android使用paho进行MQTT协议消息推送Demo


package com.example.myapplication;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class MainActivity extends ActionBarActivity  implements MqttCallback{

    private MqttClient mqttClient;

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

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void clickButton(View button){
        switch (button.getId()){
            case R.id.register:
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        int qos             = 2;
                        String broker       = "tcp://iot.eclipse.org:1883";
                        EditText editTextID = (EditText)findViewById(R.id.id);
                        String clientId     =  editTextID.getText().toString();
                        MemoryPersistence persistence = new MemoryPersistence();
                        try{
                            mqttClient = new MqttClient(broker, clientId, persistence);
                            MqttConnectOptions connOpts = new MqttConnectOptions();
                            connOpts.setCleanSession(true);
                            mqttClient.connect(connOpts);
                            mqttClient.subscribe(clientId);
                            mqttClient.setCallback(MainActivity.this);
                            runOnUiThread(new Runnable() {
                                public void run() {
                                    Toast.makeText(getApplicationContext(), mqttClient.isConnected() ? "连接成功" : "连接失败", Toast.LENGTH_LONG).show();
                                }
                            });
                        }
                        catch (Exception e){
                            e.printStackTrace();
                        }

                    }
                }).start();
                break;
            case R.id.send:
                EditText editTextTargetID =(EditText)findViewById(R.id.targetID);
                final String targetID = editTextTargetID.getText().toString();
                String content = ((EditText)findViewById(R.id.content)).getText().toString();
                final MqttMessage message = new MqttMessage(content.getBytes());
                if(mqttClient==null || !mqttClient.isConnected()){
                    Toast.makeText(getApplicationContext(),"MQTT未连接",Toast.LENGTH_LONG).show();
                    return;
                }
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try{
                            mqttClient.publish(targetID, message);
                        }
                        catch (Exception e){
                            e.printStackTrace();
                        }
                    }
                }).start();
                break;
        }
    }

    @Override
    public void connectionLost(final Throwable cause) {
        this.runOnUiThread(new Runnable() {
            public void run() {
                Toast.makeText(getApplicationContext(), "失去连接:" + cause.getMessage(), Toast.LENGTH_LONG).show();
            }
        });
    }

    @Override
    public void messageArrived(String topic, MqttMessage message)
            throws Exception {
        final String msg = new String(message.getPayload());
        this.runOnUiThread(new Runnable() {
            public void run() {
                Toast.makeText(getApplicationContext(), "收到:"+msg, Toast.LENGTH_LONG).show();
            }
        });
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
        try {
            final String msg = new String(token.getMessage().getPayload());
            this.runOnUiThread(new Runnable() {
                public void run() {
                    Toast.makeText(getApplicationContext(), "发送完毕:" + msg, Toast.LENGTH_LONG).show();
                }
            });
        }
        catch (Exception e){
            e.printStackTrace();
        }
    }

}

 


<LinearLayout 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"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="50dp"
        android:orientation="horizontal">

        <TextView
            android:layout_width="50dp"
            android:layout_height="fill_parent"
            android:gravity="center"
            android:text="ID:"/>

        <EditText
            android:id="@+id/id"
            android:layout_width="100dp"
            android:layout_height="fill_parent" />

        <Button
            android:id="@+id/register"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:text="register"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"
            android:onClick="clickButton" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="50dp"
        android:orientation="horizontal">
        <TextView
            android:layout_width="80dp"
            android:layout_height="fill_parent"
            android:gravity="center"
            android:text="接收方ID:"/>
        <EditText
            android:id="@+id/targetID"
            android:layout_width="50dp"
            android:layout_height="fill_parent" />
        <TextView
            android:layout_width="40dp"
            android:layout_height="fill_parent"
            android:gravity="center"
            android:text="内容:"/>
        <EditText
            android:id="@+id/content"
            android:layout_width="100dp"
            android:layout_height="fill_parent" />
        <Button
            android:text="Send"
            android:id="@+id/send"
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:layout_below="@+id/textView"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"
            android:onClick="clickButton" />
    </LinearLayout>

