论与地理编码相关的意图并且仍然得到相同的错误，所以我不确定它在哪里找到空指针。

这是我得到的错误代码：

05-17 01:50:11.583: E/AndroidRuntime(23183): FATAL EXCEPTION: main
05-17 01:50:11.583: E/AndroidRuntime(23183): Process: com.binarsunset.topic, PID: 23183
05-17 01:50:11.583: E/AndroidRuntime(23183): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.binarsunset.topic/com.binarsunset.topic.CreateTopicActivity}: java.lang.NullPointerException
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2198)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2257)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.ActivityThread.access$800(ActivityThread.java:139)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1210)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.os.Handler.dispatchMessage(Handler.java:102)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.os.Looper.loop(Looper.java:136)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.ActivityThread.main(ActivityThread.java:5097)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at java.lang.reflect.Method.invokeNative(Native Method)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at java.lang.reflect.Method.invoke(Method.java:515)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at dalvik.system.NativeStart.main(Native Method)
05-17 01:50:11.583: E/AndroidRuntime(23183): Caused by: java.lang.NullPointerException
05-17 01:50:11.583: E/AndroidRuntime(23183):    at com.binarsunset.topic.CreateTopicActivity.updateCharacterCountTextViewText(CreateTopicActivity.java:118)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at com.binarsunset.topic.CreateTopicActivity.onCreate(CreateTopicActivity.java:71)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.Activity.performCreate(Activity.java:5248)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
05-17 01:50:11.583: E/AndroidRuntime(23183):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
05-17 01:50:11.583: E/AndroidRuntime(23183):    ... 11 more

所以我从活动TopicActivity开始，但它不是我的主要，这是代码：

package com.binarsunset.topic;

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

/**
 * Created by Douglas on 5/3/2015.
 */
public class TopicActivity extends ActionBarActivity {

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

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
            case R.id.Create: {
                aboutItemCreate();
                return true;
            }


            default:
                return super.onOptionsItemSelected(item);
        }
    }

    private void aboutItemCreate(){
        Intent intent = new Intent(getApplicationContext(), CreateTopicActivity.class);
        startActivity(intent);
    }


}

我单击操作栏上的创建活动，这将带我到CreateTopicActivity，这里崩溃的地方是CreateTopicAcvivity的代码：

package com.binarsunset.topic;

import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.location.Location;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.parse.ParseACL;
import com.parse.ParseException;
import com.parse.ParseGeoPoint;
import com.parse.ParseUser;
import com.parse.SaveCallback;

/**
 * Created by Douglas on 5/16/2015.
 */
public class CreateTopicActivity extends Activity {

    // UI references.
    private EditText createTopicEditText;
    private TextView characterCountTextView;
    private Button createButton;

    private int maxCharacterCount = Application.getConfigHelper().getPostMaxCharacterCount();
    private ParseGeoPoint geoPoint;

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


        Intent intent = getIntent();
        Location location = intent.getParcelableExtra(Application.INTENT_EXTRA_LOCATION);
        geoPoint = new ParseGeoPoint(location.getLatitude(), location.getLongitude());

        createTopicEditText = (EditText) findViewById(R.id.create_topic_title);
        createTopicEditText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
            }

            @Override
            public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
            }

            @Override
            public void afterTextChanged(Editable s) {
                updateTopicButtonState();
                updateCharacterCountTextViewText();
            }
        });

        characterCountTextView = (TextView) findViewById(R.id.character_count_textview);

        createButton = (Button) findViewById(R.id.create_topic_button);
        createButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                createTopic();
            }
        });

        updateTopicButtonState();
        updateCharacterCountTextViewText();
    }

    private void createTopic () {
        String text = createTopicEditText.getText().toString().trim();

        // Set up a progress dialog
        final ProgressDialog dialog = new ProgressDialog(CreateTopicActivity.this);
        dialog.setMessage(getString(R.string.progress_topic));
        dialog.show();

        // Create a post.
        AnywallPost topic = new AnywallPost();

        // Set the location to the current user's location
        topic.setLocation(geoPoint);
        topic.setText(text);
        topic.setUser(ParseUser.getCurrentUser());
        topic.setInt(1);
        ParseACL acl = new ParseACL();

        // Give public read access
        acl.setPublicReadAccess(true);
        topic.setACL(acl);

        // Save the topic
        topic.saveInBackground(new SaveCallback() {
            @Override
            public void done(ParseException e) {
                dialog.dismiss();
                finish();
            }
        });
    }

    private String getTopicEditTextText () {
        return createTopicEditText.getText().toString().trim();
    }

    private void updateTopicButtonState () {
        int length = getTopicEditTextText().length();
        boolean enabled = length > 0 && length < maxCharacterCount;
        createButton.setEnabled(enabled);
    }

    private void updateCharacterCountTextViewText () {
        String characterCountString = String.format("%d/%d", createTopicEditText.length(), maxCharacterCount);
        characterCountTextView.setText(characterCountString);
    }

}

这是我的清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.binarsunset.topic"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="11"
        android:targetSdkVersion="19" />

    <permission
        android:name="com.binarsunset.Topic.permission.MAPS_RECEIVE"
        android:protectionLevel="signature" >
    </permission>

