1

我的应用程序工作正常，但是当应用程序进入后台时，它应该恢复时崩溃。正如您在源代码中看到的，我记录了 onStart、onStop 等事件。

在我的日志中，当我启动应用程序时，我可以看到 onStart、onResume。当我按下返回键时，我看到：onStop、STOP、onPause 和 onDestroy。

当我尝试重新启动应用程序时，它会立即崩溃，除了“无法启动 Activity ComponentInfo java lang.NullPointerException”之外，日志中没有其他消息。

我怎样才能防止这种情况？

public class Start extends Activity {

private Handler handler = new Handler();
private ArrayList<String> discussionThread;
private EditText textMessage;

private ListView listview;

private ConnectionConfiguration config;
private Presence presence;
private MultiUserChat muc;
private DiscussionHistory history;
private PacketFilter filter;
private MyCustomAdapter discussionThreadAdapter;
private XMPPConnection connection;


/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    try {
        initConnection();
    } catch (XMPPException e) {
        e.printStackTrace();
    }

    final EditText textMessage = (EditText) this.findViewById(R.id.message);        
    listview = (ListView) this.findViewById(R.id.list);

    discussionThread = new ArrayList<String>();
    discussionThreadAdapter = new MyCustomAdapter();
    listview.setAdapter(discussionThreadAdapter);

    Button send = (Button) this.findViewById(R.id.send);
    send.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            String text = textMessage.getText().toString();

            Message msg = new Message(ROOM, Message.Type.groupchat);
            msg.setBody(text);
            connection.sendPacket(msg);
            discussionThreadAdapter.notifyDataSetChanged();
            textMessage.setText("");
        }
    });


    textMessage.setOnKeyListener(new OnKeyListener()
    {
        public boolean onKey(View v, int keyCode, KeyEvent event)
        {
            if (event.getAction() == KeyEvent.ACTION_DOWN)
            {
                switch (keyCode)
                {
                    case KeyEvent.KEYCODE_DPAD_CENTER:
                    case KeyEvent.KEYCODE_ENTER:
                        SendText();
                        return true;
                    default:
                        break;
                }
            }
            return false;
        }
    });
}


private void initConnection() throws XMPPException {
    config = new ConnectionConfiguration(SERVER_HOST, SERVER_PORT, SERVICE_NAME);
    connection = new XMPPConnection(config);
    connection.connect();
    connection.login(LOGIN, PASSWORD);
    presence = new Presence(Presence.Type.available);

    connection.sendPacket(presence);

    muc = new MultiUserChat(connection, ROOM);
    history = new DiscussionHistory();

    history.setMaxStanzas(25);

    muc.join(LOGIN, PASSWORD, history, SmackConfiguration.getPacketReplyTimeout());

    filter = new MessageTypeFilter(Message.Type.groupchat);

    connection.addPacketListener(new PacketListener() {

        public void processPacket(Packet packet) {
            Message message = (Message) packet;
            if (message.getBody() != null) {
                String fromName = message.getFrom().substring(48);
                String nieuweRegel = fromName + ": " + message.getBody();

                fromName = fromName.toUpperCase();

                if (fromName.equals(LOGIN.toUpperCase())) {
                    discussionThreadAdapter.addVanMijItem(nieuweRegel);
                } else {
                    discussionThreadAdapter.addVanAnderItem(nieuweRegel);
                }

            }
        }
    }, filter);

}

private void Notify() {
    discussionThreadAdapter.notifyDataSetChanged();
    listview.setSelection(discussionThreadAdapter.getCount());
}

private class MyCustomAdapter extends BaseAdapter {

    private static final int BERICHT_VAN_ANDER = 0;
    private static final int BERICHT_VAN_MIJ = 1;
    private static final int TYPE_MAX_COUNT = BERICHT_VAN_MIJ + 1;

    private LayoutInflater mInflater;

    private TreeSet<Integer> mySet = new TreeSet<Integer>();

    public MyCustomAdapter() {
        mInflater = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public void addVanAnderItem(final String item) {
        discussionThread.add(item);
        handler.post(new Runnable() {
            public void run() {
                Notify();
            }
        });

    }

    public void addVanMijItem(final String item) {
        discussionThread.add(item);
        mySet.add(discussionThread.size() - 1);
        handler.post(new Runnable() {
            public void run() {
                Notify();
            }
        });
    }

    @Override
    public int getItemViewType(int position) {
        return mySet.contains(position) ? BERICHT_VAN_MIJ : BERICHT_VAN_ANDER;
    }

    @Override
    public int getViewTypeCount() {
        return TYPE_MAX_COUNT;
    }

    @Override
    public int getCount() {
        return discussionThread.size();
    }

    @Override
    public String getItem(int position) {
        return discussionThread.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        int type = getItemViewType(position);
        if (convertView == null) {
            holder = new ViewHolder();
            switch (type) {
                case BERICHT_VAN_ANDER:
                    convertView = mInflater.inflate(R.layout.bericht_van_ander_item, null);
                    holder.textView = (TextView)convertView.findViewById(R.id.textline);
                    break;
                case BERICHT_VAN_MIJ:
                    convertView = mInflater.inflate(R.layout.bericht_van_mij_item, null);
                    holder.textView = (TextView)convertView.findViewById(R.id.textline);
                    break;
            }
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder)convertView.getTag();
        }
        holder.textView.setText(discussionThread.get(position));
        return convertView;
    }

}

public static class ViewHolder {
    public TextView textView;
}

private void SendText() {

    InputMethodManager imm = (InputMethodManager)getSystemService(Context.INPUT_METHOD_SERVICE);
    imm.hideSoftInputFromWindow(textMessage.getWindowToken(), 0);

    String text = textMessage.getText().toString();

    Message msg = new Message(ROOM, Message.Type.groupchat);
    msg.setBody(text);
    connection.sendPacket(msg);
    textMessage.setText("");
}

public void onStart() {
    super.onStart();
    Log.i("CONN", "onStart");
    startConnection();
}

public void onRestart() {
    super.onRestart();
    Log.i("CONN", "onReStart");
    startConnection();
}

public void onResume() {
    super.onResume();
    Log.i("CONN", "onResume");
    startConnection();
}

public void onPause() {
    super.onPause();
    Log.i("CONN", "onPause");
    stopConnection();

}

public void onStop() {
    super.onStop();
    Log.i("CONN", "onStop");
    stopConnection();
}

public void onDestroy() {
    super.onDestroy();
    Log.i("CONN", "onDestroy");
    stopConnection();
}

private void stopConnection() {

    if (connection != null) {

        Log.i("CONN", "STOP");

        connection.disconnect(presence);

        connection = null;
        filter = null;
        history = null;
        muc = null;
        presence = null;
        config = null;
        discussionThreadAdapter = null;


    }

}

private void startConnection() {

    if (connection.isConnected() ) {

    } else {

        Log.i("CONN", "START");

        try {
            initConnection();
        } catch (XMPPException e) {
            e.printStackTrace();
        }
    }
}

}

好的，我更改了以下内容：

   private void startConnection() {

    if (connection != null ) {

        Log.i("CONN", "RUNNING");

    } else {

        Log.i("CONN", "START");

        try {
            initConnection();
        } catch (XMPPException e) {
            e.printStackTrace();
        }
    }
}

我启动应用程序，一切正常。日志：

05-12 08:40:21.743: D/AndroidRuntime(491): >>>>>>>>>>>>>> AndroidRuntime 开始 <<<<<<<<<<<<< 05-12 08 :40:21.743: D/AndroidRuntime(491): CheckJNI 开启

05-12 08:40:22.065: D/AndroidRuntime(491): --- 注册本机函数 ---

05-12 08:40:23.353: D/AndroidRuntime(491): 关闭虚拟机

05-12 08:40:23.363: D/dalvikvm(491): 调试器已分离；对象注册表有 1 个条目

05-12 08:40:23.393: I/AndroidRuntime(491): 注意: 附加线程 'Binder Thread #3' 失败

05-12 08:40:24.184: D/AndroidRuntime(499): >>>>>>>>>>>>>> AndroidRuntime START <<<<<<<<<<<<<<

05-12 08:40:24.184: D/AndroidRuntime(499): CheckJNI 开启

05-12 08:40:24.523: D/AndroidRuntime(499): --- 注册本机函数 ---

05-12 08:40:25.873: I/ActivityManager(70): 开始活动: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=nl.yeswecanclinics。聊天/.开始 }

05-12 08:40:25.965: D/AndroidRuntime(499): 关闭虚拟机

05-12 08:40:25.973: D/dalvikvm(499): 调试器已分离；对象注册表有 1 个条目

05-12 08:40:26.034: I/AndroidRuntime(499): 注意: 附加线程 'Binder Thread #3' 失败

05-12 08:40:26.105: I/ActivityManager(70): 启动 proc nl.yeswecanclinics.chat 活动 nl.yeswecanclinics.chat/.Start: pid=506 uid=10032 gids={3003, 1015}

05-12 08:40:27.843: I/global(506): BufferedReader 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:40:27.843: I/global(506): BufferedWriter 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:40:28.294: W/System.err(506): java.security.KeyStoreException: KeyStore jks implementation not found

05-12 08:40:28.294: W/System.err(506): 在 java.security.KeyStore.getInstance(KeyStore.java:134)

05-12 08:40:28.294: W/System.err(506): at org.jivesoftware.smack.ServerTrustManager.(ServerTrustManager.java:61)

05-12 08:40:28.294: W/System.err(506): 在 org.jivesoftware.smack.XMPPConnection.proceedTLSReceived(XMPPConnection.java:832)

05-12 08:40:28.304: W/System.err(506): 在 org.jivesoftware.smack.PacketReader.parsePackets(PacketReader.java:268)

05-12 08:40:28.304: W/System.err(506): at org.jivesoftware.smack.PacketReader.access$000(PacketReader.java:44)

05-12 08:40:28.313: W/System.err(506): at org.jivesoftware.smack.PacketReader$1.run(PacketReader.java:71)

05-12 08:40:29.004: I/global(506): BufferedReader 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:40:29.014: I/global(506): BufferedWriter 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:40:29.483: D/dalvikvm(506): GC_FOR_MALLOC 在 153 毫秒内释放了 3668 个对象/280752 个字节

05-12 08:40:29.663: I/CONN(506): onStart

05-12 08:40:29.685：I/CONN（506）：正在运行

05-12 08:40:29.685: I/CONN(506): onResume

05-12 08:40:29.693：I/CONN（506）：正在运行

05-12 08:40:30.633: I/ActivityManager(70): 显示的活动 nl.yeswecanclinics.chat/.Start: 4712 ms（总共 384269 ms）

05-12 08:40:37.114: D/dalvikvm(175): GC_EXPLICIT 在 122 毫秒内释放了 444 个对象/22064 个字节

我按下返回按钮

05-12 08:41:07.253: W/KeyCharacterMap(506): id 0 没有键盘

05-12 08:41:07.253：W/KeyCharacterMap(506)：使用默认键盘映射：/system/usr/keychars/qwerty.kcm.bin

05-12 08:41:07.403: I/CONN(506): onPause

05-12 08:41:07.403: I/CONN(506): 停止

05-12 08:41:07.784: W/InputManagerService(70): 在非聚焦客户端 com.android.internal.view.IInputMethodClient$Stub$Proxy@45066cf8 (uid=10032 pid=506) 上开始输入

05-12 08:41:07.804: W/IInputConnectionWrapper(506): 非活动 InputConnection 上的 showStatusIcon

05-12 08:41:08.173: I/CONN(506): onStop

05-12 08:41:08.173: I/CONN(506): onDestroy

我通过单击图标重新启动应用程序

05-12 08:41:30.583: I/global(506): BufferedReader 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:41:30.623: I/global(506): BufferedWriter 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:41:31.663: W/System.err(506): java.security.KeyStoreException: KeyStore jks implementation not found

05-12 08:41:31.663: W/System.err(506): 在 java.security.KeyStore.getInstance(KeyStore.java:134)

05-12 08:41:31.663: W/System.err(506): 在 org.jivesoftware.smack.ServerTrustManager.(ServerTrustManager.java:61)

05-12 08:41:31.674: W/System.err(506): 在 org.jivesoftware.smack.XMPPConnection.proceedTLSReceived(XMPPConnection.java:832)

05-12 08:41:31.674: W/System.err(506): 在 org.jivesoftware.smack.PacketReader.parsePackets(PacketReader.java:268)

05-12 08:41:31.683: W/System.err(506): at org.jivesoftware.smack.PacketReader.access$000(PacketReader.java:44)

05-12 08:41:31.683: W/System.err(506): at org.jivesoftware.smack.PacketReader$1.run(PacketReader.java:71)

05-12 08:41:31.984: I/global(506): BufferedReader 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:41:31.994: I/global(506): BufferedWriter 构造函数中使用的默认缓冲区大小。如果需要 8k 字符的缓冲区，最好是明确的。

05-12 08:41:32.043: D/AndroidRuntime(506): 关闭虚拟机

05-12 08:41:32.043: W/dalvikvm(506): threadid=1: 线程退出未捕获异常 (group=0x4001d800)

05-12 08:41:32.214: D/dalvikvm(506): GC_FOR_MALLOC 在 147 毫秒内释放了 5507 个对象/388504 个字节

05-12 08:41:32.226: D/NativeCrypto(506): 释放 OpenSSL 会话

05-12 08:41:32.234: E/AndroidRuntime(506): 致命异常: main

05-12 08:41:32.234: E/AndroidRuntime(506): java.lang.RuntimeException: 无法启动活动 ComponentInfo{nl.yeswecanclinics.chat/nl.yeswecanclinics.chat.Start}: java.lang.NullPointerException

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.ActivityThread.access$2300(ActivityThread.java:125)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.os.Handler.dispatchMessage(Handler.java:99)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.os.Looper.loop(Looper.java:123)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.ActivityThread.main(ActivityThread.java:4627)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 java.lang.reflect.Method.invokeNative(Native Method)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 java.lang.reflect.Method.invoke(Method.java:521)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 05-12 08:41:32.234: E/AndroidRuntime( 506): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)

05-12 08:41:32.234: E/AndroidRuntime(506): at dalvik.system.NativeStart.main(Native Method)

05-12 08:41:32.234: E/AndroidRuntime(506): 由: java.lang.NullPointerException 引起

05-12 08:41:32.234: E/AndroidRuntime(506): at org.jivesoftware.smackx.muc.MultiUserChat$1.connectionCreated(MultiUserChat.java:114)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 org.jivesoftware.smack.XMPPConnection.initConnection(XMPPConnection.java:618)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 org.jivesoftware.smack.XMPPConnection.connectUsingConfiguration(XMPPConnection.java:565)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 org.jivesoftware.smack.XMPPConnection.connect(XMPPConnection.java:991)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 nl.yeswecanclinics.chat.Start.initConnection(Start.java:131)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 nl.yeswecanclinics.chat.Start.onCreate(Start.java:71)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)

05-12 08:41:32.234: E/AndroidRuntime(506): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)

05-12 08:41:32.234: E/AndroidRuntime(506): ... 11 更多

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2 回答 2

1

虽然 Marek 的回答肯定不正确（这实际上可能是您得到 a 的原因NullPointerException），但我知道的一件事是您不应该尝试在 UI 线程上建立连接。这将不可避免地导致您的应用程序在建立连接的时间超过几秒钟的情况下崩溃。您应该在AsnycTask那里进行连接和状态更改。

于 2012-05-10T08:29:26.513 回答
0

您设置了stopConnection方法null，connection因此当您尝试进行检查时，if(connection.isConnected())您会收到null，因为您设置了它。如果不是，您应该检查startConnection方法，否则您必须调用方法。connectionnullinitConnection

于 2012-05-10T08:20:26.513 回答