</LinearLayout>

android里Service和IntentService的区别

Service:运行于主线程,所以在运行过程中会造成UI没有响应;必须要调用stopService()或者stopSelf()方法去停止。
IntentService:会创建一个独立的新线程,所以不会影响UI;执行完成后自动停止,不必调用stopService()或stopSelft()方法。

android的webview中java调用javascript函数返回值的问题

在android项目中,我们使用webview将我们自己或他人的web应用嵌入到我们开发的android应用中。
通常我们在嵌入html网页的同时往往会用到javascript。我们需要java和javascript进行函数互相调用。安卓官网上已经介绍了二者之间基本的调用方法。下面讲一下java如何调用javascript有返回值的函数,并得到返回值。

1. 首先用ADT新建一个android工程。
2. 修改layout布局文件activity_main.xml。内容如下:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    tools:context=".MainActivity" 
    android:orientation="vertical">
	<WebView
    	android:id="@+id/webview"
    	android:layout_width="fill_parent"
    	android:layout_height="200dp"/>
	<LinearLayout
	    android:layout_width="fill_parent"
	    android:layout_height="35dp"
	    android:orientation="horizontal">
	 	<EditText 
	 	    android:id="@+id/edit1"
	 	    android:layout_width="50dp"
	 	    android:layout_height="fill_parent"/>
	 	<TextView android:text="+"
	 	    android:layout_width="30dp"
	 	    android:layout_height="fill_parent"/>
	 	<EditText 
	 	    android:id="@+id/edit2"
	 	    android:layout_width="50dp"
	 	    android:layout_height="fill_parent"/>
	 	<TextView android:text="="
	 	    android:layout_width="30dp"
	 	    android:layout_height="fill_parent"/>
	 	<TextView 
	 	    android:id="@+id/sum"
	 	    android:layout_width="50dp"
	 	    android:layout_height="fill_parent"/>
	</LinearLayout>
	<LinearLayout
	    android:layout_width="fill_parent"
	    android:layout_height="50dp"
	    android:orientation="horizontal">
		<Button 
		    android:layout_width="fill_parent"
		    android:layout_height="fill_parent"
		    android:onClick="clickSumBtn"
		    android:text="sum calculation"/>
	</LinearLayout>
</LinearLayout>

2. 修改MainActivity类。


import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.webkit.JsResult;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

	private WebView myWebView;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		myWebView = (WebView) findViewById(R.id.webview);
		//开启js
		WebSettings webSettings = myWebView.getSettings();
		webSettings.setJavaScriptEnabled(true);

		myWebView.setWebChromeClient(new MyWebChromeClient());
		myWebView.loadUrl("file:///android_asset/hello.htm");
		
	}
	
	public void clickSumBtn(View view){
		EditText editText1 = (EditText)findViewById(R.id.edit1);
		EditText editText2 = (EditText)findViewById(R.id.edit2);
		String str1 = editText1.getText().toString();
		String str2 = editText2.getText().toString();
		String str = "javascript:alert(sum(" + str1 + "," + str2+ "))";
		myWebView.loadUrl(str);
	}
	
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
	
	final class MyWebChromeClient extends WebChromeClient {

		@Override
	    public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
	        TextView sum = (TextView)findViewById(R.id.sum);
	        sum.setText(message);
	        result.confirm();
	        return true;
	        
	    }
	}

}

3. 在assets目录下新建文件hello.htm。内容如下:

<html>
	<head>
		<script type="text/javascript">
			function sum(v1, v2){
				return v1+v2;
			}
		</script>
	</head>
	<body>
		hello, world!
	</body>
</html>

4. 运行
输入2个数后点击下面的按钮,结果如下图。
QQ图片20140202234351

说明:

我们在安卓布局layout文件里定义了一个加法运算的界面。我们输入2个数后,java调用javascript求和函数计算两数之和,最后需要将结果返回给java。
这里我们定义了一个内部类MyWebChromeClient,它继承了WebChromeClient。我们覆盖了onJsAlert方法。我们通过调用myWebView.loadUrl(“javascript:alert(js函数(参数))”);的方式,在onJsAlert方法里捕获到了js函数的返回值。
这种方法的缺点是会影响到正常情况下使用alert方法。