    <uses-permission android:name="com.parse.anywall.permission.MAPS_RECEIVE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <!--
     The following permission is not required to use
     Google Maps Android API v2, but is recommended.
    -->
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <application
        android:name=".Application"
        android:allowBackup="true"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:screenOrientation="portrait" />

        <meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="AIzaSyCVz0h90fBZwkcgagi1Q7WV1W_cVgd0_QA" />

        <meta-data android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />

        <activity
            android:name=".LoginActivity"
            android:label="@string/title_activity_login"
            android:screenOrientation="portrait" />

        <activity
            android:name=".SignUpActivity"
            android:label="@string/title_activity_signup"
            android:screenOrientation="portrait" />

        <activity
            android:name=".DispatchActivity"
            android:noHistory="true" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".WelcomeActivity"
            android:label="@string/app_name"
            android:screenOrientation="portrait"
            android:theme="@android:style/Theme.Holo" />
        <activity
            android:name=".PostActivity"
            android:label="@string/activity_post_title"
            android:windowSoftInputMode="adjustResize" />
        <activity
            android:name=".TopicActivity"
            android:label="Topic" />
        <activity
            android:name=".PostCommentsActivity"
            android:label="PostComments" />
        <activity
            android:name=".SettingsActivity"
            android:label="@string/title_activity_settings" />
        <activity
            android:name=".LocationActivity"
            android:label="Location" />

        <activity
            android:name=".CreateTopicActivity"
            android:label="CreateTopic" />

    </application>

</manifest>

这是我的activity_create_topic.xml：

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".PostActivity"
>

    <EditText
        android:id="@+id/create_topic_title"
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:background="@null"
        android:hint="@string/create_topic_title"
        android:inputType="text"
        android:gravity="top"
        android:layout_above="@+id/create_topic_details">
        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/create_topic_details"
        android:layout_width="fill_parent"
        android:layout_height="300dp"
        android:layout_above="@+id/character_count_Create_Details"
        android:background="@null"
        android:hint="@string/create_topic_details"
        android:inputType="textMultiLine"
        android:gravity="top" >
        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/create_topic_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentEnd="true"
        android:text="@string/Create_text" />

    <TextView
        android:id="@+id/character_count_Create_Details"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentEnd="true"
        android:layout_marginBottom="@dimen/activity_vertical_margin"
        android:layout_above="@id/create_topic_button"
        android:text="@string/character_count_placeholder"
        android:textAppearance="?android:attr/textAppearanceSmall" />


</RelativeLayout>

如果您需要任何其他代码，请与我们联系。谢谢你的时间。

编辑：我在CreateTopicActivity中注释掉除了布局创建者之外的所有东西，它运行时没有崩溃所以看起来问题出现在CreateTopicActivity的代码中。这让我相信它的地理编码或应用程序的引用，但即使我知道这是错误我仍然是新的，所以我真的不知道我将如何解决问题或为什么这是一个问题第一名。

Answer 1

在初始化characterCountTextView之前初始化createTopicEditText，如下所示

    characterCountTextView = (TextView) findViewById(R.id.character_count_textview);
    createTopicEditText = (EditText) findViewById(R.id.create_topic_title);
    createTopicEditText.addTextChangedListener(new TextWatcher() {
        @Override 
        public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
        } 

        @Override 
        public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
        } 

        @Override 
        public void afterTextChanged(Editable s) {
            updateTopicButtonState(); 
            updateCharacterCountTextViewText(); 
        } 
    });

请注意，在您的代码中调用characterCountTextView方法时，代码updateCharacterCountTextViewText()尚未初始化 createTopicEditTexts TextChangedListener

Answer 2

指向不在活动布局中的视图返回NULL

您在ID character_count_textview中引用的TextView在活动布局activity_create_topic中不存在。因此发生了NULL POINTER异常。

Answer 3

我认为你的maxCharacterCount为空。

尝试将以下代码行移至onCreate。

  maxCharacterCount = Application.getConfigHelper().getPostMaxCharacterCount();

如下所示

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

   maxCharacterCount = Application.getConfigHelper().getPostMaxCharacterCount();
    Intent intent = getIntent();
    Location location = intent.getParcelableExtra(Application.INTENT_EXTRA_LOCATION);
    geoPoint = new ParseGeoPoint(location.getLatitude(), location.getLongitude());
    characterCountTextView = (TextView) findViewById(R.id.character_count_textview);
    createTopicEditText = (EditText) findViewById(R.id.create_topic_title);
    createTopicEditText.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
        }

        @Override
        public void onTextChanged(CharSequence arg0, int arg1, int arg2, int arg3) {
        }

        @Override
        public void afterTextChanged(Editable s) {
            updateTopicButtonState();
            updateCharacterCountTextViewText();
        }
    });

    createButton = (Button) findViewById(R.id.create_topic_button);
    createButton.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            createTopic();
        }
    });

    updateTopicButtonState();
    updateCharacterCountTextViewText();
}

Answer 4

由于updateCharacterCountTextViewText ()方法仅调试，您收到错误，并且createTopicEditText和maxCharacterCount都不为空并将characterCountTextView = (TextView) findViewById(R.id.character_count_textview);移至createTopicEditText.addTextChanged方法之前< / p>

错误：“无法启动活动ComponentInfo ... Java.lang.NullPointerException”

4 个答案: