再次：Android MQTT无法创建客户端

我正在尝试在 Android上创建一个MqttClient,在ADT上使用Android模拟器(Nexus7)(在Linux Fedora17上使用Eclipse 3.8.0).
我发现这个问题回答了 (Android MQTT unable to create client),但它未能解决我的问题.

我创建了一个活动,允许用户进入存储presistence文件的目录,但是没有办法避免捕获异常.
我试过“/ mnt / sdcard /”,“/ mnt /”,“/ mnt / sdcard / tmp /”等.

在Eclipse项目中,我是否需要关注Android模拟器中的特定设置？
是否有任何使用权限包含在应用程序中？

我看了引用的回答问题中提到的各种mqtt资源,但我无法找到答案.

这是我的代码：

package com.storassa.android.mqttsample;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttDefaultFilePersistence;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.AutoCompleteTextView;
import android.widget.Button;
import android.widget.TextView;

public class MqttSample extends Activity {

    Button okButton = null;
    AutoCompleteTextView inputTextView = null;
    TextView errorTextView = null;

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

        okButton = (Button)findViewById(R.id.okButton);
        inputTextView = (AutoCompleteTextView)findViewById(R.id.InputText);
        errorTextView = (TextView)findViewById(R.id.errorText);

        okButton.setonClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // Todo Auto-generated method stub
                try {
                    String dir = inputTextView.getText().toString();
                    MqttDefaultFilePersistence mdfp = new MqttDefaultFilePersistence(
                            dir);
                    MqttClient client = new MqttClient("tcp://127.0.0.1:1833","0001",mdfp);
                }
                catch (Exception e) {
                    String errorText = "";
                    for (StackTraceElement error : e.getStackTrace())
                        errorText += error.toString() + "\n";
                    errorTextView.setText(errorText);
                }
            }
        });


    }

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

}

这是堆栈：

MqttException(0) at
org.eclipse.paho.client.mqttv3.MqttDefaultFilePersistence.open(MqttDefaultFilePersistence.java:74)
org.eclipse.paho.client.mqttv3.MqttClient.<init>(MqttClient.java:183)
com.storassa.android.mqttsample.MqttSample$1.onClick(MqttSample.java:38)
android.view.View.performClick(View.java:4202)
android.view.View$PerformClick.run(View.java:17340)
android.os.Handler.handleCallback(Handler.java:725)
android.os.Handler.dispatchMessage(Handler.java:92)
android.os.Looper.loop(Looper.java:137)
android.app.ActivityThread.main(ActivityThread.java:5039)
java.lang.reflect.Method.invokeNative(Native Method)
java.lang.reflect.Method.invoke(Method.java:511)
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
dalvik.system.NativeStart.main(Native Method)

解决方法

如果不依赖文件持久性,也可以使用类MemoryPersistence的实例.

因此,获得客户的电话将是：

MemoryPersistence persistence = new MemoryPersistence();
MqttClient client = new MqttClient(host,clientId,persistence);